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Author Topic:   3.875 crank with 5.7 rods
jhswords
Dirt Roller

Total posts: 6
posted November 03, 2005 05:36 PM  
thinking of building anew engine using a 3.875 crank and 5.7 rods have found a set of pistons to go with the crank and rods or so they say will 5.7 rods work with the 3.875 crank

TEAMPCR
Dirt Freak

Total posts: 238
posted November 04, 2005 06:30 AM  
as long as the pistons are sized correctly to use a 5.7 rod on a 3.875 crank, it will work. If the pistons are for a , say 5.7 rod 400, (i.e. a 3.75' crank) the piston will be .125" too tall.

juliaferrell
Dirt Freak

Total posts: 370
posted November 04, 2005 11:02 AM  
They will be .0625 too tall........3.875/2+5.7 = 7.63
3.75 /2+5.7 = 7.57

TEAMPCR
Dirt Freak

Total posts: 238
posted November 04, 2005 02:14 PM  
DOH!

BiggerBill
Dirt Maniac

Total posts: 129
posted November 05, 2005 08:51 PM  
If you are using a 3.75 crank that you have had off ground to 3.875, then you (can)will have to use a 327 small journal rod which is 5.7 long, then you won't have to clearance the block and will clear the cam, I know because we have done it. I have a set of .030 350 pistons (flat top, trw) for this application, for sale if interested.

Leaf
Dirt Full Roller

Total posts: 40
posted November 06, 2005 06:37 AM  
Do you mean offset ground to 3.8 BigBill, Ive been told thats the max for a stock crank.


How much was taken off the tops of your pistons, did you re cut the valve pockets?

BiggerBill
Dirt Maniac

Total posts: 129
posted November 06, 2005 03:26 PM  
Yep, offset ground, don't remember how much we took off. What we did was assemble it and then marked the piston when it was on TDC, then put them on a metal lathe that we have at work and turned them down to the mark. These were domed pistons (not hollow domed) after one was turned down,then I checked the thickness with a micrometer to make sure it wasn't too thin. No I didn't recut the valve pockets, didn't need to.

Leaf
Dirt Full Roller

Total posts: 40
posted November 06, 2005 07:34 PM  
3.8 offset ground, 5.7 rods should have taken .040 of the top of a 5.7 rod 350 piston.

is that what you took?

what do you want for them?

BiggerBill
Dirt Maniac

Total posts: 129
posted November 08, 2005 05:22 PM  
$150 for rods and pistons, plus shipping

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