Engine Thinking About 351, Need Some Help

derekleee · Oct 10, 2016

Hey everyone, just picked up my first Mustang on Saturday for a pretty good deal. Car is in great shape but it blew a connecting rod and chewed the block up pretty good.

Currently the car has a 302, with
- Edelbrock e street heads (1.900" intake valves, 1.600" exhaust)
- Holley 670 cfm carb
- MSD ignition box, blaster 2 coil and msd distributor
- BBK shorty headers
- Weiand 174

Not too sure what it has for valve springs but it has comp 1.6 roller rockers, lifters and cam are tore up from metal containments

I'm just wondering how those heads and everything would work with a 351, or if I'm better off just finding another 302 and give it a quick freshen up?

I read that the 351w is a lot stronger in stock form than the 302, which would help keep my budget low and wife happy

Gearbanger 101 · Oct 10, 2016

I'd stick with a 302 personally. The E-Street heads were designed for the budget conscious, that want to move into an aluminum casting. Decent, but not really high on the performance scale compared to a lot of the heads out there. You didn't mention the size of the headers, but I'll assume they're 1-5/8", like most of the aftermarket offerings....which is on the small side for a 351W. It won't matter anyway, since you'll have to swap them out for 351W specific headers anyway. While you're at it, might as well ditch your current intake manifold too, as that's 351W specific as well. The Holley will work, but it too is on the small side.

Another 302 on the other hand, will bolt right in and will be leaps and bounds cheaper than trying to convert to a 351W at this point. It's true, the 351W block is much stronger, but the internals are every bit as weak (or strong, depending how you look at it) as the ones found in a 302. In any case, a 302 block and internals will take you well into the 450-500hp range....which unless you plan on adding 250hp or so to your current power levels, you're no where near in danger of exceeding. So picking a 351W block based simply on strength, is an unnecessary expense.

With the top end parts you've got, moving to a 351W at this point is likely to pick you up about 40lbs/ft of torque across the board....but not much else. There are easier and cheaper ways of making those numbers than a complete engine swap.

If your block is in otherwise good shape, this might be an excuse for you to build a stroker. The traditional 331/347 kits can be had quite reasonably now a days and will allow you to keep your current head/intake/exhaust components as well as give you the piece of mind of knowing exactly what kind of engine you have....rather than some unknown "junk yard special" you'll need to tear down to confirm it's condition anyway.

Dart68 · Oct 10, 2016

Gearbanger 101 said:
I'd stick with a 302 personally. The E-Street heads were designed for the budget conscious, that want to move into an aluminum casting. Decent, but not really high on the performance scale compared to a lot of the heads out there. You didn't mention the size of the headers, but I'll assume they're 1-5/8", like most of the aftermarket offerings....which is on the small side for a 351W. It won't matter anyway, since you'll have to swap them out for 351W specific headers anyway. While you're at it, might as well ditch your current intake manifold too, as that's 351W specific as well. The Holley will work, but it too is on the small side.

Another 302 on the other hand, will bolt right in and will be leaps and bounds cheaper than trying to convert to a 351W at this point. It's true, the 351W block is much stronger, but the internals are every bit as weak (or strong, depending how you look at it) as the ones found in a 302. In any case, a 302 block and internals will take you well into the 450-500hp range....which unless you plan on adding 250hp or so to your current power levels, you're no where near in danger of exceeding. So picking a 351W block based simply on strength, is an unnecessary expense.

With the top end parts you've got, moving to a 351W at this point is likely to pick you up about 40lbs/ft of torque across the board....but not much else. There are easier and cheaper ways of making those numbers than a complete engine swap.

If your block is in otherwise good shape, this might be an excuse for you to build a stroker. The traditional 331/347 kits can be had quite reasonably now a days and will allow you to keep your current head/intake/exhaust components as well as give you the piece of mind of knowing exactly what kind of engine you have....rather than some unknown "junk yard special" you'll need to tear down to confirm it's condition anyway.

I agree with pretty much all Gearbanger 101 said with one exception. If you're going to build a stroker you're better off starting with a 351w. You get 49 c.i. right off the bat (which is bigger than the stroker 302 kits I've seen) without any special parts and if you STILL want to stroke it, you can stroke way bigger than you can starting with a 302. IMO, don't waste your money stroking a 302. Rebuild it or replace it with good parts and put your GO foot on the back of the block!

derekleee · Oct 10, 2016

Thanks guys, yeah the block I have is beyond the point of repair. The rod that let go tore it up nicely.

