While I agree that the old SAE bhp figures are inflated, back in the day the various manufacturers offerings were at least directly comparable.

A 115 bhp 179 engine versus say a 210 bhp 307 V8 seemed in proportion as did the 300 bhp, 350 HT manual V8.

I don't believe they were any more rubbery than today, when comparing one engine with another.

Dr Terry

Anyone here have access to someone with a GMH assembled 1967 Impala or Parisienne with the 240hp 4BBL 327 in it still, wearing its original heads? Just looking for the casting number and/or the cast mark on the ends of the heads.

They are in the 1999/2000 VSIII utes sales brochure Terry, listed as either 179kW (STD) or 195kW (HBD). I have one at home from when I bought my VSIII in late 2000.

I get it now Terry, I misread what you meant!

I don't believe this to be correct. DIN takes dual exhaust into account, as does SAE net. My understanding is that this is one of the main differences between net & gross.

Holden were quoting different figures for dual vs single exhaust, way back in the VB/VC/VH/WB days, before any use of ECE standards.

AFAIK the only difference between DIN & ECE net kW is the temperature, barometric pressure & humidity of the ambient air at the time of testing.

I think the true net KW figure for the VSIII with the XT9 motor was never published & the PR department just used the Statesman figure for convenience.


The chips are the same for the VSIII 5.0 Statesman & Ute, CJYN for the auto & COYM for manual (ute only obviously). But the VT 5.0 are CJDN (auto) & CNPJ (man).

Dr Terry

All my listings show the same two O2 sensors for both the VSIII/XT9, as the VT 5.0.

Dr Terry

If that is true that explains the different Memcals, at least one reason for it anyway.

Guys
Just doing some work on the Tonawanda GTS327 and 1968 CKD Impala/Pontiac engine specs.

On paper (GMH material and US full size Chevy Engineering specs) these engines are identical in every way auto vs auto, manual vs manual (HK's sump and one side exhaust manifold aside). According to US and GMH specs these are 8.75:1 engines. According to the same sources the 1968 307 is 9:1 in the US and 8.75:1 here but aside fro GMH using the 327's distributor they are the same.

So i'm cleaning up some HK 307 (032) and 327 (290) heads to compare to see if I can explain the anomaly as these heads are both supposed to be 70cc heads (if you haven't already spotted it most of the claimed compression figures cannot be correct)(note that all these engines are flat top pistons, the only place you'll find dish tops in 1968 SBC is on the 8.25:1 high torque 307 (C40 truck) and 8:1 high torque 327 (C50-60 truck)).

I haven't got to the stage of ccing the 032 and 290 cast heads yet, but careful examination sees them apparently identical other than one thing (detailed a bit further below).

From what I understand for 1968 GM added the extra threaded sensor hole so the 291729x heads were created:

2917290 was a new 70cc head.
2917291 64cc replaced 3890462.
2917292 64cc was a higher performance 64cc head than the 291. Not much info on these.
3917293 75cc replaced 3876775 (3876775 appears to be the 1967 210hp 2BBL 327 head and also the 1967 240hp 4BBL 327 head).

For 1969 these heads were replaced with the same basic things except for accessory holes in the ends of the heads:

3927185 replaced 2917290 (this is the 1969 235hp 2BBL 327 head on this 9.0:1 engine).
3927186 replaced 2917291.
3927187 replaced 2917292.
3927188 replaced 3917293 (this is what we got on the McKinnon Industries 327 in later HK).

There were also a couple of other heads like 3947040/041 around the 1969 timeframe that appear almost identical to the 3927186 heads but have slightly smaller ports and don't get the traditional double hump cast marks - these are the heads on the Tonawanda HT GTS350 manual engines.

