331 Stroker Or 351both With Boost

[Maztang1]

Currently running a 302 in a 92 fox with trick flow street heat top end package. A 70mm throttle body and a 76mm On3 turbo kit.

Problem is I have exceeded the life of the 302 block, and now I have the great debate of either a 331 stroker or a 351. Goal is to use the same top end and turbo kit. Building a 331 looks to be way more money to build. Would I be better off trying to build 351 with a 4 bolt main if I can find one. Goal is to see over 600hp. Will a 351 block hold up to this. If so what year blocks do I need to look for.

 

[CarMichael Angelo]

There is no such thing as a "stock" 351 that came w/ 4 bolt mains, (unless you are referring to a Cleveland), and a Cleveland will not accommodate any of your Windsor stuff.

So,..That said,...a stock 2 bolt block OEM 351 will safely tolerate up to the 700 hp range, but abused with either detonation, or too much boost will land you squarely in the cap walk, split block zone after one bad tune.

There should be no "great debate"....

A stock block stroked to 331 is no stronger than a stock 5.0.

Both engine platforms have aftermarket alternative bare blocks for a high HP goal build, World, Ford, and Dart all sell bare blocks w/ 4 bolt caps for that sole purpose.

 

[Maztang1]

There is no such thing as a "stock" 351 that came w/ 4 bolt mains, (unless you are referring to a Cleveland), and a Cleveland will not accommodate any of your Windsor stuff.

So,..That said,...a stock 2 bolt block OEM 351 will safely tolerate up to the 700 hp range, but abused with either detonation, or too much boost will land you squarely in the cap walk, split block zone after one bad tune.

There should be no "great debate"....

A stock block stroked to 331 is no stronger than a stock 5.0.

Both engine platforms have aftermarket alternative bare blocks for a high HP goal build, World, Ford, and Dart all sell bare blocks w/ 4 bolt caps for that sole purpose.

With that said, I have been looking at dart blocks. Price wise would it be better to build a 331 or 351. Which one will be a better engine for boost? Was running 10 psi in the stock 302 block before I had a problem. Since i have to build a new i want to build one that is going to perform the best for the money.

Thanks again for the help

 

[revhead347]

Do a Dart 302 block (8.2" deck height). Having a 4 bolt main is the most important thing. The turbo doesn't care much about the displacement, it's going to cram whatever amount of air you request down there either way. Whether or not it's a stroker is up to your budget. I don't see rehacking all the turbo stuff to fit a stock 351 block being much of a gain. That's just the way I see it.

Kurt

 

[Davedacarpainter]

Hey Jeff, throw your thoughts in here. @TOOLOW91 Why did you go with the 8.2?

 

[RangerJoe]

A 331 will be cheaper since you don't have to buy all the 351 parts, such as headers, intake, distributor, oil pan and a few other items I am leaving out. Like Mike said, the turbo will easily make up for the less displacement. Honestly, if you stick with the 8.2 block, build it to a 363.

Joe

 

[revhead347]

A 331 will be cheaper since you don't have to buy all the 351 parts, such as headers, intake, distributor, oil pan and a few other items I am leaving out. Like Mike said, the turbo will easily make up for the less displacement. Honestly, if you stick with the 8.2 block, build it to a 363.

Joe

I would say whatever displacement the budget would allow. The 363 would be ideal, but it's pricey. I would much rather see the OP build an all forged 302 4 bolt block than force a 363 into budget with a Chinese rotating assembly. The turbo isn't going to care much about the displacement either way.

I should add that in there too, you'll need Forged pistons and a forged crank. The $200 stroker crank jobbies you see on the internet aren't rated for much power. You're going to have to turn the turbo way down to keep the crank from splitting. I have one of the last American forged Eagle cranks, but both Eagle and Scat use Chinese forgings now, and the reports back on them haven't been too favorable.