I had read some articles that said the 351w was a little stronger than the 302, which I was leaning toward as the 302 didn't survive long with 5 or 6 psi boost.

I had also found some intake adapters, not 100% if they'd work with the weiand supercharger intake or not, but I was going to check into it and see. As for the heads, I figured they'd at least be better than stock heads on a 351w. The headers and carb are minor, I can always sell what I have and put the money toward what I need

A5literMan · Oct 10, 2016

That blower and heads are too small for a 351(actually the heads are even bad for a 302 IMO). I would sell them both and put that money towards some good heads (AFR or TFS) and throw together a 351. Packaged with the right parts you'll have 400-450hp and 400+lbs torque. Even better stroke the 351 to 408" and you'll have complete torque monster.

JD1964 · Oct 10, 2016

I don't think 5-6 psi is what blew the rod. If you don't over rev, a healthy 302 can hold that much boost no problem whatsoever.

Something else had to be wrong.

derekleee · Oct 10, 2016

Yeah I was surprised too, half expecting a broken crank when I opened it up but nope

JD1964 · Oct 10, 2016

Have you had the valve cover off yet? Is it possible it dropped a valve in?

derekleee · Oct 10, 2016

Yeah heads are off, no dropped valves. Looks like the valves very slightly touched the pistons on two cylinders. Not sure if the valves are bent but looking at them there's no real marks more than the carbon was pulled off, 2 bent push rods though.

Gearbanger 101 · Oct 10, 2016

Dart68 said:
I agree with pretty much all Gearbanger 101 said with one exception. If you're going to build a stroker you're better off starting with a 351w. You get 49 c.i. right off the bat (which is bigger than the stroker 302 kits I've seen) without any special parts and if you STILL want to stroke it, you can stroke way bigger than you can starting with a 302. IMO, don't waste your money stroking a 302. Rebuild it or replace it with good parts and put your GO foot on the back of the block!

Those heads, intake, carb and exhaust either won't either physically fit, or support the needs of a stock 351W....never mind a big cube stroker. Lets also consider, that Weiand 174 will be on the ragged edge of efficiency trying to keep up with the air demands of a stock 351W and his current top end....never mind a stroked and poked 393/408W with the right supporting components.

So while I agree with you that there is in fact "no replacement for displacement" when making power is concerned, he would have to change his entire set up to meed the requirements of feeding such a beast.....and that's going to be $10,000-$12,000 minimum investment, just to get a 408W together that'll feed that need. I don't imagine he's going to be slipping that past the wife anytime soon.

derekleee said:
I had read some articles that said the 351w was a little stronger than the 302, which I was leaning toward as the 302 didn't survive long with 5 or 6 psi boost.

My guess is that the demise of your engine was either due to a not overly healthy rotating assembly to start with, or it was improperly tuned (not enough fuel and/or too much timing).

FWIW, my stock block H/C/I 331 see's 14psi from my Vortech S-Trim. If I'm not making 500rwhp when I get my fuel issues sorted out, it'll be damn close. For comparison sake, that's far more power than that top end and Weiand 174 will ever come close to supporting.....no matter what block it's bolted to. Just to give you an idea what a 302 block is capable of making and handling.

What I'm saying is, you've got 302 parts with those heads, intake, exhaust, carb and that blower....and to see power levels capable of exceeding the limits of a stock, or a stroked 302 with your current set up, you're going to have to completely abandon it and start from scratch with that 351W. As the matter of fact, with enough cubes, and the right top end and supporting components, I bet you'd make more power with a N/A 408W, than you would with that Weiand on there. It's more of a "Hot rod" type blower. It was never designed to make or support huge power levels. It's size appropriate to make a smaller engines, seem bigger, but also size deficient that it will make a bigger engine, feel smaller.....if that makes sense to you?

Bottom line. If you want to get it back on the road, for the least amount of money. Find yourself another HO long block, transfer your parts over and spend some money on a proper tune up. If you want some additional jam while you've got it down, for the least amount of money, find another 302 roller (doesn't matter out of what, because you're only using the block) spring for a stroker rotating assembly, send the block out for machine work and put it together in your garage. Several advantages to sticking to your 302 base.

1....all of our current components still physically fit.
2....your current components while not ideal, are still acceptable parts to feed a small stroker and will provide an excellent power curve for street use.
3....you'll pick up a noticable horsepower and torque increase with the added cubes that will compliment your top end.
4....the stroker rotating assembly will consist of much tougher components than the stock rotating assembly
5....you're essentially starting with a clean slate, new short block when all is said and done.

