Technical Flathead valve seat width

I had a machine shop regrind my seats for larger diameter valves and everything was good. I proceeded to relieve the block .100 deep and one cylinder the cutter pilled down and went .140 deep and nicked the top of the valve seat. I took a valve and guide and lapped them in to see if they still seated together. Where the nick is; the actual lapped seat width is about .025 wide. The rest of the lapped seat looks to be .040 to .050 wide. What are readers opinion; should I put a new seat in or will it be acceptable? I am concerned where the seat is narrow that is where I will start to get a burnt valve eventually. I installed Manley 1.60 diameter valves so they are good valves and not the cheapies. Thanks for the response in advance.

 

I wouldn't let it go, especially if it's an exhaust seat. Rather than replace the seat, you should be able to just grind the set a little deeper.

 

You gonna relieve the other cyls to .140 ?

 

Almost 50 years ago, I relieved my first flathead. My thinking was if 100-125 was good, then 250 relieved was even better,so I cut pretty close to that figure. I run a big bore(.155 over) and 3/8 stroker and it hauls ass very well. The top piston ring is decently close to the relief,but no problems as of yet and I run it up to 5000-5200 rpm regularly. Don’t have any dyno pulls to verify h.p.,but it pulls my 32 Henry cabriolet strongly.

 

Great info. I am getting ready to relieve my first block.

 

Just a suggestion. Before you do anything, go to the fordbarn.com web site and select the 32to53 section. Post your questions about relieving a block there. Most experts there say it's not worth the effort unless you are building an all out flathead. Once you relieve a block, there are several other things to take into consideration. Compression ratios, combustion chamber volumes, etc.

 

It is a fine line between good flow, and keeping the CR up.

 

Thanks, I will check it out. I also sent you a message.

 

After a good deal of consultation and a little experience, my last flattie is not relieved....the other factors mentioned above considered, and the work to do it for what, 3-4HP?? BUT, to each his own, plenty of flatties are done with relieving and run just fine. Good luck!

 

I don't know the answer to your question, but is it completely out of line to TIG & add filler to it and regrind the seat? The cost may be a wash to replacing the seat & re-grinding. Plus, aftermarket seats are hardened and don't know how well that would weld without potentially damaging the seat.

You've already made the decision to relieve the block, which was time consuming. You've made a nick in the seat and you're going to be concerned about that for the existence of the engine's life. I think you need peace of mind. I doubt it'll effect HP or longevity, but... now's the time to deal with it!

3blap.

 

I went back and re-read and this is a good point. You should add some photos...

3blap.

 

I would say now is the time to do it right.
Might be ok, but why spend all that time and money and always have to wonder?


Sent from my iPhone using H.A.M.B.

 

Where are you I would find someone to widden the seat a little.