Cut Pistons w/ Epoxy = Pinging???
Cut Pistons w/ Epoxy = Pinging??? I have been tuning on a friends 99 h/c c5 corvette and have been running into kr no matter if I set the wot timing at 25, 27, 0r 30. We have been running into kr with a ported stock maf sensor and then an untouched pro auto tech maf sensor.
When he put the cam in with his heads which are milled 30 thousanths he decided to flycutt the pistons. When he cut the pistons he cut them too deep and decided to fill them ever so slightly with epoxy. My thoughts are that the epoxy is causing hot spots on the pistons which in turn is causing pinging and kr.
I have been using a LM1 Wideband and his a/f ratio started off at 11.8-12.0/1 to a now 12.5-12.7/1.
P.S. We are pretty much getting the same kr and pinging at all different timing levels. Also, this pinging and kr is only at wot, although I did see a very short occurence at part throttle.
What are your guys thoughts.
When he put the cam in with his heads which are milled 30 thousanths he decided to flycutt the pistons. When he cut the pistons he cut them too deep and decided to fill them ever so slightly with epoxy. My thoughts are that the epoxy is causing hot spots on the pistons which in turn is causing pinging and kr.
I have been using a LM1 Wideband and his a/f ratio started off at 11.8-12.0/1 to a now 12.5-12.7/1.
P.S. We are pretty much getting the same kr and pinging at all different timing levels. Also, this pinging and kr is only at wot, although I did see a very short occurence at part throttle.
What are your guys thoughts.
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What a stupid idea. He might as well have used play-doh. I bet if you check the epoxy has blown right off (hopefully not getting caught on any valves on the way out, and is not only causing hotspots, but also much much more damage. Nice.
Originally Posted by sleeperstyle
im thinking false knock- but there is such a thing as rich knock..
If so, that's incorrect. More fuel resists detonation. Thus if you're adding more fuel you're less likely to have knock.
The epoxy must be vaporized by now. I think the good stuff is good to like 350 degrees, but the pressure and heat expansion have destroyed it without a doubt, and I would doubt that any damage occured.
Sounds like a bad knock sensor, or an aftermarket pulley to me.
Dale
Sounds like a bad knock sensor, or an aftermarket pulley to me.
Dale
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I doubt if the epoxy has completely vaporized. It has probably carbonized and probably cracked. Even "normal" carbon deposits can increase the compression ratio and act like the glow plugs used to start a diesel.
There are probably big ol' glowing hunks of carbon where the epoxy used to be, causing pre-ignition.
If there's enough carbonized residue on the valves, they may not be sealing properly and could be glowing too.
There are probably big ol' glowing hunks of carbon where the epoxy used to be, causing pre-ignition.
If there's enough carbonized residue on the valves, they may not be sealing properly and could be glowing too.
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Originally Posted by DAPSUPRSLO
I have been tuning on a friends 99 h/c c5 corvette and have been running into kr no matter if I set the wot timing at 25, 27, 0r 30. We have been running into kr with a ported stock maf sensor and then an untouched pro auto tech maf sensor.
When he put the cam in with his heads which are milled 30 thousanths he decided to flycutt the pistons. When he cut the pistons he cut them too deep and decided to fill them ever so slightly with epoxy. My thoughts are that the epoxy is causing hot spots on the pistons which in turn is causing pinging and kr.
I have been using a LM1 Wideband and his a/f ratio started off at 11.8-12.0/1 to a now 12.5-12.7/1.
P.S. We are pretty much getting the same kr and pinging at all different timing levels. Also, this pinging and kr is only at wot, although I did see a very short occurence at part throttle.
What are your guys thoughts.
When he put the cam in with his heads which are milled 30 thousanths he decided to flycutt the pistons. When he cut the pistons he cut them too deep and decided to fill them ever so slightly with epoxy. My thoughts are that the epoxy is causing hot spots on the pistons which in turn is causing pinging and kr.
