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Valve Lapping Compound

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rkr29kracing

01-29-2008 13:50:39




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I am looking to lap my own valves at home on my C and B. I know some of you guys do this. Where do you buy your lapping compound/kit? Hopefully somewhere simple like Home Depot, NAPA, etc???

Let me know. Thanks.




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Steve E.

02-04-2008 20:43:53




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 Re: Valve Lapping Compound in reply to rkr29kracing, 01-29-2008 13:50:39  
allis in the 1970s at factory service school recommended not grinding interferance angles on valve and seats.you grind valves and seats and then allis advocated lapping.these engines were designed for leaded fuel,with unleaded gas and any heavy pulling just lapping will cause problems.also check valve guide clearance,to much will cause rocking of valve against seat causing premature wear.dick lemmon is pretty accurate in his statements.during the 1970s i was factory certified mechanic. ,

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tim[in]

01-30-2008 18:53:16




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 Re: Valve Lapping Compound in reply to rkr29kracing, 01-29-2008 13:50:39  
Wow! Sometimes after hearing all the "tiny" things on here i wonder if i wouldnt be better off having mine professionally overhauled. As much as i like tinkering i need my tractors to be reliable and this valve grinding i always thought thats what lapping valves was. I really want to overhaul at least one of my old allises. a wd wd45 and a D17.Wish someone would come out with a step by step book on overhauling these engines. I know from just talk on here the video is sadly lacking on things.

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Dick Lemmon

01-31-2008 09:13:00




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 Don't Be Discouraged tim in reply to tim[in], 01-30-2008 18:53:16  
All the little things! All the little things are called details. You can find details in all kinds of places. Some can only be found in parts catalogs if you have never worked in the field. There are details that are different from one engine to another in the same brand. I love to see a person of any age learn how to do something new and different to them. It is fun to see people make progress and have a successful complete project what ever that project may be.
Take lapping. What you seemed to think lapping was you most likely got from people talking about what they heard and was not applying it properly. Lapping is a finishing touch. Lapping compound is sandpaper in paste form. Lapping is placing the compound on the bottom surface placing the top surface on it and rotating it left right left right a few times. Remove the top surface, wipe clean, put a small amount of bluing on the top surface, placing the top surface on the bottom surface and without turning lift the top surface off the bottom surface. You then look at the transfer to see if you have an even transfer of bluing which shows if you have a seal or you need to repeat the steps again. It is not possible to control the angle of the seal when lapping a valve. To try to grind your valves with lapping compound, with enough time and compound, will dig a round groove as a seat.
This would get an engine running and you could get a high compression check but you have a temporary fix at best. This is learned detail that comes time and only one of many. In the early 1960's in a factory and be being the new guy on the job I was taught the art of lapping a 1/2" wide seal that was over 6 inches in diameter. The top weighing over 40 pounds. Over 20 hours on the first job. I could not let the full 40 pounds onto the bottom surface while turning.

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ihc49er#2

01-30-2008 08:38:39




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 Re: Valve Lapping Compound in reply to rkr29kracing, 01-29-2008 13:50:39  
as far as i know thats why valves are ground with an interferance angle- so they seat easily.valves 45 deg.and seats 44 deg.for example. also the seat is ground to a measured width.no need to lap valves, thats going back to the 1930s & 40s. you didnt say if your grinding them first or just lapping . i guess thats why some guys dont know what lapping is , is because its not done anymore. well thats my story and i will stick to this.

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Dick Lemmon

01-30-2008 10:30:49




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 Re: Valve Lapping Compound in reply to ihc49er#2, 01-30-2008 08:38:39  
It goes along with the thought that with some magic juice you can heal up a rusted cylinder wall with stuck rings. I have read it on the different boards for years that rather than spend the money you dont have to grind the valves that you can lap them in with some grinding compound. The thing is if they are not real bad and (you know how to use lapping compound/grinding compound) you can get the valves to seal up for a short time. Problem is very few know how to use or when to use lapping compound or even how to check to see when you have a good mating seal. I read one time about a guy lapping his valves and then a few days later he thought one of his valve stems were bent and was wondering how to remove the valve.
I tried to explain that you could not lap valves without removing the valve first and three guys told how they had done it successful without removing the valves. There is some good wrenchers out there that know how to lap valves without removing them and can fix a stuck engine with magic juice. I am now a believer dontchayknow

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Bob

01-30-2008 08:49:11




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 Re: Valve Lapping Compound in reply to ihc49er#2, 01-30-2008 08:38:39  
AMEN to that, ihc49er#2!

Have the valves and seats properly refaced. It's WORTH IT, in the long run!



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Chad B. Allis

01-30-2008 07:07:50




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 Re: Valve Lapping Compound in reply to rkr29kracing, 01-29-2008 13:50:39  
Showing my ignorance here - what is lapping of valves?

Thanks!



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mlpankey

01-30-2008 08:04:38




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 Re: Valve Lapping Compound in reply to Chad B. Allis, 01-30-2008 07:07:50  
valve lapping usually occurs after valves have been ground . it mates the cut valve better to the ground seat. always some difference in seat cutter to valve cutter and lapping takes care of those differences.



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DARDAN

01-29-2008 22:03:24




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 Re: Valve Lapping Compound in reply to rkr29kracing, 01-29-2008 13:50:39  
After you're finished lapping be sure to carefully clean everthing VERY thouroughly. A little of that grit in the wrong place can't be good.



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Jeff Z.

01-29-2008 19:07:33




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 Re: Valve Lapping Compound in reply to rkr29kracing, 01-29-2008 13:50:39  
NAPA does have it. I use their water base.

Went to Autozone for a lapping tool and compound awhile back. They had the tool but said they didn't sell the compound.
I told them that is about as dumb as going to a drug store to buy a tooth brush and having to go to another store to get the paste.

Got a dumb look.



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Dick L

01-29-2008 16:01:11




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 Re: Valve Lapping Compound in reply to rkr29kracing, 01-29-2008 13:50:39  
When you pick up your lapping compound make sure you ask for a tube of blue. No way you can tell if you have them lapped in without blue.



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El Toro

01-29-2008 14:26:09




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 Re: Valve Lapping Compound in reply to rkr29kracing, 01-29-2008 13:50:39  
Your Napa store should have it. Hal



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