[NateDiggity]

I have a motor in my shop with a single cam journal and cam guide that are scarred up... The other journals on the head/cam are fine, just the furthest most 'forward' - meaning the one closest to the cam sprocket...

How does just one get scarred up or chewed up... and what are the repercussion of continuing to run this motor?

 

[THUMPER 01]

Your cam chain may have carryed some debree up from the bottom end. If the scarring is not to severe, dont worry. I suggest changing the oil and filter3 times with about 20 minutes of run time between to help flush the motor of debris. If something like the oneway bearing or the transmission has lost peices, you may have other issues. If you have split the bottom end, clean the pickup screan of debree and flush all bearing races.

 

[Rocket Factory]

In the 700s that have a cam bigger than a hotcam the exhaust rocker needs to be ground down where the top of the cam lobe gets closest to rocker. If you do not clearance the rocker enough the cam will hit the rocket and cause scarring on the lobe.

Not sure what would cause scarring like that on a 660 tho

 

[maxtrax]

Do you have a picture of the cam lobe? Find the cause of the issue. Like mentioned before it was probably the one-way, maybe a gear tooth or a dog off a gear. Once you find the issue you could always get them to upgrade the cam.

 

[Mad Dog]

My first thought would be a local burr, piece of debris, or other marred surface causing damage to the area as it rotates or as the cam is rotated around it.

Or, and it might not make any sense, but perhaps the cam chain is too-tight, causing excessive pressure on the gear which is then transferred to the cam itself, made most evident on the nearest journal?

 

[maxtrax]

There may also be something plugged inside the actual cam preventing it from oiling the journal properly. If something cam up the oil tube and then got stuck where the decompressor mechanism is inside the cam. A lack of oil could cause galling.

 

[Mad Dog]

Good point Max.

 

[NateDiggity]

There may also be something plugged inside the actual cam preventing it from oiling the journal properly. If something cam up the oil tube and then got stuck where the decompressor mechanism is inside the cam. A lack of oil could cause galling.

Thats actually a possibilty... now that I think about it, when I took the valve cover off the end of the cam (opposite the cam sprocket end) there was more oil sitting there then I normally see on these engines... I will tear in to the top end tomorrow night and see what I can find

 

[NateDiggity]

Wow.... the head/cover recently went together and a piece of the valve cover gasket maker made its way into the cam and up to that oiling port and promptly stopped.... glad it was caught after just a little run time. Everything still looks useable and the cam was cleaned out with compressed air and some carb cleaner.

Whats everyone else use for gasket maker? It was done with this:

 

[DrewsToy]

yamabond

 

[03LimitedEditionRaptor]

yamabond

Also known as the CORRECT stuff to use. Just cause it is gasket maker in a tube doesn't mean it will work.

The reason why you use yamabond is to maintain the proper cam jourmal clearances. RTV is thick and will cause to large of a clearance. The other problem with rtv is does what happened here. The excess that squishes out tears off. Not nessissarly pluging up the cam but pluging up the oil pump sump.

 

[Mad Dog]

Yamabond (or hondabond) is what you should be using. I have used copper permatex because I find it comes off easiest next time around.

I use absolutely tiny amounts of it though, to keep it from spilling over.

 

[maxtrax]

I have used Permatex Ultra Grey in the past but I was very careful about the amount used just because I know it squeezes out. After seeing this I am probably going to be switching to Yamabond 5 just to be safe.

 

[03LimitedEditionRaptor]

Yamabond 4 is what you need. It stays flexable. I think the 5 drys hard.

Yamabond comes off real easy. Use a rag that has been dampened with acetone and it wipes right off. The down side is paint comes too if you get acetone on it.