2270 Deck Height and CR, Pistons sitting proud of the deck, how many shims is too many shims? Options

[vjb206]

Hey folks! I have the bottom-end of my 2270 assembled and spinning freely. Thanks to all who helped me get to this point!

(IMG:http://www.914world.com/bbs2/uploads_offsite/media.giphy.com-23760-1708984357.1.gif)

To quickly recap: I bought the 2257 kit from AA Pistons (78mm stroke, 5.158" rods, etc.). And when I threw a P&C on for a test-fit last weekend, I immediately noticed the piston sitting proud of the deck height at TDC (negative deck) by about 2mm.

(IMG:http://www.914world.com/bbs2/uploads_offsite/media.giphy.com-23760-1708984358.2.gif)

Before I overreact, or buy the wrong stuff, I thought I'd ping the community...

1. Is this normal for a stroker set-up?
2. Can you stack multiple shims when getting up into the .06 >> .09 range?
3. (If no-stack) What's the best place to have custom shims cut?
4. I recall Jake saying using large shims requires lots of advance, anyone have experience here? What am I looking to adjust for upon start-up?

Once I figure out whether or not this is normal (I.E. verifying that I don't have to backtrack), I'll get into the CR questions (just waiting on clear plastic from Amazon so that I can measure my CC volume this weekend) (IMG:style_emoticons/default/biggrin.gif)

Thanks!

[MikeK]

You can shim the cylinder base, use a copper gasket from the head to the cylinder, trim the top of this piston (not the full amount), use a shorter rod, or use a combination of those things.

You might want to consider using some rubber bands across the head studs and through the small end of the rod to keep them from slapping the cylinder sealing surface while you spin it.

[Jack Standz]

You can shim the cylinder base, use a copper gasket from the head to the cylinder, trim the top of this piston (not the full amount), use a shorter rod, or use a combination of those things.

You might want to consider using some rubber bands across the head studs and through the small end of the rod to keep them from slapping the cylinder sealing surface while you spin it.

Sorry, must disagree with some of this.

A copper gasket between the head and cylinder won't fix the problem of negative deck height. You'll break the motor on start up.

A shorter rod isn't a good idea (and what size/where would you get one?) as the rod ratio is already 1.68 and going to a shorter rod would decrease it even more.

Trimming the pistons might work, but would not be the first area to consider to fix the negative deck height problem. Start with correcting the other problems and get the proper shims made.

[MikeK]

You can shim the cylinder base, use a copper gasket from the head to the cylinder, trim the top of this piston (not the full amount), use a shorter rod, or use a combination of those things.

You might want to consider using some rubber bands across the head studs and through the small end of the rod to keep them from slapping the cylinder sealing surface while you spin it.

Sorry, must disagree with some of this.

A copper gasket between the head and cylinder won't fix the problem of negative deck height. You'll break the motor on start up.

Copper gaskets are readily available in .040"-.060" and one could get custom gaskets cut. If the piston is hitting the valve/head, then yes, damage will occur. I've run them on a T4 with zero deck to get the deck to .040".

A shorter rod isn't a good idea (and what size/where would you get one?) as the rod ratio is already 1.68 and going to a shorter rod would decrease it even more.

You'd shave the rod end and re-machine it to the correct size, though I agree with you with respect to the rod ratio.

Trimming the pistons might work, but would not be the first area to consider to fix the negative deck height problem. Start with correcting the other problems and get the proper shims made.

That would depend on how much the pistons need to be cut. If your deck height varies from cylinder to cylinder, even with switching around rods, you can fine tune them with trimming the tops of the pistons. Clearly balance them after.

My point was that there are several ways to get the desired result. It's unfortunate that the T4 cylinders that they are selling with their kit don't have longer cylinders like their thick wall, 92's. It's nice to have the cylinders trimmed for the correct deck height and avoid shims altogether.

I guess a shorter stroke crank would solve multiple issues, but I doubt that would be an viable option.