Kurt

 

[CarMichael Angelo]

To me, a 363 is a race displacement, and isn't that long lived on the street (comparatively speaking) The long rod, and increased stroke push the piston pin so high up in the piston, it gets into the oil ring, and special pin buttons are needed to accommodate the oil rings.
I agree with what Kurt has said,..a strong stock displacement 302/306 with the good sht is preferable to a chinee stroked anything as long as a 70 mm turbo is in the equation. The same would go if you chose the 351 and kept it at 351.
The byproduct of a larger displacement is the lack of a need for boost to get comparative torque numbers from the smaller version.

 

[RangerJoe]

I would be interested to see someone price an all forged 302 vs an all forged 363. I would guess that $200-$300 doesn't separate the two.

Also, pin buttons are not needed for a 3.4" stroke. The old pins in the rings issue is old and has been overcome long ago.

Joe

 

[hoopty5.0]

The costs to go 351 would be absorbed staying with the factory displacement as opposed to going with an aftermarket 302. Id go 9.5 again and again. I popped my last motor and had a replacement lined up for $150. Can't beat that.

 

[droopie85gt]

There's no replacement for displacement goes the saying....except for cash. Money Always wins.

 

[revhead347]

I would be interested to see someone price an all forged 302 vs an all forged 363. I would guess that $200-$300 doesn't separate the two.

Also, pin buttons are not needed for a 3.4" stroke. The old pins in the rings issue is old and has been overcome long ago.

Joe

You need the special Mahle pistons with short skirts and box in box framing. They are expensive, my friend from college engineered them. That's kind of awesome because I have a hookup to get Mahle pistons at employee pricing. It also only works well on the BOSS block, which is considerably more than the Dart block, and isn't as strong. Basically you buy the shortblock assembled.

https://www.summitracing.com/parts/fms-m-6009-363/overview/make/ford

That's the price with a Chinese crank. Not sure what a quality 302 built costs off the top of my head. Someone should look into it.

Kurt

 

[RangerJoe]

You need the special Mahle pistons with short skirts and box in box framing. They are expensive, my friend from college engineered them. That's kind of awesome because I have a hookup to get Mahle pistons at employee pricing. It also only works well on the BOSS block, which is considerably more than the Dart block, and isn't as strong. Basically you buy the shortblock assembled.

https://www.summitracing.com/parts/fms-m-6009-363/overview/make/ford

That's the price with a Chinese crank. Not sure what a quality 302 built costs off the top of my head. Someone should look into it.

Kurt

I will say affordable piston have been harder to come by since Probe stopped making them. For a mid to moderate HP level, Probe was hard to beat.

Joe

 

[RangerJoe]

So I went to the Fordstrokers' website, since Jim is considered one of the best in the business. His all forged 363 stroker kit consist of a 4340 RPM crank (Chinese but he claims one if the best, affordable cranks on the market), RPM rods and un-named pistons, although I think he prefers Wiesco.

So I went to RPM's website. Their 3" stroke crank and their 3.4" stroke crank are the same price, same with the rods for both. So you are left with the difference of piston costs. Nothing that will blow your budget. And if the 3.4 stroke is just too much, then you can always go 3.25 and build a big bore 347.

Joe

 

[A5literMan]

Plus I think Mike is unaware that at 363" you still have another overbore available with a dart block.

There are other piston choices than just mahle

The 3.4 vs 3.25" debate is rather old and dated. Like fastdriver stayed there are other things in consideration when boosting but the rings,rod angle,etc has been settled imo.

If I were going aftermarket block I'd go 9.5" deck. No replacement for displacement.

 

[revhead347]

I don't want to ruffle any feathers, because there are a lot of experienced folks in here, but I guess we all have our opinions and the mantra "different strokes for different folks" applies more literally to this subject than almost any other, lol.

Anyways, my take is that displacement DOES matter to the turbo, because bigger displacement will spool said turbo faster, or it will let you run a bigger turbo that spools just as fast, and it will make more power with less boost, which is important if you want to make a lot of power on pump gas. etc... Incidentally, it could even have negative effects, like taking the turbo out of its efficiency island and resulting in a lower maximum power capability.

