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Advice on 308 timing adding vacuum advance
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HK1837 Offline
#21 Posted : Thursday, 19 April 2018 2:27:43 PM(UTC)
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Yeah you did say 9/73 308 on are the same as a HJ - they are not as I already explained. A late HQ or early LH 308 may look the same as a early HJ engine, but that is where it ceases. The block is different, the pistons are different, the cam is different and the timing gear on the cam is different.

Where do I say a HJ engine's performance is identical to a HQ? I know for a fact that is wrong, the HJ performs far better. I don't say that, GMH and everyone I know that owned them new (either in Torana or in a Holden) says it other than you.

I fully understand how cam and compression works. So did GM/Chevrolet and so did GMH. They used the SAME grind camshaft for all engines from 8.5:1 (GM with the 327/240 and 1971-1974 L48 and GMH with the carby VL 5.0L) up to near 10:1 (GMH with 9.7:1 HJ-HZ engine and GM with the 1967-70 L48). GMH wanted more power and torque for the HJ as they had dropped the 400ci engine, so they went back an revised the 308 for a bigger cam and more compression.

I have the full specification from GM and from GMH - cam grinds are basically identical, the difference being due to the different rocker arm ratios used on SBC vs 253/308.

All I can say is garbage to the next statement. The HJ cam is used in late red 308 at 9.4:1, blue-black 308 at 9.2:1, black VK 304 at 8.8:1 and black VL 304 at 8.5:1. All of these have the same basic heads apart from EGR port shape, only the VL has bigger valves and also run on ULP. The DIN power and torque of these do not vary much at all, and these you can compare DIN as they were tested on the same dyno with the same dual exhaust. Figures for these are:

VB Red L31 9.4:1 308 - 125kW@4200.
WB/VC-VK Blue-Black L31 9.2:1 308 - 126kW@4400.
VK black LV2 304 - I think this stayed the same as the 308.
VL black 8.5:1 LV2 304 - 122kW@4400rpm.

Hmmm, no real power drop with the drop in compression. Might be a few hp difference in peak figures on an engine dyno but not a lot to write home about.

Pollution laws started with A.I.R. for California from 1966-7, didn't happen until the rest of the country until 1968. The HJ cam has NOTHING TO DO WITH ADR27. ADR27 arrived in 8-9/73. HJ engines a year later. ADR27 and ADR27A ARE EXTERNAL stuff only, no internals were changed with the exception of the EGR valve on auto engines - it was blanked off on manuals.

SAE Gross hp figures in Engineering documents are not made up, they are read straight off the graphs. You are talking about advertised hp, but these were changed for marketing all the time and not restricted to Gross, Net or DIN were also changed by marketing. I never use marketing figures, only the Engineering data. What do you mean I know HQ and HJ performed the same, I have never said that, quite the opposite in fact, you can feel the 25 odd hp difference easily. Yes, HX was 216hp@4800 gross, compared to the HT-HQ 225hp (might have been 227hp, will confirm - edit: see bottom of this post). Garbage again on the camshaft, enough said.

Again you are wrong, NO 308 Torana EVER got a single exhaust. In fact SLR or SS 4.2 Torana were all dual exhaust until a short period post ADR27A introduction when a single exhaust appeared for a while.

Not all 308 LH Torana got a 2.78 rear axle, 3.08 was available and fitted to some especially some L34.

Most 308 (and 253) Holden from HT through to the end of HJ got a single exhaust, dual exhaust didn't become standard until HX GTS if I remember correctly (apart from the HQ SS package).

I agree, all the claims about the 308 being gutless are from people who either: drove a flogged out one with busted cam or Quadrajet badly needing a service, single exhaust or tall diff and auto. If you wee lucky enough to get a drive of an original 308 HJ manual with dual exhaust (STD with 3.36) or an LH-early LX with a HJ 308 engine then you got a totally different idea. Even the HZ 308 went well, if equipped with a dual exhaust. A9X's were certainly never lambasted as a dog like the HX's were, and GMH were very careful to ensure that the road test A9X's were not the really early A9X's with the HX engines - they always got the better running HZ engine.

L34 has flat top pistons with no dish, if used with standard heads probably would have been 10:1, but Perfectune machined the heads for bigger valves and thus the chambers were opened up a bit so compression was 9.8:1. The cam wasn't touched, it kept the early 253 cam retarded by 5deg just like every other HT-HQ 308. This was a race car, not a road car hence there was no need for GMH to use the upcoming HJ cam in it. The cam was top be changed for race duty. HDT offered the L34 bottom end in their VH based GroupIII as a HO engine, they must have decked the heads to gain some more compression back as they rated them as 10:1.

June 1970 dyno curves for HT 308 engine, statement made under oath before Public Notary by Fred James Engine Engineer. Curves give both Gross hp/torque and Net hp/torque (I think these are called GM1 and GM20 tests respectively and show the corrected barometric pressure and temperature for both tests).

Gross:
226hp@4800rpm
300ftlbs@3200rpm.

Net:
160hp@3700rpm
240ftlbs@2000rpm.

The ADR27A HX engine curves I only have NET figures for:

Net
167hp@4000rpm
251ftlbs@2400rpm.

