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wbute Offline
#101 Posted : Monday, 12 April 2021 4:21:23 PM(UTC)
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Yeah I have a Luke muffler on my WB. It’s a two into one with two tail pipes. They sound great and no idea if makes more power as it didn’t get a dyno run before and after.
However I know when you drive a 253 with that two barrel carb they are always disappointing.
HK1837 Offline
#102 Posted : Tuesday, 13 April 2021 11:14:52 AM(UTC)
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Originally Posted by: castellan Go to Quoted Post
Originally Posted by: HK1837 Go to Quoted Post
The HT to HQ timing gear (also used on LH 308 up to HJ release) also retards the cam, which is the 253 cam just retarded. They moved the new 308 cam for HJ (same cam up until VL except GroupA VK) back to upright. I suspect it was done in the XT5 4.2 to improve peak power. Remember the 4.2 was supposed to be the biggest engine in Commodore with 5.0L only in Statesman and in Police Commodore. In Fred James’s report on the HT 308 he said they experimented with different camshafts for the 308 but went for the 253’s cam retarded to meet the power goal. Commonality of parts won out in the end. They achieved 227hp SAE Gross and Advertised it as 240hp. The part number for the HJ-VL 308 cam sits neatly right near the end of the Holden V8 developed for HT.


When you look at 308 Quadrajets side by side with 350 examples they have some curious differences. I have yet to find Quadrajets in the USA identical to the Holden V8 spec carbs.


When using Gross HP figures not all Gross figures are measured in the same way you know, their is advertised Gross and other Gross curves they call them A curve and a B curve etc etc can be in the game.

And also we have Net figures that differ using what they called different curves and then DIN and ECE that Holden used 2005 on. ford kept the DIN.

So I think you will find that 227hp is real gross and 240hp is the gross advertised, they are not made up our of the blue it's the same engine.
Ford has the same thing with XB 250 advertised gross HP at 155 and another figure stating the XB 250 at 123hp I think it was about that, but in gross C curve and then another with Net 108hp B curve.
I have displayed the rating on this forum. or maybe not the C curve, if you want I will look to find it for you.


SAE Gross tested to GM20 standards is always the same. Laboratory controlled fuel, air temperature at 60degF, dyno exhaust, dyno cooling. This is SAE Gross.

SAE Net is always the same too, this is the GM1 test. It is the same laboratory fuel, but at 100degF air temperature and with (from memory) the engine cooling itself (driving its water pump) and using the dyno exhaust.

Yes that is right, the GMH dyno curves for the GM20 test of the HT 308 show 227hp. It was advertised as 240bhp. GMH did this from way back, I have plots off the GMH dynos for the 4 x HR engines with GM1, GM20 and advertised figures on the same plot. All the same engines, I even have the engine numbers for three of the four engines used (161H, 186 and 186 X2).

GMH used Advertised figures up until the end of HQ, and in some advertising material it stayed the same. In internal docs, and then advertising material from about LX release they all look to have changed from advertised to proper GM20 figures, you can see the drop in all engines below except for the 5.0 which picks up about 23hp in SAE gross terms due to bigger cam and higher compression:

----------HQ-----HJ------ADR27A
130LC---90hp---NA------NA

138LC---90hp---NA------NA

138HC---95hp---NA------NA

173LC--112hp---95hp---100hp(man),108hp(auto)

173HC--118hp--105hp---105hp(man),117hp(auto)

202LC--129hp--100hp---102hp(man),(auto NA)

202HC--135hp--110hp---109hp(man),118hp(auto)

253LC--174hp--160hp----NA

253HC--185hp--175hp---161hp(auto and man)

308HC--240hp--250hp---216hp(auto and man)

The reason for the ADR27A auto power increase on 6cyl is the bigger cam used. I also added the 138 figures from LJ data, it was also used in export HJ but I don't have the revised HJ GM20 figures for it, only the old advertised figures.

Edited by user Tuesday, 13 April 2021 11:39:03 AM(UTC)  | Reason: Not specified

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HK1837 Offline
#103 Posted : Tuesday, 13 April 2021 12:03:00 PM(UTC)
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Originally Posted by: castellan Go to Quoted Post
Originally Posted by: Smitty2 Go to Quoted Post
HK1837 wrote:
..................... The 4.2 XT5 engine did also get a revised camshaft and timing gear but you don’t get to see the full effects of it as there is so many other changes. The cam and cam timing will almost certainly to take advantage of the 4BBL intake and Quadrajet. I remember reading that they originally had problems with the 253 in development with fuel distribution, and they did fart around with different camshafts during ADR27A, and then again for XT5. However the 308/304 kept the same cam all along except for that early HT to HQ period when they compromised and used a retarded 253 cam.


