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!

[vjb206]

@MikeK great idea! Don't want any scoring.

@cgnj just knowing that this is not unique to me is very helpful. If you get to it that measurement that would be great, if not, no worries. Out of curiosity - why is the motor apart? Anything inherent in the combo that I should be aware of?

@Krieger I called AA and this is normal (I.E. they didn't send me the wrong pistons).

@VaccaRabite very useful info - thank you! I'm just not there yet... Need to take more precise measurements before doing maths. I'm looking to get to an 8.5 or 9 CR (still deciding which is best).

The cyl head is listed at 60ccs, but I will measure them with fluid this weekend.

I'll follow-up early next week with:
• Head CC ccs as measured with fluid
• _Actual_ deck height as measured with a dial gauge (as I said, the one in the picture is just a sanity check)
• Shim / head gasket plan as a result of more detail

Appreciate everyone who weighed in!

vb

[VaccaRabite]

@VaccaRabite very useful info - thank you! I'm just not there yet... Need to take more precise measurements before doing maths. I'm looking to get to an 8.5 or 9 CR (still deciding which is best).

The cyl head is listed at 60ccs, but I will measure them with fluid this weekend.

I'll follow-up early next week with:
• Head CC ccs as measured with fluid
• _Actual_ deck height as measured with a dial gauge (as I said, the one in the picture is just a sanity check)
• Shim / head gasket plan as a result of more detail

Thats the right path.

If you measure deck height along the wrist pin, a dial indicator is overkill. It does not hurt, but your calipers are precise enough for that particular job. You WILL want that dial indicator later though when you set pushrod length. The problem for this application is that its too precise. You are going to struggle to get a repeatable measurement in the thousandths of an inch that you would not as reliably get to the hundredth with your calipers.

For CR, I'd personally target 8.6:1 for a street engine. This lets you run on regular gas. More importantly, the AA cylinders are iron and uncoated, and will struggle to shed the heat produced by a 9:1+ CR. BTDT. (IMG:style_emoticons/default/headbang.gif) If you want the higher compression, you are going to want to get your pistons coated and the inside of your heads too. And then do the measurements again, as you will have added thickness to the pistons and reduced the CCs of the heads.

The important thing is to pick a CR and get precise - don't pick a range (8.5-9) pick a number and work to that. The changes from 8.5 to 9 are pretty small in terms of deck height. But it makes a big difference in power output and heat and drivability - especially for longer drives.

Zach