Author Topic: lapping made leaks worse!?!?! (Read 15556 times)

USCG_C130 · « **on:** April 27, 2012, 02:35:27 PM »

so today i got my missing valve stem seal and put it on to leak check the valves, well 4 were almost good, 4 were bad, so i read up on the forum and got some tube and a drill and thought id give that a try, all seemed to be going well, but after i re-lapped all my exhaust valves they all leak badly now and the bad ones before got worse! i am guessing i will have to recut the seat? i don't know why lapping made them worse i didn't think i over lapped them by any means. so does any one have some input or thing i should try to resolve this or am i just going to have to recut? if needed ill try to get some pictures up on sunday, thanks for all the help in advance!

Pecantree · « **Reply #1 on:** April 27, 2012, 02:39:45 PM »

Bummer.
Hopefully more experienced will chime in but did you keep each valve married to its cylinder?
I had no problems with this.
Good luck
Steve

USCG_C130 · « **Reply #2 on:** April 27, 2012, 02:49:29 PM »

yea i bagged and tagged them on on cardboard im sure i didnt get them backwards…… well now you have me thinking, i really think i kept them straight though.

trueblue · « **Reply #3 on:** April 27, 2012, 02:54:46 PM »

The valve guide should keep them straight while lapping, just a thought, you didn't put the exhaust valves in the inlet holes and vise versa, the inlet valves are slightly larger. Another thing that can cause them not to seal properly is if you still have a little lapping paste on the valve seats, it will hold the valves off their seats slightly, just a couple of ideas that could possibly be your problem.

dave500 · « **Reply #4 on:** April 27, 2012, 02:58:52 PM »

can you post a photo?

USCG_C130 · « **Reply #5 on:** April 27, 2012, 03:03:30 PM »

well i went back and looked at photos i took and they all seem to be in the right order my #4 has a distinct little indent in the end of the valve shaft and it matches where it should be and i was thinking about the paste being an issue when i was putting them back but wipped them out well maybe ill take them off again and clean really well and see if that helps at all. and @ dave yea im about to head out to a birthday and tomorrow ill be at work for 24 hrs but i will try to get a few pics up on here sunday, thanks guys

grcamna2 · « **Reply #6 on:** April 27, 2012, 03:43:26 PM »

I haven't been following you're build but just wondered,how are you're valve guides ?

lucky · « **Reply #7 on:** April 28, 2012, 09:43:41 AM »

Quote from: USCG_C130 on April 27, 2012, 02:35:27 PM

so today i got my missing valve stem seal and put it on to leak check the valves, well 4 were almost good, 4 were bad, so i read up on the forum and got some tube and a drill and thought id give that a try, all seemed to be going well, but after i re-lapped all my exhaust valves they all leak badly now and the bad ones before got worse! i am guessing i will have to recut the seat? i don't know why lapping made them worse i didn't think i over lapped them by any means. so does any one have some input or thing i should try to resolve this or am i just going to have to recut? if needed ill try to get some pictures up on sunday, thanks for all the help in advance!

The mistake was using a drill to lap the valves.
You always lap valves by hand by putting one hand on each side of the lapping stick with suction cup and rubbing your hands back and forth.

But never in a drill.

You will have to recut the seats, and the valves might have to be replaced too.
Sorry.
See photo below.

lucky · « **Reply #8 on:** April 28, 2012, 10:04:19 AM »

Question...Were the valve seats recut?
Was the valve checked for wobble in the guide?

The Clymers shop manual shows a photo how to check the guide.
Max wobble is about .004 thousandths.

Pecantree · « **Reply #9 on:** April 28, 2012, 10:13:49 AM »

Thinking what Trueblue said about some paste left.
I wash them in solvent after lapping. Thinking it might be hard to get 100% of grit off just by toweling.
Hope you don't have to get new.
In the manual is the spec for max face grind on the valve.

good luck
Steve

LesterPiglet · « **Reply #10 on:** April 28, 2012, 12:33:00 PM »

I find myself agreeing with lucky. The way to lap valves is by hand, rotating the tool both clockwise and anticlockwise.

killersoundz · « **Reply #11 on:** April 28, 2012, 12:39:16 PM »

Using the drill screwed it up mang

754 · « **Reply #12 on:** April 28, 2012, 12:58:37 PM »

If valves are bent lapping, may not help.. You should have run em back and forth..grinding might ?? save some of it.
Being a bit more thorough on your reasearch before starting, might be help[ful..

