Flathead Valve Guides - replace or bore & reline?

Unknown

I just posted the following on the "dead-as-a-doornail" Chrysler sight where it will probably languish unseen for an eternity. I hope that you forgive my asking you a question about my Dodge engine, but I'm sure that the issue I raise will soon be an issue when I bring my Commodore eight engine in to the shop, as well:

I'm in the process of rebuilding the flathead six from my '36 Dodge. I recently spoke to a machinist about having some of the usual shop work done on the block (boiling, installing cam bearings, valve seats and new guides, etc). I've accumulated all of the parts that it will need including valve guides. He suggested, however, that he could just as easily bore some material out my old guides (in place in the engine) enough to install new "valve guide liners". Perhaps this is a good idea because he would be using (I pressume) some new, modern wonder metal ideally suited for this purpose. The truth of the matter is that he simply wasn't all that forthcoming about which method would best in the long run. In my limited experience this just isn't something that I've run into before. Do any of you have any insight to share?

Unknown

James... Seems very strange to me that your machinist would not be forthcoming with precise information about ... exactly what he is doing to YOUR ENGINE for YOUR MONEY. As much as it costs to redo one of our engines, I would have to know exactly what the machinist has in mind before providing parts or monies. Perhaps Randy Mass or one of the machinists who come here can add specifics ... my two cents.



Good Luck

Unknown

I simply meant that he was vague about which would be better in the long run.

[Deleted User]

Is your machinist familiar with older engines? and with removable valve guides? it seems to me to be easier to knock out the old ones and put in the new ones.



When I worked in my Dad's garage we used to bore out the guides in the V8 engines during rebuilds and press in new bronze guides. This was because the old guides were worn and not of the removable type.

Unknown

In older engines the normal procedure was to install new guides if they were the replacable type and the old guides were worn to the point of not having proper clearance. In engines without replaceable guides, they were reamed out to fit valves with oversize stems. Do you have new valves as well? If so your machinest could tell you what the clearance is between them and the old guides and if necessary install new guides. In any case new valves and guides are the way to go,

Unknown

Tombpa, Thanks very much for your explanation. I've never encountered valve guides that weren't replaceable. I understand now why relining the old guides was a nescessity in some engines. I do have new valves and guides for both my Dodge six and my Commodore eight and I'll see to it that both engines get new guides installed. Again, thank you!

James

Uncle Josh

Just went thru this. See thread

http://www.classiccar.com/forums/showthread.php?t=4670

At $6 per new guide, it's gonna be a lot easier and cheaper to replace them.

Geoff

Use the new guides. Cheaper and quicker, and how many miles are you going to do??? You will never wear them out. Most engines did at least 100,000 miles before the guides were worn enough to need replacing. I have seen several engines (early Hudson and Essex super Six) done with bronze liners in the guides, and in each case they had to be stripped down and reamed out further, as there is insufficient lubrication in the exhaust valve guide, and the valves jam and stick. What I have done several times (before I ran out of a supply of old engine blocks), was take the inlet guides out of a worn block, and use them as exhaust valve guides in the block I was rebuilding. The inlets don't wear, as they suck a small amount of oil up the stem and get lubricated. The exhausts need a couple of thou extra clearance to cope with the heat, and lack of lubrication. A used inlet guide provides this. But you will have to re-cut the seat whenever you replace a guide. Good luck,

Geoff.