ugghh ... did not want to bring that up as it slightly muddies the waters of this part of the topic
but you are correct. GMH did change the camshaft, camshaft timing via different cam gear on 4.2 XT5s
and
I have no confirmation, only guesses.. its to do with extra output in compliance with ADR/EPA numbers
with XT5 4.2 litre engines

Overall ....
What GMH did was unusual... yes, new 4BBL Quaddie to suit the XT5 blue 253 which has leaner primaries (needles and jets) than
the 308 which is understandable...BUT richer (very much) secondary jetting. The secondary rod hanger is the same for both 253 and
308 XT5 Quaddies but the rods differ... a lot. The 253 uses CX rods* ( a finer so richer rod when they lift) and 308 used DP rods.

The 253 4BBL Quaddie is therefore richer at higher revs (both use the same secondary jets) or WOT compared to a 308 . Strange..!
and also remember back then, the Quaddie for both used the same core, same fuel bowl body and was a 750cfm casting...
(late 308s used the desirable 800cfm casting)

but
back to the camshaft... HK1837 is correct, 4.2 XT5 engines got a revised camshaft... which curiously was more aggressive than previous
with the longer duration, marginally higher lift (.005") and tighter LSA BUT ... and here is the weird bit. The new cam gear when installed
RETARDS the cam timing (which is why you NEVER use this cam gear on any other Holden V8)

More aggressive cam .. but installed 'retarded' means an engine with that setup is more responsive at high revs which suits the 253 Quaddie
jetting but for a street engine that has to comply with driveability and pollution standards???

In a word... weird ! (...for a car company like GM/GMH) And interesting! Think



*CX rods these days are the desired ones for Holden V8s... street, strip or track, they are the ones to get. You cannot buy them here
but Summit, JEGS and other USA parts places - Quadrajet Parts sell them. I have a number of sets of CX rods and run them in the race
Quaddies I put together for the racecar.

The yank carb builders seem to prefer AY secondary rods for Quaddies going on SBC ... look at their carb build parts lists and AY (or CE)
seem to be a favourites. AY is just about the same as CX except leaner on secondary valve initial opening...

Lets say for argument that the HT-G-Q 308 Camshaft was a 20/60 and a 253 was set 5deg retarded making such a 15/65. now by rights the 253 should rev out a bit better and the same if the 308 was set 5deg retarded, now I think the LH L34 had this setup std factory but you got the big camshaft in the boot to fit if you wanted to.
So that would make the factory L34 a bit more revving over the L31 not to mention the bigger valves and higher compression etc.

So if we were to have a stock L31 and retard the cam timing by 5 deg we would have an engine with less running compression volume efficancy so if we were to try and make a gain in performance I would not retard a stock L31 at all as you will gain noting and loose mid range torque. but if you had more compression like 9.7:1 maybe you may pick up a bit more top end rive ability and better mid range than with 9.0:1

The L34 308 Torana with better flowing heads with such must of been worked out by Holden as the best way to go with such as was.

As for this 253 why they did such well the heads flow real well for one and it was promoted as a fire breathing thing for the masses that was predicted to hope sell the most engines.


The original 253 camshaft was't retarded, it stood upright. It was the HT-HQ (and pre-HQ LH including L34) that used the 253's cam but retarded 5deg. From HJ the 308 and later 304 got the bigger cam with the 253's timing gear. They did it in the HT-HQ 308 to get better peak power, with the compromise to use a common part with the 253. Probably saved 10c an engine and one less spare to keep. They needed bulk more power and torque for the HJ 5.0L as the 350/400 was to be dropped. The heaviest GMH passenger car yet, the HJ Caprice needed the extra power for its wight and for the air and steer and the bigger alternator. GMH contuinued to use the same cam from HJ onwards with 9.7:1, 9.4:1, 9.2:1, 8.8:1 and 8.5:1 compression.

The L34 didn't come with a cam in the boot. It came delivered exactly how it was. GMH helped racers by putting together a HP pack if you needed, but GMH never fitted it. It included a bigger cam, 780/800cfm Holley (as per PhaseIII or 1968 Z28) and roller rockers plus other stuff.

The 253 had heads on it suitable for a 308, so yes it went well especially if you threw the 2BBL away and fitted dual exhaust. The HQ SS shows you what it was capable of. It was a dual exhaust with 3.36 rear axle. It was faster than a stock 308 manual HQ of similar weight, which also used a 3.36 rear axle standard. The difference was the stock 308 had a single exhaust.

