Help with piston compressions by looking at them?
 

Hey All,

I have several (3) 944 engines that I know are all from 86-87 944s. All are stamped M44/07 or 08(indicating an auto trans) but I'm wondering is there a way to distinguish pistons that have a CR of 9.5:1 in '86 from those that have a CR of 10.2:1 in '87? I'm sure it's simple if you have 2 in front of you that don't look the same but so far I have only removed one set of pistons and one other head and those pistons all look the same. Does anyone have a picture that shows the differences? It should be pretty obvious when looking at them next to each other right? Or maybe I can tell from the other code stamped on the engine? Thanks for the help guys.

These are 9.5:1 CR pistons. (ebay pic from a '84 944)

http://forums.pelicanparts.com/uploa...1194413208.jpg


Here's the 10.2:1 pistons. (from http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/372207-aftermarket-pistons-na.html)


http://forums.pelicanparts.com/uploa...1194413242.jpg


There are also ero spec 10.6:1 CR piston with an even smaller circle, but I can't find a picture of them.

Thank you much. Looks like I've got me some 10.2 pistons.

I dont think any of the 87 had 10.2 only 88 and up, but I could be wrong

It may be 1987 build date with 88 model year.

http://www.connact.com/~kgross/FAQ/944faq02.html

Unless that's wrong, all '87 944s had 10.2 CR

I think that link is wrong. I Know the 924S doesnt have a 9.7/1 cr and Im pritty sure that all 1987 944 had the 9.5cr not the 10.2, Well at least must stuff besides that link and the pelican chart that I have read shows different numbers. I think its time to find the true answere, I'LL see what I can find just to make sure cuz I might be wrong

'87 944 has 9.7:1 according to my owners manual..though the general consensus is all 944's from '83 - '87 had 9.5:1...this is because there is no difference in pistons between '87 and prior years. I could be wrong on that though.

http://www.pelicanparts.com/944/tech_specs/944_model.htm

Here it states that 87 had 10.2

I dont think that information is correct. I know for a fact my '87 does not have 10.2:1 pistons (ive had the head off before). Owners manual states 9.7:1 .and almost all other factory documentation (specs booklet and factory manuals) all state 9.5:1. Only '88 models had 10.2:1 .

The weights also off i think... maybe add 150lbs to each curb weight to get what the owners manual (and the general consensus of most people) say they weigh.

Thanks Jon,
I was wondering if that was correct or not.
I'll belive you. :)

Well ill say this, i wish it was correct. I wish my car made 158hp (which is correct for a 10.2:1 compression) and i absolutely wish it weighed 2637lbs. In reality its probably sub 147bhp after 100k miles and 20 years, and probably around 2800lbs.

Hopefully after the test pipe goes in it will be back at 147bhp and after i get these fiber glass bucket seats in, in the sub 2700 range.

my car was weighed at the last safety inspection. it came out to around 3200 pounds with the tech guy in it and a full tank of gas. the specs say something like 2900, so i think the above information is correct, at least for my car.