Early last year I posted a question on the old forum re: guide knurling. Ted responded that he prefered screw-in bronze guides, etc., and yet my mechanic (who worked at a Ford dealer in the late 50s) still feels that if the original guides are not really worn, and geometry is near perfect, mild knurling would be fine for a stock motor (he did this with many Y-blocks over the years, successfully). Though I can find no one else who agrees, I was not convinced he is wrong as I DO like the idea (better lubrication/expansion fit/valve cooling characteristics of iron, AND lower cost, etc.).

It has occured to me recently though, that he likely has not knurled the guides on a Y-block overhaul using the stainless STEEL valves I will supply. Nor has he had the chance to follow-up on one that has seen high mileage on unleaded fuel (lead was a great upper-cylinder lube). Most of his vintage rebuilds become show cars, or VERY low use, occasional drivers (since I put at least 8K a year on my '55, I will rebuild with longevity in mind). Though I am sure he will follow my instructions, he DOES require a lot of stroking to get him off the dime and start any vintage project at his age, so I had better have something more specific to tell him than "nobody does guide knurling anymore".

I need to make a decision before he starts the head work (likely when the snow slows down his normal shop business). Any suggestions?

6 VOLTS/POS. GRD. NW INDIANA

Guide knurling and piston knurling was standard practice during the 50's and 60's and would get you a few more miles out of a set of heads or pistons. We used to do it all the time back then at the ford dealerships that I worked at and it seemed to work pretty good. Would I do it now on one of my engines? NO!!!!  Pop for the replacement guides and hard seats if you plan on driving it.

Glen Henderson



Freedom is not Free

Letohatchee, AL

I’ll still put knurling in the car lot repair category.  Knurling simply raises a very small area or strip on each side of the knurling groove to restore the desired clearance back to valve stem.  This is ultimately a very small percentage of the guide area and ends up not being a high mileage repair.  If the camshaft is a performance grind with higher than stock lift, then the wear problem associated with knurling becomes compounded.  If the guide is worn enough to need repair, then guide replacement is at the top of my list.  I’m simply more partial to screw in bronze guides over other guide styles as their success rate and longevity is high in the applications for which I’ve used them.

Lorena, Texas (South of Waco)

Ted,



I'm thinking that the valve cooling effect of integral guides is likely less important with stainless valves/hard seats. Could the wear characteristics of stainless steel against bronze also be superior? Is bronze a more porous (oil retaining), or harder metal than iron?



Since I am really not familiar with the technical specifics of the mechanical knurling procedure, I had only presumed that a guide not significantly worn could be knurled, and then reamed so that the contact surface was nearly continuous. Wouldn't a guide in a NOS head (blueprint spec.) when knurled, and then reamed back to it's original size be identical to the others? Wouldn't the guide/valve contact area depend entirely on how much wear the knurling corrected, or am I missing something (like compaction/surface disruption of the iron)?



Regardless, if the stainless valves/bronze guides combination wears best, then the extra latitude allowed in rocker geometry would be more than worth the money spent installing spiral guides, just by saving the trial & error labor needed to get things perfect.

6 VOLTS/POS. GRD. NW INDIANA

Daniel, as Ted said, the knurling process only raises a small contact area. A easy way for you too understand the process is to take a center punch to any metal object. You will notice that the metal around the punched area is raised slightly, then if you take a file to it you are back down to the orginal surface (equates to wear). You will notice that it only takes a couple of file strokes. If you file the orginal flat surface, it takes several file strokes to remove the same thickness of metal.

Glen Henderson



Freedom is not Free

Letohatchee, AL

Glen,



And if you made a large number of punches in a very SMALL area, logic would seem to indicate that the file strokes required would increase proportionally.



None the less, it has occured to me that the question I posed earlier (re: a NOS guide knurled and reamed) is rather silly. Since reaming REMOVES material rather than compressing it, the knurled guide would still have less surface area.



Another point: If you were building up a set of NOS heads for longevity (hard seats/stainless valves), would you take the trouble to install bronze inserts in fresh, unworn guides? The oil-holding characteristics of spiral inserts (?), and the fact that steel is harder than iron would seem to justify the expense.






6 VOLTS/POS. GRD. NW INDIANA

Here in nascar country they use the guides for the reasons you 're quoted and I do all my with the bronze guides.The better oiling goes a long way.

-Gary Burnette-

forgot to put the word engines in my post.

-Gary Burnette-

I agree that the bronze valve guides are the best solution to worn guides in a high preformance/race motor. What ever became of .015 oversize valve stem replacement valves? Does anyone know of a source of stock or oversize valve head for a 292/312. For most street motors this seems to be more cost effective if the valves are still sold. Pete

Oversize valve stems would be a more desirable fix for worn guides as opposed to knurling as this would allow the surface area of the guide to be maximized.  Keep in mind that the guide area is where the heat is transferred from the valve to the head so anything (ie. knurling) that minimizes this area will keep the valve itself from cooling as quickly.  But off the shelf availability of oversize stems is decreasing as time goes along making this a less viable option.  As far as wear characteristics of stainless on bronze, the bronze guides themselves prefer additional stem clearance regardless of the valve material and this has to do with the expansion rate of bronze versus that of iron.

Lorena, Texas (South of Waco)