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When I had the 489 engine built for my '68 L36 4 speed/3.08 here in the UK I worked on the basis that if the Vette chassis was good enough for GM's L88 engine and its supposed 550 or so hp then it would be good enough for my project. I wanted to retain stock driveline components so the car could be returned to stock if required. The L88 style hood was certainly needed with the Performer Air Gap inlet and yes, underfloor 2 1/8" Super Comp headers were also required (along with their very limited ground clearance). A DeWitt OEM style radiator was also needed for cooling. With a 234/240 flat tappet hydraulic cam and Brodix Race Rite Oval port heads it ran 571hp/606ft/lbs tq at 5900/3800 on the dyno. I installed a Centreforce Dual Friction clutch and steel flywheel, also 285/40/18's on the rearend for grip........and the driveline has all held togther (so far). With its 950 dp carb cruise fuel economy was surprsingly fractionally improved over the old 427 engine.
Sounds really close to my 496 build.
What compression are you running in your 489?
Have you thought about a GM crate LS motor at all? They make big power out of the box and are light and reliable. More work, and more money maybe but the end product is very satisfactory.
When I had the 489 engine built for my '68 L36 4 speed/3.08 here in the UK I worked on the basis that if the Vette chassis was good enough for GM's L88 engine and its supposed 550 or so hp then it would be good enough for my project. I wanted to retain stock driveline components so the car could be returned to stock if required. The L88 style hood was certainly needed with the Performer Air Gap inlet and yes, underfloor 2 1/8" Super Comp headers were also required (along with their very limited ground clearance). A DeWitt OEM style radiator was also needed for cooling. With a 234/240 flat tappet hydraulic cam and Brodix Race Rite Oval port heads it ran 571hp/606ft/lbs tq at 5900/3800 on the dyno. I installed a Centreforce Dual Friction clutch and steel flywheel, also 285/40/18's on the rearend for grip........and the driveline has all held togther (so far). With its 950 dp carb cruise fuel economy was surprsingly fractionally improved over the old 427 engine.
Your results sound almost identical to my 467 I built with AFR 265 and a 229/229 camshaft. I ended up with 572 hp @ 5700 rpm and 604 tq @ 4200 rpm.
Your results sound very similar to mine. Except I handicapped mine the old-tech OEM L88 heads.
For some reason that was what I wanted, and it is too late to turn back now.
500HP@5700 / 550TQ @ 3400 w/ a 230/240 dur cam wil go just fine. 468.
But I have since learned the exhaust ports of those 50 year old heads are so bad, and the new AFRs are so good, that the AFRs would be worth 60-70 HP on my shortblock. roughly 570 HP then.
If I ever re-do it I will just epoxy the Winters "W" on the AFR heads LOL!
I spent $13k all-in 2 years ago, but it is all 4 bolt and forged and built right. Make sure you get the good HD parts.
Sounds really close to my 496 build.
What compression are you running in your 489?
10.5 cr - have to use ethanol free UK Super Unleaded 99 RON octane. Like all of us perhaps looking back I would have like to have done things a little different......but finances dictated the direction I chose. A 540 with roller lifters perhaps. That new small diameter Hamburgers centrifugal huffer looks interesting. Fuel injection most definately.
Last edited by roscobbc; May 12, 2023 at 09:26 PM.
10.5 cr - have to use ethanol free UK Super Unleaded 99 RON octane. Like all of us perhaps looking back I would have like to have done things a little different......but finances dictated the direction I chose. A 540 with roller lifters perhaps. That new small diameter Hamburgers centrifugal huffer looks interesting. Fuel injection most definately.
