3.2l Carrera Deck Hight Question, Competition Eng. Method

[Determined]

Hello everyone,

Today's project was to confirm deck height on my 3.2L Euro High Compression engine. After carefully installing my piston rings and piston into the cylinder without breakage of any of the rings, I went on to perform my deck height measurement. I did have my heads resurfaced and I used 1mm cylinder base gaskets to start. The solder I used was about 3.20mm thick before compression, after following Walt's procedure outlined in Wayne's book I measured my solder which was now compressed at 2.20mm. Does this mean that my deck 1.0mm if I subtract them? I'm a bit confused and any help is greatly appreciated. If this is correct, will this create a problem with valve clearance, do I need to add another .25mm gasket?

Best Regards,

Alex

[Eagledriver]

This is not a deck height measurement. It is a piston to cylinderhead clearance measurement. The deck height is how far below the top of the cylinder the piston top is. Usually people measure that with a depth guage of some kind. What you are measureing is the clearance between the piston top and the head. The two are different because the head has a beveled edge around it that slopes away from the piston. You want to make sure you have at least 1mm of clearance so your pistons don't hit the heads. You don't want this gap to be too big because it can hurt the combustion process and cause loss of performance or detenation.

-Andy

[Determined]

Andy,

Thanks for the clarification, it is clear and I reconfirmed it as well in Wayne's book. I missed that comment in the book. So, it appears that I have about 1.0mm clearance between my piston and head according to my results above with a 1.0 mm cylinder base gasket. I just removed it and inserted a .25 mm base gasket to compare results, after performing the test with a new piece of solder I got more squeeze on the solder. It now measures 1.60 mm after compression. Before it was 3.20 mm so 3.20-1.60 is still 1.60mm. I noticed that in Wayne’s book for stock engines it recommends a clearance of 1.25 mm to 1.50 mm. For high compression performance engines it recommends 1.0 mm. I'm clearly over the 1.50 mm by 0.10 mm, is this a problem if I decide to stay with this setup using the .25mm cylinder base gasket and will it increase compression even more if I'm over 1.50 mm?

Thanks a million!

Alex

[Eagledriver]

I'm a little confused by your posts. I think you are doing math you don't need to do. Are you trying to figure out what clearance you would have with no gasket? All you need is to have the correct clearance with the gaskets you use. This is a direct measurement of the thickness of the solder after it is crushed.

If you use a thicker gasket you will get more clearance and you will lower the compression ratio of your engine. I'd stick with the .25mm gasket. The detonation problem that others have mentioned is related to the shape of the combustion chamber when you have excess clearance. It is not a result of a change in compression ratio. (the compression ratio would actually be lower with more clearance).

-Andy

[Determined]

Thanks Andy,

It's clear now, I ended up using the .25mm base gaskets this morning. Is it necessary to check each piston/head for clearance with solder method or can I just perform the check on a couple of heads?

Thanks,

Alex