Whats really upsetting about this Decision by GM back in the day, the only difference in the 250 and 275HP engines were 2 part numbers, the 1.94 intake valves vs the 1.72 inch we got and the bare head castings. Both of these items added zero cost to production so would have resulted in cost to Holden the same as the engines we ultimately received.
I guess from history we know the GTS 327 was never challenged in a straight line by the XT GT so in the end the choice by Holden was a good one. This was not the case for the next model HT 350, that 300HP 350 was absolutely no match to the Windsor HO 69 XW, a real pity.

ABI

Remember though that whilst John Bagshaw wanted the 327 for the HK, the car was never intended to race at Bathurst. The intention was for Group C (Improved Production), and this is why GMH started the association with Norm Beechey using the first of their factory racers, the EH S4. For Improved Production you only needed the 327's capacity and could use any hi-po 327 from the US parts bin. The stock 4BBL 327 with hydraulic lifters was chosen, back at planning stage it was 230hp. The decision to race the car at Bathurst and in selected Series Production races only came about after Ford (after hearing about GMH's upcoming special car) produced the XR GT and won the Gallagher 500 in 1967. GMH changed the suspension on the GTS327 early in 1968 so that it could be competitive.

There would have been a cost to run the 275hp 327. For the HK GTS327 GMH used exactly the transmission and rear axle that GM used for that L48 250hp engine in the same sized car, the Saginaw and the 10-bolt. In a Camaro the 275hp engine triggered a heavier duty Saginaw (same as the GTS350 got) and a 12 bolt, both added cost. The optional 12-bolt for a HK GTS327 cost over 10% of the car's purchase price at the time, although in production this would have been less. GMH took some poetic licence with the HT GTS350 manual as by rights that engine should have got a Muncie and 12 bolt in a HT sized vehicle, but for the HK the engine and box was exactly as it would have been in a Camaro or ChevyII except for the 1967 pre-AIR carby fitted (in the USA all 1968 engines got AIR carbs, even our 1968 327 Impalas and Parisiennes got AIR carbs, AIR was basically ADR27 here introduced in 8-9/73) and the bits changed to make the engine fit (sump and an exhaust manifold). Even the distributor was the same unlike all other HK-HG SBC engines. Also for the HK GTS327 GMH had to have Dunlop make special tyres for the car as a tyre to match the performance of the car did not exist at the time in Australia, a more powerful engine again may have seen added cost here too. And as we know in hindsight the HK wheel and tailshaft were not up to the task of what was required so maybe more cost.

GMH also aimed the GTS327's price deliberately below the GT, and wanted the GTS327 to be seen as equivalent in performance to a GT. They even had Falcon GTs present at the Lang Lang Press test day (a week before the Surfers Paradise release). We now know that the GT was no match for the GTS327.

The GTS350 was a match for the GT-HO, even the hobbled Press Test cars were faster than an XW GT-HO to 50mph. In Sports Car World's December 1969 test of the XW GT-HO quote: "Line it up at the traffic lights and you can still get done by a 350 GTS Monaro - which is cheaper by a very large margin. And you can be held all the way up to the open road speed limit (prima facie or absolute)." This is talking about the GTS350's they tested that were deliberately masked in their true potential that only managed to achieve average standing quarters of 15.8s and 0-100mph of 18.9s (SCW posted the GTS's test figures next to the GT-HO which showed 14.8s quarter and 16.7s). A properly tuned GTS350 only ever made it into the Press's hands twice (two different HG GTS350's), and they never got to do acceleration figures, but commented that the car was so much faster than the cars they tested originally and was very close to the GT-HO (and GT-HO II). There was never published road tests of a GTS350 until AMC Magazine tested a properly tuned and virtually untouched 40,000 mile car in about 2010 using historical testing methods (car even had its original clutch in it). They achieved standing quarter mile average of 14.78s and 0-100mph of 15.95s which is all but as quick as even the GT-HO III (Wheels 10/71 1/4 mile 14.7s and 0-100mph 15.2s), although that comparison is all but irrelevant as the HG GTS350 was killed off before 1971 came around and the Phase III had only just been released a few months earlier.

