Valve Seating Question

old28

old28

Senior Member
When installing new over size intake (1.75) and stock size exhaust, all in stainless do you have to install hardend seats? This is my first model A motor build.

This motor will only be run twice a year in Trog beach racing for few hours each time.
 
I wouldn't do it. Enlarging the valve seat to take those valves leaves little enough metal between them and the cylinder. A hardened seat will leave even less.
In my last engine build, I cut 0.100 off the larger valves so there was a half way decent amount of meat to the cylinder. My motor is for long distance touring where durability is also a necessity, not racing though.
 
built more than one with oversize intakes. hardened seats not necessary - intake or exhaust. unless original seats are severly pitted.
 
If you have it down to bare block, why not get it done? It's not a bad thing since we no longer have the lead in the gas to lube the non-hardened seats and valves.

Take the time and get it done even for those 2 days a year. Who knows, if it runs as great as you can make it, why limit it to the sand?
 
All good stuff, thanks to all for the reply's. I have read a few threads on not cutting in valve seats as it will thin the area near water jackets. Is this correct?

I would like to stay with a 1.750 intake, but can have them cut to 1.650 if that is needed.
 
DaWizard said:
If you have it down to bare block, why not get it done? It's not a bad thing since we no longer have the lead in the gas to lube the non-hardened seats and valves.

Take the time and get it done even for those 2 days a year. Who knows, if it runs as great as you can make it, why limit it to the sand?
Click to expand...
model a valve springs aren't springy enough to require hardened seats nor is the compression there to warrant it either. IF they are badly pitted then yea have them installed but if they are fine leave em alone.
 
I never install seats unless the original seat is too recessed. A few guys have had seats installed just because they were told it's the thing to do. Too bad some of those seat later fell out while driving down the road. Of course properly installed seats don't fall out, but why add to the cost and take that chance.
 
Replacement seats are just something else to fail. Putting stainless seats in for todays gas is just a way for builders to get into your wallet. There was no leaded gas in the early 30's and all 20's. Most of the negative suggestions here are BS.
 
old28 said:
All good stuff, thanks to all for the reply's. I have read a few threads on not cutting in valve seats as it will thin the area near water jackets. Is this correct?

I would like to stay with a 1.750 intake, but can have them cut to 1.650 if that is needed.
Click to expand...

My car has 24,000 miles on 1.750 intakes, and no seats. You do not need harden seats. I have replaced some for some that have falling out. Not good for the pistons. If they are put in right they will stay. But some are not doing it right, why take a chance.
 
Not needed, especially on intakes as they run cooler than exh. I would boost the spring pressure a little because the bigger valves are heavier than stock.
 
SeaSlugs -- Tom Wesenburg -- James Rogers -- George Miller

Thanks guys for setting me down the right path. :)

Jim Brierley -- I felt that a stock seat was the way to go from your book, just wanted to make sure for my first A motor build. I will be using V8 springs with 85# pressure. Glad I got some real world information from guys that have installed & ran 1.75 intake. This motor will run on a mild race gas and 7.1-7.6 CR head.
 
Be sure to check the valve/combustion chamber side clearance. Depending on your head you may have to open up the chamber a bit for good mixture flow. Doing that dropped my CR about .2.
 
Thanks PC/SR -- I am planning on running one of Tod's Iron Crow Foot heads in the 7.5 range and will check the side clearance for sure. If getting it right only cost a few tenth's on compression we can live with that or mill a bit off the head.
 
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