As for the 253 carby, the SBC engines show you best how it strangles. That WW 2BBL is basically the same specs as the stock 2 barrel Rochester (aka 307 HK-HT carby). Identical bore size, very close in cfm. The 327 small 2BBL was 210hp. 9:1, GP hydraulic cam etc. The IDENTICAL engine in the 1969 Chevrolet other than having the large 2BBL (as per L65 350) was 235hp. Again, the IDENTICAL engine but with a Quadrajet (the GTS327 engine also option L73 in North America) was 250hp. So that means a 9:1 327 picks up 40hp simply by moving from a little 2BBL to a Quadrajet. So to put this in 253 terms, a HT-HJ 253 should in theory go up maybe 30hp from 175hp SAE Gross to somewhere in the ballpark of 205hp. Then go look at a VB 4.2 dual exhaust to a VC 4.2 dual exhaust. 96kW DIN to 115kW DIN, both at 4400rpm. That is 19kW, which is 25.5hp.

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castellan Offline
#104 Posted : Tuesday, 13 April 2021 1:47:53 PM(UTC)
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Originally Posted by: Smitty2 Go to Quoted Post
Originally Posted by: castellan Go to Quoted Post
Originally Posted by: wbute Go to Quoted Post
Blue 253 was light years better than the red 253. All due to the carb and ignition.


I believe as to a stock 253 the best value for performance is single 2 1/4 free flow exhaust and that's about it.

....................


I bought (GMH employee purchase) my missus this.... VH Vacationer wagon
with blue 253, N10, other xtras and M20 4 speed ( + HD axle and 4 wheel disc brakes)



and after a couple of years... chucked the exhaust system, added a set of
extractors (Lukey) and also a 2 1/4" into 2 1/2" y pipe system also from Lukey ...
(similar to what Lukey provided for the VK Grp A SS)

Why Lukey? my brother was Holden car line product manager there at Lukey Moorabbin
he was the one in a moment of madness who arranged this...



ps... that VH wagon sure got up and went after the exhaust mod Applause


As to the VK SS Group A in the photo like, now I had seen one dude a car dealer that had one from new had one size pipe and then another dude that I knew who owned a Pub had the same type of car but from new with a bigger exhaust than the other one had, now I believe that he said that he went for the bigger exhaust, must of been an option back then from Holden ? this dude bought the next VL SS Group A as well with a 5sp box and had a exhaust like the car dealers VK SS Group A.

As for your system you put on, it depends on the muffler in how it flows. mine was a Hills sports muffler straight through type, such got somewhat less noise as you revved it out in one regard as a dog leg type can be quieter down low and mid but bark up high revs.
castellan Offline
#105 Posted : Tuesday, 13 April 2021 3:01:34 PM(UTC)
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Originally Posted by: HK1837 Go to Quoted Post
Originally Posted by: castellan Go to Quoted Post
Originally Posted by: Smitty2 Go to Quoted Post
HK1837 wrote:
..................... The 4.2 XT5 engine did also get a revised camshaft and timing gear but you don’t get to see the full effects of it as there is so many other changes. The cam and cam timing will almost certainly to take advantage of the 4BBL intake and Quadrajet. I remember reading that they originally had problems with the 253 in development with fuel distribution, and they did fart around with different camshafts during ADR27A, and then again for XT5. However the 308/304 kept the same cam all along except for that early HT to HQ period when they compromised and used a retarded 253 cam.


ugghh ... did not want to bring that up as it slightly muddies the waters of this part of the topic
but you are correct. GMH did change the camshaft, camshaft timing via different cam gear on 4.2 XT5s
and
I have no confirmation, only guesses.. its to do with extra output in compliance with ADR/EPA numbers
with XT5 4.2 litre engines

Overall ....
What GMH did was unusual... yes, new 4BBL Quaddie to suit the XT5 blue 253 which has leaner primaries (needles and jets) than
the 308 which is understandable...BUT richer (very much) secondary jetting. The secondary rod hanger is the same for both 253 and
308 XT5 Quaddies but the rods differ... a lot. The 253 uses CX rods* ( a finer so richer rod when they lift) and 308 used DP rods.

The 253 4BBL Quaddie is therefore richer at higher revs (both use the same secondary jets) or WOT compared to a 308 . Strange..!
and also remember back then, the Quaddie for both used the same core, same fuel bowl body and was a 750cfm casting...
(late 308s used the desirable 800cfm casting)

but
back to the camshaft... HK1837 is correct, 4.2 XT5 engines got a revised camshaft... which curiously was more aggressive than previous
with the longer duration, marginally higher lift (.005") and tighter LSA BUT ... and here is the weird bit. The new cam gear when installed
RETARDS the cam timing (which is why you NEVER use this cam gear on any other Holden V8)

More aggressive cam .. but installed 'retarded' means an engine with that setup is more responsive at high revs which suits the 253 Quaddie
jetting but for a street engine that has to comply with driveability and pollution standards???

