I've got my case together and was checking my deck ht. My readings average from .074" to .080" for all four cylinders without any shims. The problem is I am shooting for .040" to get my compression ratio up to 9.5:1. This is my first T4 build. I have built several Vee motors in the past and never had this problem. Is it possible to shorten the cylinders? I just did a quick measure of the height of one cylinder. It is 3.62" from the case sealing surface to the top. Does this sound about right? Everything was going to well. Something had to go wrong

are you using any base shims between the cylinders and case?

what are your heads cc'd at? if you can only get your deck head down to, say, 050 or 060, you could always flycut the heads at bit more. i've also seen guys machine off the tops of the cylinders.

in any case, having the d.h. vary up to 006 is too much to me. it's not hard to get things down to 001.


i've just been told to stop typing and go retrieve a piece of fruit for my gf.

HHHmmmm...

I have a couple of questions for you.

First off. Is this a bone stock piston, cylinder, setup with Mahles and STOCK rods?

Are there ANY aftermarket parts in your combo?

Have you measured all 4 cylinders for height? If so. What are the heights for EACH cylinder? (Top Sealing surface to bottom sealing surface)

Have you checked wrist pin location to see if they are all the same?

And lastly.... What device are you using to hold your cylinders to the block for deck height measurement's?

Lets get through these hurdles and get on to the issue at hand.

C

Lets start there.........

I answered this in depth on my forum..

The cylinder measurement you are coming up with is standard for aftermarket cylinders. OEM cylinders generally measure exactly 3.600.

You'll either have to:
1- Trim the cylinders in a lathe
2- deck the case registers in a mill\
3- Flycut the heads for a tad less chamber volume
4- Live with the difference

We can help with 1-3, and don't recommend #4, that said I'd trim the cylinders.

the pistons/cylinders are 96mm A-A units.

the rods are stock-rebuilt by Remco, so they may be a little on the short side.

I only measured one cylinder as it is getting late tonight will take more measurements in the am.

I used a short piece of angle iron with some spacers to hold down cylinders using the short studs and then stacked some sockets on the long studs and tightened them up. I know it's kinda quick and dirty, but I was anxious to get some readings.

I brought the cylinders up to TDC using a dial indicator and then used a dial caliper to measure down from the edge of the cylinder to the top of the piston.

What Jake said... He answered your question at his forum...

Question. Is this a 2.0 block?

If so... I just had to deck my block to get it dead nuts flat and parallel to the bore.


Guess what... All my decks are even at 30 thou now...... Kewl...!!!! (Thanks Joe J!!!!!)

C

I found the problem:

The AA cylinders are .020" longer than stock.
The AA pistons are .030" shorter pin-top

bummer.

k

this thread is real interesting to me, as I was looking at those pistons/cylinders.

find a good set of 94mm oem cyl opened up for 96mm. next get a 96mm KBs with the correct pin heigth and be done with it.

k

That was my initial approach....but i heard recently that the aa pistons and cylinders can work out well if you use Jake's rings or something to that effect.


Jake...any comment on that?

Shnap. That is not a good thing to hear, since I just bought a set of those (cylinders).

I got a set of 94mm P&Cs for sale in the classifieds.

brandholio...

you know machinists.... have em lathe em down a bit

Unfortunately these variances are what come with the economy cylinder/piston sets- I don't like it, but there isn't much wew can do about the issues and eep the price down..

My Keith Black arrangement is the better solution.

Yeah but... Last thing I want to spend double money on. If I had access to a lathe I would just do it myself... Maybe I can call the resident german-ator...

.03 shorter pin to top?
So by cutting a set of OE 94 Mahles and using the AA Pistons
your back to .01 ? what would that theoretical CR be?

Actually 0.05" difference in height than stock without gasket or shims. The piston is 0.03" shorter, the cylinder is 0.02" longer. Add the two...

So you either need different pistons and machined cylinders, or lose the CR.

or longer rods

Or...

Off set bush the small end of the rods......... Hee... Hee..

Then re-balance the whole assembly......

Naw...... Just cut the cylinders Brando.

OR:

Sell em on samba. Cut your 1.8s and buy KBs.!!!!!!!

C

I have a question.
Is there a reason that these set are manufactured like they are?
I assume that a run was made, and that needs to be sold off.
Can input be provided to the manufacturer/distributor to change the specs for future runs of these parts?

Seems like it should happen if tha parts are just wrong...or are they correct for a BUS motor and wrong for a 914???

Rich

Already got the KB pistons... Just need the cylinders machined down. I'm trying to sell my old 94's with their pistons since they only got like 3k miles on them...

Ah well. It's only money, right?

My original intent was to buy the KB pistons with the AA cylinders, but when I finally got around to order them, they weren't available. I was told something to the effect that they weren't worth the extra expense. Now I believe they available again????

I have found a local machine shop (Ray's Precision in Santa Clara) to cut the cylinders down. Now all I have to do is figure out how much. I was shooting for .040" deck ht, but several people have questioned that as being "borderline" LOL

bill, you may in fact be "borderline" lol, but 040 is an absolutely fine deck. i wouldn't go much lower, but you should be fine at 040. what are you heads cc'd at?

9.5:1 ought to work fine on 91-octane.

I think the lowest you can go is .030" if you want to roll the dice on a 'moneyshift'. It all depends on your valvetrain geometry. Radical lift and duration increase the chances of slamming valves into cylinders with low deck heights.

They have been like this for years the spec of those cylinders really hasn't changed since 1998!

The newer AA cylinders aremuch better, we finally convinced to change their castings late in 2006 and because the cylinders are so much better we can actually offer a massaged 96mm cylinder specifically adapted to the KB pistons and hastings rings.

Several times I have contemplated dropping the entire AA line due to fluctuating component quality. we have to QC all those components with high scrutiny, but when we have bad parts they swap them out without issue..

Im keeping all my 94mm cylinders from now on....just put them on the shelf for future motors...get them opened up to 96mm when needed.

Rich

Whoops. So Ok back to .03 short of OE pin to top if using the opened Mahles
and AA Pistons. Assuming stock CC volume what whod the CR be...
I need one of dem calculators

lots of calc here http://www.ajdesigner.com/phpengine/engine...ssion_ratio.php