Trying to wrap my head around it...

[casual]

I can't seem to figure this out. I'm trying to get some info on a 4.6L long rod stroker...
When building a long rod stroker, how much further are the pistons down in the cylinder holes? I'll be using the off the self KB pistons.
And can you dish the KB's even further to get your acquired compression ratio?

So if the stock deck clearance is .0215...what will it be with a long rod stroker & the KB pistons?

[casual]

Come on guys someones got to know...how much farther down are the pistons when doing a long rod stroker?

[SilverXJ]

IIRC they are around .030" in the hole.

[casual]

Thanks silver. I'm going off your build lol. Taking advice & such. Like keeping the pistons in .007 & such...
I'm planing(?) the head .005 to straighten it up & want the pistons in .007 @ TDC. So how much would I need to deck the block?

Stock clearance is .0215, so I subtract (.005 for planing the head +.007 for pistons @ TDC) .012 & get .0203..Thats with stock clearance.
So I would add .030 to it? Which is .233 is that correct?? So I would deck the block .233?

[jbxx]

When I did it I had the machinist mock up the assembly. There is
some slop in the tolerances. Then deck the block to whatever the highest piston is

[SilverXJ]

When I did it I had the machinist mock up the assembly. There is
some slop in the tolerances. Then deck the block to whatever the highest piston is

x2. There are too many parts with less than perfect tolerances. It needs to be mocked up, measured and then cut.

Also, milling the head has nothing to do with the deck clearance.

[gradon]

More like .023". .233" would make that block worthless(and your machinist would charge you a boatload). X2 on it being ~.030" down the hole. Assemble, measure each piston @TDC and cut the amount =or<than the smallest clearance.

[casual]

lol thanks on the fix gardon. You've helped me quite a few times now, I just keep changing my mind lol. Much appreciated!! I would have wrote down .233 lol, that would have went BAD
& ya silver I remember reading your thread how 1 of your piston was above the deck....so assemble then measure, then measure, then measure & then cut lol.

for a rough estimate though, does this sound right?
.0215(stock clearance) - .007(pistons in the hole @ TDC) = .0208 + .030= .0508? Is that about right roughly?
Trying to get a price from my machinist. Good thing he doesn't have my block yet because I'm still waiting for pistons. So now I'll be able to measure in my garage, but he wanted to know roughly what had to be done!

[SilverXJ]

No, .0508" is not correct. Its around .030"

[gradon]

The extra stroke of the 4.2 crank and the smaller pin height of the KBBs means you need to totally forget the .0215" stock clearance--it no longer applies so don't use that figure in any calculation. If you go to the general discussion tab then go down to calculator, then go halfway down the first page to "try this", you will find an xls calc where you can input your kbb's variables and it'll tell you that with a 9.353" deck height(spec is 9.350-9.356", so you'll have to physically measure yours), the piston will be .0295" down the hole. 4.0 rods are spec'd at 6.123", but maybe you have one that is 6.125"; maybe one of the KBB's pin heights are 1.355(instead of 1.353), so that piston/rod combo might be .004" higher in the bore than another in your set. You have to install, measure, then you know what the max you can cut before one of the pistons is zero decked.

[casual]

thanks gardon, I got it now lol.

[gradon]

it's gradon, by the way.

[casual]

I did that last time to lol...call me dumb, but how the hell do you work that calculator?

I punch in my info on the top half..& then where it says "calculated information" just says "#value!" Nothing actually calculates?

[jbxx]

You must have entered somthing that the calculator didn't like?
Post the values that you entered into each variable, then we can help you t-shoot this!
J.B.

[casual]

Actual head volume: 58.00cc
Bored over: .030"
Stroke of Crank: 3.895
Decking block: .000"
Planning head: .005"
Custom piston cc: 21.00
Rod Length: 6.123
Piston Height: 1.353"


This is all the stuff I changed...I can't think of why it won't work?