BBC Cam Dowel Gear Drive issue

We lost the cam dowel on a test warmup, fortunately everything was still held together by the 3 loose cam bolts and we found the problem when checking the lash before running again. I got a new Chevy cam dowel which is 0.25", it's a tight fit in the cam. However the dowel hole in the Rodeck gear drive is 6.5mm and the hole in the distributor drive/pump drive spud is 7mm (drill shanks of those sizes are a good tight fit).

My plan is to drill & ream both hub & cam to 7mm if the hub is not too hard. If it is, I will just ream the cam to 6.5mm. Then I will fit a dowel to suit, or a piece of a drill shank. I've been told the bolts need to be torqued to 45lbf.ft, which they probably were not.

Has anyone else encountered the dowel size issue?

 

No comment on the dowel but I red Locktite all of the bolts and nuts that are not serviced regularly....Cam & gear drive - flywheel - etc. and blue Locktite the gear drive cover and any other bolts/studs/nuts that are not part of service....so most any fastener other than rods and mains get red or blue Locktite (red into steel and blue into aluminum)....not sure what engine builders recommend but this has been our practice for years....basically any fastener on the car that does not come apart regularly gets some sort of thread sealer (red or blue)...maybe not on topic here but thought I should mention it...

 

Things that go bump in the night.
I had the gear come loose and shear the pin on one of my own engines after building maybe a hundred the same way.
First time I called it a fluke.
Second time made me look closer.
Both times it happened during the burnout. It was obvious something was way off.

I had a new cam and different bolts.
This particular cam did not have the holes tapped as deep as previous cams and the bolt was a thread longer than the previous bolts. End result, even with a torque wrench and loctite the bolts seemed tight but were right at the point of contact with the gear and no real stretch.

 

I was told Blue on all cam drive bolts. The reason was ...if there is a harmonic going on in the engine....the red loctite will turn to powder and let the bolts loose. The blue stays "soft" enough to do the job.

 

Real interesting theory but I has me doubts.
Wonder if the loctite company can shed any light on it.

 

found the same thing Dave found bolts bottoming out allways red locktite

 

Don't wanna hijack this thread and turn it into a Locktite discussion, but when I first started racing I had many incomplete runs due to stuff falling off the car.....just little things came loose and the car quit...so I became "Locktite Scott" and also use nylon or crush type nuts on anything that does not need to be serviced during the season. The Locktite does need to be cleaned with a wire wheel before re-assembly, but stuff does not fall apart anymore!!

 

Here we go again...
Never talk about Loctite with color, learn what you need by research for yourself ! All 3 colors can vary from "why bother" to " you ain't getting it off" !! Here is the perfect example for this discussion, learned from Loctite engineers that told me I was not as anal as I thought.

General around the shop "High Strength" Red color # 271 standard for ring gear bolts...WRONG, use # 263 for use in oil environment !!!
General around the shop " Medium Strength" Blue color #242 for cam drive bolts...WRONG again, use # 243 for use in oil environment !!!

 

Thanks for your input guys especially Scott & Bob. My driver has been in the game for nearly 40 years & he is always telling me to use threadlocker or nylock nuts as appropriate.

 

Thanks Bob - I will check my numbers and make sure to have the oil environment compatible Locktite on hand!!

 

Bob there are many colors the same But all have a different number for a specific use-- Your getting old but still not Seenow.

 

A lot of the variance in the number system has to do with blended activators for different end uses. The Loctite Adhesive Sourcebook is a great source for getting all the details correct for your specific application. We have one in the shop.

Online Adhesive Sourcebook

You can also call them up and request a paper copy for the head.

Chris Saulnier - Team Tigges
Mechanic Falls, Maine

 

Mikey; yes I am getting senile, and the fun meter is on it's way down. I've seen a lot of the world, it's time to see the rest!