TR4a Compression problems

[qkingston]

Strip down of US import TR4a continues, body nearly ready to come off. With an engineer friend I decided to do some engine checks before disconnecting fuel/electrics etc; When I purchased the car, I was told that the last US owners had spent money on the engine fairly recently but I have yet to find out exactly what and why. So I started her up (3rd or 4th time since buying the car), starts fine, oil pressure straight up to 50psi, exhaust slightly smoky on choke but settles down once choke off and warmed up (don't know what state the tuning is in, running on std UK unleaded so probably different to the US fuel it will have been set up on). First problem noted was that once warm the radiator expansion tube started emitting coolant, a fairly steady flow which continued whilst running. No noticeable nasty noises. Stopped the engine and did cylinder compression measurements using a Gunson tester. #4 read 12bar, #3 was 12bar, #2 13.8bar and #1 was zero!!!!!

Took off the rocker cover and #1 rocker gap was around 5mm, all the others looked about right, adjusted the rocker gap to 0.010"and tested the compression again....still zero. So although I can see the valve moving as expected I suspect the valve is sticking/not shutting. As you can see from the attached pic, the head looks very clean and I guess that is what was replaced in the US, but I have no idea how well that was done and whether the engine was run much after it was worked on.

So I suspect there are 2 seperate problems:

1. A sticking valve (it's the furthest right), need to take the head off to look at the base of the valve

2. A blocked radiator....all the hoses look quite new as does the thermostat housing (but I guess that could be defective and not opening when the coolant heats up)

 

All thoughts/advice much appreciated!!

 

Regards

 

David

[Waldi]

David,

Looking at #1 valve adjusting screw it looks as if it is turned in deeper. This may indicate a worn lobe, explaining the 5 mm clearance. To verify this, measure the lift of rocker 1 and conpare with the other outlet rockers.

A sticking valve can also be the cause, and is even more likely. Measure how high valve 1 is above the head when in TDC at firing position, and compare with the other outlets,

I say outlet because Im not familiar with the tr4.

If it is lower, remove the rockershaft, apply lubricant, tap it with a hamer and piece if hardwood and see (hope) if it comes up.

Waldi

[ChrisR-4A]

Hi David, as number 1 is an exhaust valve it could be a loose valve seat if head has been unleaded. Water being forced out of overflow could indicate a head gasket failure so may be head off anyway. If it was a loose valve seat I would expect this to make quite a racket at that end of the engine.

[qkingston]

David,

Looking at #1 valve adjusting screw it looks as if it is turned in deeper. This may indicate a worn lobe, explaining the 5 mm clearance. To verify this, measure the lift of rocker 1 and conpare with the other outlet rockers.

A sticking valve can also be the cause, and is even more likely. Measure how high valve 1 is above the head when in TDC at firing position, and compare with the other outlets,

I say outlet because Im not familiar with the tr4.

If it is lower, remove the rockershaft, apply lubricant, tap it with a hamer and piece if hardwood and see (hope) if it comes up.

Waldi

Thanks Waldi, the rocker screw was turned in to try and reset the gap on the valve, that's how much I had to adjust it!! I'll take some measurements and report back!

 

Rgds

 

David

[qkingston]

Hi David, as number 1 is an exhaust valve it could be a loose valve seat if head has been unleaded. Water being forced out of overflow could indicate a head gasket failure so may be head off anyway. If it was a loose valve seat I would expect this to make quite a racket at that end of the engine.

Thanks Chris, there was no noise evident from the top end...head off it is

 

Regards

 

David

[Motorsport Mickey]

David,

 

If you are taking the head off remember the engine liners sit on Figure of 8 gaskets midway down their length into the engine block. DON'T try and use the compression of the engine to lift the head after removing the cylinder head studs, it may well disturb the Fo8 seals which will then leak water into the sump when the engine is run.

The head is distressingly heavy and unless you can get an overhead crane lift attached to pull on it ( which sometimes threatens to lift the car ! ) will sometimes take some parting from the block having to "wiggle" it's way up the head studs. Try "double nutting" and removing some of the studs through the head whilst it's in position to reduce the friction, climbing into the engine bay and straddling the engine allows a healthy lift to be applied to the head if a crane is not available.

 

Mick Richards

[ChrisR-4A]

Zero compression suggests a valve still partly open, check No1 is not slightly bent.