In a word... weird ! (...for a car company like GM/GMH) And interesting! Think



*CX rods these days are the desired ones for Holden V8s... street, strip or track, they are the ones to get. You cannot buy them here
but Summit, JEGS and other USA parts places - Quadrajet Parts sell them. I have a number of sets of CX rods and run them in the race
Quaddies I put together for the racecar.

The yank carb builders seem to prefer AY secondary rods for Quaddies going on SBC ... look at their carb build parts lists and AY (or CE)
seem to be a favourites. AY is just about the same as CX except leaner on secondary valve initial opening...

Lets say for argument that the HT-G-Q 308 Camshaft was a 20/60 and a 253 was set 5deg retarded making such a 15/65. now by rights the 253 should rev out a bit better and the same if the 308 was set 5deg retarded, now I think the LH L34 had this setup std factory but you got the big camshaft in the boot to fit if you wanted to.
So that would make the factory L34 a bit more revving over the L31 not to mention the bigger valves and higher compression etc.

So if we were to have a stock L31 and retard the cam timing by 5 deg we would have an engine with less running compression volume efficancy so if we were to try and make a gain in performance I would not retard a stock L31 at all as you will gain noting and loose mid range torque. but if you had more compression like 9.7:1 maybe you may pick up a bit more top end rive ability and better mid range than with 9.0:1

The L34 308 Torana with better flowing heads with such must of been worked out by Holden as the best way to go with such as was.

As for this 253 why they did such well the heads flow real well for one and it was promoted as a fire breathing thing for the masses that was predicted to hope sell the most engines.


The original 253 camshaft was't retarded, it stood upright. It was the HT-HQ (and pre-HQ LH including L34) that used the 253's cam but retarded 5deg. From HJ the 308 and later 304 got the bigger cam with the 253's timing gear. They did it in the HT-HQ 308 to get better peak power, with the compromise to use a common part with the 253. Probably saved 10c an engine and one less spare to keep. They needed bulk more power and torque for the HJ 5.0L as the 350/400 was to be dropped. The heaviest GMH passenger car yet, the HJ Caprice needed the extra power for its wight and for the air and steer and the bigger alternator. GMH contuinued to use the same cam from HJ onwards with 9.7:1, 9.4:1, 9.2:1, 8.8:1 and 8.5:1 compression.

The L34 didn't come with a cam in the boot. It came delivered exactly how it was. GMH helped racers by putting together a HP pack if you needed, but GMH never fitted it. It included a bigger cam, 780/800cfm Holley (as per PhaseIII or 1968 Z28) and roller rockers plus other stuff.

The 253 had heads on it suitable for a 308, so yes it went well especially if you threw the 2BBL away and fitted dual exhaust. The HQ SS shows you what it was capable of. It was a dual exhaust with 3.36 rear axle. It was faster than a stock 308 manual HQ of similar weight, which also used a 3.36 rear axle standard. The difference was the stock 308 had a single exhaust.

As for the 253 carby, the SBC engines show you best how it strangles. That WW 2BBL is basically the same specs as the stock 2 barrel Rochester (aka 307 HK-HT carby). Identical bore size, very close in cfm. The 327 small 2BBL was 210hp. 9:1, GP hydraulic cam etc. The IDENTICAL engine in the 1969 Chevrolet other than having the large 2BBL (as per L65 350) was 235hp. Again, the IDENTICAL engine but with a Quadrajet (the GTS327 engine also option L73 in North America) was 250hp. So that means a 9:1 327 picks up 40hp simply by moving from a little 2BBL to a Quadrajet. So to put this in 253 terms, a HT-HJ 253 should in theory go up maybe 30hp from 175hp SAE Gross to somewhere in the ballpark of 205hp. Then go look at a VB 4.2 dual exhaust to a VC 4.2 dual exhaust. 96kW DIN to 115kW DIN, both at 4400rpm. That is 19kW, which is 25.5hp.



I think that the 307 carby is 350CFM and the 253 carby is 320CFM.
Not to mention a 2V CFM and a 4V CFM is rated differently, so the 2V are not as small rated CFM as one would expect.

From what I am lead to believe is that the L34 came with the bigger Camshaft optional for you to fit yourself.

I am sure that the N10 was all that a 253 needs, it's still quiet tho, for most back in the day the cheaper way was just 2 1/4 free flowing single and you got a good sound, but if you wanted it quiet go the N10.
As for 308's the freer the flow the better power 308's hate restriction as such it kills power real badly.

