4 inch stroke 4inch bore sbc

sanfordandson · Post by **sanfordandson** » Tue Jan 06, 2009 2:00 pm

has anyone tried this combo lately? i am considering building one for a heavy dirt circle track car with a 2bbl. no ci or compression limit. currently run a standard 4.155 bore 406 but would like to try more stroke but keep the cubes. these heavy cars can use the stroke and torque. i'm thinking valve shrouding wont be an issue since our restriction is a 7448 2bbl and we typically run a 2.02 1.6 valve.

thanks for any info!

xstfudonniex · Post by **xstfudonniex** » Tue Jan 06, 2009 4:14 pm

That ends you up with an awful short rod or piston, or both.

sanfordandson · Post by **sanfordandson** » Tue Jan 06, 2009 4:58 pm

it would be a 6 in rod and 1in ch. same as your typical 434sbc, just a smaller bore.

ProPower engines · Post by **ProPower engines** » Wed Jan 07, 2009 1:35 am

What heads and port volumes are you wanting to use?
With a small carb you might need a longer rod to control piston speed to fill the cylinders.

sanfordandson · Post by **sanfordandson** » Wed Jan 07, 2009 7:55 am

eq 200 runner heads. planning on a flat top pistons and angle milling the heads to get around 13 to 1 compression.

Post by **3V Performance** » Wed Jan 07, 2009 8:35 am

I think it will work good but would be a very low rpm engine. 5500?

Horndog · Post by **Horndog** » Wed Jan 07, 2009 10:29 am

3V Performance wrote:I think it will work good but would be a very low rpm engine. 5500?

That's what I was thinking.....maybe 6000 max.

ProGSX · Post by **ProGSX** » Wed Jan 07, 2009 10:33 am

Here's a pm I recieved with some good info.
This crank can be used in any GM 350 1 pc seal block from 1987 to 1998 to built a 408ci with a 4.030 bore. You will need to use a SMALL BASE CIRCLE CAM with this 4" stroke crank.

If you use a SIR6000BBLW or CRS6000BLW Eagle rods, these cranks are not that difficult to install in a 1 pc 350 block. You will need to use a small base circle cam, and with the SIR6000BBLW rods, you might need to clearance the rods a little more for the cam, this is very easy to do, the rods already come cnc clearanced, you can use a belt sander to add clearance. Also by flat milling the rod bolts as indicated below, you can greatly reduce the amount of block clearancing.

When using a H-beam rods the "ROD BOLT" is what intersects the pan rail, it is very simple to flat mill the rod bolt head .075 thousands. This makes the 4.00 stroke crank go into the block about the same as a 3.875 stroke. Realize stroke only moves the rod out towards the pan rail 1/2 the distance of the total stroke, so the difference between the two strokes would be .125 and a difference of .062 towards the pan rail. Removing the material from the bolt has no effect on strength, you just need enough material to torque the rod bolt. Even with a Small base circle cam, you might still need to clearance a standard CRS6000B3D rod. The CRS6000BST/2000 rods are cnc CAM clearanced, and you can use any CAM with these rods and a 4" stroke.

sanfordandson · Post by **sanfordandson** » Wed Jan 07, 2009 11:07 am

we currently run our 406's 6500rpm. the limit is the 350cfm carb. i was thinking i could get close to that or at least over 6000rpm.

as for the clearance issues we've been using the scat pro comp i beam rods with the shorter bolts in 3.875 stroke engines and we've gotten away with not needing a small base circle on them. i'd assume i'll have to get a small base with the added stroke. mahle makes a shelf piston for this and i was hoping to use a callies crank in an oem block (rules) with pro gram main caps.

Mark O'Neal · Post by **Mark O'Neal** » Wed Jan 07, 2009 12:32 pm

I have never run the combination...but the piston sales on that number are pretty decent.

It surprised me.

sanfordandson · Post by **sanfordandson** » Wed Jan 07, 2009 1:36 pm

b20, i did not see that article but i'd assume the clearancing is no different than clearancing for a 434. same stroke different bore.

does anybody know if the scat pro comp rods come in 2.00 sj rod size?

Mark O'Neal · Post by **Mark O'Neal** » Wed Jan 07, 2009 1:55 pm

sanfordandson wrote:b20, i did not see that article but i'd assume the clearancing is no different than clearancing for a 434. same stroke different bore.

does anybody know if the scat pro comp rods come in 2.00 sj rod size?

No it doesn't.

But they do have the 2-IRC6000-2000....the same rod without the profile.

They also have an H-Beam

robert1 · Post by **robert1** » Wed Jan 07, 2009 2:45 pm

When installed in a 400 block it has extra rod bolt clearance cast into the block. In a 350 block it's going to be tough. I would think with the right rod they would have the bolt moved up in the rod as much as possible. Going small journal will difinitely help.

sbchevy1 · Post by **sbchevy1** » Wed Jan 07, 2009 4:58 pm

I actually built a few of those engines, I have used the scat i beam with the 7/16 cap screw, the pro comp, i believe. And a .880 base circle cam. I had to just touch up a couple of rods, i mean barely anything. Now the block was another story, i recomend at least a 1/2 fill before you start, If you are useing a stock block.. If you are useing an aftermarket block dont worry about filling it.

af2 · Post by **af2** » Wed Jan 07, 2009 5:53 pm

xstfudonniex wrote:That ends you up with an awful short rod or piston, or both.

Can you elaberate running the same

I have to give it a