MTFCA Forum

When reaming for oversized valve stems, does the reamer follow the worn guide and produce satisfactory results? Is some kind of fixturing required to be sure the new valves will land squarely on the seats? Thanks.
Mike

Depending on how steady your hand is, it should. BUT! It would be helped by a plug that is installed in the valve seat hole and held in place with a clamp. I would after reaming the holes, recut the seat and make sure the valve seats 360.

You need a fixture to keep the reamer square to the deck surface. I had 2 valve guides that had broken off and someone glued them back on. It didn't hold up. One of those guides was angled from wear. I installed thick bronze guides to fix it. A friend made a reamer guide for me. There are better designs out there but mine worked acceptably.

Hi Mike,
Mark has good advice but I don't remember any of the venders selling the plug or guide so you may have to make it yourself. I have never made
one & tried the steady hand method & have had trouble getting the seat cut to give a complete seat in the block. I now have a Thor valve seat
grinding setup because the last engine I worked on had seats installed that where so hard that my cutters squeaked & didn't make a mark in the
seats? I will be making a plug the next time I ream guides.
Craig.

36mike wrote: ↑

Mon Sep 22, 2025 12:40 pm

When reaming for oversized valve stems, does the reamer follow the worn guide and produce satisfactory results? Is some kind of fixturing required to be sure the new valves will land squarely on the seats? Thanks.
Mike

As others have stated, you need a guide to keep everything in line. You also should have a valve guide reamer, (i.e. not just any reamer). They look like this. Notice the leading 1/3 of the reamer has a built-in pilot/guide.

Jerry,
Can I ask where you found that reamer?

Scott

Attached are a couple of pictures showing my 1919 engine getting reamed. The standard .312 valves wobbled around in the guides. The engine machine shop owner who was helping me said the wobble was too much. So I decided to install .327 valves, which required reaming. I asked the machine shop owner do it. In the picture you will see that the bottom of the reamer does not have grooves on it. It follows the existing valve guide, as per the description on Snyder's website. I measured the width of the bottom "plain" end of the reamer and it was made to fit .312. After reaming the first guide he slipped a valve in then pulled it out and a smile crossed his face when it made a nice "POP" sound.

South Park Zephyr wrote: ↑

Mon Sep 22, 2025 2:28 pm

Jerry,
Can I ask where you found that reamer?

Scott

Scott,

I did a Google search for "valve guide reamer" and that was one of the first images that popped up. There were many more of the same style.

Thank you,
I assumed it was a specialty tool.
I should have done some research

Scott

Do you self a favor and find the thread from a few years ago about the reproduction valve spring cups. Unless the problem has been solved don’t use them. I only install Ford 390 modern valves that use split locks. Dan

South Park Zephyr wrote: ↑

Mon Sep 22, 2025 2:28 pm

Jerry,
Can I ask where you found that reamer?

Scott

I bought mine from Lang's.

Reamers always follow the hole they are used in. It’s just what they do. Any kind of guide tool would just bind it up. I have reamed countless T blocks out to 11/32” with zero problems. It has to be done in two stages.

either through lack of experience or plain ineptitude, I have never been able to get a reamer to jam with this tool - though it will center the new hole all but perfectly to the valve seat regardless of how worn the original valve guide hole is, and final seat concentricity/clean-up with a Neway cutter is a snap:

Most likely super rare but once tried to ream guides to install oversized valves ( Chevy valves ) The reamer went halfway down & seized up
would not back up & trying to back it up it snapped off in the guide. I had to make a punch & drive the broken reamer out! I found the reamer wrapped in brass when it came out. Turns out the guides had been reamed to .030 over & brass thin wall guides installed to bring them to stock
size. had to make a driver to remove the remaining half of the brass guide. Turns out the bronze or brass guides where in like new condition so
ordered a set of STD. valves & one .030 over to do the valve job. If the engine looks like it has been worked on before check the guides for a
yellow color before reaming just to be safe,
Craig.

In response to two questions, I purchased my .327 valves and the reamer shown in the 2 pictures from Snyder's.