Edited by user Thursday, 19 April 2018 8:16:46 PM(UTC)  | Reason: Not specified

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castellan Offline
#22 Posted : Friday, 20 April 2018 11:46:39 AM(UTC)
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Boy now the truth comes out.
HT-G-Q 308 Net 160hp 3700 / 240Lb 2000
HX 308 Net 167hp 4000 / 251Lb 2400
There is your proof that the HX has more power than the pre ADR27A has and all them people know that when ADR27A came out they performed better.

Gross figures ? well I think there is different types of such, because I have Gross figures on 1975 Ford 250ci 6 cyl that states 155hp and then another stating 111hp Gross and 106hp Net Ford call it under a B curve and a C curve and so we can see that advertised can mean anything they may want to but the B or C curve with numbers is much more to the point, nearly as good as DIN figures, GM1 and GM20 test I will have to look into, but I will have to look up the Ford Curves if you want.

Why I go into such is because I am not trying to argue and I do appreciate that someone does bother to do as you do and I don't just follow blindly nor would I want anyone to follow me blindly.
I like that you do have your opinions, I may even come to talk to you one day if you like, I am in Brisbane.

I was tyred last when I wrote and just could not remember if the L34 had the flat top for sure I thought they did but with all the performance cam and gear that could come with it I just forgot, your the Holden man but I am into Fords as well.
The retarding of the stock L34 Cam looks to be done to lower the dynamic compression to me to keep it much the same as the 9.0:1 L31. I take it that Holden use such a point due to the 97 octane fuel we had to play it safe for all round Australia conditions, Static compressions mean bugger all in reality and are worthless as an engine is running. so if you put in a bigger cam one wants to increase the static compression so as not to loose the dynamic compression, raising the static compression does not make more power but volume efficiency does and that's were the cam comes into it's own on the grind and the heads etc are another side dish again, but the fundamentals of the grind can not be ignored to their value as a key point.
If I move a stock 308 Cam and advance it or retard it, such will make an effect on how it's going to work and this will effect the dynamic compression due to volume efficiency.
If I were to have a HT-G-Q 308 Cam and I retarded it by 5 deg what do you think will happen to it's dynamic compression ? it will go down I would say. what if I were to increase the duration on the closing end ? I would say dynamic compression would drop, now I have only touched on the intake side just so as not to complicate things mind. so you see Holden were not stupid in raising the new HJ 308 Cam with more static compression, because this was only done to keep the dynamic compression near the same value, because if they did just keep it at 9.0:1 the dynamic compression would drop below the HT-G-Q 308 not that's a fact and not good for performance.
Now the only reason why one would do to a cam what they did to the HJ 308 is to pump more heat the exhaust up more so as to burn up more un burnt fuel.

So when I start looking into putting in a modified Cam into my 308 I asked my self what is it I need from this Cam, now I want a stock performing engine not a supped up hot rod with a big cam mind, and that's becomes another whole can of worms again.
But my intent is only within this frame work to try to improve, so what Cam stock should I look at, ok their is two, oh I can put in the HJ cam, now what should I do I would advance it if anything, but knowing that the point of such a grind is not truly about power when talking to a Cam Doctor now Cam Doctor says ok you want max power over a stock working range, yep ! do you want fuel economy yes or no, now he can make up such with much the same duration because duration is not everything and maybe even the lift is the same and one can go on and on. but I am not interested in heating up the exhaust I want performance and fuel economy and I got the cam that I truly wanted more than happy with it because I did my home work, I did not go looking for high static compression as it did not need it.

I will just say that in regards to a HQ 308 and a HJ 308 stock dual exhaust it was not much in it all and that with a HX-Z 308 their was a great difference of loss in power compared to the HQ-J and I will never believe anyone who says otherwise, sure their are engines in the same model that do go better than others for sure, so one could easy of had a HQ HJ 308 performed what ever, same or a HQ was faster or HJ was faster and that's using the same diff ratios mind and in good nick and tune. I have seen it's true.

A9X were just as gutless as any ARD27A 308 as was, the same can be said with the 5.8L XC Cobbra Hardtop gutless as.

Dual exhaust on the HX sedan only, wagon and ute pvan were all single.
But by the time I was driving only a fool would put a stock single exhaust on a 308.
All 308 Torana's I seen had dual, so what if some only had single.
My LH SL/R 5000 had a 3.08 LSD but it had 14in alloy wheels on it when I got it.

I know the difference of 8/1973 on looks much the same at a glance and to most that is the case as such sticked out like dogs balls. what I was reflecting on was to you, was did they change to the HJ then, I was asking your opinion.

I can tell the points of where a HT Holden V8 engine looks different to the HG I can pick it, and the HQ V8's from them just at a glance.

So what is it that you are claiming about the compressions of the 308 with the same Cam, this has nothing to do with the reason of the HJ being 9.7:1 but other reasons, if they went higher I would have some concern but lower no.
I don't know why you say that the HJ is not a pollution Cam, when in fact it is proven such directly in the HX and the 253 from HX on is on the same grounds not to mention that the pre HJ 308 Cam would not pass ARD27A now would it.

