engine and drivetrain Engine rebuild question....

[Guest Anonymous]

I have an engine with an E12 head, and matching block....and the piano style pistons are shot...

My question is, can I use flat top pistons of the same diameter with the E12 head and block? what kind of compression changes will I experience? and is this alright to do?

TIA

02Mike

[Guest Anonymous]

Going to flat top pistons drops your compression down to about 8:1.

Zymgut Motors (www.bimmerparts.com) sells 0.5 mm oversize 9.5:1 pistons on eBay regularly for <$375. Spend the extra bux, have your block punched to oversize and you'll appreciate the difference.

Cheers!

John N

[Guest Anonymous]

I guess I'm not as finicky about performance as some other folks, but I'm quite happy with the street performance of my flat-top/e12/stock cam motor. I've had it up over 100mph, it pulls just fine. You can feel that over 5500rpm the oomph starts to fall off, but a lumpier cam would probably extend that up to the redline. Nice thing is that you can use regular gas without knocking, it never overheats even with an old stock radiator, and its nice and smooth for around-town driving.

If it's what you've got, and you don't have much cash, go for it.

Mike

[Guest Anonymous]

If you can't afford new pistons, and the flat tops are what you have lying around, they'll work fine with the E12 head. You will have about 8.1:1 compression, which is only slightly lower than the 8.5:1 you'd have with the stock non-tii piano tops. I had this setup in a worn out old motor that was in my 2002 when I got it, and it ran smoothly and had ample power with a 32/36 Weber. It felt about the same to me as a stock carb '02. If you do this, definitely hone the cylinders and install new Deves rings on the pistons.

Good Luck

Colin