Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties Hardened valve seats

Hardened valve seats

Moderators: Curt!, Pa

Post Sat Jun 01, 2013 6:04 pm

Posts: 93
Location: paradise california

When redoing cylinders do people normally cut hardened seat inserts into the cylinders? I had a engine builder insist that this should be done. Any thoughts?

Post Sun Jun 02, 2013 1:45 pm

Posts: 745
Location: Pa. , USA
Not normally Warren but if your builder insist on doing it by all means let him and please let us know the results , any modern up grades to extend the life of these old irons are welcome ..
Vintage roadracing, Class C, AHRMA # 335

Post Mon Jun 03, 2013 1:01 pm

Posts: 470
Location: Six miles East of Cheney, Wa.
I'd like to hear more...between the light use my UL will get, and adding Mystery oil most of the time and lead additve some of the time, I'm not too concerned...but it does sound like a reasonable upgrade.

Post Mon Jun 03, 2013 5:03 pm

Posts: 426
Location: Tucson Arizona

The original as well as the new reproduction cylinders have localized hardening that is good for up to 4 builds if the seat itself isn't damaged and the builder doesn't go crazy with the seat grinder.

The problem I've had and heard of is the hardened seats is failing, falling out & cracking between the inserts.

Ander's and I talked about an insert that would include both valves instead of one per valve.......nothing happened with it though.

But as I said, the oem and repo's have localized hardening and I have thousands of miles on mine running unleaded with no issues whatsoever.


Post Mon Jun 03, 2013 7:29 pm

Posts: 470
Location: Six miles East of Cheney, Wa.
Someone needs to invent a lead pill that slowly dissolves in the gas tank. :-) But, it does not sound like the need is all that great.

Post Wed Jun 05, 2013 3:21 pm

Posts: 176
Location: Carmarthen, Wales, UK
I fail to see the need for hardened valve seats on "normal" 45's. My advice on the subject came from Fred Warr who knows a thing or two about 'em; he reckoned that since flatheads burn oil by design, the standard trick of dropping the throttle on a run to bring oil up the bores gave the engine as much "fuel additive" as you'd ever need to compensate for the missing lead halides.

I sent my 72 Ironhead for a top-end strip and refurb some years ago, it had about 35K miles on it then and had never been rebuilt. This after about 3 years of running solely unleaded fuel; the engineer reported back that there were no signs of valve seat recession, and I used that thing pretty hard!
72 Ironhead, goes better than it stops!



2005 XL1200R.... well ya gotta have a rat-bike!

Post Wed Jun 05, 2013 9:39 pm

Posts: 2677
Location: Los Angeles, CA
I have heard that there is a guy who welds your overground seats with a material that is good and hard. I don't remember who or where he is.

Post Thu Jun 06, 2013 1:34 pm

Posts: 90
Location: Norway
Hi. I have had hardened seats in my BTSV for many years now. Never regretted this. I am positive that this extends the live of valves and seats. And it brings new life to sylinders with valve seats that is ground many times.

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