The Ford Barn

36tudordeluxe · 02-09-2018, 05:35 PM

After lapping the valves/seats and segmenting my pulley in 4 equal sections to correspond with TDC on all cylinders the leaking valves have gotten worse when I re-did the leak down test.....way worse! With intake manifold off it was very easy to identify leaking intake valves, would having intake manifold and carb.off exacerbate the condition? Bottom line, if piston is at TDC, both valves on their seats and valve stems not making contact with the lifters I should have very little leakage? On an earlier post Ol'Ron suggested to look for "overlap split" on intake and exhaust valves but already had heads on, would this be worth doing at this point?

Mart · 02-09-2018, 05:40 PM

Do you have the piston at the "right" TDC?

You get two TDCs for each turn of the cam. You need the firing TDC where both valves are closed.

For each cylinder identify the TDC where the valves are one just closing and one just opening. Now rotate the crank one whole turn until back at TDC. That is the one you want.

Mart.

flatjack9 · 02-09-2018, 06:22 PM

The intake manifold and carburetor have nothing to do with the valves sealing. If both valves are closed and the stems are off the lifters, you are on TDC firing. What Ron said has nothing to do with setting the valves. That position is not for setting the valves.

51 MERC-CT · 02-09-2018, 07:20 PM

And of course you have correctly set the valve to lifter clearance ??

Ggmac · 02-09-2018, 07:32 PM

If both valves are not touching the lifters AND no sticking or bent valves , or broken valve springs , you should have very little air flow . Also check with a vacuum line to your ear to see if intake , exhaust or crankcase .

36tudordeluxe · 02-09-2018, 07:55 PM

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Understand about 2 TDC’s, regardless of which TDC I’m at as long both valves closed stems not contacting lifter, locks and retainers are in place, I should have very little leakage right?Anyway, will rotate crank full turn to TDC #1 again and see what happens.
Thanks for the help guys.

jrvariel48 · 02-10-2018, 05:12 AM

Valve seats may not be concentric or angled correctly. I had trouble with this when I cut mine by hand with a special cutter. I had a custom pilot machined to go down through the valve guide and that solved the problem. It took a lot of time to cut the 3 angles and to get the proper margin size and it's location on the valve face

Ronnie · 02-10-2018, 10:10 AM

How was the valve job done. Stones or cutters. Also what pilot system.

R

36tudordeluxe · 02-10-2018, 01:00 PM

Am beginning to think when the machine shop did the valve job it was done incorrectly; as to how it was done I have no idea, it was done over 20 years ago. The engine has fewer than 500 miles on it and when it was in the car I thought it ran quite well even though it suffered from low compression from the very beginning. I replaced it with a 276 and never looked back. Been sitting in the corner of the garage for years and finally decided to sell it but don't want to sell it to someone when I know theres something wrong with it.

After lapping the valves I thought problem would be solved, but if anything I made the problem worse.

Ggmac · 02-10-2018, 02:15 PM

What is you wet cranking compression ?

36tudordeluxe · 02-10-2018, 02:46 PM

oil on the rings and 12V'S 70-80 lbs.

Ggmac · 02-10-2018, 04:26 PM

Quote:

Originally Posted by 36tudordeluxe

oil on the rings and 12V'S 70-80 lbs.

And dry is near that ? What I'm trying to understand if it's just leaking thru the valves or valves and rings . If the valves were the the only problem , it's minor compared to rings and valves . It would still be a good item to sell as long as the buyer understands the issue .

JSeery · 02-10-2018, 04:37 PM

If you laped the valves you should know what condition they were in. When you lap them you are looking for things like seat width and if there is full contact on both the valve and seat.

kiwitony · 02-10-2018, 04:57 PM

your wet and dry test has already answerd your question. little change between the two means your rings are fine.If you can run the engine it might hammer the valves in a bit there maybe some residue from the lapping process causing the issue. I would double check that you have valve clearance as this is the most likely cause.

Ronnie · 02-10-2018, 05:45 PM

Does the engine have 2 piece guides

R

Jack E/NJ · 02-10-2018, 05:47 PM

>>>I thought it ran quite well>>>I replaced it with a 276 and never looked back.>>>

And does your 276 measure up to its expected numbers using your same test techniques? Jack E/NJ

Bored&Stroked · 02-10-2018, 08:15 PM

They should not be leaking when they're fully closed and not touching the tappets. It sounds to me like whomever did the valve job - didn't do it correctly and/or may have had the incorrect tools/mandrels to do the job (causing incorrectly centered seats, etc).

Even with the earlier split guides, when I used to build my early racing engines I would pour lacquer thinner into the intake ports (during the valve setup process) and insure that there was no visible "weeping" of the thinner around the valve. If any valve leaked the slightest amount - out it came to resolve the problem.

