My first GUESS would be a very loose liner with oil between the liner and muff .... it overheats the piston and combustion chamber causing knocking and partial piston seizure.
Impending bearing failure?
- Thread starter hmaskill
- Start date
I have had this problem before: When the engine warms up, the muff expands and if the head joint is not made correctly, the liner moves up and down with the piston and the resulting noise is as you describe.
For a total cure you will require a modern, well made muff complete with a liner with the correct interference fit.
The liner top flnge thickness must be compatable with head recess so that when ground together they have total contact.There should be a gap between the face of the muff and head when the grinding is complete.
Hope this helps,
Robin.
For a total cure you will require a modern, well made muff complete with a liner with the correct interference fit.
The liner top flnge thickness must be compatable with head recess so that when ground together they have total contact.There should be a gap between the face of the muff and head when the grinding is complete.
Hope this helps,
Robin.
H.,
A leak down test requires a gauge like a compression tester, but it has a small regulator and an additional gauge to show how much air is leaking out of your engine. I warm up the engine, I usually do the test after the last race of the weekend, then I take out the pushrods through the rocker adjuster holes. You then hook the gauge up to an air source like a compressor and adjust the regulator to say 100 lbs. Hook up the gauge to the spark plug hole and with the pushrods out the engine will move on its own to bottom dead center, but both valves will be closed. Then look at the "percentage gauge" which tells you how much your cylinder is leaking. On a new rebuild it is usually 5% and when the after running it will drop to 1or 2%. When I broke a top ring it registered 60% and the air was rushing out the breather. If the head seal is leaking it will be rushing out there. If the intake is leaking it will be rushing out the carb and if the exhaust is leaking you can hear it in the pipe.
It is a very quick way to check the state of tune of the top end without disassembly. A fellow motorcyclist or auto enthusiast may have one or it can be purchased for about $50 (here in the states.)
Good luck
David
For proper liner to muff fit with an oversize liner I would bore close and finish the i.d. of the muff with a 600grit stone on the Sunnen for maximum contact and heat transfer.... a .006" interference fit. After heating the muff
and inserting a cold liner I would quickly place the assembly in a jig I made for my hydraulic press and keep the lip of the liner under pressure while the muff cooled and contracted. If this is not done the lip of the liner will
be proud of the muff when cooled.
and inserting a cold liner I would quickly place the assembly in a jig I made for my hydraulic press and keep the lip of the liner under pressure while the muff cooled and contracted. If this is not done the lip of the liner will
be proud of the muff when cooled.
The leakdown tester is one of my favourite diagnostic tools. Not only to be used when building a race motor , before assembling the cams+ followers. I magine this- you are asked to fault find a 12 cylinder car engine for a "suspected head gasket "(a regular occurence for a Jaguar specialist) Where to start? the answer is our freind the leakage tester. Tells not only which cylinder has the problem but what the problem is . Saves 3days work to pull it all down, go staight to the scource of the trouble.
Roy,
Didja ever try "Total Seal" gapless rings...... with the bore done right and true..... the leak down test will amaze you!
Didja ever try "Total Seal" gapless rings...... with the bore done right and true..... the leak down test will amaze you!
Rip, total seal rings are real good! But you got to remember to fit valve stem seals on both. The first time I left them off, the smoke from the tailpipe was emarrasing but the old girl won the race.(3.8 Jag sedan)