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Tool Talk Discussion Forum

Grinding Valves

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Jeff McBride

06-29-2007 17:42:35




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Do they make a grinding stone for dressing up valve seats? I know about having a machine shop do it but what I want to do is just dress them up a little. Like you do the cylinders with a hone. If they do where can I get one? Auto parts store?
Thanks
Jeff




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Earl-IL

07-01-2007 11:57:33




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 Re: Grinding Valves in reply to Jeff McBride, 06-29-2007 17:42:35  
I would like to hear from some of the automotive ,heavy duty machine shop people on their valve grinding ,machining experience. I am retired automotive & heavy duty machinist. 40 yrs.I sold engine rebuilding equipment a few years. Yes I know about valve lapping, tri cutting seats.1 deg interferance angle.I have seen some terrible valve jobs the last few yrs. We have a wide range of engines running today. The engines of low rpm & light spring pressure seems to be a problem I see with valves not seating properly.Loose guides will make Tri. cutting a problem. Yes the diesel heads need to follow spec to the exact. Most heads that come into shops today need guide ,valves replaced due to wear or fatigue from high ex. temp.Springs need to be checked for seat pressures.Most cyl heads need to be resurfaced with the correct finish.Overhead cam engines with head warpage need to follow factory spec ,because if the gasket surface is off so is the cam bearing alignment. I am not much in favor of straighting of the alum heads.But shops are doing it today.Over the years I have talked to the major valve manufacures TRW, SEALED POWER, PERFECT CIRCLE, EATON about valve face finish. & about refacing a new valves .I have had many different reply. The exhaust valves with face coating we always chucked in the machine and ran a dial indicator to see if face ran true. If not we returned them as defective. The antique tractors everyone wants them to idle perfect.Go back to basics look for manifold warpage ,vacuum leaks.Use the old time vaccum gauge it will help you a lot.Timing, or maybe a leaky valve that was suppose to be perfect will hinder your rebuild. Thanks for your comments. Earl

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Joe(TX)

06-30-2007 15:20:14




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 Re: Grinding Valves in reply to Jeff McBride, 06-29-2007 17:42:35  
The stones come in a valve seat grinder set. They normally sell from $500 to $2500 used. Stone cost over $35 (the cheap part) and you need the pilots, drivers, and the drive motor are needed on top of that. Take the head to a shop. You will be money ahead.



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Jeff McBride

06-30-2007 06:51:41




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 Re: Grinding Valves in reply to Jeff McBride, 06-29-2007 17:42:35  
I think I may just take it to the shop afterall. I do want it to be right. Thanks to all.



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msb

06-30-2007 05:22:35




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 Re: Grinding Valves in reply to Jeff McBride, 06-29-2007 17:42:35  
Most manufacturers will tell you , DON"T use lapping compound. Wipe it off all you want and there will still be enough compound to keep right on cutting after the engine is reinstalled. They recommend the newer cutting style seat cutters and then use blueing to check the fit.



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Earl-IL

06-30-2007 13:41:18




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 Re: Grinding Valves in reply to msb, 06-30-2007 05:22:35  
Which manufacture is telling you to not use valve lapping compound? Thanks Earl



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Allan In NE

07-01-2007 05:01:17




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 Re: Grinding Valves in reply to Earl-IL, 06-30-2007 13:41:18  
All manufactures will tell you that.

Valves seal by using an "incidence angle", which is a different cut angle between the seat and the angle cut on the valve (usually 1 degree).

Lapping totally destroys that angle.

The practice is akin to repairing buggy wheels; just not done anymore, as it has outlived it's purpose.

Allan



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msb

06-30-2007 18:07:18




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 Re: Grinding Valves in reply to Earl-IL, 06-30-2007 13:41:18  
John Deere and General Motors. I worked for Deere several years and father in law was a service managere for a GM dealer for 30 years. He always insisted that all pistons be knurled too.



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Allan In NE

06-30-2007 03:37:31




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 Re: Grinding Valves in reply to Jeff McBride, 06-29-2007 17:42:35  
Jeff,

As always, this is just my opinion. But, you are getting ready to cut that engine's life by about 70%.

This isn't 1935 anymore.

That "refacing" of the seat is a 3-stone process, which puts the seating point exactly in the middle of the valve face for proper operation/cooling.

If you just re-dress the seat'valve, it would be about the same as "lapping" the valve. This is an old "Model A" repair. Worked fine on engines that turned 800 rpm and had a shelf life of 10 to 15,000 miles.

Good luck,

Allan

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buickanddeere

06-29-2007 21:35:05




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 Re: Grinding Valves in reply to Jeff McBride, 06-29-2007 17:42:35  
If it's diesel don't grind the seats & valves.



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Joe(TX)

06-30-2007 15:13:48




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 Re: Grinding Valves in reply to buickanddeere, 06-29-2007 21:35:05  
I have to disagree with buickanddeere It is just as imprortant to have good valve sealing on a diesel as a gasoline engine. Maybe more important.



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Allan In NE

06-30-2007 17:12:57




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 Re: Grinding Valves in reply to Joe(TX), 06-30-2007 15:13:48  
Joe,

What he is getting at is that on some diesels, you can't regrind the seats/valves as it lowers the compression too much by dropping that valve down in the hole too far.

Any IH tractor with a German engine is this way. Deck specs have to be exact on the darned things or they won't start.

Allan



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jdemaris

07-01-2007 06:27:03




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 Re: Grinding Valves in reply to Allan In NE, 06-30-2007 17:12:57  
Yes, and that's a particularly bad problem with some Deere engines. Valve-head depth in head is critical for good cold starting. Also, many automotive diesels, e.g. Isuzu and GM use a hard-surface Nitride process on the valves and seats that is ruined when ground.



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davejoe

06-29-2007 18:50:48




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 Re: Grinding Valves in reply to Jeff McBride, 06-29-2007 17:42:35  
your valve seat needs to be centered with the valve guide, without being accurate you might cause more of a problem than you have now. if lapping them does not handle your situation get them cut at a shop. dave



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LKM

06-29-2007 18:16:15




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 Re: Grinding Valves in reply to Jeff McBride, 06-29-2007 17:42:35  
If you want to just clean and face them up; after cleanng all the carbon deposits from chamber seats and valves and they have no bad burn spots or large pits, get some lapping compound at any auto supply. It usually comes in a can with both course and fine grit. Insert the valve through the guide,and hook your drill to the stem. Coat the valve face and while pulling gently lap them by frequently reversing direction and adding grit as needed. Throughly clean any excess grit off after lapping. A little effort will produce remarkable results.

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Jeff McBride

06-29-2007 18:54:36




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 Re: Grinding Valves in reply to LKM, 06-29-2007 18:16:15  
That is the answer I was looking for. Normally I take them to the shop but this one looks real good. The springs still have all the paint on them. One of the guides has broken off even with the top of the head. Will this be allright or does it need replaced?



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lucasss

06-29-2007 19:42:55




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 Re: Grinding Valves in reply to Jeff McBride, 06-29-2007 18:54:36  

you didnt say what engine it is,but id say yes that broken guide needs replaceing.



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Stumpalump

06-29-2007 19:04:41




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 Re: Grinding Valves in reply to Jeff McBride, 06-29-2007 18:54:36  
If Im doing an old lawn mower and don't feel the need for a shop I have been known to put some heavy emery on a flat surface like the table saw.
I chuck up the valve in a drill and spin it on the emery. Then I lap the heck out it. Works great for a mildly burnt valve on a Briggs.



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