Dart68 · Oct 11, 2016

Gearbanger 101 said:
Those heads, intake, carb and exhaust either won't either physically fit, or support the needs of a stock 351W....never mind a big cube stroker. Lets also consider, that Weiand 174 will be on the ragged edge of efficiency trying to keep up with the air demands of a stock 351W and his current top end....never mind a stroked and poked 393/408W with the right supporting components.

So while I agree with you that there is in fact "no replacement for displacement" when making power is concerned, he would have to change his entire set up to meed the requirements of feeding such a beast.....and that's going to be $10,000-$12,000 minimum investment, just to get a 408W together that'll feed that need. I don't imagine he's going to be slipping that past the wife anytime soon.

Other than actual fitment, it would seem that the current intake system in its entirety would be insufficient for any stroker. Maybe he should consider nitrous...just gotta be careful not to use so much that you turn the pistons inside out...or is it using too much boost that does that <shrug>.

I guess it would come down to whether or not the 302 will make the kind of power he wants. If so, then that's definitely the way to go.

I don't imagine he's going to be slipping that past the wife anytime soon.

Oh man, ain't it the truth!

derekleee · Oct 11, 2016

Thanks for the replies guys, pretty new to these mustangs and small block fords, and I also can't comment on the tune or anything like that as I got the car with the motor already cratered.

I was told it was a 306 but I didn't bother putting any more time investigating it once I confirmed the damage. No idea what it has for a cam or anything like that.

I'll probably stick with a 302 to make use of the parts I have, probably a budget rebuild on a short block, keep the compression ratio decent (maybe 9:1?) and a bit of a cam. I think it'll go pretty good as it has 4:10s in the rear and the baby supercharger should help a bit

Gearbanger 101 · Oct 11, 2016

derekleee said:
I'll probably stick with a 302 to make use of the parts I have, probably a budget rebuild on a short block, keep the compression ratio decent (maybe 9:1?) and a bit of a cam. I think it'll go pretty good as it has 4:10s in the rear and the baby supercharger should help a bit

Just keep in mind, if you "basic rebuild" consists of anything more than re-ringing the stock pistons and adding a new set of bearings, you should consider a stroker assembly. If you've got to add pistons to your rebuild, you're going to find yourself about $600 in for just the slugs right off the bat. More if you have to factor in the cost of an overbore.

If that's the case, you'd already be better than half way through the cost of a half decent stroker assembly.

My stroker assembly was $880 about 4-years ago....and that included balancing. They're up around $1,000 now, but still in the grand scheme of things, it just doesn't make sense anymore to add pistons only and keep the stock rods and pistons.

As stated prior, you not only gain the added cubes with the stroker, but a tougher rod and piston combination than stock as well.

Just something to ponder.

derekleee · Oct 11, 2016

Or with the small amount of boost, would I be able to run a little higher than 9:1 and be fairly safe?

I've heard good things about the FRPP E303 cam, and I think it should work with those e street heads as the lift is under .500" and it keeps the powerband in the street range and the rods hopefully intact lol

derekleee · Oct 11, 2016

Gearbanger 101 said:
Just keep in mind, if you "basic rebuild" consists of anything more than re-ringing the stock pistons and adding a new set of bearings, you should consider a stroker assembly. If you've got to add pistons to your rebuild, you're going to find yourself about $600 in for just the slugs right off the bat. More if you have to factor in the cost of an overbore.

If that's the case, you'd already be better than half way through the cost of a half decent stroker assembly.

My stroker assembly was $880 about 4-years ago....and that included balancing. They're up around $1,000 now, but still in the grand scheme of things, it just doesn't make sense anymore to add pistons only and keep the stock rods and pistons.

As stated prior, you not only gain the added cubes with the stroker, but a tougher rod and piston combination than stock as well.

Just something to ponder.

True enough, the exchange rate just sucks right now. But a tougher bottom end would be nice.

Engine Thinking About 351, Need Some Help

derekleee

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Gearbanger 101

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Dart68

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derekleee

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A5literMan

At least it is lumpy...

JD1964

there is enough sticking out to grab on to

derekleee

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JD1964

there is enough sticking out to grab on to

derekleee

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Gearbanger 101

Straight Outta Locash

Dart68

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derekleee

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Gearbanger 101

Straight Outta Locash

derekleee

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derekleee

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