Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties valve guides

valve guides

Moderators: Curt!, Pa

Post Mon Oct 04, 2010 6:14 pm

Posts: 541
Location: Wa, USA
What is the correct amount of press fit for BTSV valve guides? I have looked in Palmer's, the factory service manual and searched this forum and have not found the answer.

Post Tue Oct 05, 2010 8:19 am

Posts: 1671
Location: Interlaken, NY USA

Woody, Don't know the exact spec. However, when I redid mine awhile back, I took them to my friend who's been doing these motors for years. He actually Hammers them in. The rationale is the abrupt shock is less stress overall in the fitting process. I tried .002 over guides and they wouldn't go. We turned them to about +.0005 and heated the jug with a Bernz o matic torch 'till it was warm, pulled the guides out of the snowbank and bam, bam, bam they were in! I've always chided him on his crude method, but in the right hands, a hammer can be a tool of finesse.
Long and short, the holes in the block don't change much, and std or slightly oversize should do the job.
This may not help you, but I thought I'd pass it on anyway.
DD

Post Tue Oct 05, 2010 8:59 am
panic

If it goes in easy, it's not stable.

Post Tue Oct 05, 2010 6:44 pm

Posts: 541
Location: Wa, USA
Thanks, Panic.

The reason for the question is that I am making my own guides. Every guide that I have bought has the ID at .005" to .006" over the valve diameter. This puts the starting clearance at the top of the specifications (.003' to .0055"). Unless someone has more information, I will go with a press fit of .001". I will be heating the cylinders to 250 deg. F and using Sunnen 200L press fit lube. If you have not used it, it makes a big difference.

Post Sat Oct 09, 2010 2:29 pm

Posts: 919
Location: RENO,NV. U.S.A.
I would recommend 0.002-0.003" as a press fit,especially with this installation,in a heat environment. Check your local library for a machining reference for further details. BREWSKI

Post Sun Oct 10, 2010 5:27 pm

Posts: 17
Location: Marcy,N.Y. USA
Hi Woody. I use Rowe cast guides with excellant results. Rowe advertizes them as being .374 id and normaly they will need to be finished to size after instalation. Fit them at .001 to .0015 with cylinder at approx. 250 degrees and guides at room temp or chilled if you prefer.As these guides are quite long, .002 or more is a little stiff and not really necessary,but will sure close up the id. Hope this helps.

Post Tue Oct 12, 2010 6:04 pm

Posts: 541
Location: Wa, USA
Thanks to all who replied. I went with .001" press, heated to 250F, and used Sunnen press fit lube. Flawless installation. Everything went perfectly. .001" is exactly right.

Post Wed Oct 13, 2010 1:48 am
jib

Posts: 575
Location: devon,england
woody did you make your own guides in the end? what material did you use if you did , regards jib
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years

Post Wed Oct 13, 2010 8:18 pm

Posts: 541
Location: Wa, USA
Yes, I did. I used Durabar cast iron.

Post Thu Oct 14, 2010 6:02 am
jib

Posts: 575
Location: devon,england
cool ,cheers jib
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years


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