Valve Grind a must at Head Gasket replacement? (1 Viewer)

[Flyin Tyes]

Pros Cons on not grinding valves at head gasket replacement?
Is there a risk of early ring failure if you do it?

Are the valve seals at risk and will fail soon?
I would think the head will function better if the valves seats mate like new.

I've been warned that it may cause ring failure and I shouldn't.
Others obviously would do it.
Not sure now and could use some suggestions.

History:
Discovered coolant in my oil and white smoke.
I took my head off, ordered gasket kit and other misc. parts to replace while doing the work. I took the head to a local crank and head grinding shop. I asked that they clean and scrape the gasket marks off the head. I didn't know if i was going to have the valves ground and reworked. Frankly this isn't something I have done and don't have the tools either.


1994, 160,000 +/- miles
Basically Stock

 

[IdahoDoug]

In a worn engine there is blowby via the valve seats, valve seals and rings. I get that renewing the valves means slightly higher cylinder pressures and theoretically more blowby past the rings. I say theoretically because it stands to reason but I've never seen test data on it. Let's accept it for purposes of discussion, though.

More blowby means more combustion byproducts passing through the rings so perhaps there is something to it. However, weak rings also pull more oil and oil vapors up from the crank case and that stronger cylinder pressure would cause an equal increase in cylinder vaccuum when the piston is on the down stroke. Meaning there's more oil lubing the rings which causes a reduction in ring wear. So, I'd call it a wash in terms of the rings. I don't buy the ring failure issue.

Having the valve seals and seats renewed will provide smoother and more economical operation, and help ensure you don't have valve train issues over the next 160,000 miles. Since the head's off and it may never be off again I'd be inclined to invest the $150 added cost or so if you're going to keep it.

DougM

 

[Flyin Tyes]

Thanks Doug.
I removed the valves and will be getting the grinding done this week.
I am glad I took them out, as a cleaning seamed due. although everything looks like normal wear.

Anyone have recommendations on a quality grinding shop in Salt Lake?
Jake

 

[Flyin Tyes]

So the shop i am planning to use is likely going to tip the valve to compensate for the grinding.
as the guy thinks this will be better than trying to get new shims.

I guess i will wait to see what happens with the measuring and grinding and what they think before i order any new valves or shims as they could run me another couple hundred bucks.

 

[Bearcat80]

So the shop i am planning to use is likely going to tip the valve to compensate for the grinding.
as the guy thinks this will be better than trying to get new shims.

absolutely do this! I had to wait for some shims that were made from unobtanium because I saved a couple of bucks not getting the valves tipped.

 

[Flyin Tyes]

my local toyota dealer asked for my vin number when i asked about valve shims.
I am worried that i won't be able to find that "thinner wafer/ shim" that might be needed by ordering the original shims?
The mechanic at the head shop seconds this concern.

In speaking with the mechanic he said if there wasn't a lot of pitting at the valve seat and the head gasket was the known failure then grinding the valves could be done but isn't necessary.
he recommended i measure the clearance with a feeler gauge and adjust the shims as necessary to achieve proper clearance.

 

[Bearcat80]

The easy way to test is to pull the head and lay it on the bench upside down on some towels.
Pour some water in the compression chamber and then wrap an air nozzle with a shop towel stick it in each exhaust port or intake port and blow air. If your valves don't seal, you will get air bubbles. That being said, if it runs good now, it's probably not really necessary. If you don't do a valve grind, the HG is a one weekend affair.
As far as ordering shims, it's not that bad, as you wind up reusing most of your old ones in different spots. There's always one that's not in stock locally. My mistake was not ordering them from Cruiserdan.

 

[Flyin Tyes]

Status Update...
After talking to the head shop I was planning to go to for the valve grinding and explaining the situation they thought i would be better to not grind the seats. The pits in the exhaust were very minimal and none at the intake side. I hand lapped the seats with the valves and grinding compound and installed the new oil seals that came in the gasket kit.
I finally got everything back together yesterday afternoon and it started right up.
Scared me a bit to see so much white smoke from the tailpipe after about 2 miles of driving. but the smoke is done and it seems to be running better than the day I bought it. Hopefully this continues.
Thanks to all for the advice.

 

[Rookie2]

The easy way to test is to pull the head and lay it on the bench upside down on some towels.

Be sure to reinstall the camshafts before turning the head upside down, elst the plunking sound you'll hear are the shims and followers sliding out of the head. It's real fun trying piece back which one goes where.



I'm not sure I completely follow the OP's decision tree here, but ultimately what you decided to do was... instead of having the head reworked, you had it cleaned, replaced the valve seals yourself and skipped the valve grind and subsequent need for tipping or shim replacement?

 

[Flyin Tyes]

Be sure to reinstall the camshafts before turning the head upside down, elst the plunking sound you'll hear are the shims and followers sliding out of the head. It's real fun trying piece back which one goes where.



I'm not sure I completely follow the OP's decision tree here, but ultimately what you decided to do was... instead of having the head reworked, you had it cleaned, replaced the valve seals yourself and skipped the valve grind and subsequent need for tipping or shim replacement?

on the decision tree...
I decided not to do the full grind after talking it over with a the shop and my father in law who has rebuilt quite a few motors. He looked at the valves and valve seats and after I lapped them myself there wasn't any pitting.

 

[Bearcat80]

Be sure to reinstall the camshafts before turning the head upside down, elst the plunking sound you'll hear are the shims and followers sliding out of the head. It's real fun trying piece back which one goes where.

Right, forgot about that part. I had already taken the shims and pucks off prior to the flip. Someone who hadn't already done so could have been playing musical shims wthout your advice. Thanks.

 

[jlg32281]

On a Supra head (very similar), I was swapping cams and put it all back together to get a horrible noise on the first start up. One of the shims broke (guess I put it in the wrong spot) and chewed up one of the cams, not cool. I will definitely make sure to keep track of what goes where.

 

[baxter650]

I agree with what your mech. said, i pulled the valves and with a fine lapping compound hand lapped to check the condition of the seats.
Mine did not need any further work (179K)

 

[NaterGator]

Did you do a compression test before you started?

I've got lowish compression in #2 cylinder and I may just go "all the way" and replace the rings once I commit to the HG job. I guess it will depend on what I see re: the cylinder wall, but IMO if your compression is within spec and your cylinder walls look as good as most 1FZs seem to be, I'd not hesitate to grind the valves.