MTFCA Forum

Ok….312 is new….. I just took a micrometer to my valves stems. The worst one is 308 and a half…the rest are split 309-310
So….2 to 3.5 thousandths under….how much is too much…. I’m tempted to use standard valves….. there appears to be very little side movement when I put the 310 valves into the valve guides…thoughts?

There are several factors to consider. If this is a total rebuild including hardened valve seats, rebored cylinders, and a new camshaft, the valve guides should be reamed to the next size. If only a valve job, I would use the old valves. The guides will last until the next the next major rebuild, which may not be too far away.

If the engine is out of the car, the crankshaft babbitt should be evaluated.

My opinion, others will have other thoughts

Art Mirtes

Proper fitting valve stems/guides will give the least smoke and most consistent fuel mixture. For every .001" reduction in stem diameter, you'll likely measure .002" guide wear.

Time to buy a set of ball gauges and "map" the hour-glass shape of the guides and let that sway your decision.

Not a recommendation for the brand (I prefer Starrett), but an example of what you need to start your measurement journey: https://www.amazon.com/QWORK-Small-Gaug ... 63418&th=1

You can use the old valves, however, if they happen to be the 2 piece valves, which are usually identified by the two holes at the top of each valve and the head is different piece than the stem. They should be replaced. If one of the head comes off it could cause great damage to the engine. If they are the one piece valves, go ahead and reuse them.
Norm

New valves. .004 wear is excessive. Actually a standard valve has the clearance built in & the guides are bored .3125"
If they are sloppy in the guides, my first choice is to knurl the guides.
It is less common to have the valve stems wear & not the guides.
I have encountered several motors where the lifters wore but not the lifter bosses. New, standard lifters fit great.

Back in the day, when I was rebuilding engines for a living. I would replace any valve with .002" wear on the stem. I would always knurl the valve guides. If they did not clean up completely when reamed, I would either replace or sleeve them, depending on whether they were cast in or press fit.

Proper valve guide clearance is essential for good oil control, good fuel mixture control, and accurate valve seating with minimal wear. Valves that seat properly and run in properly fitted guides with correct valve lash will run cooler, quieter, and last longer.

Where does one find a valve guide knurling tool for the standard size? Maybe I have not looked deep enough into the bowels of the inter-web.

I have bought my most recent on TBAY. Lisle brand. They were available @ automotive machine shop supply houses.(Other brands)
When I was looking, they were more expensive

It is cheaper to ream the guides & buy oversized valves. Goodson sells knurling arbors 5/16 is # WKA-312-G @ $104.99 guides are sized with
a Carbide sizing ball 5/16" is # CL-53125 @ $54.99 you can ream them a reamer will be $52 Goodson .com 1-800-533-8010 I think the only
reason I would try knurling is that I have a new set of Std. valves the knurling arbor & the reamer. In the 1970's we found that knurling guides
on a skiny block chevy was only good for 50,000- 75,000 miles before the heads were junk. Thats with new valves, using the old valves cut that
in half. Guides are not knurled two times and the wear may make it hard to ream them straight if they have to be done again.
Craig.

We used the UTP knurling tools. They are far superior to the KD type knurling tools like Goodson sells. There are different sizes cutter wheels for guides that had more wear. They came in sizes from .155 up to .195. The reamers are in .001" increments, not just a one pass process like the others. That allows for a custom fit. When done properly it creates a completely new wear surface with a groove to retain lubrication.

Well, gentlemen, I want to thank everyone who took the time to post replies…… I ordered a set of standard valves, which I will try in the guides…. If the valves have slop, I will return the stock valves….. buy oversize valves and a reamer…..Scott Conger…..just ordered a telescopic small bore gauge….I too like Starrett…. and I purchased it direct from them…..many thanks boys…Cheers!