If you put L34 valves say or go bigger valves than standard with the stock 253 you loose performance. even porting out a 308 exhaust too much will kill performance.

The 308 HJ camshaft is only breathing in a bit more and the exhaust duration like so only kills performance, it's a shit camshaft and it's not identical to the V8 chev at all in reality.

Most people think that the higher the flow the better the performance is and that's just stupid wood duck response that you get everywhere sadly.
A engine only needs what it needs and that's it. going beyond such is nonsense. Vacuum secondary's work fine as stated.

I have seen people put huge flowing intake manifolds on the street engine such is pathetic and the worst thing that you can do as it kills torque down low and mid range, such is just another typical wood duck response. I had a Suzuki RM125S back in the days of such thinking, yep it works and the engine was a fire breathing monster that was all or nothing, you needed to have balls to get the most out of that beast or you would be shit, the power came on with a bang and it would take off like a scolded cat, but when the RM125B came out it was much easy to ride and much faster over all on any track, any idiot could ride such because it was not such a beast but performed better over all and around same top end power. you would swear the S had more but it was only more savage in how it delivered that power. and what happened over the years as the bikes progressed you would see that they were tailoring the power and torque delivery in the best way with gearing and all and chasing the maxim HP became not the issue.

When we read max HP that's only part of the story, you need a HP and a torque graph to show what's truly going on.

Even nowadays one will come up with stars in their eyes pissing on about the power of a Falcon XY GT-HO C'mon ! it's a shit heap in todays standards. gutless ! ill handling crap thing to drive, but like the RM125S They were the ducks nuts back in the days and I love them for what they are.

Here drive a stock HT 350GTS or a XA GT 4SP and then a 5.7L GEN 3 what a huge difference in power delivery, the Gen 3 has nothing on the early 350 or 351 for right down low torque.
HK1837 Offline
#106 Posted : Tuesday, 13 April 2021 4:45:18 PM(UTC)
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Put it this way, the small 2BBL Rochester has 2 x 1.09" diameter verturis with a 1.25" SAE flange size and 1.44" throttle bore diameter.

The WW-2 Stromberg has two 1.188" venturis on the same 1.25" SAE flange with 1.44" throttle bore diameter.

Both are major restrictions on a 253 or a 308. It is a well known fact, and the 327/210 vs the 327/250 proves it. The old 283 2BBL used the same carby, and it picked up bulk hp and torque with a 4BBL.

Whomever told you that the L34 came with a different cam in the boot is full of it! If it did it'd need lifters too.

GMH never offered a bigger single, it was a single or dual with balance pipe.

The HJ cam is significantly bigger. Fred James states as much in his original report:

"For economic reasons we preferred, if possible, to retain the same camshaft as for the 253, After a number of tests we found that by retarding the camshaft by 5deg, we obtained our output targets without deteriorating idle quality. This expedient retained the event durations, overlap and overlap area factor, buy delayed the inlet valve closing. This delay was not sufficiently large to deteriorate the low end torque, but was sufficient to get the high end hp we aimed for. However, the development potential of the engine remains considerable;e as our subsequent experimental work has shown that remarkable top end power increases can be obtained without an appreciable low end torque loss just by cam changes alone".

Fred is talking about the HJ cam and other tested cams in that last sentence. The HJ cam part number is consistent with that development period. It is simply the GM GP hydraulic profile ground on a Holden cam casting. Sure the 253/308 has slighty less lifter lift as it uses 1.6 rockers instead of the SBC's 1.5. But its the same profile, same timing, same overlap, same lobe centre. The differences are obvious, all at 4thou I believe:

27 63 270 71 19 270 (46 overlap), 400/400 thou lift 253
32 58 270 76 14 270 (46 overlap), 400/400 thou lift 308
28 72 280 78 30 288 (58 overlap), 400/400 thou lift 5.0L
28 72 280 78 30 288 (58 overlap), 390/410 thou lift SBC GP

I agree, torque curve is important, I only detailed power above, too much work to do torque too but it also increases in the HJ.

Agree, XY GT-HO is about 330hp, when you plug in its weight plus two people and the test figures of new ones you get between 325-335hp, with teh rev limiter in place.
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gmholdman Offline
#107 Posted : Tuesday, 13 April 2021 4:56:33 PM(UTC)
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HK1837, Check your inbox, may be full, sent paint info. AL.
HK1837 Offline
#108 Posted : Tuesday, 13 April 2021 5:22:58 PM(UTC)
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It’s always full, I don’t use it or I get 100’s of questions!
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gmholdman Offline
#109 Posted : Tuesday, 13 April 2021 5:39:24 PM(UTC)
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E-mail ok ??? AL.
bazza30555 Offline
#110 Posted : Tuesday, 13 April 2021 6:36:48 PM(UTC)
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Found this info a while back on a US site
Rochester 2G
1.25 1.44 1.09 278 cfm
1.50 1.06 l.19 352 cfm
1.50 1.06 1.25 381 cfm
1.50 1.06 1.31 423 cfm
1.50 1.06 1.38 435 cfm
also
Grey twin Strombergs
2 x 1.05 200cfm
Red twin Strombergs
2 x 1.23 230 cfm
HK1837 Offline
#111 Posted : Tuesday, 13 April 2021 7:27:07 PM(UTC)
HK1837

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Originally Posted by: gmholdman Go to Quoted Post
E-mail ok ??? AL.