Next, my 331's oil ringlands intersect the piston pin to no ill effect, and I believe CP knows what they're doing. I knew full well about this common idea before I had them do it, anyway. However, there are other reasons for using a 3.250 stroke instead of a 3.400, particularly on a boosted car.

There are pros and cons to all of these choices. Sticking with a stock block is cheap and easily replaceable. An aftermarket 8.2 302 gives access to the entire aftermarket. An 8.7 deck lets you increase stroke without other ill effects. A 351 is pretty cheap compared to aftermarket blocks, more displacement, and holds more power than a stock block. An aftermarket 351 is the king of displacement in our engine family, but also the most expensive way to go.

I just wouldn't go with a stock block 331, because you'll max out a stock block's capability easily at 302 c.i. on pump gas with a turbo that spools plenty fast. In that case, the extra displacement really isn't any advantage IMO.

If the OP goes above stock deck height at all, even that half inch, it means hacking and cutting to make it fit. I don't see that as worth it.

So I went to the Fordstrokers' website, since Jim is considered one of the best in the business. His all forged 363 stroker kit consist of a 4340 RPM crank (Chinese but he claims one if the best, affordable cranks on the market), RPM rods and un-named pistons, although I think he prefers Wiesco.

So I went to RPM's website. Their 3" stroke crank and their 3.4" stroke crank are the same price, same with the rods for both. So you are left with the difference of piston costs. Nothing that will blow your budget. And if the 3.4 stroke is just too much, then you can always go 3.25 and build a big bore 347.

Joe

I trust Jim's word without fault. If he says he can do it for about the same price, then I believe him.

Kurt

 

[revhead347]

Plus I think Mike is unaware that at 363" you still have another overbore available with a dart block.

There are other piston choices than just mahle

The 3.4 vs 3.25" debate is rather old and dated. Like fastdriver stayed there are other things in consideration when boosting but the rings,rod angle,etc has been settled imo.

If I were going aftermarket block I'd go 9.5" deck. No replacement for displacement.

Absolutely. The 347 hysteria came about when some were packaging kits to work with stock 5.08" rods. The 5.4" rod combos don't have any problems.

I have an unfair bias towards Mahle's because I have a friend who designs them; constantly telling me why they are better than the competition. I will say that Mahle's ring design makes them a bitch to install. My engine builder swears by them though. If you don't have a tapered ring compressor, you are in for a long night. I got 3 pistons in before I gave up and ordered the tapered ring compressor. I'll never put a piston in any other way.

Now this is where the more complicated stuff comes in. With a turbo, being able to build an engine around the optimum compression ratio is also more important than displacement. You are shooting for somewhere between 8.5:1 and 9.5:1 depending on what kind of fuel you are running, what your valve angle is, the combustion chamber volume, the cam, the valve shrouding, the bowl area in the piston, and how much boost you want to run. These are discussions you want to have with your engine builder, not people on stangnet. That is way above my paygrade. The best place to start is with someone reputable, like Fordstrokers, who can build an engine around your needs. Don't talk to people who are selling you an engine that is already built and on the shelf. They are going to try and convince you that the engine they have available to sell is the one you need.

Kurt

 

[revhead347]

I agree. It's a conceptual discussion. I would agree that a lower compression ratio is better for boost simply because centrifugal compression is far more efficient than reciprocal compression. There is an optimum point though, and I don't know where that is for a given combination. That is to say, if 8.5:1 is better than 9.5:1, why not go down to 7:1? When I built my first stroker engine, I opted for the lowest compression piston available, simply because I was 19 years old, and I had no concept of dynamic compression. I got lucky, and the engine ran strong. I also didn't know anything about valve springs, and I couldn't understand why it felt like I had pushed on the brakes when I hit the 1000' marker.

Kurt