Any 350-380 cube engine with a 4” bore will go just as hard as each other with the right heads for the desired outcome, all other factors relatively equal. Even a humble 327 done right is really quick. I got hold of Wheels (Peter Robinson’s) road test of Dave Bennett’s GTS327 the other day, will add the figures here when I’m at the PC next. It was pretty much stock GM parts and there would have been nothing in Australia in 1968-9 (or even in the 70’s) that would have even come close to it in top speed, quarter mile, 0-100mph or anything else. I doubt even one of the 308 engined LJ GTR’s that NSW Police had in 1972-3 would have kept up with it.
Here is the basics of the article, it was December 1968 Australian Motor, not Wheels. Off topic somewhat but good stuff.
Dave Bennett got the car on August 2 1968. It was a 3.08 axle car. He ran it in for 1200 miles over the next week and then tuned it to factory specs on his chassis dyno and achieved 167rwhp. As a comparison Dave properly tuned an XT GT to 146bhp, just so you can get a real world comparison.
He then ran it at Calder, using 4700rpm as the shift point it did 15.44 on the original D70 Sovereigns.
He then removed the exhaust from the resonator back, richened it up and fitted Michelin XAS (optional HK GTS327 tyres) and got 14.92s.
At this stage it was still unopened, and then was run at Sandown where it was crashed.
As the car was repaired, Dave got hold of an imported L76/L84 327 short motor. This is the 1964 high performance 327 that was rated at 365hp (Holley carb) or 375hp (injected). It was a solid cam engine with over 11:1 compression when fitted with Fuelies (this info about getting the Corvette engine was in another article, this magazine just talks about the parts).
Dave rebuilt the Monaro's original bottom end using the forged L76 pistons and 30-30 "Duntov" factory mechanical camshaft and lifters, crank will be the original HK 327. Flywheel was left stock other than balancing. As B/S class had to retain the factory heads, the original HK 327 heads were modified to take larger valves and screw in studs. As the HK heads were 69-70cc and fuelies 63-64cc, the engine was 10.64:1 static (quoted by magazine). Perry made Dave some extractors with 4" collectors that could be uncapped for drag racing, and he changed the diff to 3.36 ratio.
He then dynoed it and it made 332rwhp on 100 Octane fuel. It then set a new B/S class record of 13.61s at 6500rpm shift points. When the exhaust was capped and the aircleaner refitted for road use it made 285hp at 5500rpm, magazine says it was not peak power as power was still increasing at 5500rpm they just didn't take it any further.
The road tests of the car in this state (with exhaust capped and air cleaner back on, with Michelin XAS 185R14 tyres) are:
0-60mph 6.8s
0-100mph 14.6s
1/4 mile 14.1s
Speed in gears (6000rpm shifts):
1st 51mph (6000rpm)
2nd 70mph (6000rpm)
3rd 90mph (6000rpm)
4th 142.7mph+
The 4th gear speed was measured at 135mph at 6000rpm but it was still accelerating and they ran out of speedo. So they tried using the tacho which was correct and used the whole test track. They said they saw 6700rpm which equates to 142.7mph by extrapolation. They say "we ran out of road with plenty of throttle left. I have no doubt this is a genuine 150mph motor car, given a long enough road".
As you can see this was one impressive car for 1968. It retained the factory GTS327 intake, Quadrajet, air cleaner, mechanical fan, fuel lines and pump (you can see it all in the photos). Only the extractors look non standard. Sure it was balanced, and stock GM 327 cam/lifters and pistons. Heads were the original small port 307/327 heads with bigger valves and screw in studs. Bennett would have ported them a bit, but you cannot open these castings up to even as big as a stock fuelie. If he'd used stock L76 fuelies (2.20/1.6 valves with screw in studs) he probably would have made it go even quicker and cracked into the 13 second quarters with it with exhaust and air cleaner. You can even see the HK 290 head casting mark in the photos! Just shows you what GMH could have done with the GTS327 if they had bit the bullet and even fitted the 275hp L30 327, a Saginaw would still have been OK with this engine but should have got a 12-bolt (although they kept a 10-bolt in the HT whereas both of the HT 350 engines should have got a 12-bolt). Imagine if they'd fitted the 1965-68 L79 to it? The L79 was basically an L76 but used the performance hydraulic cam. These were rated at 325hp with 2" exhaust manifolds or 350hp with Corvette exhaust manifolds. Supercar scare come early!
Edited by user Monday, 21 October 2019 6:53:42 PM(UTC)
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