Lapping in valves

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1930

1930

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I thought it best to start a new thread, less confusion.

Id like to hear everyones technique for lapping in the slant valves.

It was suggested to get some permatex lapping compound from Napa, I called Napa and evidently the oil based lapping compound is no longer avail, only a water base which I have read on-line is next to useless.

I can get some compound off of e-bay it looks like but evidently there are many different grits from start to finish and everything in between.

I did find this useful thread whilst doing a search. http://www.slantsix.org/forum/viewtopic.php?t=14394&sid=959f3987bede409291b85587dc9512fe

http://www.slantsix.org/forum/viewtopic.php?t=30918&sid=a50a2c1a25ad64e22514dd02a052cacf

Thanks for any advice
 
66fs said:
Are you trying to Lap the valves instead of doing a valve job?
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Yes, I would like to learn how to lap the valves. I am working on getting a slant engine together and running merely for the experience. I am not looking for any sort of longevity necessarily.

I have another slant project I have been working on for some time that I am being more cautious with in regards to repairs.
 
I have used the water based compound on a few heads and it works fine.
 
It is easy to lap valves, I lap them to check my valve jobs. It is pretty time consuming to seal the valves that way. To get the suction cups to work, you should clean the valves up, both sides of the head. I use a wire wheel on the valve head and stem in the valve bowl. I try to minimize contact with the stem that contacts the guide. Lapping just a little bit will give you a good Idea of where the valve is not sealing. Typically the exhaust valves stem and guide will be worn out of tolerance with the intake stem and guide being pretty good. Water based compound is fine for lapping.
 
Ok, Ill check it out than, thanks everyone

Id like to know though still/also why there are various grits of lapping compound, only makes sense that the coarser the grit the faster its going to cut. I guess I need to look for very f^ valves or vale seats whilst doing this and should consider a coarser compound if needed?

There are alot of videos on U-tube that show steps.
 
Felpro also sells lapping compound it is a oil base compound I use 180 grit everyday and it works great you will also need some Diken Machinist Dye, but this is not a substitute for a valve job you can never fix worn valves and or worn valve guides. Good Luck
 
Still looking into the whole procedure, evidently it would be best that I do a leak down test with soap and water ( or just water ) to determine which valves ( other than the obvious ) is not sealing properly.

I will do this test first, mark the ones needing extra attention and go from there.
 
hemi446 said:
Felpro also sells lapping compound it is a oil base compound I use 180 grit everyday and it works great you will also need some Diken Machinist Dye, but this is not a substitute for a valve job you can never fix worn valves and or worn valve guides. Good Luck
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Im not looking at it running top notch, if I was than I would have the head gone thru properly, I am just trying to gain some experience with what I can do myself.
 
Lapping valves yourself is pretty hard-core. I have always been amazed how cheap it is to get heads rebuilt at a shop, even w/ hardened seats installed (consider that if you don't have, to run unleaded gas). My understanding is that shops no longer lap valves, they just rely on the accuracy of the grinding machines.
 
Y'all need to settle down, I've lapped several heads with permatex and they came out real good.

I'm a firm believer in the backyard hone, re-ring, bearing, lap and go. Contrary to the majority of thought around here, not every job has to visit a machine shop. Some folks want the experience.


Start with heavy compound, act like your starting a fire with a stick, lift and tap ever 5 seconds to keep the compound in the valve, and when the grit stops working, inspect the valve.


Once the valve looks uniform switch to the lighter grit, and do the same action, you'd find out the grit stops working when the surface finish is where it needs to be.

Go back and forth between grits until it looks uniform and clean.

Inspect the valve and make sure there aren't any pits in the valve or the seat that aren't smoothed out real nice.
 
PoisonDart74 said:
Y'all need to settle down, I've lapped several heads with permatex and they came out real good.

I'm a firm believer in the backyard hone, re-ring, bearing, lap and go. Contrary to the majority of thought around here, not every job has to visit a machine shop. Some folks want the experience.


Start with heavy compound, act like your starting a fire with a stick, lift and tap ever 5 seconds to keep the compound in the valve, and when the grit stops working, inspect the valve.


