Engine Break-in Issue
- Thread starter Omni
- Start date
I just spotted this.
Never saw a big block Mopar with any amount of miles on it not have worn exhaust guides.
Good Morning
My 'hope' is to get it to the 1000 mile range. I can live with that.
I am 'on the fence' about removing the heads and just get new guides and the upgraded seals (the ones with the two wires).
The goal for the car is have a road-trip cruiser.
Omni
My 'hope' is to get it to the 1000 mile range. I can live with that.
I am 'on the fence' about removing the heads and just get new guides and the upgraded seals (the ones with the two wires).
The goal for the car is have a road-trip cruiser.
Omni
From what I've read several places AND from my late machine shop operative, if the clearance between the valve stem and the guide is more toward the bottem end of the clearance specs, then oil intrusion into the intake tract is minimized, even without valve seals. My late machine shop operative further elaborated that the guide needs a certain amount of oil in it anyway and to use a "better seal" to do that can reduce the amount enough to accelerate guide wear and make things worse rather than better. Plus that the "white scraper" seals keep too much oil out of the guide, which means they are for "race engines only", where the complete engine is frequently torn down and freshened between uses.
When stem-to-guide clearances get toward or past the top end of the specs, that's when the valve can wobble a bit as it goes up and down and then can also wobble a bit as the valve seats/closes. That wobble also decreases valve guide seal life, just as when the drive shaft yoke wobbles in its bushing in the trans tailshaft housing, that rear trans lip seal also quickly degrades. It's those valve wobbles which lead to burnt valves, by observation.
So, using the latest version of the OEM valve seals, very possibly with silicone in them, if not mostly silicone, might be investigated. In the case of Chry B/RB engines, the last-gen Chevy 454 went to orange silicone umbrella seals, which need to be trimmed to length to be used in the Chry B/RB motors (same valve stem diameter). My late uncle bought a new '74 Caprice 454. As it aged, it started to use oil, which was normal for them back then. It progressed until it was 1 qt/tank of gas. When he was moving from Virginia to Nevada, for his last duty station, he came by to see us. I asked our service manager about the oil use. He suggested those 454 orange silicone valve stem seals. So we installed a set. Between DFW and Las Vegas, not quite 1 qt of oil was used just from that one change. They were pleased. BTAIM
Enjoy!
CBODY67
John Kirby
Active Member
If the valve guides are worn it's likely the engine will backfire through the carb. If you have none of that I would discount worn guides. My engine used to backfire through the carb until I did a rebuild. Had the heads rebuilt with new guides and it never does it now. It wouldn't hurt to go to a better quality valve seal. A low cost attempt at fixing the issue if you replace them yourself.
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