Building a stroker motor

[Moofus02]

Looking at prices and there isn't much difference from 3.75 stroke to 4 inch. Anyone put a 4 inch crank in a 350 block?

 

[Scooterwrench]

The more you stroke it,the bigger it gets!

 

[99xcss4]

are you using a 1pc or or a 2pc rms block the bigest crank that they make for the 1pc rms as far as I know is 3.875 if a 1pc rms block can be clearenced for a 4 inch stroke crank you will need one of these https://www.summitracing.com/parts/aaf-all26126

 

[Road Trip]

Looking at prices and there isn't much difference from 3.75 stroke to 4 inch. Anyone put a 4 inch crank in a 350 block?

I can't speak to a 4.00" stroke in a SBC, but I do have firsthand experience with the 350 block stuffed
with the 3.75" stroke 400 crank. (aka: 383ci) Of course everyone knows about the need to relieve the
bottom of the block to clear the rods. (see attached)

But given the need to have to worry about running into interference issues the entire 360° of the crank/rod
travel, when we spec'd out a new cam we decided to order the smaller base circle version to avoid this:

You must be registered for see images attach

(credit: Old Chevrolet Power Manual from the '70s. NOTE: This is what to check when putting a big cam into a 3.48" (350ci) motor. 3.75" stroker is ~1/8" more to fit in there!)

This unfortunate cam lobe vs rod bolt phasing is only a couple of places out of 16. But it goes to show just how complicated
everything can get when you are swinging a rod through a 3.75" stroke where 3.48" used to rotate & adding more cam lift
at the same time. When motorheads get greedy...you get caught. :0)

Given I've seen it with my own eyes on a vintage 4-bolt #3970010 block, I believe I could replicate this
on another SBC without hitting the water jacket in the bottom or any of the cam lobes with the right cam choice.

But if you were to ask me if I could guarantee being able to fit another 1/4" of stroke into the same space
as a 'close fit' 3.75" 383 in a stock block? I'm not so sure...and I like to push the limits in order to give myself the
most grunt possible in any given engine bay. :0)

For what it's worth here's a pretty decent discussion amongst people who've been there, done that, and have
shared their opinions on if they would recommend it & why or why not. (speed-talk on building 4" stroke SBCs)

And of course up 'til now we've only looked at schwing room headaches. Is the wrist pin up in the oil ring land
with the rod length they're using? Can this rack up a lot of quality miles on the street, or is it more of a track toy
thing?

If this was something you and I were brewing up in your garage, the difference in displacement between a 383 and a
408 is only 25 cubic inches, or ~6.2% gain. I can hear myself recommending the 'proven-good' 383 stroker kit plus
a set of cylinder heads that flowed at least 6.2% better than the ones you currently have. (And porting 6% more
flow out a decent set of heads is realistic & do-able.)

****

Then again, if you had an obnoxious big block neighbor and you had just won the lottery...and you absolutely *needed*
to shut him up once for all, then sure, we step up to the much stronger aftermarket SBC blocks featuring the camshaft
bearings moved up and out of the way of the crank throw, so we can do the 4" stroke plus the 4.155" bore, plus top of
the line cylinder heads, and end up with a 305ci looking 434ci SBC that would deliver just the right amount of Humble Pie.
It *can* be done, but with a nontrivial amount of time, effort, planning, checking, and a whole lotta piggy bank.

But it's fun to contemplate. :0)

**** Optional reading ****

By the way, if all your deliverables are done and you have a little time to spare, I'd recommend watching this
dad & lad machine shop clearance a 350 block for a 383 stroker kit. These guys have a great vibe, for I can watch
them and actually be a little less irritated at the world by the time that the video is over:
(Jim's Automotive SBC stroker kit clearancing)

Good stuff. I'm always up for building a sleeper. Underpromise visually, Overdeliver dynamically, and then laugh like a
small child at the playground...

 

[Sean Buick 76]

Yes 383 or go to a BBC

 

[99xcss4]

https://www.summitracing.com/compare https://www.summitracing.com/search...geSize=100&SortBy=Default&SortOrder=Ascending https://www.summitracing.com/search...geSize=100&SortBy=Default&SortOrder=Ascending https://www.summitracing.com/search...geSize=100&SortBy=Default&SortOrder=Ascending

 

[99xcss4]

for what ever it is worth all of the chevrolet performance 383 crate engines us a 4 inch bore and a 3.800 stroke with that being said imho a 3.800 crank will swig just fine if gm dose it I do not se why any one else can not as well and I could be wrong but I also think that if you have a good strong block and can clearence it a 3.875 crank should work okay now a 4 inch or either a 4.125 or a 4.250 need a aftermarket block imho

 

[Drunkcanuk]

https://www.summitracing.com/compare https://www.summitracing.com/search...geSize=100&SortBy=Default&SortOrder=Ascending https://www.summitracing.com/search...geSize=100&SortBy=Default&SortOrder=Ascending https://www.summitracing.com/search...geSize=100&SortBy=Default&SortOrder=Ascending

That's some pricy toy shop! Lol

 

[99xcss4]

That's some pricy toy shop! Lol

yes it is but for the few that can swing it looks really good and us poor people can always dream right

 

[Moofus02]

I know you can swing a 4 inch in a standard block but a reduced base circle cam is almost mandatory. I've got 350 blocks coming out my ears and the parts to do a 408 are only about another 400 bucks. Just kicking stuff around but I'd like to try it. Aftermarket block would be great but that might be more than I can explain to the wife