400 block max overbore for boost

[octusis]

I recently had a 400 block given to me and it’s currently already .030 over but it has some pitting in one of the cylinders. From my research it seems not to be the “best year” block so I’m kind of leary on it. What’s the max oversize these can typically go? I’m going to be aiming for around 700hp with a turbo and stock stroke, street driven. Thanks

 

[dvw]

Sonic check is always the best. That being said we run a 360 block that's .040". Its been run to 22psi many times.
Doug

 

[cal30_sniper]

Not as thick of mains as the 72-only block, but but all the blocks are still pretty good. Your 77 has the advantage of the reinforced motor mount ears.

The weak point I’d think is going to be the stock stroke crank. Have you found an aftermarket forged crank in the stock stroke length? Molnar makes rods in the right length, but I haven’t seen a forged crank other than the factory 383 crank.

 

[octusis]

Not as thick of mains as the 72-only block, but but all the blocks are still pretty good. Your 77 has the advantage of the reinforced motor mount ears.

The weak point I’d think is going to be the stock stroke crank. Have you found an aftermarket forged crank in the stock stroke length? Molnar makes rods in the right length, but I haven’t seen a forged crank other than the factory 383 crank.

I’m going to take a look and see who has aftermarket options although I’m fairly certain I may have access to a couple of 383 cranks for little to no price worst case. The rest is going to be forged with arp fasteners everywhere I can. Maybe even girdle but I’ve heard mixed things about them so not 100% on that yet.

 

[33 IMP]

Piston selection is awfully poor for stock stroke 400s. Have you even found any forged pistons for it?
For that reason alone, I'd stroke it , to get forged pistons. You won't need a huge stroker kit, but find one with the pistons you need.
If it's just one hole, you could sleeve it. Done properly, it might be the best hole in the motor. Otherwise, hope that .040 cleans it. I really wouldn't want to go .060 if avoidable.

 

[octusis]

Piston selection is awfully poor for stock stroke 400s. Have you even found any forged pistons for it?
For that reason alone, I'd stroke it , to get forged pistons. You won't need a huge stroker kit, but find one with the pistons you need.
If it's just one hole, you could sleeve it. Done properly, it might be the best hole in the motor. Otherwise, hope that .040 cleans it. I really wouldn't want to go .060 if avoidable.

I hadn’t really thought about of sleeving it. Machine shops in my area are hit or miss so I’d have to see if I can find a place to do it. Definitely not opposed to a small stroker, eagle kits any good?

 

[cal30_sniper]

Scat makes a 451 kit that looks good. I’ve looked hard at it, but will probably go the Molnar 470 or 512 kit for mine.

An option I was looking at for a stock stroke build was having a 383 crank ground to BBC rod journal sizes and selecting a BBC rod that works well with available compression height pistons. You could also have a slight offset grind done to get the right compression height for your deck.

 

[furious70]

Pay attention to cubic inches and what turbo or turbos you want to run. You'll be ill sized pretty quick or spending cubic dollars and making 1500hp

 

[33 IMP]

I MUCH prefer scat to eagle. Molnar would be my first choice.
For a Boosted/power adder app, 451 kit would be my choice, shorter stroke≈ less stress on a stock block.
N/A, I'd build a 512.

 

[octusis]

Pay attention to cubic inches and what turbo or turbos you want to run. You'll be ill sized pretty quick or spending cubic dollars and making 1500hp

I’ve heard it’s sometimes ok to go cheaper on turbo as long as sized properly but to go big $ on watergate. What’s your opinion about that?

 

[octusis]

I MUCH prefer scat to eagle. Molnar would be my first choice.
For a Boosted/power adder app, 451 kit would be my choice, shorter stroke≈ less stress on a stock block.
N/A, I'd build a 512.

Does anyone make a 451 kit or would I just have to get a 440 crank ground to fit? Cant seem to find anything other than using stock 440s 3-3/4 crank.

 

[furious70]

You want to be confident of all the hardware. Most of the really cheap stuff is not well sized for a v8 with any real displacement. There are good options when you're "LS" sized however

 

[dvw]

Standard off the shelf pistons aren't designed for much boost. The tops aren't thick enough. We've sagged them in the middle. So availability isn't issue. Order custom of what you need. More costly? Yes. Cheaper than replacing with a second set when they fail.
Doug

 

[33 IMP]

Forced induction on a standard stroke 400 would mean it would HAVE to have custom pistons.
Who even makes a forged shelf piston for a 400?
(Icon might, can't say either way.)
The trw cast 400 pistons I had had an insanely thick piston head, but I wouldn't think of running them turbocharged.

 

[67MPRFAN]

Standard off the shelf pistons aren't designed for much boost. The tops aren't thick enough. We've sagged them in the middle. So availability isn't issue. Order custom of what you need. More costly? Yes. Cheaper than replacing with a second set when they fail.
Doug

This is from a turbo car running lean, 400 block

 

[33 IMP]

This is from a turbo car running lean, 400 block

View attachment 1537541

Cast? Hyper?

 

[67MPRFAN]

Not sure a friend sent me that picture, when we were talking about boosted cars

 

[33 IMP]

Not sure a friend sent me that picture, when we were talking about boosted cars

Has the look of a speed pro, don't think they make a forged 400 piston, but I could certainly be wrong.

 

[68-500]

Standard off the shelf pistons aren't designed for much boost. The tops aren't thick enough. We've sagged them in the middle. So availability isn't issue. Order custom of what you need. More costly? Yes. Cheaper than replacing with a second set when they fail.
Doug

I second custom pistons. Maybe that would clean up at .040 over