ALFAGTV6.COM

[Murray]

I just got my hands on a set of new AE Borgo pistons and liners which I'm going to plug into my 2.5L 12V this winter and I have a couple of questions.

1) Is there anyway of identifying the compression ratio of these pistons ? The AE no.is 6120\T 88.In researching this I understand that the AR original piston was 9:1 but I've read that current standard pistons are 9.5:1.

2) So once I get that settled I'm thinking that I would like to get my CR up a bit to work with my S cams.I would do this by having the heads shaved a bit.So the question is how much would I need to remove to get somewhere near 10:1 - obviously that depends on the ratio produced by my new pistons.

Needless to say I'm doing this on the cheap otherwise I would have gone out and bought some 10.5:1 pistons and be done with it,but the wife is keeping a close eye on me these days

If Jim K's new V6 book was out I'm sure all these questions would be answered

[Barry]

Murray,This is easy..
Use the 1 " downfill method of getting the dome volume of the pistons..Once you have that figure,measure the chamber cc AND the headgasket thickness..(should be 1.6mm)
Now you have your static cr..

Simply work out the new required chamber volume for the new cr..

[Murray]

Use the 1 " downfill method of getting the dome volume of the pistons

Barry seems like I must have been out in the hall when they covered this in internal combustion engines 101
Sounds like I would have to use a measure of liquid (beer ?) to detemine volume ?
Keep in mind we're talking about pistons that are sitting in a box,and I need to detemine approx static CR before installation.

[Mats]

I think Barry means that you drop them into a liner 1" from the top and seal the piston crown to liner with some grease. Them add liquid with a burette to se what the volume is, calculate the empty cylinder equivalent and subtract the volume you measured = piston dome volume.
Then you need the CC volume too of course, and don't forget the gasket.

[Murray]

Thanks Mats so

Them add liquid with a burette to se what the volume is

Volume of liquid shown in red in my drawing is what I'm after ?

calculate the empty cylinder equivalent

So would that be the volume if the piston was flat on top ?

Does all this mean that if Borgo went from 9:1 - 9.5:1 this would have been achieved strictly by reshaping the dome ie: the wrist pin centre to piston edge dimension (DIM A) would not have changed ?

[Barry]

Thats excactly what I mean...Hey Murray..
Pin center height or deck height would not have changed at all..

Your downfill method number is simply subtracted from a 1" cylindrical volume that you quickly do mathematicly..

0.7853982x0.88x0.88x0.683x0.254
101.5cc

Simply subtract your measured number from the above..

gasket volume will be 6.6cc`s

[Murray]

Thank you Barry -time to steal the wife's turkey baster

[Mats]

you need to keep track of how much you poured in though, does the turkey baser feel like a good instrument for that?

[Barry]

I`d use the thermometer instead.....

[Murray]

does the turkey baser feel like a good instrument for that?

Mats we Canadians only use high precision basters on our birds

Fortunately the wife's a nurse so I have ready access to graduated syringes.

I`d use the thermometer instead

Barry would you recommend oral or anal

Now back to business.
Read the following on the Alfabb.Any idea if the same logic would apply to a 2.5 ?

With my race engine, I measured a .25 point increase in compression for each .010" cut off the head. This is pretty consistent with his 4/10 for .020". I would also recommend checking clearances, though.