Installing valve seats

[BillLee/Chandler, TX]

What is the procedure for installing valve seats in a Model A block?

We have seats that are labeled "16875-5". They measure 1.691+/- OD

How big should the seat be bored to give the proper fit of the new seat? I've read .005 interference when pressing the new seat into the block.

No, I'm not doing the machining myself, just trying to understand the process.

Thanks

Bill Lee

[BILL WILLIAMSON]

Datsun 210's would lose #4 exhaust seat. New heads came with center punch marks around the seat, to hold it in, worked well.
Anyone seen this done?
Bill W.

[colin1928]

New seats will have inst5"ructions with sizes
generally depending on material of the seats 0.003"-0.005" interference for cast iron
I go 0.005"-0.006" in side valve engines

[George Miller]

Originally Posted by BILL WILLIAMSON

Datsun 210's would lose #4 exhaust seat. New heads came with center punch marks around the seat, to hold it in, worked well.
Anyone seen this done?
Bill W.

The best way I have found is a small chamfer around top of seat. Then you use a rolling tool that comes with valve seat tools. Then they will not come out.

To answer your question yes center punching would work if the seat has a chamfer around the top or seat is a little below the top. But putting in below the top is not the best way.

The real best way is to not use a seat unless you really need them, which is not often unless the seat is cracked.

[johnneilson]

I would be real careful about putting seats in.
The big issue I see with the Mod "A", "B" is the deck thickness.
You can crack under the seats when setting them if too deep.
I have used seats 3/16" tall and not had problems.

YMMV, John
BTW, it is easy to make seats, 4130 tubing works very well and you can control the size.

[zzlegend]

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Originally Posted by johnneilson

I would be real careful about putting seats in.
The big issue I see with the Mod "A", "B" is the deck thickness.
You can crack under the seats when setting them if too deep.
I have used seats 3/16" tall and not had problems.

YMMV, John
BTW, it is easy to make seats, 4130 tubing works very well and you can control the size.

I have heard of this problem of deck thickness some where before. Thanks for restating this John. Bonneville is getting closer. Mark.

[johnneilson]

Mark,

no problem, I just cringe when I hear seats being put in.
I guess this is from the past when I had turbocharged small block v8s that cracked the heads under the seats after some 30 lb boost sessions. Thanks to Bars-leaks to get me home.

Yes, August is coming way too fast..........

[Synchro909]

I never use valve seat inserts. I see no value in removing good, original cast iron and weakening the already prone to cracking area between the valves and the bore.

[BRENT in 10-uh-C]

Originally Posted by Synchro909

I never use valve seat inserts. I see no value in removing good, original cast iron and weakening the already prone to cracking area between the valves and the bore.

Your point is well taken however from time to time I find an exhaust seat that is pitted or has a burned groove (from a burned valve) that I need to deal with. Short of finding a slightly oversized valve, what are you proposing as options?

[Synchro909]

Originally Posted by BRENT in 10-uh-C

Your point is well taken however from time to time I find an exhaust seat that is pitted or has a burned groove (from a burned valve) that I need to deal with. Short of finding a slightly oversized valve, what are you proposing as options?

In those situations where the option without putting in an insert is to scrap the block, by all means use an insert. For a pitted seat, an oversized valve would be less cats iron lost than an insert so I'd look at going that way. I was assuming the block was sound and usable with the original seats. I don't like the idea of putting them in otherwise.

[BillLee/Chandler, TX]

Originally Posted by BRENT in 10-uh-C

Your point is well taken however from time to time I find an exhaust seat that is pitted or has a burned groove (from a burned valve) that I need to deal with. Short of finding a slightly oversized valve, what are you proposing as options?

This is precisely the situation I am in! So that one valve is having a seat installed now.

[CarlG]

Here's my sad story:

The engine that was in my pickup when I bought it had valve seats that were put in when the engine was "rebuilt" for the PO when the vehicle was restored some 30 years ago. That engine only had about 1500 miles on it when I acquired the vehicle.

Making a long story short, after I had put about 2500 additional miles on the engine, two of the seats came loose and were digested by the engine.

Took the block to a local machine shop who then replaced all the valve seats. I got 50 more miles out of that engine before the block cracked between two of the valves.

And while I have no proof either way, I suspect that the interference fit was just too much and first time it got warmed up to operating temp, the cast block just couldn't hold it any longer.

[Synchro909]

Originally Posted by CarlG

Here's my sad story:

The engine that was in my pickup when I bought it had valve seats that were put in when the engine was "rebuilt" for the PO when the vehicle was restored some 30 years ago. That engine only had about 1500 miles on it when I acquired the vehicle.

Making a long story short, after I had put about 2500 additional miles on the engine, two of the seats came loose and were digested by the engine.

Took the block to a local machine shop who then replaced all the valve seats. I got 50 more miles out of that engine before the block cracked between two of the valves.

And while I have no proof either way, I suspect that the interference fit was just too much and first time it got warmed up to operating temp, the cast block just couldn't hold it any longer.

Exactly why I avoid them like the plague!
You guys are lucky that things like engine blocks are so readily available - Looks like you'll be needing one.

[Tom Wesenberg]

Originally Posted by George Miller

The best way I have found is a small chamfer around top of seat. Then you use a rolling tool that comes with valve seat tools. Then they will not come out.

To answer your question yes center punching would work if the seat has a chamfer around the top or seat is a little below the top. But putting in below the top is not the best way.

The real best way is to not use a seat unless you really need them, which is not often unless the seat is cracked.

In the 80's when I was working at the shop installing guides and seats I did it just as George said. I used a locking liquid on the seat, then rolled the head metal over the chamfer. Never had a problem. I also told many guys they didn't need seats installed. This was during the scare period when lead was first removed from gas, and lots of guys thought they all needed seats.

[BILL WILLIAMSON]

[QUOTE=Tom Wesenberg; This was during the scare period when lead was first removed from gas, and lots of guys thought they all needed seats.[/QUOTE]
YES, I remember that "SCARE" When everybody said,"YOU GOTTA' PUT IN HARD SEATS & STAINLESS VALVES"
Sorta' like when Emission Controls made cars SO LEAN & everybody said, "IT'LL FRY THE PISTONS"
Bill W.

[updraught]

Fairly unlikely a 4:1 engine of the mid twenties was designed for lead.

https://www.damninteresting.com/the-...oisoned-earth/

[George Miller]

Originally Posted by Tom Wesenberg

In the 80's when I was working at the shop installing guides and seats I did it just as George said. I used a locking liquid on the seat, then rolled the head metal over the chamfer. Never had a problem. I also told many guys they didn't need seats installed. This was during the scare period when lead was first removed from gas, and lots of guys thought they all needed seats.

Yes I used the locking liquid also, it is black in color. I still use a seat if there is no other option. I have also replaced a few that some one did wrong.
Like Tom knock on wood, have never had one come out since the 50 tees.When we did them in my Dads garage where we did what ever it took to fix the cars and trucks. But we never used one unless there was no other choice.