Help me Oppo, you're my only hope! In my last post about high-RPM V8s, we arrived at a pretty stout conclusion: Ford Windsor FTW. But now a new challenger has reared its head.
The Chevy 302. The Legendary SCCA Z/28 motor. It was a 4" bore 3" stroke engine (same as a Ford 302W) with a ton of high-rpm parts. Now, obviously, getting ahold of one of these motors is pretty much impossible for a budget build. But that doesn't rule out its capability.
You see, the 240z can fit a Chevy 350 with off-the-shelf components, the support for the swap is a lot higher. And I may or may not have recently found a source for a very cheap 350 out of a mid-70s Corvete. While I hope it is a L82, it may be a L48, the base model engine, rated at 180HP or so. Let's assume it is an L82, which has 4-bolt mains, and let's assume that even if it isn't, I could acquire an L82 for the same time/cost as a Mexican block 302.
Unlike the Ford 289, a shorter stroke is readily available: for about 800$ you can have a 3" stroke. It's not as good as the 289, but it has stronger 4-bolt mains, and a taller deck height that would allow for about the same peak RPM as the 289, but with some added weight.
So now here is my question for Oppo, which bottom end would yeild the highest potential HP/dollar for 7500+ rpm? Assume that the top end is going to be quality and where most of the money is going to go. My power goals are either 350-450 N/A, and possibly 550-650 on a turbo later down the road, so I don't want to buy any aftermarket components that are good for 450, but won't take 650, so that I don't have any redundancy in parts.
Here's the two theoretical builds. Let's assume that I can get both engines for about the same price, and that the cost of the custom mounts on the Ford is about the same as the cost of the forged crank and rods on the 302, which (while available) are going to need to be purchaged for it to work, whereas the 289 could come together using easy-to-find stock parts.
Windsor: 289 CI Hybrid
Mexican 302 Block (~2" mains, 2 bolt)
289 Stock Crank (2.87" stroke)
289 Stock rods (5.110" rod)
302 Pistons: (1.6" Compression height)
Deck Height: 8.206
TDC: .061" below deck.
Compression ratio on 69cc heads, 0.03" gasket, and flat pistons (For comparison): 7.7:1
4000ft/min mean piston speed at: 8250rpm
Rod/Stroke ratio: 1.78
Bore/Stroke ratio: 1.39
Weight: -25lbs from stock
Position: About 3 inches further back and a few inches lower than the 350, almost an front-mid-engine position.
Cons: Custom, expensive engine and transmission mounts. No aftermarket crank.
Pro: Great fit if mounted properly, excellent-high RPM possibilities, sexy bore/stroke ratio.
Chevy 302 Hybrid
Chevy L82 Block (unknown mains, 4 bolt)
Aftermarket forged crank (3" stroke)
Aftermarket forged rods (5.85")
350 stock pistons (1.56" compression height)
Deck Height: 9.025"
TDC: .115" below deck
Compression ratio on 69cc heads, 0.03" gasket, and flat pistons (For comparison): 7.2:1
4000ft/min mean piston speed at: 8000rpm
Rod/Stroke ratio: 1.95 (!!)
Bore/Stroke ratio: 1.33
Weight: +25lbs from stock
Position: Significantly more forward than the stock motor (due to the rear-mounted distributor and simple-yet-cheap off-the-shelf mounts) with more weight at the top. Clearance for throttle bodies or velocity stacks could be difficult unless I raise the hood on the inside.
Cons: Heavier, worse position, slightly lower RPM, more expensive, and it's a Chevy! D= (not that big of deal, but I'd rather see the car with a Ford engine...).
Pro: 4 bolt mains. The money I save on mounts could go to some forged rods and the crank, so that between the good rods, crank, much better rod/stroke ratio, I think that the heavier, longer stroke assembly would probably be able to spin at a higher RPM due to the improved strength of the components for the same money.
So the real question is: Does the bulk, height, and not-ideal positioning of the 302 get outweighed by its much better rod/stroke ratio, stronger mains, and stronger (if heavier) rotating assembly? Could it actually reach a higher RPM with a built top end than the 289, despite the 289's short stroke?
Assume the added cubic inches are completely outweighed by the added weight and the lower compression ratio of the 302.
Assume the drop in compression ratio doesn't matter (if I plan to boost it later, that is) and it can always be adjusted depending on what heads go onto the motor, and aftermarket pistons. So I could put small-chamber heads on now to get either one to 8.5:1 easily, and then when I go to boost, drop it back down with new dished pistons.
I don't want to go Chevy, but maybe if I drop the motor in, shave off all identifying marks, and (after all of this cobbling together) I could just tell people it's a custom 302, neither Ford, nor Chevy.