valve guides- knurled or interrupted spiral?

[Brian Monticello]

I purchased a set of "completely rebuilt" cylinder heads - a '66 462 casting and a 67 291 casting. I've Cc'd these heads and all combustion chambers are within 2 CC's of one another. They have had 2.02 installed, the intake valve has been unshrouded, new springs, quality undercut valves, screw in rocker studs, and they have a mild port job - all very professionally done.

I get the set and am very pleased by the exterior work - as soon as a pull a valve, my happiness goes away as I see that the valve guides have been knurled. I had a friend look at these and he says they might be what's called "interrupted spiral" guides - not knurled.

I did a quick search and see K-line liners offer interrupted spiral but what I have are cast iron inserts, not liners. What I thought was knurling starts at the top of the guide and continues all the way through the guide except for the bottom 3/4" or so. That bottom 3/4" or so lools like a plain old guide.

The heads appear to be very nicely done (and I don't want to spend any more $$) so I find it hard to believe someone would put a bunch of money into heads and get the guides knurled.

Have any any you guys ever seen "interrupted spiral" thick walled inserts? Comments?

here's a shot of the top of the guide:

Thanks,
Brian

p.s. sorry for the large photo

[Clem Z.]

Re: valve guides- knurled or interrupted spiral?

i would think those guides would wear fast because of all the material that has been removed. we used a special coarse thread tap to put internal grooves part way down in the guides to hold the oil before better guide material came on the market. any good shop should be able to install cast iron sleeves inside those guide.

[Craig S.]

Re: valve guides- knurled or interrupted spiral?

Brian - Most of the spiral liners I have see were bronze wall, but you may want to poke around on the Goodson Tools and Supplies Engine Builders site....here is the link to just some of the valve rebuilding tools and linners page.....Craig




Goodson Tools and Supplies

[Joe L.]

Re: valve guides- knurled or interrupted spiral?

Brian------

I've got good news for you. This type of valve guide is one of the best out there. Most folks consider this type of guide "beneath their dignity" and feel that it is inferior to bronze guides. That's not the way it is, though. This type of guide is the most durable and best performing guide out there.

My late machinest had well over 50 years of engine building experience. He built everything from stock motors to those for use in competition dragsters. He built MANY engines that were winners at the old Fremont, CA dragstrip. He told me once-upon-a-time that this was the ONLY type of guide that he would use for ANY street engine.

[Clem Z.]

Re: valve guides- knurled or interrupted spiral?

joe i will differ with you as there is a lot of surface area removed with this type of guides,knurled, and i have seen them get loose in 10,000 miles of running. cast iron or meinite(sp?)a better grade of cast iron, guides are the best wearing for street engines especially if the valve stems are not hard chrome plated. never use bronze wall guides without the hard chrome stems as the stems will wear very quickly. as i posted above we cut spiral grooves in the guides with special ground tap to hold the oil but we did not remove anywhere near as much material form the guide bore as shown in these pictures. it looks like 40% area of the guide wall is removed by this method. if this is a corvette that will not be driven a lot of miles you could be OK JMHO

[Joe R.]

Re: valve guides- knurled or interrupted spiral?

Joe,

Clem is 100% accurate in his evaluation of this guide. It is a poor mans choice and a poor choice for controlling oil in valve guides. Your old mechanic was exactly an old shade tree mechanic. Study the new methods for replacing or renewing valve guides and you will throw rocks at that shade tree.

Regards,

JR

[Joe L.]

Re: valve guides- knurled or interrupted spiral?

clem-----

Actually, as I think about it, the ones that Al used to use were not exactly like these. They were thinner wall cast iron and were installed after over-boring the original guides. The wall thickness was about 3/16" to 1/8". The internal surface of the guide was "knurled". However, it was NOT a spiral (i.e. it was NOT like threads). There were COMPLETELY PARALLEL "ridges" and "valleys" in the guide bore. I also recall that Al said that they were manufactured of a special grade cast iron. He described them as similar to the configuration of older Oldsmobile V-8 cylinder head valve guides.

I recall Al saying that he had used only this type for street engines for many years and never had any reported problems with them, whatsover. If a customer wanted bronze guides for a street engine he would install them as long as they understood that they couldn't come back complaining to him when they wore out in 10,000 miles, or less. He said that the cast iron type that he used were good for 100,000+ miles. On his recommendation, those are the ones that I had him install for me and I never had a bit of trouble with them. No guide wear, at all, after about 100,000 miles on them. Just like he said!

[Clem Z.]

Re: valve guides- knurled or interrupted spiral?

we found out later the best way to keep the guides from wearing was to use a piece of 220 grit emery paper to put a cross hatch pattern on the valve stem to hold the oil just like a cylinder wall.

[Brian Monticello]

Re: valve guides- knurled or interrupted spiral?

Thank you for the comments. I will call the shop that did these heads and see if they were knurled or if these guides are some sort of of "special" guide. All the work was done by Bischoff Engine Service in Indiana. I just can't accept the possibility that someone had these heads built with knurled guides!

http://www.besracing.com

Brian