jss

gotcha thanks guys im gonna roll with the y8 gear and hope for the best.

Fabrik8

If you have both blocks, you can take an accurate measurement between the crank and cam centerlines and see what the difference is. Then you can do some math and figure it out what the timing error will be. I might be know to approach things slightly different than most people do though.

jhholloway

OK that would work, but once you have the measurement how do you find the correlation between the difference of the centerline measurement and mechanical timing of the motor?

jss

shooott just thought of something else.. im looking for the ecu to buy and i wanted a p2p because of the y8 head but since the block wont have a knock sensor and maybe even other things do i have to go obd1 with a p28??

Fabrik8

The difference in centerline distance makes an angular difference based on the diameter of the cam gear. It's pretty straightforward to calculate a ratio of length to angle based on the cam gear circumference, it's all really simple math.

Measure the cam gear diameter or radius, then calculate the circumference (2*pi*radius or pi*diameter depending on whichever is easier), then divide the circumference by 360. Then you have a linear belt distance per degree of rotation. So if you have a difference in centerline distance, you can now find out how many degrees of timing that will be. There will be a tiny bit of error because the belt is at some angle to the pulleys (the crank and cam pulleys are different sizes) but that change will be very small so the error will be very small also.


If you're changing the thickness of a headgasket, you can use the same concept. The calculated number of degrees will actually be a tiny bit off if the block deck is not at 90 degrees (perpendicular) to the timing belt (which it won't be, especially with a DOHC engine), but it will be close enough to find out whether the change in timing will be enough to worry about.

jss

fabrik8 do you have any idea on my ecu's? ^^

Fabrik8

I'd use a P28 if you want to get tuned. If you want to use the P2P, you'll have to install a knock sensor on the block and make sure you have both O2 sensors installed in the exhaust. I don't know if that block already has a convenient mounting boss for a knock sensor, so that may or may not be an issue. The P2P calibration will probably work decently with the new block, unless something like compression ratio has changed dramatically. Probably good enough for a cheap min-me swap though.

crasy87rexsi

Go OBD1 dude, honestly there is no point staying OBD2. P28 doesn't have a knock sensor input, IIRC no D series ECU's have it. The P28 will run it just fine.