Cast Piston Warning!

[DOCTOR FIELDS]

I just ran into something ive never seen in my 11 years of Chevette racing. I mocked up an engine to measure the deck height, to see how much needed to be milled off. My measurements kept coming up closer to the top in the front and .006" lower on the rear on #1 & #4 pistons. My first thought was the pistons were cut wrong. So i measured all the pistons and they were the same thickness. I knew it had to be something wrong with the wrist pin. I took #1 piston out turned it around, mocked it back up, and sure enough i got the same measurements, but on opposite sides (Front lower than the rear).

These pistons are Sealed Power (Federal Mogul) 474P and are a "Matched Set" All you guys running cast pistons, check the pistons as soon as they come out of the box! I know from now on, i'll definitely be checking to make sure the wrist pin is casted straight before i start any other work.

[chevetteman]

what kinded of damege will it do to a motor.

[zackbandyr12]

So Fields ur saying that the wrist pin was not strait though?

[bigtoyracer]

No what he is saying is that the wrist pin holes are cast offset from each other and are not in line with each other.

[DOCTOR FIELDS]

Chevetteman, If you have a set of pistons with the wrist pin casted on an angle, 1. your deck height will be off. For instance If the front of these pistons were level (zero) with the deck, the back would be .006" in the hole. This will cause loss of potential compression, uneven flame travel, and other flow issues. 2. The rings wont seal properly. 3. The pistons and rod bearings will wear prematurely. Just all around not a good situation.

I triple checked this thing to make sure i ruled out all factors. I made sure the pistons were square in the bores, double checked the compression heights on the pistons on both sides of the wrist pin and everything matched.

[chevetteman]

thanks for the info.
johnny