You can email via the site, I just don’t use PM’s.
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HK1837 Offline
#112 Posted : Tuesday, 13 April 2021 7:39:27 PM(UTC)
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Originally Posted by: bazza30555 Go to Quoted Post
Found this info a while back on a US site
Rochester 2G
1.25 1.44 1.09 278 cfm
1.50 1.06 l.19 352 cfm
1.50 1.06 1.25 381 cfm
1.50 1.06 1.31 423 cfm
1.50 1.06 1.38 435 cfm
also
Grey twin Strombergs
2 x 1.05 200cfm
Red twin Strombergs
2 x 1.23 230 cfm


The top one is the 275/283/307 and 210hp 327 carby. I’ll have to check which of the others was used on the 235hp 327 and the 245/250hp 350. The 250hp version is identical to our 275hp auto HT-HG engine except the 275hp version got the 4BBL intake and Quadrajet. The 245hp is the same as the HQ 350 except the HQ 350 had a 4BBL intake and Quadrajet. The 5hp difference is a drop from 9:1 down to 8.5:1 courtesy of dished pistons. Same difference between HT-HG 350 auto and HQ, all that changed that mattered was the HQ had dished pistons.
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castellan Offline
#113 Posted : Wednesday, 14 April 2021 11:10:56 AM(UTC)
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Originally Posted by: HK1837 Go to Quoted Post
Put it this way, the small 2BBL Rochester has 2 x 1.09" diameter verturis with a 1.25" SAE flange size and 1.44" throttle bore diameter.

The WW-2 Stromberg has two 1.188" venturis on the same 1.25" SAE flange with 1.44" throttle bore diameter.

Both are major restrictions on a 253 or a 308. It is a well known fact, and the 327/210 vs the 327/250 proves it. The old 283 2BBL used the same carby, and it picked up bulk hp and torque with a 4BBL.

Whomever told you that the L34 came with a different cam in the boot is full of it! If it did it'd need lifters too.

GMH never offered a bigger single, it was a single or dual with balance pipe.

The HJ cam is significantly bigger. Fred James states as much in his original report:

"For economic reasons we preferred, if possible, to retain the same camshaft as for the 253, After a number of tests we found that by retarding the camshaft by 5deg, we obtained our output targets without deteriorating idle quality. This expedient retained the event durations, overlap and overlap area factor, buy delayed the inlet valve closing. This delay was not sufficiently large to deteriorate the low end torque, but was sufficient to get the high end hp we aimed for. However, the development potential of the engine remains considerable;e as our subsequent experimental work has shown that remarkable top end power increases can be obtained without an appreciable low end torque loss just by cam changes alone".

Fred is talking about the HJ cam and other tested cams in that last sentence. The HJ cam part number is consistent with that development period. It is simply the GM GP hydraulic profile ground on a Holden cam casting. Sure the 253/308 has slighty less lifter lift as it uses 1.6 rockers instead of the SBC's 1.5. But its the same profile, same timing, same overlap, same lobe centre. The differences are obvious, all at 4thou I believe:

27 63 270 71 19 270 (46 overlap), 400/400 thou lift 253
32 58 270 76 14 270 (46 overlap), 400/400 thou lift 308
28 72 280 78 30 288 (58 overlap), 400/400 thou lift 5.0L
28 72 280 78 30 288 (58 overlap), 390/410 thou lift SBC GP

I agree, torque curve is important, I only detailed power above, too much work to do torque too but it also increases in the HJ.

Agree, XY GT-HO is about 330hp, when you plug in its weight plus two people and the test figures of new ones you get between 325-335hp, with teh rev limiter in place.


When measuring the cam timing from Holden's perspective points is one thing and if we were to look at such from say the old standard of 0.006 or the new 0.050 would be interesting.

What I see in this is a HT-G-Q 308 intake is 32/58 and HJ 28/72. now the later duration needs more static compression to keep it on par volume efficiency that's why the move from 9.0:1 became 9.7:1 and this later duration helps it rev more higher by rights. so if we made it 33/67 would make more torque by rights and gain the more performance out of such a small cam. I would advance this cam to make the best of it.

