JC Perf? Raylar? Anyone got a clue?

[txriverrat2001]

A good friend of mine came by last night while changing the plugs in the NorTech and had his exhaust valve guides in his hand - had a pushrod break and discovered this after replacing the pushrod and lightin it back off. Both come from #4 & #6. The pictures suck - but you can see where it peeled the guide back like a banana peel. It looks like on one of them someone took a torch to it. The part that is peeled up/broke faces the exhaust header - so you see it directly with the header off - if you know what I mean. The only thing he thought was odd was that after a couple of hard runs (5800 - 6000) the inside header would steam a bit - but the engine temps were fine. Tops of the pistons are identical to the rest on that bank - plugs are all the same color - no indication of it leaning out or getting water as everthing is still "sooty".

Have you ever seen one peel up like that? If so - what caused it?

[Airpacker]

My first though is that the guide stuck to the valve. the valve drove the guide down where it lodged and then the tulip split the guide when the valves were repeatedly trying to close.

[Ted]

I would be looking for lean outs in those cylinders at high rpms. Were the engines dynoed with EGT probes?

[txriverrat2001]

My first though is that the guide stuck to the valve. the valve drove the guide down where it lodged and then the tulip split the guide when the valves were repeatedly trying to close.

The guides were still in the original place .....

[MERPerformance]

Are those guides from an alum. head? If they are where is the step on the guide? If those guides came out of the head I would guess the fit was to loose, sometimes when guides are driven out they remove the material from the head, then if you reinstall them the fit is loose. If they drive out easy they need to be over sized. I always heat my heads before installing new guides, plus they stay straight on the I.D. before sizing them. also ifthe valve wastight in the guide it would stick than the piston would bend the valve, not remove the guide from the head. Any more info on this would help.

[GB]

Great tip thanx

[MERPerformance]

I looked at those guides again, after a good nights rest. Exhaust as you say; still in the same location not moved from the boss. The guide from what I see is a intake guide , has a taper on the end, right? It lookslike someone used the wrong guide first of all then they installed it and allowed it to hange in the exhaust port not cutback to the port roof. This is going to put it in the HOT ehaust flow and make it brittle, crack and break. Just a .250" will split and crack the guide. ARE THE EXHAUST GUIDES OVER LENGHT IN THE PORT?

[OBNOXUS]

. ARE THE EXHAUST GUIDES OVER LENGHT IN THE PORT?


What he said !!!

[txriverrat2001]

sorry it took so long to get back - It appears the problem had to do with the programming - it's a really long story, but basically while dyno'ing the engines the tuner adjusted a timing compentsation table when the motor was making boost and never removed it (had a couple of meltdowns before that issue was resolved) ... thus building a bunch of heat, stickin the guide, pullin it down, and slammin the valve back up against it.....

Heads have been gone through - timing compensation crap removed - should have it back in the water in the next week or so.....

[Chris]

You still shouldn't have pulled the guide out of the head. I would check them all for fit and length.

[Knot 4 Me]

When I stuck a valve in the guide it did not pull the guide down, it simply bent the pushrod. Weird that it pulled it down...

[Chris]

That's what I mean- if properly installed, there are other things in the valve train that would fail first. Like the pushrod.