4.0L on 302 block

Ardent

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Dec 1, 2006
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I've got a project in mind and I want a really small bore Ford small block for it. I'm wondering if on a 302 block I can get Scat to custom grind a short stroke crank, and with the right piston combo, get a roughly 4L displacement for a screaming little smallblock for a custom, ultralight, non street legal road racer.

All the above seems like it will work, not hard just $, but where I run into question marks is with the engineering of it, mainly the now very short stroke ~4" bores. How is having a stroke much shorter than your bore diameter going to affect the engine? Valve lift will be lower, or faster, but the amount of volume to move is lower as well by 20%. What I'm after here is a top end power band, low end torque is going to be non-existant, I'm aware. Just wouldn't mind hearing from people who know a lot more than I do on the subject.
 
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For the fellow who brought up the 221, 260 etc I'm well familiar but I'm building on a 4 bolt main block (not available in the older smaller 3.5" or 3.8" bores) and all the internals of those old engines are cast pieces of junk, not something I want to build on. Hence the 8.2" deck, 4" bore block.

As for why, I beg to differ but it's not a "stupid idea" as one here put it. What I'm after is a powerband running up to, maybe over 9,000rpm. I love the sound of small bore V8's screaming down the track, and like how they drive. One of my favorites for sound are tuned Rover 3.5 and 4.0L V8's, but I prefer a small block Ford's design and aftermarket. So, I want to build a screaming small block. As for the lack of torque down low, not really an issue, this is a track toy only for track days at Spokane, WA, and Mission BC (Canada). The whole chassis minus engine/trans will be around 1200lbs, so huge power and torque is not required. This isn't for any particular class, just a toy and personal curiousity for me. I've been riding supersports and superbikes for years and want a car that approximates the performance and feel of my bikes, but with an American V8, and a screaming little one.

I know going a bit below 289 isn't going to be a challenge, I can do that on production cranks, but I'm after 245ci range. The thing will sound unreal, if it works.
 
I think it's kind of a cool idea, but you're going to run into the problem of having an expensive valvetrain that can sustain the RPM you're looking for. You're going to need shaft mounted rockers for sure with 9,000 RPM or greater. Solid roller lifters are also a must at that point. As much as you like the idea, maybe a 4.6 wouldn't be a bad tradeoff since they're meant to rev?
 
I think it's a pretty cool idea. Maybe not really practical, but still cool. I almost mentioned buick/rover v8's, but then I saw you already thought about those.

It seems to me you would need to have a custom crank built, and that would probably end up being very expensive.

I'd sure like to hear it if you ever get it built, it would sound like a freakin F1 car.
 
I think it sounds like a cool idea. As a mechanical engineer this idea really intrigues me. My first thought is around rotating mass. I think you'll want a lower rotating mass if you are going to rev the engine this high. This might be difficult to accomplish with a short stroke engine. You've got me thinkin on this one. I'm curious of what all would be needed to do such a thing.
 
I think it's kind of a cool idea, but you're going to run into the problem of having an expensive valvetrain that can sustain the RPM you're looking for. You're going to need shaft mounted rockers for sure with 9,000 RPM or greater. Solid roller lifters are also a must at that point. As much as you like the idea, maybe a 4.6 wouldn't be a bad tradeoff since they're meant to rev?

I agree with you on all counts here, I'm looking to sink some $ into this one, even been considering a Dart aluminum block. I already have a 4.6 in my GT convert, been playing with that for awhile, but I gotta face it I like non-electronic, pushrod valvetrain V8's. It's still a though as the 4.6 is downright cheap compared to what I'm looking at, but it's also a bulky engine with the OHC's.


Ardent
I know i'll get flamed for this... but have you considered a Mazda rotory engine?

Not my cuppa tea though I appreciate the engineering, I'd go for a high strung 4 cyl if I wanted to part from the V8, but for this build it's gotta be a Ford small block, love that sound.


Are you dead set on making it smaller? Why don't you just build a 302 to spin to 9k?

I've seen 289's that do, and 289 is the default choice if I either don't want to spend the money for the custom crank when the time comes or I run into too many problems trying to go sub 150ci.

Still a dumb idea, if you’re not running a head restricted class or a lbs per c.i. class. This thread might enlighten you... hell read the whole site there is several threads about destroking, ect. And people actually know their **** over there...
http://bbs.hardcore50.com/vbulletin/showthread.php?t=34077&page=2&highlight=rpm+displacement

I'll give it a look and see, sounds interesting.
 
I always thought the 3 inch stroke was small enough And I know it is caperable of 9000 if built right. I would think a forged 5140 or 4340 steel crank that was balanced to 28oz and aluminum components would be light enough and the had the counter weights cut smoothed and shaped would definetly help
 
turbo 2.3 ford with no exhaust pushin 30psi, ported head, essy cam, and a holset turbo with a hellacious intercooler, and a stand alone. I was building one of these this summer and damn they can be krazy fast, sound good, and if tuned right can be very reliable, and make 350-700hp depending on all the crap you want to do with it.
 
This is a bit silly if you think about it....you don't need 9k RPM if you can make the same power in 6k. Also if you're really serious about this, you can build a sick 289 with aftermarket parts but even then you're not going to save THAT much weight over a 302. Also, a shorter stroke 302 isn't going to make it any more ultra light than a stroked 347/302.

Back in the day it wasn't uncommon to see 289s pushing 8-9k RPM in race applications....with today's head technology you could possibly even see 10k if you invest in some serious valve components (titanium valves for example). Rick Anderson has built several 347/302s that redline around 8200RPM but you're talking some serious serious money spent in porting and your valve train, and then you're also talking about one season of racing before you have to rebuild.