I have been using a LM1 Wideband and his a/f ratio started off at 11.8-12.0/1 to a now 12.5-12.7/1.
P.S. We are pretty much getting the same kr and pinging at all different timing levels. Also, this pinging and kr is only at wot, although I did see a very short occurence at part throttle.
What are your guys thoughts.
Put your tools down and back away from the car!
Wash This is not my car guys. Actually my car runs 11.62 with nothing more then a cam, boltons, m6, and at 3545 raceweight so I can assure you mine runs fine. The car I speak of is a 99 corvette.
This nock is not false, I can hear the car pinging. I will have to get back to him and get back to you guys on the kind of epoxy he used and its heat qualities. I still think this is his problem.
Anybody ever had any experience with the pro auto tech maf sensors? I don't think this is his problem but I am just curious.
This nock is not false, I can hear the car pinging. I will have to get back to him and get back to you guys on the kind of epoxy he used and its heat qualities. I still think this is his problem.
Anybody ever had any experience with the pro auto tech maf sensors? I don't think this is his problem but I am just curious.
Originally Posted by washguy
Put your tools down and back away from the car! Wash
Wash TECH Addict
Joined: Feb 2004
Posts: 2,826
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Originally Posted by DAPSUPRSLO
This is not my car guys. Actually my car runs 11.62 with nothing more then a cam, boltons, m6, and at 3545 raceweight so I can assure you mine runs fine. The car I speak of is a 99 corvette.
This nock is not false, I can hear the car pinging. I will have to get back to him and get back to you guys on the kind of epoxy he used and its heat qualities. I still think this is his problem.
Anybody ever had any experience with the pro auto tech maf sensors? I don't think this is his problem but I am just curious.
This nock is not false, I can hear the car pinging. I will have to get back to him and get back to you guys on the kind of epoxy he used and its heat qualities. I still think this is his problem.
Anybody ever had any experience with the pro auto tech maf sensors? I don't think this is his problem but I am just curious.
Run the engine and pull the oil cap and see if she's smoking inside (keep your face away from the hole). You can also check the cylinders and see if they lose compression.
I don't know much about these maf sensors, they seem to be a corvette only product. We had pinging with a stock ported sensor also. I will check on it. Hell, maybe I'll try to get him to find a stock maf and try that although I don't think that is his problem but hopefully for him it is. Thanks guys, keep the replies coming.
Originally Posted by slow
pro auto tech maf sensors .... more info on this product?
most likely this has something to do with your detonation problems.
Ryan
most likely this has something to do with your detonation problems.
Ryan
I would say its hot spots caused by the epoxy...Holy crap...I can't believe he used epoxy on his pistons. Combustion temps would immeditately soar way beyond the limits of any epoxy. Also, who knows how the epoxy (or whats left of it) transfers heat, so again, localized hot spots.
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If you went through the piston, that is very very bad. I can't honestly believe anyone would use expoxy. I'm honestly suprised its held together. Have you thought about putting the stock MAF on there to check for KR with it. But no matter what, the motor needs some attention...
BTW, What was this guy thinking. Most valve reliefs are .60 to .80 at the most. The piston is like .220 -.250 so you have to really try to cut that deep...
BTW, What was this guy thinking. Most valve reliefs are .60 to .80 at the most. The piston is like .220 -.250 so you have to really try to cut that deep...
Custom grind that I came up with. 230/236 107lsa 107icl 576/574.
We are going to try the stock maf and see if that helps although I don't see how it could as his a/f was never leaner then 12.7 to 1.
He is going to be running the 402 slp shortblock soon anyway so it is no big deal but if he pulls the heads I would be glad to take pics. Thanks guys.
Originally Posted by un4giv3n
off topic... what cam are u running?
We are going to try the stock maf and see if that helps although I don't see how it could as his a/f was never leaner then 12.7 to 1.
He is going to be running the 402 slp shortblock soon anyway so it is no big deal but if he pulls the heads I would be glad to take pics. Thanks guys.