Once the valve looks uniform switch to the lighter grit, and do the same action, you'd find out the grit stops working when the surface finish is where it needs to be.

Go back and forth between grits until it looks uniform and clean.

Inspect the valve and make sure there aren't any pits in the valve or the seat that aren't smoothed out real nice.
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Yeppers,my kind of build...
FWIW,O'Reilly's does make a rough/smoother grit ,two tube pack. About five bones,Versa-Chem part number 13209. Used it on my Magnum build,helps having multiple grit compounds.
 
I'm a firm believer in the backyard hone, re-ring, bearing, lap and go. Contrary to the majority of thought around here, not every job has to visit a machine shop. Some folks want the experience.
Click to expand...

Hillbilly, you didn't use a ridge reamer.
 
I prefer the Permatex stuff. It's fairly fine grit. If you don't get a concentric, even grey band after a few turns, lapping isn't the answer.
 
As long as the seats and valve faces are not pitted, there's not a thing in the world wrong with a basic lap valve job. All you need to end up with is a good SOLID grey line all the way around the seat and valve face, with no breaks in the grey. As long as the seats and valve faces are in good enough shape to do that, you are fine. I actually prefer lapping over grinding or cutting, because you end up with much less metal removed and the valve stem heights are hardly changed. Just less machine work all the way around. How can that be a bad thing?
 
Abodybomber said:
Yeppers,my kind of build...
FWIW,O'Reilly's does make a rough/smoother grit ,two tube pack. About five bones,Versa-Chem part number 13209. Used it on my Magnum build,helps having multiple grit compounds.
Click to expand...
Thanks for the info, I agree it will help at some point to have a heavy and fine grit, maybe not with this project but possibly the next. At 4.29 I can get this two pack and the permatex, I can store what I dont use.
 
BillGrissom said:
Lapping valves yourself is pretty hard-core. I have always been amazed how cheap it is to get heads rebuilt at a shop, even w/ hardened seats installed (consider that if you don't have, to run unleaded gas). My understanding is that shops no longer lap valves, they just rely on the accuracy of the grinding machines.
Click to expand...
I have read this bit of info on-line in several places, worth considering I guess so I will post it here............

valve lapping is out of date. lapping is for old engines before hard seats were introduced. all of the B&S valves and seats are hardened and lapping will only slightly polish them. not worth the time.................

it has been shown that once an engine reaches operating temperature, the valve and the seat - being different materials and surrounded by different masses - have expanded at different rates, so the lapped areas on the valve and the seat do not contact each other in the same areas as when they are cold.

Lapping valves is a waste of time.......................

Still going to lap my valves but I will continue to look into this, not sure where Im going to find any sort of definitive answer but maybe something will come to mind. Somehow I believe calling any local machine shop will just yield more opinions instead of scientifically proven facts.

I will be calling Clover Monday, they carry a full line of lapping compounds, while I am sure they will be biased as far as the performance of lapping compounds I also believe they will have a bit more experience with these things than I do.

In the meantime I am still going to play with whats avail over the counter too me.
 
1930 said:
I have read this bit of info on-line in several places, worth considering I guess so I will post it here............

valve lapping is out of date. lapping is for old engines before hard seats were introduced. all of the B&S valves and seats are hardened and lapping will only slightly polish them. not worth the time.................

it has been shown that once an engine reaches operating temperature, the valve and the seat - being different materials and surrounded by different masses - have expanded at different rates, so the lapped areas on the valve and the seat do not contact each other in the same areas as when they are cold.

Lapping valves is a waste of time.......................

Still going to lap my valves but I will continue to look into this, not sure where Im going to find any sort of definitive answer but maybe something will come to mind. Somehow I believe calling any local machine shop will just yield more opinions instead of scientifically proven facts.

I will be calling Clover Monday, they carry a full line of lapping compounds, while I am sure they will be biased as far as the performance of lapping compounds I also believe they will have a bit more experience with these things than I do.

In the meantime I am still going to play with whats avail over the counter too me.
Click to expand...

none of the above will do any good if the guide clearance ain`t good!:banghead:
 
Im going to be checking all of that out. Will keep everyone posted
 
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