Back to the 307, GM created the 3911032 heads for the 1968 307, apparently replaced in 1969 by 3927185 heads. Why not just use the 3917290 heads? As I said looking at them, taking basic measurements of ports, chambers, valves etc they look physically identical. However when running my fingers up inside the ports and comparing to the 290 heads the 032 heads have a small casting lump on the roof of the ports not far from the manifold face. Basically in the same spot the 882 smog heads have a larger lump. Anyone hazard a guess as to why?? I have read the 882 heads had it added there to either slow down exhaust flow or the keep the heads hotter to reduce emissions or something like that. Maybe the 1968 307 needed this? The other possibility I guess is that all HK-HT 307's are McKinnon Industries build, whereas all HK-HG 4BBL engines other than the final HG engines are Tonawanda build (McKinnon didn't build 4BBL SBC engines until sometime later in 1969). It may well be that the 032 heads are the same thing as 290 but 032 is unique to McKinnon and 290 unique to Tonawanda (ignoring the Flint plant for the time being).

Back to the purpose of me doing all this. GM claim 9:1 for the L14 1968 307. GMH claim 8.75:1. CCing both heads to check they are both approx. 69-70cc will show that GMH were right, 8.75:1 will be spot on for the 307. As for the 327, it cannot be 8.75:1 with 69-70cc heads if the 307 is 8.75:1. It will be at least 9:1, just as GM state for the 1969 235hp 2BBL 327 wearing 3927185 70cc heads. I'm also hearing from some US sources that some of their 1968 250hp L73 327 engines have 3917293 75cc heads - this info matches almost spot on the Combustion Chamber size (head plus gasket plus deck clearance) stated for the 1968 L73 327, and would result in approx. 8.55:1 compression (as per the second type HK McKinnon engine with 188 heads) which as per normal would be rounded up by GM to the nearest 0.25:1 compression ratio of 8.75:1. Some more work needed here, but one possibility is that the test engines used for the Engineering documents (combustion chamber volume measurement dyno testing etc) were almost certainly Flint engines, and as stated before perhaps the 290 cast heads were unique to Tonawanda, so 250hp 327 engines from Tonawanda will be 9:1 and those from Flint may have the 293 heads and 8.55:1 (rounded to 8.75:1).

Will advise once I find more, although i'd be interested to hear what others think about the lumps in the 032 exhaust ports.

I'm not using gaskets. The Engineering specs state actual measured combustion chamber volumes, which includes the head chamber and the gasket and cylinder volume above the piston at TDC. This is the figure used in the formula:

CR = (X+Vc)/Vc. Where X is the swept volume of each cylinder (or the engine cuin/8), CR the compression ratio and Vc the CC volume.

If you plug into these figures the stated Vc and the cylinder swept volume (for a 327 is 4 x pi x 3.25 or 327/8)) you get the CR's stated in the Engineering specifications (or a number within 0.25:1 lower). Except for the 1968 L73 250hp figure. This can be found in 3 x locations and they are all the aame: 1968 Chevrolet full size, 1968 Chevelle and 1968 Trucks (El Camino).
The figure you get (around 8.55-8.6:1) for the L73 250hp 327 engine is correct if it has 75cc heads. But our 327 engines do not have 75cc heads, they are around 69-70cc.
Trouble is people in the USA are stating they get both 290 and 293 heads on these engines, the 0.5:1 point of compression between engines with these 2 x heads will make a significant difference to their peak power output especially running on Australian Super fuel rather than US regular fuel.

Doing the same thing for the 307 using the Engineering Specs shows 8.75:1.

Except for the HT-HG manual engines GMH actually specified significantly MORE (or the same for the HK's 327) centrifugal advance than GM did, as all the US engines (bar the 10.25:1 350's) were setup for 90-91 Octane Regular fuel. The 10.25:1 L48 engines in HT-HG were designed for 100 octane fuel in the US, we had 97 Octane or something below 90 so all these engines had to run on Super in Australia. GMH used the same specification distributor in all of them except maybe the last of the non-81837 HQ's and dialled in considerably more advance other than in the HK 327 and the HT-HG 350M - consequently GMH also claimed higher output figures for all of the engines as well other than for the HK 327 and HT-HG 350M engines where the total advance wasn't changed. The earlier auto HQ's got something like 10deg more advance than the exact same engine in the USA.