[marclar]

What exactly is "pinning" the seats?

when they drill the head for the newer style seats and install them. they will use a punch to 'pin' around the seat to expand the aluminum for a much higher retaining clamping force. basically they just whack some divits in the material.

 

[marclar]

Our 1st Escort dropped the #3 seat just a month after we bought it. We took it to an engine rebuilder for repair and he pinned all 4 exhaust seats in place.

while this is good advice, it is the intake seats that fall out on the cvh/hemi engines. It is not impossible for the exhaust to come loose but its is extremely unlikely. pinning exhaust seats was a thing of the past when shops would do 'inhouse' valve jobs without the assistance of milling machine. basically they just whack the old seat out and put in a new one. this typically left the material a bit loose since it was not milled to the next higher size, so they pinned to hold them in. sort of an obsolete practice by todays standards.

 

[Joey_Twowagons]

I call this technique "peening", which is what my Briggs manual calls it.
I was curious if there were little pins involved with "pinning".
I tried peening the loose exhaust seat into my 5hp Briggs years ago, but it didn't hold. So I machined for and installed a bigger OD seat.

 

[marclar]

there are no actual pins or any extra holding devices, its just the process of expanding the surounding metal using a punch of some kind

 

[Mark Eric Roth]

Hmmmm. It was a long time ago (the Focus was still in the future), but I recall the same fellow saying that there were no seats on the intake side as it was cooled by incoming air/fuel.

After the seat is installed, two non-parallel holes are drilled through the seat, preferably not where the valve will make contact with it, into the head and a hardened dowel pin is pressed into the hole. The guy must have used tweezers to put them in, I can't imagine his big blunt machinist fingers handling those tiny pins.

 

[Mark Eric Roth]

Peening works, but the term I use is swaging. That is hammering (in this case) around the hole to reduce the diameter. Aluminum is a perfect candidate for this, but it may not always work. I use this method when repairing American Flyer locomotives with loose zamac driving wheels. There, now you know something else about me!

 

[marclar]

Hmmmm. It was a long time ago (the Focus was still in the future), but I recall the same fellow saying that there were no seats on the intake side as it was cooled by incoming air/fuel.

all engines since the 30's and the flat head era have had valve seats. he must be horribly mistaken, or otherwise didn't understand the context. I agree that 'pinning' was a thing but that is going waaaaaaaaaaaaaaaaaaaaaaaaaaay back, probably before any of our fathers were born. that was an attempt to increase engine block life due to the short mileage intervals requiring valve re grinds. engines back then did in fact just have machining on the cyl block for the valves to sit on and as you can imagine the soft cast didn't last long before pitting out. a complete valve job was required every 15k back then

 

[Mark Eric Roth]

In times past valve seats were features machined directly into the cylinder head or block. As long as compression was low enough and/or the octane was high enough there was no problems with the valves, in most cases, for the life of the car. The problem comes with higher compression and, especially, unleaded gas. Lead was used to raise octane numbers but it also cooled and lubricated valves, not an issue with intake valves which are cooled by incoming fuel, but a lifesaver for exhaust valves. Without lead the seat overheats making it susceptible to misshaping (think of a piece of carbon getting stuck to the valve and hammering the seat) and getting soft resulting in faster wear. To compensate for this, separate hardened valve seats were invented, that is a valve seat that is a separate part from the cylinder head or block and the part that can fall out, regardless of whether or not it is an intake or exhaust valve. Pinning is just a way to keep that from happening.
As an aside, my first, and for a long time only, car is a 1956 Ford Ranch Wagon. After I rebuilt the engine the valves lasted over 180,000 miles and needed replacing only after I could not find leaded gas anymore. Nick's (same guy that rebuilt the Escort's engine) fix was installing, you guessed it, hardened exhaust valve seats. The intakes were okay.

 

[Itchigo]

The combustion chamber looks a little beat up but nothing that can't be cleaned up. The top of the number 4 piston also looks beat up on top, but the cylinder looks good. It even still has some crosshatching left.

 

[marclar]

pix

 

[Itchigo]

Ok finally....

 

[Itchigo]

After the valve job ($350). Ther bad cylinder is number 4 on the far right.

 

[Joey_Twowagons]

Better check that the "fire ring" on the head gasket does not seal over one of the little pits. Maybe you can put some gasket goop on it if it does.

 

[Itchigo]

Yeah, the shop noticed that too. We'll get it sealed though. I got a new set of rod bearings and rings so she'll be good as new.