Shovelhead Guide and Seat Service

[dukekleman]

I had a shop call this week. They were looking for repair options on a set of shovel cylinder heads they were rebuilding on a customers 74" shovelhead motor.

I can say out of the hundreds of these I've done over the years, it's been awhile since I've seen such worn out rocker arms, shaft's, valves, guides and seats. They were really bad!

We talked about valve seat replacement or installing oversized valves. The shop and owner of the motorcycle decided on going the route of oversized valves.

New oversized valve guides were measured up for the guide bores, pressed in place and honed to the required clearances.
IMG_20250905_100621099.jpg
Note how sunk the valve seats are and shrouded
the valve were in the photo above.

IMG_20250905_152908619.jpg
This image shows the new valve seat angles plus a radius radius and unshrouded chamber. Valve seat margins are lapped in shown in the photo as well.

IMG_20250905_152852939_HDR.jpg
Intake valve with margins set on the left and exhaust margins set shown on the right.

Valve stem protrusion heights were all set to the exact height measured with my dial indicator and custom tooling . Meeting factory specifications.

I normally would have installed all new seats, however the owner didn't want to invest that much into the heads at his age and miles he will ride this secondary motorcycle of his.

I'll top them off with a set viton valve seals to control combustion chamber oil contamination and he will get many, many miles out of these.

I hope this helps make decisions on options available for others that may encounter similar scenarios...

Duke Kleman

[micmac]

Thanks for sharing Duke. I always loved my shovels. I bought one new in 1982 80 CI never had a problem.

[dukekleman]

Pete,

While I've never bought one brand new, I bought my first Harley Davidson my senior year in Highschool.
It's a 1971 FLH. It was the local HD dealership personal motorcycle. I still have it today. I've put just under 150,000 miles on it and it's still my favorite.
My kids grew up riding on it and drive it now themselves. They think it's a great motorcycle!
So I agree with you, I love my shovelheads and have a few of them in my fleet.

Duke Kleman

[joe fxs fxr]

My 79 FXS is my favorite bike to ride, it looks, sounds and feels right to me.

[chuckthebeatertruck]

Thanks for sharing, Duke.

I appreciate your realism about the owner and the many miles they will get out of this work. While it’s always best to do the full job; I’ve been amazed several times at how well sub-optimal valve jobs actually ran. . .and how long they last in old bike use.

I did a set of ironhead stroker heads a few years ago. I didn’t even try to use what was left in the original rocker box save the shafts. It was a super budget rebuild with donated labor, so I dug through my spares and assembled a very good set. When it came to the valve job, it got fun. I didn’t know you could wear the exhaust guides as badly as these were, so the bouncing really beat the hell out of the seats. Intakes were horribly installed at an angle and goo coated from protruding too far into the chamber. I was able to hone the exhaust bores and still have a great fit with std guides, but intakes required honing oversize to correct the cocked previous replacement.

All that done, the seats needed extensive cutting and throating, which sank them quite deeply. They really needed new seats. . .but it was out of the budget. I corrected the protrusion challenges, hand ground the heads to relieve the shelves/wells the valves were sitting in, and off we went.

It sounds horrible to do such work, but I knew from experience the owner would see 25-35,000 miles before the heads needed servicing. Truthfully, this is 40 percent of a good service life had I done a 100 percent job. However, the bike won’t see but 500-1500 miles a year. So, the 35k limit isn’t in the owners lifetime, probably not the next owner either. The budget was met and the bike roaring.

oh, and holy stink that bike was torquey and had a surprisingly quiet top end. It really shouldn’t have run so well. . .but it did.

[dukekleman]

Great story Chuck!
Somethings are truly a surprise and/or a head scratcher in the end.

Duke