36tudordeluxe · 02-10-2018, 11:46 PM

One piece guides. The 276 has excellent compression and never did a leak down test on it.
After laping the valves, valve bottom and seat had nice uniform gray surface all the way around.
Valves are set go/no go method at .011 on intake and .013 exhaust. Regardless of the lash, if stems aren't making contact with lifters and valve components are good I should have very little leakage.
Next step is off to machine shop out of area to re-do inserts and valves.

cas3 · 02-10-2018, 11:54 PM

if you used a marker pen while laping, it should have shown the contact area, which you said you did, and it showed good. if thats true, the only thing that can be wrong is you are adjusting the lash at the wrong time on the cam. forget the machine shop, and study up the correct sequence to adjust valves

Mart · 02-11-2018, 04:52 AM

If visual check shows uniform grey surface and the gaps are correct, with respect to a leak down test I'd trust my eyes and judgement better than the results. there may be a problem with the equipment of test method.

If the valves have passed visual inspection, have been hand lapped, seats are visually good, and gaps set correctly, and results are low after a dray and wet compression test, I would be wondering about cam timing.

Can't give you a magic bullet reply, but I think you have done everything you can to rule the valves out. So, we have to ask ourselves, "What else could it be"?

Is there anybody in your area that might be able to pay a visit and get a fresh pair of eyes on it?

Mart.

02-09-2018, 05:40 PM	#2
Mart Senior Member Join Date: May 2010 Location: Solihull, England. Posts: 8,754	Re: Leaky valves Do you have the piston at the "right" TDC? You get two TDCs for each turn of the cam. You need the firing TDC where both valves are closed. For each cylinder identify the TDC where the valves are one just closing and one just opening. Now rotate the crank one whole turn until back at TDC. That is the one you want. Mart.

02-09-2018, 06:22 PM	#3
flatjack9 Senior Member Join Date: May 2010 Location: Oshkosh, Wi Posts: 4,527	Re: Leaky valves The intake manifold and carburetor have nothing to do with the valves sealing. If both valves are closed and the stems are off the lifters, you are on TDC firing. What Ron said has nothing to do with setting the valves. That position is not for setting the valves.

02-09-2018, 07:20 PM	#4
51 MERC-CT Senior Member Join Date: May 2010 Location: East Hartford, Ct Posts: 5,898	Re: Leaky valves And of course you have correctly set the valve to lifter clearance ?? __________________ DON'T RECALL DOING SOMETHING FOR MYSELF BASED ON SOMEONE ELSE'S LIKES OR DISLIKES

02-09-2018, 07:32 PM	#5
Ggmac Senior Member Join Date: Jul 2016 Location: Lake worth Florida Posts: 1,100	Re: Leaky valves If both valves are not touching the lifters AND no sticking or bent valves , or broken valve springs , you should have very little air flow . Also check with a vacuum line to your ear to see if intake , exhaust or crankcase .

02-09-2018, 07:55 PM	#6
36tudordeluxe Senior Member Join Date: Feb 2012 Location: Las Vegas, NV Posts: 1,260	Re: Leaky valves Sponsored Links (Register now to hide all advertisements) Understand about 2 TDC’s, regardless of which TDC I’m at as long both valves closed stems not contacting lifter, locks and retainers are in place, I should have very little leakage right?Anyway, will rotate crank full turn to TDC #1 again and see what happens. Thanks for the help guys.

02-09-2018, 05:35 PM	#1
36tudordeluxe Senior Member Join Date: Feb 2012 Location: Las Vegas, NV Posts: 1,260	Leaky valves After lapping the valves/seats and segmenting my pulley in 4 equal sections to correspond with TDC on all cylinders the leaking valves have gotten worse when I re-did the leak down test.....way worse! With intake manifold off it was very easy to identify leaking intake valves, would having intake manifold and carb.off exacerbate the condition? Bottom line, if piston is at TDC, both valves on their seats and valve stems not making contact with the lifters I should have very little leakage? On an earlier post Ol'Ron suggested to look for "overlap split" on intake and exhaust valves but already had heads on, would this be worth doing at this point?

