Valve marks on pistons?

[icanfixall]

Thats a really bad sign on those pistons. I'm with typ4 about the gear timing being off one tooth or the oil pressure regulating plunger may have stuck closed. A bore scope may help but it may not. I'm afraid the front covr may need to come off to see the timing marks. This is what they look like when they are correct.

 

[hesutton]

Holy crap! That's scarey man. My WAG is also with cam to crank timing. Worn guides can let the vavles get stuck on the seat, but that would not put a uniform, slight imprint on the both the intake and exhaust valves and not on mulitple pistons. It would put a nasty gash in the piston and end your day.

You have to pull the front cover. Have to. You need to know for certain the timing of the crank to cam gears. If you haven't planned on it already, I'd get new valves, rockers, springs, guides, and push rods. I'd be concerned all the parts of the valve train may be damaged.

Heath

 

[Drew2010]

Holy crap! That's scarey man. My WAG is also with cam to crank timing. Worn guides can let the vavles get stuck on the seat, but that would not put a uniform, slight imprint on the both the intake and exhaust valves and not on mulitple pistons. It would put a nasty gash in the piston and end your day.

You have to pull the front cover. Have to. You need to know for certain the timing of the crank to cam gears. If you haven't planned on it already, I'd get new valves, rockers, springs, guides, and push rods. I'd be concerned all the parts of the valve train may be damaged.

Heath

My other heads will be all redone, these heads will not be used again. Already have new springs (comp 910's), new melling rockers, should I get pushrods and lifters also? I have the pushrods and lifters from my old engine. Could I use those? Perhaps make sure and check all push rods for straightness.

I have concluded that I will pull the front cover. The gasket kit for it is only $20 bucks so its just more time. but I agree, the piece of mind of knowing it is right or wrong is worth the time. I try and get it off today, then I will post up my findings.

 

[PwrSmoke]

Depending on how long you've had this truck, its sometimes hard to figure what was done before and it shouldn't be taken for granted. I would recommend measuring valve protrusion as well as head thickness and piston height before bolting the heads back on. Also crushed head gasket thickness (as best you can). If nothing obvious is found, then check the oil pressure as noted. I know next to nothing about the type 4 cam but if some of the clearances above are off, the extra lift could be just enough to throw it over the edge where it wouldn't on an engine whose clearances were all correct.

Whoops, I didn't look at page 2 but my question is whethr this engine would run and apparantly run well, with cam timing off a full tooth... how many degrees is that? Anyway, we'll know soon enough I guess. Be interesting to see (for us anyway, Drew, you gotta be on the edge of hershey-squirting by now ( : < ). Good luck

 

[Drew2010]

Depending on how long you've had this truck, its sometimes hard to figure what was done before and it shouldn't be taken for granted. I would recommend measuring valve protrusion as well as head thickness and piston height before bolting the heads back on. Also crushed head gasket thickness (as best you can). If nothing obvious is found, then check the oil pressure as noted. I know next to nothing about the type 4 cam but if some of the clearances above are off, the extra lift could be just enough to throw it over the edge where it wouldn't on an engine whose clearances were all correct.

I just put this engine in about 2000 or 2500 miles ago, before that, I tore it all down and re-gasketed everything, there were no issues like this then. Something had to of happened, I can almost guarantee that the timing gears were lined up properly, but I cant rely on my thoughts, I need to check it again, if the cam gear is aligned properly, I will have to see about getting a magnetic dial indicator and check on the cam or lifters for lift specs.

By the time this is all over and done with, I am going to have to drive an IDI FOREVER... because I will pretty much know everything inside and out. lol

 

[hesutton]

Yeah, I'd certainly check the push rods for straightness. As far as the lifters. You've got it down this far, you might as well have a look at them.

Heath

 

[Drew2010]

Yeah, I'd certainly check the push rods for straightness. As far as the lifters. You've got it down this far, you might as well have a look at them.

Heath

how do you determine if a lifter is bad?

 

[typ4]

was the key on the cam before the gear got pushed on?

 

[hesutton]

how do you determine if a lifter is bad?

If they have a significant wear edge on the body (from moving thousands of times in the lifter bores) that may cause them to bind in the bore. Flat spots on the rollers. I've never torn one down, but Russ has. I'm sure he'll be along shortly with some more info on that.

Heath

 

[typ4]

they dont stick externally but the inside will varnish up, I took mine apart and cleaned them and polished with 400 grit, because the new replacements had bushings in the roller not needle bearings.

 

[Drew2010]

was the key on the cam before the gear got pushed on?

yes sir. its in there

 

[Drew2010]

well guys. I got the front cover off just now and guess what. The timing gears are in fact lined up. So timing is apparently out of the question

Back to any other ideas...

 

[typ4]

yes sir. its in there

just checking its happened before.

 

[Drew2010]

okay guys so now it looks like its down to springs or the oil relief sticking.

is there a way to check the relief w/o running the engine?

 

[riotwarrior]

pushrod length could be an issue if too much was machined...
JM2CW...