Engine won't turn...

[EricH]

Now, my fear is about the possibility of a bent valve. After I applied some force on the ratchet with an extension (while trying to turn the cam to tdc while the crank was already at tdc), I had to change the shim on the exhaust on the #4 piston. The previously measured clearance was .017 then after it was .025. So I changed the shim and everything seems to be working fine, but should I opend the head to check before I refit the engine in the car? Is there another way to check?

If the clearance changed after you applied force...

I really really hope I'm wrong, but I'd be betting nine chances out of ten that the valve is bent. (the tenth chance is that the .017 was measured with the cam lobe not quite in position, or something more unlikely).

Do not put the engine back in the car until you've resolved this. It's all just so much easier to do this stuff on the bench.

You can do a leak down test, see if the valve is still sealing properly. I'd do that before I pulled the head, but I already have the air compressor and a cheapie leak down tester from Harbor Freight.

 

[DanielForest]

Leak...

Hi,

I had no time since end of June to work on the car. I tried closing the exhaust valves while sending air with a compressor thru the spark plug holes. I tried them all 4 to be able to compare. On 3 of them there was no air, instead the air exited thru the intake valves. But on the 4th one, the one I had to re-adjust the shims, there was a small leak. Just enough to make a piece of paper moving while there was absolutely nothing in the 3 others. So, I guess I have a bend valve, but not by much. I guess it would be stupid to put the engine back on the car without taking care of that. Even if I'm not loosing much power, I invested enough time and money to get a bigger cam, a modified head, hi-compression pistons, etc. to avoir loosing all the power gain because of that.

At least, I'm not back to square #1. The engine is clean and rebuild, this is just a valve (oversize!) I have to change. In French we have a saying going like "You have to pay to learn"...

Daniel Forest
Montreal
1987 Bertone X1/9
1980 Fiat X1/9

 

[kmead]

Bummer. Better to be safe than sorry later. Its a whole lot easier to take it apart and put it together on the bench.

Good luck.

Karl

 

[EricH]

I guess it would be stupid to put the engine back on the car without taking care of that.

A leaking exhaust valve guarantees that the car will run like crap and can destroy both the valve and the seat when combustion gases go blowtorching out through the leak. So yes, you have to fix this, and it's going to be easier to fix before you put the motor back in the car.

The good news is that you probably won't have to do any more than pull the head and replace the one valve. You never turned the motor past the one colliding valve, so won't have but one damaged valve, and using only hand tools it's hard to apply enough force to hork up the valve guide or anything in the bottom end.

Be sure to lap the new valve some and look for a nice even lapping marks, just to be sure the guide is still good. If it laps nicely and nothing else looks damaged, I'd be inclined to think you'll be OK just replacing that valve. (Hmmm... but what's that gagging noise? is it possible that I'm hearing Bernice reacting to this suggeston all the way over on the other coast?)

 

[m5art]

rats..

what size of valves do you have in this head? I am looking for some 37.5mm Tipo valves and if you have a good source I would tag along.

Thanks Daniel,