MTFCA Forum

Apparently the head gasket leak between #3 and #4 was not the whole story. I installed a new gasket but compression was still low. I thought maybe I hadn't used enough copper coat for a good seal, so I pulled the head again, cleaned everything up, and reinstalled it with lots of goo. This morning I tested my compression gauge to see if it's working properly. It is, and I get wet readings of 36, 20, 13, and 16. Looks like I need to go to work on valves.

First thing to check is the valve to lifter clearance. Adjustable lifters can change. I would never use adjustable lifters with new valves. Standard lifters and grind the valve stems for correct gap.

I tore a speedster motor down last summer and all but two valves had zero clearance. It has adjustable lifters. Might be a good check.

John S. - You said,..."I would never use adjustable lifters with new valves." Why???

I don't know whether you checked the surfaces of both the top of the block and of the head. If not completely flat, you could still have a compression leak at the gasket even though you torqued the head properly. A blow down test could determine where the leak is occuring. You install a tire valve inside a sparkplug and screw into the cylinder head. Then with the piston up on top dead center with valves closed pump in about 50 psi and listen to whether the air escapes into the carburetor, or the exhaust or the crankcase. If it is into the crankcase, your rings are at fault. If into the carburetor, it is an intake valve or into the exhaust it is the exhaust valve. If you have the other plugs out and the air excapes into an adjacent cylinder, your head gasket is leaking.
Norm

I am Jim, but my reason for not using adjustable lifters. One thing is the cost and also you likely will only adjust valves once in many years. New valves are extra length and you must grind the stems any way. If you must grind valves later, just re grind for proper gap. adjustable lifters can change settings. Just my way of thinking . By the way I have used adjustables .

Never seen adjustable lifters changed as stated in 30 years. Just sayin’

Hank

Me neither Hank - in 53 years...but many thanks for that test technique Norm. I hadn’t thought of something that simple.

What Norm describes is a cylinder leakdown test and is exactly what should be done next. It will provide a definitive answer to where your lost compression is going. Most likely it will be valves but there are several possibilities. The trickiest part of this test is getting the engine on perfect TDC and keeping it from turning when air pressure is applied to the cylinder.

Hi Steve, what Norm suggests is the way to go, a simple test that gives you a clue as to where to look for the source of your troubles, better then starting another teardown looking for a fix without really knowing where to look

Hold it . Hold it. what were the dry readings? Did they go up when you wet it or stay the same? Stayed about the same it's (usually) valves. That's quite low for just valves. they must be quite a bit out of adjustment or burned. Good Luck.

I just finished a 1912 engine.

Here is what I did with the block and the head.

Took off: - 0.1mm on the bottom.
- 0.4mm on the top
- 1.0mm on the head
Redone the valve seats for the new valves and adjustable tappets.
At the same time I looked after three bolt holes with stripped tread and installed V-coils.

Andre
Belgium

Steve,

I looked your other tread about that engine.
On the photo you posted, there is a change in color at the rear section of the engine.
Your problem is there.
If it should be mine, I should take the engine out, disassembled it, grind all the surfaces flat and do a valve job.
After grinding watch and look for cracks, sometimes they are the reason for the start of your problem.

Just what I should do.

Andre
Belgium

It's a model T, it will keep you busy.