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.

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, Check your inbox, may be full, sent paint info. AL.

E-mail ok ??? AL.

You can email via the site, I just don’t use PM’s.

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.

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.

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.

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.