broke cam shafts and messed up head. how? - Honda Prelude Forum

92ludersi4ws · 04-17-2010, 03:34 PM

ok i got a 92 prelude si from a guy for 900 and he just said the timing belt was broke. so we were trying to put a new time belt on and i figured i was take the head off to look at the valves. we got the frist camholder of and the cam gear and end off cam came off. also it wallered(mean like grinded it out) out the front off the head. i was wondering how this could of happened.

CHR1234 · 04-17-2010, 07:29 PM

Looks like the camshaft starved for oil and seized up and broke

TJ97SH · 04-18-2010, 10:28 AM

Wow. That is crazy. I have no theories as to why this could happen other than what was already suggested.

92ludersi4ws · 04-18-2010, 12:17 PM

Would that also be why it griinded the first cam holder down to?

TJ97SH · 04-18-2010, 01:00 PM

Not sure what you mean by "ground the first cam holder down too". I don't know if you understand material strength principles or not, but this is most likely a shear failure. Also, I am not sure what you know about how the internals operate inside an engine. What happens is that the camshaft is locked into the cam gear by a keyed slot. The cam gear is attached to the timing belt. If either of these did not want to move in sync with each other, they will both take on alot of extra stresses. It is unusual that a camshaft would shear like this as opposed to the timing belt failing. If I had to guess as to what happened, these would be some possibilities:

1) Lack of oil in causing very high increase in friction. If the motor is trying to turn with too much friction, things will get damaged. Usually it is not the camshafts however

2) A sudden obstruction in the timing assembly. Not sure what this could be, but in theory if the motor is running (especially at higher RPMs) and the timing belt suddenly stops, the internals of the motor will continue to try to rotate and the camshaft will try to turn. If it is fixed on one end (by the timing belt being stuck) there will be a great deal of shear stress on the shaft. This would likely cause it to fail in the mode seen here. Again, I don't really know what would cause this. Possibly the water pump or crankshaft seized up. I would imagine that the timing belt would break before a camshaft though.

It is possible that the camshaft was defective or damaged in some way. Your most likely cause of failure is probably not enough oil - or maybe none at all.

Good luck.

willybv · 04-18-2010, 04:26 PM

It was likely the timing belt that caused your snapped camshaft. I've seen this happen several times at the dealership I work at. As mind-boggling as it seems, a timing belt actually has the strength to snap a camshaft. If the cam locked (possible heat/lubrication issues, or a bad journal or scuffed cam) the timing belt could have snapped the cam off. Also, a water pump lock up can cause this, so check that too (as I'm sure you have or will). Unfortunately there are only two things to do now: Check for piston contact and go through and rebuild a new head. Or sell it to someone for $900.

92ludersi4ws · 04-18-2010, 08:09 PM

when i say ground out im talking about the camshaft grinding against the head to where it would look like it does in the second picture. i haven checked the water pump but sense i was just goin to change the timing belt i got one but sense we just pulled the vavle cover off and started taking the cams out and saw that i just figured might as well stop here and save for a new head. but thanks for all yalls input it all has been dually noted and i need to check for leaks and go from there. when it comes to cars i am somewhat of a green horn and i just got this one to work on. so i guess i picked the perfect one.

indylude18 · 04-18-2010, 08:19 PM

My vote is for a misshift causing a very bad over-rev leading to the snapped camshaft.

TJ97SH · 04-18-2010, 10:18 PM

I completely disregarded the second picture earlier. It is too small to really see what I am looking at. After zooming in about 400% I can see now what you are trying to show us. I am guessing that this is the side of the head (cam journal - I guess you would call it) where the camshaft rests. I believe the camshaft is supposed to rotate on this point as well as on all the rocker arms. I mean that there is supposed to be contact here. If this is correct, there will be some wear. I cannot really tell how damaged it is from the picture.

What I would suggest is taking it to a machine shop. One that rebuilds engines should be able to diagnose the problems and potentially nail down the specific problem that caused this. They should also be able to tell you what needs to be done and probably can do the machining themselves and reassemble the motor. I had a shop strip my engine, soak it all, and give me a list of work that needed to be done for $90. I had a different machine shop do the work as the first one acted like I needed to replace all my rocker arms (motor only had 84k miles on it) which would have cost an extra $800ish. Usually if you have the motor taken apart and cleaned up and diagnosed, and you end up having that shop rebuild it they will waive the fee for that initial diagnosis/cleaning.

92ludersi4ws · 04-20-2010, 01:14 PM

Im acturally think about buy a head that alreaddy has crower cams and retainer kit and then own down the road take that head to a machine shop and go from there so if they can fix it ill just have a spare incase something like this happens again. Thanks for all your help. i guess right away i should start looking for an oil leak some where. i got a gasket kit to so im just goin to change all of those and see if that works.