Now as to the exhaust duration well what happens by rights is that closing such later from 14 to 30 makes not much difference but for such will put more heat into the exhaust, it was done as a pre cat converter thing so as to burn more fuel in the exhaust.

We could see a advertised cam saying 30/70 intake and then look at another and another that says the same but they are not the same at all even if they are measured a the same rate on just that one point alone, not to mention all the rest are claimed the same readings, but they are not truly the same thing. if you change the lift you change things on the ramps.

On a dual cam you can play with the intake and exhaust timing so you can work some magic with such a setup tuning such giving more to play with in such a tune. so I could advance my intake and retard my exhaust timing or narrow both down retard the in and adv the exh and feel the difference but playing with the intake makes the biggest difference by rights.

As for 1/4 mile HP what is that based on Gross HP figures or Net, the GT-HO P3 best was 350hp net in race trim that could be about 400hp in gross figures or maybe 420hp.
Most driven on the street were anything maybe flat out making 300hp net, 350hp gross.

What did a GTS350 and GT 4V 351 make around 222hprw.
280hprw = about 350hp net ?

A stock XB GT made 215hp net, and a XB 351 2v with the 350CFM 2 BBL carter made 183hp net that's with dual exhaust but you jump 32hp with the big 4 BBL carby on this but where is the advantage of the big carby only up top in the rev range does it count.
XD 5.8lL with single exhaust makes 198hp DIN.

The VK SS Group A had a single exhaust tip out the arse, I never said it was a single system.
The VK SS came with dual pipes out the arse end but not the VK SS Group A that I remember seeing back when they were new. old mates at the pub shore the hell was a big single at the rear and it was brand new. and the red VL SS Group A he had was as well, only smaller diameter than the blue Group A had. maybe a 2 1/2 and the blue was 3in. both had a resonator, it was not just a piss pipe.
I am sure that Blue VK SS Group A resonator was stainless steel it was shining like but his VL was not. I thought they were both Brock Commodores.
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#114 Posted : Wednesday, 14 April 2021 1:22:58 PM(UTC)
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The cam isn't the reason they moved to 9.7:1. This cam was tested in the 9:1 HT 308 but they chose to use the 253 cam retarded for economics. The HJ cam was used in all 308 and 304 except groupA engines, so it was used on engines with 9.7:1 (HJ to mid HZ), 9.4:1 (VB and late HZ), 9.2:1 (WB/VC-VK), 8.8:1 (VK 304) and 8.5:1 (VL). GM did the same thing, this camshaft profile was used in engines from 8.5:1 up to 10.25:1 from 283ci right up to 400ci.

It is hard to go by original timing, I get that. GM and GMH quote them as "including ramps" and "excluding ramps". The figures on that GP hydraulic cam from GM are:

Including ramps: 38 92 310, 88 52 320.
Excluding ramps: 28 72 280, 78 30 288.

I'm pretty sure the including ramps (zero lash) is about 4thou lift.

However this cam is reproduced by Comp Cams and they quote it as:

Advertised: 49 81 319, 98 42 320 measured at 1 thou. They also quote the lobe centre as 112deg, plus the same lift figures as GM of 0.39" intake and 0.41" exhaust.

They do give 0.050" duration of 195 intake and 202 exhaust.

Here it is: https://www.compcams.com...evrolet-small-block.html

HT-HG GTS350 were 300hp SAE Gross, made about 205-210rwhp.
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#115 Posted : Thursday, 15 April 2021 7:12:32 AM(UTC)
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It’s a shame the 253 didn’t get the fuel injection update like the 5 litre. I know time moves on, but it had to have been a better engine that the V6 that replaced the smaller capacity engines.
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#116 Posted : Thursday, 15 April 2021 7:50:23 AM(UTC)
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It was gone by the end of 1985 though. And it’d need different heads as the ports on the EFI 5.0L were really too big for 5.0L, and the combustion chambers would have to have been smaller plus smaller valves too. The V6 was a ready to use engine. It’d have been an interesting exercise to cost it though, as they’d have had the added advantage that there was only one fitment including one 4L60, one bellhousing, one radiator, harness, hoses, pipes etc.
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wbute Offline
#117 Posted : Thursday, 15 April 2021 1:07:35 PM(UTC)
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Yeah I don’t think it would have been totally unrealistic. Selling it to the everyday motorist might have been an uphill battle though, being a V8. Could have made a great engine out of it. I always thought it was under-developed.
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#118 Posted : Thursday, 15 April 2021 1:20:59 PM(UTC)
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If they’d done it they may have kept the Trimatic and converted it to the 4spd version as used overseas.
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#119 Posted : Thursday, 15 April 2021 5:00:02 PM(UTC)
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Originally Posted by: HK1837 Go to Quoted Post
The cam isn't the reason they moved to 9.7:1. This cam was tested in the 9:1 HT 308 but they chose to use the 253 cam retarded for economics. The HJ cam was used in all 308 and 304 except groupA engines, so it was used on engines with 9.7:1 (HJ to mid HZ), 9.4:1 (VB and late HZ), 9.2:1 (WB/VC-VK), 8.8:1 (VK 304) and 8.5:1 (VL). GM did the same thing, this camshaft profile was used in engines from 8.5:1 up to 10.25:1 from 283ci right up to 400ci.