02-10-2018, 05:12 AM	#7
jrvariel48 Senior Member Join Date: Jan 2012 Location: New Jersey Posts: 1,425	Re: Leaky valves Valve seats may not be concentric or angled correctly. I had trouble with this when I cut mine by hand with a special cutter. I had a custom pilot machined to go down through the valve guide and that solved the problem. It took a lot of time to cut the 3 angles and to get the proper margin size and it's location on the valve face

02-10-2018, 10:10 AM	#8
Ronnie Senior Member Join Date: May 2010 Location: Canada Where it snows Posts: 2,058	Re: Leaky valves How was the valve job done. Stones or cutters. Also what pilot system. R

02-10-2018, 01:00 PM	#9
36tudordeluxe Senior Member Join Date: Feb 2012 Location: Las Vegas, NV Posts: 1,260	Re: Leaky valves Am beginning to think when the machine shop did the valve job it was done incorrectly; as to how it was done I have no idea, it was done over 20 years ago. The engine has fewer than 500 miles on it and when it was in the car I thought it ran quite well even though it suffered from low compression from the very beginning. I replaced it with a 276 and never looked back. Been sitting in the corner of the garage for years and finally decided to sell it but don't want to sell it to someone when I know theres something wrong with it. After lapping the valves I thought problem would be solved, but if anything I made the problem worse.

02-10-2018, 02:15 PM	#10
Ggmac Senior Member Join Date: Jul 2016 Location: Lake worth Florida Posts: 1,100	Re: Leaky valves What is you wet cranking compression ?

02-10-2018, 02:46 PM	#11
36tudordeluxe Senior Member Join Date: Feb 2012 Location: Las Vegas, NV Posts: 1,260	Re: Leaky valves oil on the rings and 12V'S 70-80 lbs.

02-10-2018, 04:37 PM	#13
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: Leaky valves If you laped the valves you should know what condition they were in. When you lap them you are looking for things like seat width and if there is full contact on both the valve and seat.

02-10-2018, 04:57 PM	#14
kiwitony Senior Member Join Date: Aug 2010 Location: Whangaparaoa New Zealand Posts: 263	Re: Leaky valves your wet and dry test has already answerd your question. little change between the two means your rings are fine.If you can run the engine it might hammer the valves in a bit there maybe some residue from the lapping process causing the issue. I would double check that you have valve clearance as this is the most likely cause.

02-10-2018, 05:45 PM	#15
Ronnie Senior Member Join Date: May 2010 Location: Canada Where it snows Posts: 2,058	Re: Leaky valves Does the engine have 2 piece guides R

02-10-2018, 05:47 PM	#16
Jack E/NJ Senior Member Join Date: May 2010 Posts: 2,173	Re: Leaky valves >>>I thought it ran quite well>>>I replaced it with a 276 and never looked back.>>> And does your 276 measure up to its expected numbers using your same test techniques? Jack E/NJ

02-10-2018, 08:15 PM	#17
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,067	Re: Leaky valves They should not be leaking when they're fully closed and not touching the tappets. It sounds to me like whomever did the valve job - didn't do it correctly and/or may have had the incorrect tools/mandrels to do the job (causing incorrectly centered seats, etc). Even with the earlier split guides, when I used to build my early racing engines I would pour lacquer thinner into the intake ports (during the valve setup process) and insure that there was no visible "weeping" of the thinner around the valve. If any valve leaked the slightest amount - out it came to resolve the problem.

02-10-2018, 11:46 PM	#18
36tudordeluxe Senior Member Join Date: Feb 2012 Location: Las Vegas, NV Posts: 1,260	Re: Leaky valves One piece guides. The 276 has excellent compression and never did a leak down test on it. After laping the valves, valve bottom and seat had nice uniform gray surface all the way around. Valves are set go/no go method at .011 on intake and .013 exhaust. Regardless of the lash, if stems aren't making contact with lifters and valve components are good I should have very little leakage. Next step is off to machine shop out of area to re-do inserts and valves.

02-10-2018, 11:54 PM	#19
cas3 Senior Member Join Date: Jan 2011 Location: sw minnesota Posts: 4,577	Re: Leaky valves if you used a marker pen while laping, it should have shown the contact area, which you said you did, and it showed good. if thats true, the only thing that can be wrong is you are adjusting the lash at the wrong time on the cam. forget the machine shop, and study up the correct sequence to adjust valves

02-11-2018, 04:52 AM	#20
Mart Senior Member Join Date: May 2010 Location: Solihull, England. Posts: 8,754	Re: Leaky valves If visual check shows uniform grey surface and the gaps are correct, with respect to a leak down test I'd trust my eyes and judgement better than the results. there may be a problem with the equipment of test method. If the valves have passed visual inspection, have been hand lapped, seats are visually good, and gaps set correctly, and results are low after a dray and wet compression test, I would be wondering about cam timing. Can't give you a magic bullet reply, but I think you have done everything you can to rule the valves out. So, we have to ask ourselves, "What else could it be"? Is there anybody in your area that might be able to pay a visit and get a fresh pair of eyes on it? Mart.