Piston to valve contact, are my pistons trash now?
08-13-2009, 08:36 PM
#1
Piston to valve contact, are my pistons trash now? I acidentally over boosted the other day, it was only for a very short moment though. As some of you suggested I pulled all the plugs and did a compression test. I did 2,4,6,& 8 one day and did 1,3,5,&7 the next. Plugs all looked great, no issues what so ever. Thought I may have seen a ringland trying to lift up on #7 with my bore scope but when I got the head off it turns out that it was just a light mark made by the bore scope. What I did find was 3,5,&7 were all smacked by the exhaust valves. My compression test readings were low but I just attributed that to my cheap auto zone guage, the readings were all within 15psi, lowest being 115 and highest being 130. I was getting ready to put on some 317's but now I'm not sure if I need new pistons or not. 
08-13-2009, 09:33 PM
#3
If the pistons aren't cracked and the lands are fine, there is no reason to replace them. You can grind out any small (heck even some larger) nicks and polish them.
Make sure and check the valves very closely to make sure they still seat fully. Also, pull the pushrods and check to make sure they are straight (rolling them on a flat surface works just fine).
Make sure and check the valves very closely to make sure they still seat fully. Also, pull the pushrods and check to make sure they are straight (rolling them on a flat surface works just fine).
08-13-2009, 10:00 PM
#4
I'll get some up tomorrow, it was 3 pistons on that side and I'm sure there will be some on the other side.
I think these "custom valve releifs" were from my nitrous days before the turbo, I think I have been running it this way for a while now. Back then I raised my rev limit higher than I felt comfortable with because of some strong suggestions from non LSX nitrous guys I lowered it when I pulled the gas off.
I did roll the pushrods on glass and they are in good shape. The valves look a little funny but I cant really tell if they are bent. I have another set of (317) heads with valves that I plan on having Patriot do a valve job on before I slap them on if the pistons can live a little longer.
If the pistons aren't cracked and the lands are fine, there is no reason to replace them. You can grind out any small (heck even some larger) nicks and polish them.
Make sure and check the valves very closely to make sure they still seat fully. Also, pull the pushrods and check to make sure they are straight (rolling them on a flat surface works just fine).
Make sure and check the valves very closely to make sure they still seat fully. Also, pull the pushrods and check to make sure they are straight (rolling them on a flat surface works just fine).
I did roll the pushrods on glass and they are in good shape. The valves look a little funny but I cant really tell if they are bent. I have another set of (317) heads with valves that I plan on having Patriot do a valve job on before I slap them on if the pistons can live a little longer.
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08-14-2009, 07:08 PM
#10
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Thats a bit more than a kiss !!
I would be checking for bent valves.
N/A i would maybe run them again, but seeing as they are factory pistons which aren't the strongest on boosted cars at the best of times i would be a little nervous re-using them.
Might be a good time for forged pistons and rods, least you'll be able to crank the booost up then, so not all bad.
I would be checking for bent valves.
N/A i would maybe run them again, but seeing as they are factory pistons which aren't the strongest on boosted cars at the best of times i would be a little nervous re-using them.
Might be a good time for forged pistons and rods, least you'll be able to crank the booost up then, so not all bad.
08-14-2009, 07:42 PM
#11
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Hell I call that flycut. We've had a couple stock motors with pistons that looked just like that with no problems. None of them were boosted though. I think you should be fine as long as you keep the boost resonable. I'm sure the valves and pushrods are toast though.
08-14-2009, 09:21 PM
#12
Nope the pushrods are straight, as I posted above I rolled them on glass and they are good. I really think I have been running it this way for a while, the valves may be bent but I'm not worried about these heads.
I'm pretty torn between running these pistons and spending almost 3k I dont have on new rods & pistons.
I'm pretty torn between running these pistons and spending almost 3k I dont have on new rods & pistons.
08-14-2009, 10:55 PM
#14
08-15-2009, 12:15 AM
#15
You could pull the valve on the worst looking cylinder and have it crack tested. Since the heads are off I would just replace those valves and add some stronger springs if possible. Check the guide clearance and replace the seals while you're at it. I suspect the pistons are fine.
Jim
Jim
08-15-2009, 06:46 AM
#16
You could pull the valve on the worst looking cylinder and have it crack tested. Since the heads are off I would just replace those valves and add some stronger springs if possible. Check the guide clearance and replace the seals while you're at it. I suspect the pistons are fine.
Jim
Jim
08-15-2009, 09:58 PM
#20
I think I'm gonna pull the other head & if the worst are a few valve dents I'll have Patirot get my 317 heads ready and I'll put them on and run it like that for a little while. I go to the track about twice a year and I dont drive it hard on the street at all so I think I can make it live a little while longer.
