The Dodge Challenger Message Board

New member, first topic...

Rebuilding my original 340 T/A block/heads

Valve guides to stem clearance is to high. According to the machinist, bronze guides cannot be pressed in, because the top of the cast guides have been already machined for Teflon seals.

Looking for original style 2.02/1.60 valves with .005 to .010 oversize valve stems

Any idea where to get them ?

Thanks for answers

Interesting. I can get bronze guides in almost any length from www.goodson.com part#CL-1830 in 3/8 .030 oversized for finish ream to 3/8"(.375), then you would have a bronze guide that would fit with the proper clearance of .001-.0008 and you can fit a dual spring with teflon seals for better oil control on the intake. The exhaust can be left without a seal if the clearance is at spec or a bit below. Another option to decrease the clearance is to knurl the valve stem. Or you could e-mail the various valve manufacturers like ferrera or Victory, I'm sure they can make a set for you, but then you'll be stuck with oversized valves that will only fit a guide thats larger. Also it will add a tad more weight. www.titaniumvalve.com can make a custom set for you.

My 340 has bronze guides and teflon seals. It also had a few chips in the top of the original castings so I see your machinists point. The seal covers it though and the guide is full height.

Can't remember exactly how thin they were, maybe 0.15- 0.20. Also which operation went first, guides, or seal machining.

Thanks for your useful answers

Here is the pic of my valve guides. As you sure know, machining for Teflon seals leaves thinner walls in the top of the guide.

"a" in my guides is only 0,08 left. The original size for umbrella type seals is "c". It seems that reaming and inserting a bronze guide is high risk for cast breakage.

You can notice on the pic that my guides have been already knurled (previons owner).

One more question: When you purchase any kind of new quality stainless 3/8 valves, what is THE REAL DIAMETER OF THE STEM. Is it 0.375 (=3/8) or less ?

My stem/guide clearance is not so bad: if new stems are 0.375, it will be just acceptable with new seals

Thanks again

I think you machine off that thin bit of existing guide and just push the new guide into place leaving a bit sticking up for an umbrella seal to sit against?

First topic. Very honored to have answers from the 2 leaders of the board.

Bronze inserts the machinist showed me seem a lot smaller than original umbrellas diameter.
Don't know if bronze guides with outer diameter large enough to accomodate Teflon seals exist?
Don't want to ruin my heads with unpredictible machine work: these are original T/A heads.

I guess the most conservative treatment is to slight ream original cast guides for the first oversize valve stem (if available !): 0,005 oversize would be perfect for my application.

I think you might have to use the original type seals and forget the teflon.

The whole point of bronze guides is that they are self lubricating so you can run tighter on the valve stem. So you don't need great seals anyway.

This is what happened to my heads.

I ordered Mopar performance new valves. They were announced 3/8 stem valves. The intention was to ream the original cast guides. I called twice MP tech line: the confirmed these valves had true .375 diameter stem. I received the valves (overseas) and measured: WRONG: stems were .372!!!

After talking again with my machinist, we decided to go for bronze guides. He did a kind of "socket" inserted around the already cut original guides, to prevent breakage when inserting the bronze guide (see picture). For proper clearance, instead of using the usual tool (which increases the diameter of the guide by pressure), he reamed the top of the new guide.
I can stay with Teflon positive seals.

Thanks to everyone for your help. Careful with tech lines...

Well when you PM'ed me I did tell you the stock valve stem diameter is listed as being between 0.3715 - 0.3725".

Glad you got sorted out in the end though. Thanks for the update.