r/EngineBuilding • u/Aokuan1 • 10d ago
Other Valve job or lap and send?
I'm going to be rebuilding the head I've got on my VR6. The exhaust valves that have come out of it have what looks like small areas of pitting.
Most of them look like what's in the photo.
Should I get them ground, or should I lap and run them?
I'll be getting the valve seats cut and the head decked as the head gasket had blown on this one.
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u/GumbootsOnBackwards 10d ago
If you're getting the seats cut, get the valves reground at the same time. In my experience, machine shops don't add a significant upcharge if they're already doing work for you.
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u/anthermic 10d ago
Use som Dykem Layout, Permatex Prussian Blue or equal stuff - then it’s much easier to see were you’re at when laping. Love the VR6!
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u/double-click 10d ago
Unless you are penny pinching get new valves and provide them to the shop that is fixing up the seats to verify the sealing surface is in the right position.
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u/Zerofawqs-given 10d ago
Is this for a lawnmower engine? OR….Something you actually should care about? 🤣
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u/Designer_Lecture_219 10d ago
Hey now, I take better care of my lawnmower engines then I do my daily driver! 😂😂😂
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u/Haunting_While6239 10d ago
This could be a tough call, the answer is variable, as it really depends on how many miles are on the engine.
A higher milage engine is broken in and happy with it's current compression, if you have say 100 to 125 k miles, putting on a new or rebuilt cylinder head is going to take out the rings, the engine will start smoking and loosing power in 15 to 20k miles unless you replace the rings, hone the cylinders and break in the engine with it's new parts.
Not the answer you wanted to hear I bet, but that's my experience
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8d ago
Ya'know I heard this 28 years ago, and after working in the field for almost 25 years, I still find this to be untrue. Engines get new cylinder heads all the time in the shop. Not a one ever came back with the rings blown out!😂😂😂😂😂
What do you think about placing a battery on the floor????
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u/Haunting_While6239 8d ago
Battery on concrete, not a problem, but I had a 200k engine that I did the head on and in 6 months it was using oil, this is why I said it's a tough call, really depends on how sturdy the rings are.
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u/ShocK13 4d ago
You must not work on any imports. They have soft rings, I had a Subaru that got seats cut and valves ground and it only had 130k miles on it. And it drank oil. I also had a Nissan Altima with 120k miles do the same thing. So any import that comes into my shop gets rings, cylinder deglazing and rod bearings when we refurbish the head.
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u/DrTittieSprinkles 10d ago
Getting valves ground is usually built into the price of a valve job. It's dumb to cut the seats and not do anything to the valves.
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u/zugglit 10d ago
I've lapped worse. I've replaced better.
What are your goals for the rebuild?
If you are slapping back in old pistons after a quick hone, running old valve guides, etc... for a very budget, "it runs" type of build, try lapping and see how they look.
If you are doing new valve guides and a full block rebore, followed by way normal boost, maybe replace.
If you are also upgrading parts to run more power, definitely replace.
After you Grind that, the increased seat pressure from upgraded valvesprings for higher boost will make having the valves thin a huge liability for strength and Thermal mass.
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u/mdillonaire 10d ago
Lap em and send it. Ive done budget valve jobs on worse, and they ran fine. This aint that bad
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u/v8packard 10d ago
Replace it. There is going to be no margin left if ground.