It is hard to go by original timing, I get that. GM and GMH quote them as "including ramps" and "excluding ramps". The figures on that GP hydraulic cam from GM are:

Including ramps: 38 92 310, 88 52 320.
Excluding ramps: 28 72 280, 78 30 288.

I'm pretty sure the including ramps (zero lash) is about 4thou lift.

However this cam is reproduced by Comp Cams and they quote it as:

Advertised: 49 81 319, 98 42 320 measured at 1 thou. They also quote the lobe centre as 112deg, plus the same lift figures as GM of 0.39" intake and 0.41" exhaust.

They do give 0.050" duration of 195 intake and 202 exhaust.

Here it is: https://www.compcams.com...evrolet-small-block.html

HT-HG GTS350 were 300hp SAE Gross, made about 205-210rwhp.

Yes I know the Comp Cams etc do have replacer Cam grinds but they are not truly the same at all in fact at they are not allowed to copy any Cam grind unless they pay for the rights of such.

The reason for the drop in compression in the 308 from 9.7 to 9.4 and then 9.2 and then 8.8 and then 8.5 is not because they have to run 9.7 but they just tailor it due to ADR2A in the tune and the 8.5:1 is due to lowering to 92 octane.
The 8.8:1 was electronic ign control what would be happening is they would be tuning the spark timing closer to max than with the older points system so lowering the comp to 8.8:1 you can advance your timing more overall with safely, as that's were your fuel economy comes into it and performance.

When you look at a EFI 5.0L say 165kw and the SS 185kw nothing has changed but spark timing in the main has been advanced and that's why they put a knock sensor on them so the bastard when it kicks in drops spark timing 12 deg directly to save the engine.

With the 5.0L sequential engine this tune is even more advanced system and this has the ability to drop back by 2 deg 4 then 6 then 8 then 10 or all the way back to 12 deg as it sees fit in regards to what it's dealing with, so it's saving fuel economy and giving you more performance, because 12 deg retarded timing you will know it has kicked in directly.

The VT 179KW was created for 95 octane as it's compression was increased to 8.8:1 Holden said this was so, as 91-92 was earmarked to go, but PM Gillard put a stop to such going ahead.

Have a look at the HSV VN 5.0L 200kw it has 9.0:1 but they need 95 octane fuel to perform 200kw on 91 may be lucky to make 150kw.
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#120 Posted : Thursday, 15 April 2021 5:13:28 PM(UTC)
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The 5.0L stays at 9.7:1 at ADR27A introduction mid 1976. It stays at that until mid 1978 when it drops to 9.4 then 9.2 at blue engine release. The drop from 9.2 to 8.8 has nothing to do with spark, it was the 5.0L being de-stroked to fit under 5000cc, it dropped the piston a bit. The drop to 8.5 is the ULP VL engine, it is done as the chambers were enlarged in the heads for deshrouding the bigger valves.
The 4.2 goes from 9.1 to 9.4:1 at ASR27A introduction.

GM using that similar grind across multiple engines with varying compression ratios is nothing to do with pollution either. They used the same cam in the 2BBL 1968 8.75:1 200hp 307 that they used in the 1968 10:1 275hp 327 and the 1969 10.25:1 300hp 350. All they did was calibrate the distributors for the target fuel. The 307 dizzy was calibrated for regular fuel, the other two for higher octane fuel. The same cam was used in the low compression truck 327 and 350 engines that were as low as 8:1.

GM and GMH used the one cam whenever they could. It cost GMH $25000 in early 1977 to change the 4.2L cam contour to eliminate valve gear noise at 2400-2600rpm. It took 26 weeks from sign off to get the engines re-certified for emissions and to get the new cam into production for SOP of HZ. I reckon they still didn’t resolve it properly and changed the standard HZ 4.2L rear axle from 3.55 to 3.36.

Edited by user Thursday, 15 April 2021 5:30:41 PM(UTC)  | Reason: Not specified

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