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Old 01-30-2002, 06:57 AM
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Red face Camshaft Failure

I have just run my fully modified 1300cc Triumph Spitfire engine for the first time. The engine is a very high spec and is meant for circuit racing. I did not build the engine but maybe I should have.

The camshaft lobes disintegrated in about 20 miles, WHY? The following lists my thoughts

1:bad lubrication
2:Coil binding
3:hardening not completer correctly on camshaft after reprofiling
4:bad rocker geometry

I have also discovered 1 bent pushrod, could this be a clue as to what happened to the cam.

Any help identifying the problem would be appreciated.

Russ

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Old 01-30-2002, 10:51 AM
Tom Tom is offline
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the number one reason for early camshaft failure is improper break in procedure .....the cam and lifters should be coated in either cam lube or an assembly lube the valves should be adjusted to near specs timeing set to close then the engine started and run up to about 2500 rpms and allowed to run there for 30 minutes.did you do this? most cam wear happens in the first few minutes of break in
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Old 01-30-2002, 11:03 AM
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Red face

I would ask who did the cam first, secondly, cam lobe failure is more often the rusult of,if you know that oiling is not the weak link, coil bind . Now coil bind cannot happen if the geometry is correct. You will have to ascertain the cam validity, thru the manufacturer, Then you must measure the seat and load travel short of binding, or refer to manufacturer recommendation for the spring and valve travel then compare them to the connecting rocker travel to know if your overall working equation is proper. Next I would check for valve collision with the piston, as this can frequently end up as a probable that could occur in this scenerio. Good Luck,,Diesel Cam Lobe Failure and Why!
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Old 02-01-2002, 03:15 AM
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The cam should have been lubricated ok. Oil pressure was up at 60PSI all the time while driving.

The valves were not hitting the pistons. I checked this through the plug holes! Theres about 1.5 mm clearance on full lift.

I have also had another thought which would put the rocker geometry out. The block has beed decked and the head has had a considerable skim but the pushrods are standard length items. Surely shorter pushrods are needed to maintain the correct geometry.

Russ
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Old 02-01-2002, 09:12 PM
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Talking

I agree with TOM. Improper break in will give you a 50% chance of failure. Bud
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Old 02-06-2002, 09:21 AM
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you said you did not biuld this engine.which
brings me to the subject of cam lube and break in
what the guy said about cam lube is wrong.you put
cam lube on the cam lobes onley.what happens when
you put lube on the lifter and istall it is it
acts like glue between the lifter body and lifter
bore. the lifter can not spin on start up and
it wipes out the cam lobes mushroons on the
bottem and stiks in the bore binding pushrodsand
makeing a mess.the guy who talked about braek-in
is 100o/o right.geo is not the problem here.and i
doubt coil bind to.bind only binds pushrods it
does not wipe out cams.
pat
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Old 02-18-2002, 09:24 AM
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Exclamation

Sorry for chimeing in late, but its important to clarify that lube does go on the bottom of the lifter during installation but DEFINATELY not all over the lifter. You might as well pour liquid nails in the lifter valley if you did the later.
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