Exhaust valves hitting pistons
#21
Senior Member
MASTER BUILDER
Join Date: Dec 2005
Location: Rutherfordton North Carolina
Posts: 192
We run the int clearance down to .040 on all our high compression stuff to keep from loosing c.c. and reduce the dome size. on the ex with .0765 you will get into trouble.As Ed said .100 is bare minimum with .125 preferred.
We are a W.D. for J-E and they are 3 weeks out but they have an expedited service if $$$ don't count. 7 working days is 25% more 5 working days is 40% more or 3 working days is 50% more.Bill
We are a W.D. for J-E and they are 3 weeks out but they have an expedited service if $$$ don't count. 7 working days is 25% more 5 working days is 40% more or 3 working days is 50% more.Bill
#22
Member
MASTER JOURNEYMAN
Thread Starter
Join Date: Oct 2004
Posts: 36
Thanks for the offer on the pistons Ed. We disucssed the the options of replacing just the two pistons and talked it over with Wade who does the balanceing for us, Harry over at HD Machine who was going do the valve pocket cutting and Mike at Chapmans. Wade said that it would not be a good idea to just replace the pistons and not rebalance the rotating assembly. And when I told Harry about the clearance I had, he told me just what Ed and Bill are saying. Made comment that I have been dodgeing the bullet for some time now. Harry said he set his clearances to .090" min.
So I have bought a new set of pistons and will start over and set all the clearances back to where they belong.
When the head gasket blew on the left bank, we had the heads resurfaced in Boise Id, (we were racing at Firebird in the Ignitor and didn't want to come home, so we repaired it in the trailer at the track) at a machine shop that a local racer suggested. The only thing I can think happened is that they machined more that the .009" that they claimed. And I have no one to blame other than myself for not checking the clearances after they machined the heads.
That is what happens when you get in a hurry. That is why I am using the backup engine and take my time with the main engine.
But HEY, thanks for the advice everyone. I have learned something again. This problem won't happen to me again.
So I have bought a new set of pistons and will start over and set all the clearances back to where they belong.
When the head gasket blew on the left bank, we had the heads resurfaced in Boise Id, (we were racing at Firebird in the Ignitor and didn't want to come home, so we repaired it in the trailer at the track) at a machine shop that a local racer suggested. The only thing I can think happened is that they machined more that the .009" that they claimed. And I have no one to blame other than myself for not checking the clearances after they machined the heads.
That is what happens when you get in a hurry. That is why I am using the backup engine and take my time with the main engine.
But HEY, thanks for the advice everyone. I have learned something again. This problem won't happen to me again.
#23
Senior Member
DYNO OPERATOR
Join Date: Feb 2006
Location: VA Hospital, Dallas, Tx (214 302 1924) cell-972-464-7400
Posts: 540
HEY, thanks for the advice everyone. I have learned something again. This problem won't happen to me again
Ed