Plummer · « **Reply #13 on:** April 28, 2012, 01:40:46 PM »

Hi Guy's , New to the forum , long time lurker ! I lapped mine with a drill "SLOW" , both directions with light pressure ! Great results ! seats and valves turned out nice , seal great ! I however have a 750 ?

andrewk · « **Reply #14 on:** April 28, 2012, 01:57:45 PM »

Quote from: lucky on April 28, 2012, 09:43:41 AM

Quote from: USCG_C130 on April 27, 2012, 02:35:27 PM
so today i got my missing valve stem seal and put it on to leak check the valves, well 4 were almost good, 4 were bad, so i read up on the forum and got some tube and a drill and thought id give that a try, all seemed to be going well, but after i re-lapped all my exhaust valves they all leak badly now and the bad ones before got worse! i am guessing i will have to recut the seat? i don't know why lapping made them worse i didn't think i over lapped them by any means. so does any one have some input or thing i should try to resolve this or am i just going to have to recut? if needed ill try to get some pictures up on sunday, thanks for all the help in advance!

The mistake was using a drill to lap the valves.
You always lap valves by hand by putting one hand on each side of the lapping stick with suction cup and rubbing your hands back and forth.

But never in a drill.

You will have to recut the seats, and the valves might have to be replaced too.
Sorry.
See photo below.

Absolutely correct. If you spin the valve 360 you'll never know if there are high/low spots in the valve face or on the seat.

I'm not sure if the auto parts store rents a seat cutter or not, but if not, a good machine shop should be able to help you out with fixing the problem. I would say at the minimum, the seat needs to be restored properly, and the valves/valve guides inspected- I bet you'll find one or the other needs replacement.

dave500 · « **Reply #15 on:** April 28, 2012, 02:24:35 PM »

i lap valves with a reversible drill on slow no problem,ive done heaps of them,those suckers were invented before reversible power drills were common.

jaguar · « **Reply #16 on:** April 28, 2012, 03:05:59 PM »

Always lap by hand..
Using a drill increases the risk of damage.

dave500 · « **Reply #17 on:** April 28, 2012, 03:12:40 PM »

ham fisted people must not use the drill.

LesterPiglet · « **Reply #18 on:** April 29, 2012, 02:05:05 AM »

Or impatient people. It's easy to keep going in one direction because of lazyitis.

mycb750k6 · « **Reply #19 on:** April 29, 2012, 06:07:49 AM »

It's funny, there are many threads on how to lap using a drill with flex tubing. I've done on three heads with great results. To make the statement to never use a drill is just incorrect. If you do it properly with the correct speeds and rotation, you will have good results. To say never use a drill because something could go wrong is ridiculous. There are plenty of people who've used a drill with great results. It's the technique, not the tool the matters.

Bailgang · « **Reply #20 on:** April 29, 2012, 06:51:16 AM »

Quote from: mycb750k6 on April 29, 2012, 06:07:49 AM

It's funny, there are many threads on how to lap using a drill with flex tubing. I've done on three heads with great results. To make the statement to never use a drill is just incorrect. If you do it properly with the correct speeds and rotation, you will have good results. To say never use a drill because something could go wrong is ridiculous. There are plenty of people who've used a drill with great results. It's the technique, not the tool the matters.

Good point. I was always taught to lap valves by hand so I was rather shocked when I started reading threads about using a drill but I guess technique is the key because you can possibly screw up doing it by hand or using a drill if you don't know what you're doing. For now though I'll stick to doing it by hand but that's just my preference.

grcamna2 · « **Reply #21 on:** April 29, 2012, 07:58:45 AM »

I think it's a lot easier to mess up w/ a drill then it would be doing it carefully by hand.

Pecantree · « **Reply #22 on:** April 29, 2012, 08:03:46 AM »

.........USCG_C130............
Keep us posted with what you discover.
Steve

lucky · « **Reply #23 on:** April 29, 2012, 10:35:10 AM »

Were the seats recut before lapping?

andrewk · « **Reply #24 on:** April 29, 2012, 11:33:18 AM »

Quote from: mycb750k6 on April 29, 2012, 06:07:49 AM

It's funny, there are many threads on how to lap using a drill with flex tubing. I've done on three heads with great results. To make the statement to never use a drill is just incorrect. If you do it properly with the correct speeds and rotation, you will have good results. To say never use a drill because something could go wrong is ridiculous. There are plenty of people who've used a drill with great results. It's the technique, not the tool the matters.

There's lots of threads on lots of things, and about half of them are incorrect anyway.

I agree that it CAN be done, but that doesn't mean you should. Care and attention to the process will give you good results no matter what method you use, but if you are in the situation where you have a serious issue with the valve sealing area, as the OP apparently does, using a drill will hide this problem from you the first time you spin the valve 360 degrees. If do it by hand, you see it right away.

I speak only from real world experience- hard lessons don't have to be hard for everyone

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Author Topic: lapping made leaks worse!?!?! (Read 15556 times)