I was pondering into the Export 253 in the HJ being the same compression as the HQ but having 175HP@4800/ 240LB@3000 this lead me to think that the HJ got the ARD27A Cam, you understand where I am coming from, now just because it may be said that such is such this led me to question such if it truly is in fact or are we just swallowing things that are possibly not true, I am like Lt Columbo I have to tick off all the loose ends or Hercule Poirot if thing don't look correct maybe they truly are not. you understand and when one ask me if something is true well I have to say it is not conclusive or a fact to me to put any real faith on.
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HK1837 Offline
#23 Posted : Friday, 20 April 2018 2:55:42 PM(UTC)
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Yes the ADR27A 308 engine has more PEAK power and torque than the HT-HQ engine in both SAE Gross and NET, I've always known that. It is the advertised figures that confuses people. It is obvious when you think about it as the heads are the same (other than the EGR ports) and the HX has 9.7:1 and the better camshaft. It was the driveability of the HX engines, especially the 6cyl and the 253 that gave them a bad name, the 308 didn't suffer as bad but it still did suffer - GMH corrected this a little with the HZ. BUT it is clear that the intake manifold (the only relevant change between a HJ and a HX 308 on an SAE Gross or Net dyno test) severely restricts the HX 308 compared to the HJ 308, it loses over 30hp peak and not far off that net. As we have agreed most people wouldn't even have noticed the extra hp available on a HJ 308 as it would never have a chance of making it with single exhausts on 90%+ of the cars and probably 75% or more of HJ 308 were auto, most with 2.78 rear axles. If GMH hadn't made the HJ 308 so much better than the HQ people may not have even noticed the change from a HQ 308 to a HX 308. The change from a HJ to a HX 308 was a remarkable step backwards though, particularly in a car like an LX SS that showed the true performance potential of the HJ engine as it had dual exhaust standard.

Remember Gross figures are very differ to advertised figures. I'm almost thinking that old Fred James gives us a hint in his original report, where he says significantly more is available out of the 308 with a better camshaft. I'd almost bet that the 240hp and 315ftlbs (gross) advertised for the HT-HQ engines is actually the HT engine with the HJ cam in it. The part number for the cam certainly places it smack bang near the end of Holden V8 development. Bump the compression half a point or so from 9.0 to 9.7 and there is your extra 10hp and 10ftlbs, and that gain is totally what i'd expect.

L34 only came with aftermarket cam, rockers and carby if you paid for it, but it didn't come with the car. The L34 differences were mainly in strength (block webbing and material used), rods etc. The only performance engine parts were bits that you couldn't change under 1974 Group C or ARDC rules: pistons, heads, intake, exhaust manifolds and dizzy. The L34 cam wasn't retarded, it was the same as any other HQ or early LH 308. Same cam, and same timing gear. All the HT-HQ and early LH 308 engines including L34 used the 253's cam with a timing gear that retarded the cam by 5deg.

HJ is not a pollution engine, nothing about it is any more pollution than a later HQ engine is. 308 manual never even got EGR, so there is no need to heat up the exhaust. All GMH have done is used a tried and tested GM camshaft grind, just like most of the aftermarket did for 308 in the 70's (like using Erson grinds) and added more compression to take advantage of it. Voila, bigger cam and more compression made significantly more power, around 25hp to be exact. This is camshaft 101! You can even see a similar effect on our 327's here, the ONLY performance difference between a 1967 (240hp) and a 1968 327 (250hp) is a raise in compression from 8.55:1 to 9:1, and there is 10hp extra. Add some more compression (up to 9.8:1) and bigger valves/ports (by use of fuelies) keeping the same cam and you get another 25hp (this is the L30 327 275hp). Everything else is the same bar some spark tweaks. Add some more cam (solid) and compression (via lumpy tops) and you get 300hp (325 in Corvette).
ADR27A has ZERO internal modifications to the 308, it is called Evaporative and Emissions controls. Evaporative was already there from later HJ (sealed fuel tank, vapour separator, canister and captured carby bowl vapours). Exhaust was basically two things. Firstly the removal of full vacuum advance when the engine was cold or not in top gear, and only providing ported advance otherwise - this made no difference to a manual as a manual only ever had ported advance anyway. Secondly the addition of an EGR valve to add some exhaust gasses to the intake to reduce Nitrogen Oxides (I think it was NOx they were after) - again no effect on a manual as these had no EGR valve. So the only effect on a manual 308 was the compromised intake manifold put there to add EGR on an auto engine, plus of course the little restriction in the LH exhaust put there to direct LH bank exhaust across the engine to heat up the manifold for the choke to operate.

The export HJ engines are the same as the local HJ engines from 1974 (pre canister). 253 is identical to HQ, 308 is the higher power engine. These remain as the export engines for HX, HZ and VB. The 175hp you are reading for the HJ 253HC engine is part of the de-rating I was talking about for HJ - they all dropped to more realistic figures other than the 308 which went up to 250hp. The 308 is the only HJ engine that changed from HQ if I remember correctly, the only difference I can think of is the 253 block changed to the L34 style thicker webbed block just like the HJ 308 did, but that makes no difference to power output.
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