Edited by user Thursday, 18 October 2018 3:28:13 PM(UTC)  | Reason: Not specified

If of interest and you have the time, have a read of the following link. This is the engine that would have been nice to see in the HK GTS327, the L79 327. The first part of the article talks about the early engines, the 1968 version is near the bottom. Great read and at the bottom is a test by Hot Rod magazine in May 1968, published basically days after the first GTS327 was assembled. In a dead stock 1968 ChevyII manual with 3.55 rear axle it ran a 14.6@95mph. Tyres I think say they were 7.35x14, and a Chevy II is the same wheelbase as a HK coupe (111"). By the looks the ChevyII is about 100kg heavier than a GTS327. This is the 325hp L79 with the small exhaust manifolds (Corvette rated at 350hp with the bigger exhaust manifolds).


http://www.superchevy.co...-0732-chevy-l79-engine/

The hydraulic cam is the same as what was in the 1969 L46 350hp 350, and if HK had got the L79 the HT would have got the L46. The LT1 was basically the same engine as the L46 but ran the solid 30-30 cam from the older L76 1964-5 365hp 327, alloy intake and big Holley. L46 had cast intake and Quadrajet.

The heads that are the subject of this thread are not related to the L79 though, were only ever used on the L30 327 and L48 350 in 1968. The L79 and L46 engines were Flint V8 assembly only and used respectively 291 (1968) and 186 (1969-70) heads.

With flat tops it is down on compression compared to the factory setups on the ‘68 L79 and ‘69 L46 - these had lumpy tops for about 11:1. Yours should have 10:1 or close to it, but 10:1 with iron heads and a bit more overlap should be good for 98. From memory the 461X were from the big hp 327’s around ‘63-‘64 and have marginally bigger intake ports than other fuelies. They have different shape chambers to the later 462/291/040/186/041 fuelies if I remember correctly.

This is the cam i’d like to run:
http://www.compcams.com/....aspx?csid=189&sb=2

But with 1.6 rockers it a fraction too much lift on the exhaust (0.5552”) as my valve springs only go to 0.550”. Intake will be close too st 0.544”. So I have to use offset collets or go the next can down:
http://www.compcams.com/....aspx?csid=188&sb=2

That would be the ideal, but I already have the rockers. Will have a better chat to the engine machiners/builders. If I do go for that XR282 cam rather than the smaller XR276 I'd probably just run the 50 thou up collets on the exhaust side or I can get springs for the heads (Alexs Parts in the USA sell all the bits for the LT1 heads) that do up to 0.570" lift. They do two sets of springs, 120lb and 135lb closed and the XR282 sits right on the borderline between the two sets of springs. I already have the 120lb springs and all the hardware to fit them on the LT1 heads.

Do you mean a cam more like this?
http://www.compcams.com/....aspx?csid=1258&sb=2

Edited by user Tuesday, 23 October 2018 6:08:15 AM(UTC)  | Reason: Not specified

You could also grab a set of the higher performance Fuelies that already have screw in studs and 2.02/1.6 valves, although they will never be as good as more modern stuff. The old school hi-po Fuelies will give you about the same hp as these LT1 heads I have or even Vortecs, let alone modern aftermarket stuff which is streets ahead again. You will find them off old L76 and L79 engines normally in the pre-accessory hole engines, although most will be 462's and some 291's I think there were some 461 heads done like this too from around 1963-64 for L76 (365hp) or L84 (375hp) 327 but no 461X were 2.02/1.6. The later ones from 1969 and 1970 come off Z28 engines (302 or 350) or Corvette L46 350 engines, but these will be 186 castings.

Cool, thanks for that. I'll have a closer look at some other of the shelf cams.