Offset valve guides???

General engine tech -- Drag Racing to Circle Track

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Offset valve guides???

Post by PFC1 » Thu Oct 11, 2007 8:31 pm

Has anyone ever heard of anyone making a replacement guide that could move the placement of a valve say... .030 or .040 away from the other valve?

This looks like it could be an easy way to install a bigger valve in a head that has canted valves that are to close to use larger valves as is.

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Dan Barton
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Post by Dan Barton » Thu Oct 11, 2007 9:23 pm

You use an oversized o.d. guide and offset bore the guide hole in the head with a boring head in a Bridgeport or similar mill... keep in mind that the seat will also need to be replaced and the port will more than likely need to be welded on atleast one side if not all the way around on the seat ring. I have done this sort of thing on DRCE and wedge heads for competition eliminator before. It can end up being a fairly costly and labor intensive project and thats why I have probably only done it on max effort type projects!

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C Stevens
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Post by C Stevens » Thu Oct 11, 2007 10:51 pm

You can move the valve that way but, it plays hell with the rocker geometry especially in a CV setup.
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Post by HG » Mon Oct 15, 2007 9:56 am

Have seen this done on wedge type heads without too many issues. However as previously noted you can expect geometry problems with the canted valves.

Dan pretty much hit the nail on the head moving the valve .030" to .040" is probably going to involve some welding and will more than likely get pretty expensive. I would only consider doing this for an all out competition application.

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Post by thundair » Mon Oct 15, 2007 5:14 pm

We moved the intake on one of our racing heads and the valve was re-angled from the rocker contact point. And @ .017 per inch per degree it was one half degree change that moved the 4.5" long valve .040..


Post by bevans6 » Tue Oct 16, 2007 11:53 am

Full race Mini engines used to do this in the 60's. They would offset the exhaust valve by an amount that allowed you to cut a new seat that overlapped the stock seat, but larger than otherwise as you kept the side nearest the intake valve in the same location. I don't think they do it anymore.


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