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914World.com _ 914World Garage _ Connecting rod to camshaft clearance

Posted by: keske968 Oct 3 2012, 06:37 AM

I am building my own engine and have a question that I can not find the answer to on the searches that I have done. When putting in a stroker crankshaft one of the connecting rods comes very close to hitting a camshaft lobe. What is the recommended clearance between these two parts? I know that they will expand slightly when the engine warms up and currently we only have .006" between them. I am concerned that this is not enough clearance.

Thanks for all the help you guys provide.

Posted by: two-strokejohn Oct 3 2012, 07:49 AM

http://www.ephotomotion.com/914engine/index.htm

check out this web site . I think it is covered there.......... good reading on a rebuild.

Posted by: Racer Chris Oct 3 2012, 09:19 AM

I don't allow less than .030".

Posted by: keske968 Oct 3 2012, 09:40 AM

QUOTE(two-strokejohn @ Oct 3 2012, 08:49 AM)

http://www.ephotomotion.com/914engine/index.htm

check out this web site . I think it is covered there.......... good reading on a rebuild.

I have used his site extensively (great resource) and it looks like he only allows for .008" clearance. I was not sure that was enough to cover the thermal expansion.

Posted by: Racer Chris Oct 3 2012, 10:16 AM

I'm more concerned with crank flex than thermal expansion.
The case is certain to grow more than the camshaft or crankshaft/rods, which would move them further apart.

Posted by: Mark Henry Oct 3 2012, 11:57 AM

QUOTE(Racer Chris @ Oct 3 2012, 11:19 AM)

I don't allow less than .030".

Web cams for "larger displacement engines" have a reduced base circle thus helping with rod clearance, after that you have to start removing material from the rod itself.

Posted by: Joe Sharp Oct 3 2012, 08:41 PM

Had a motor that had a shinny spot on a cam lobe and never heard a thing from it. It was being touched by a rod nut.