The Ford Barn

oldspert · 04-17-2024, 08:27 AM

The engine block I bought has one intake valve that is recessed about .030 lower than all of the other valves. Need opinion on whether to replace the seat or just do the valve job and let it go. The block has already had babbit re-poured and is bored .080 with new pistons, counter balanced crank and is ready to assemble.
Ed

Fullraceflathead · 04-17-2024, 08:36 AM

I would use it as long as the seat width is within spec it's fine.

Jim Brierley · 04-17-2024, 11:45 AM

I would too, .030" isn't much.

nkaminar · 04-17-2024, 12:13 PM

The bring a seat back to the correct width, cut the seat to 45 degrees. Then cut the bottom of the seat to 60 degrees and the top to 30. As you are cutting, check to make sure the width of the seat that is at 45 degrees is in the center of the valve face. Do a light lapping of the valve to the seat. Just to the point of having a uniform grey ring on the valve. Some mechanics will cut the seat to 46 degrees which provides a sharp edge at the top of the valve face and, it is thought, a better seal.

oldspert · 04-17-2024, 05:23 PM

Quote:

Originally Posted by nkaminar

The bring a seat back to the correct width, cut the seat to 45 degrees. Then cut the bottom of the seat to 60 degrees and the top to 30. As you are cutting, check to make sure the width of the seat that is at 45 degrees is in the center of the valve face. Do a light lapping of the valve to the seat. Just to the point of having a uniform grey ring on the valve. Some mechanics will cut the seat to 46 degrees which provides a sharp edge at the top of the valve face and, it is thought, a better seal.

Good info to give to my machinist. I always lap valves just enough to leave a grey ring on the valve face. An old timer told me once to take a lead pencil and mark the seat with it, if the valve removes the mark when you rotate the valve, the seal is good.

Kurt in NJ · 04-18-2024, 07:49 AM

Sponsored Links (Register now to hide all advertisements)

it depends on how recessed the other valves are and as has be mentioned- the form and width of the seats
I have seen them cut so deep that the mushroom on the valve stem was almost gone and the keeper resting on the tappet with the top cut to narrow it the seat
almost under the gasket.

Take some pictures.

oldspert · 04-18-2024, 09:10 AM

Quote:

Originally Posted by Kurt in NJ

it depends on how recessed the other valves are and as has be mentioned- the form and width of the seats
I have seen them cut so deep that the mushroom on the valve stem was almost gone and the keeper resting on the tappet with the top cut to narrow it the seat
almost under the gasket.

Take some pictures.

The valves are not stock. they have straight stems so shortening them is not a problem. Adjustable lifters too. All of the other valves are above the block surface.

johnneilson · 04-18-2024, 12:00 PM

Typically having a valve low will not cause too much trouble other than limiting port flow
It should be noted that removing material from the seat will never raise the valve up
Replacing seats is an option but there can be complications if not done properly
So, if you have late model valves already I would look for a larger valve to replace the offending one or two
This allows for the seat to be corrected and get the valve raised back up

John

04-17-2024, 08:27 AM	#1
oldspert Senior Member Join Date: Aug 2012 Location: Texas Posts: 228	valve recession The engine block I bought has one intake valve that is recessed about .030 lower than all of the other valves. Need opinion on whether to replace the seat or just do the valve job and let it go. The block has already had babbit re-poured and is bored .080 with new pistons, counter balanced crank and is ready to assemble. Ed

04-17-2024, 08:36 AM	#2
Fullraceflathead Senior Member Join Date: May 2012 Location: Chillicothe, Missouri Posts: 1,182	Re: valve recession I would use it as long as the seat width is within spec it's fine. __________________ "If I asked people what they wanted they would have said faster horses." -Henry Ford "Primitive technology is not a design flaw" 1928 Ford Model A Roadster Pickup 1930 Gordon Smith Air Compressor 1941 Willy's Pickup 1960 Thunderbird-For Sale 1964 Buick Riviera 2x4 425 1965 Pontiac GTO, 455 Super Duty 2004 Dodge Ram SRT-10, V-10 Viper 1977 Charger Jet Boat,460 Ford,Jacuzzi Jet Front Engine Nostalgia Dragster,Supercharged 296 "Fullrace Flathead" Ford Engine Build up on DVD ask

04-17-2024, 11:45 AM	#3
Jim Brierley Senior Member Join Date: Jun 2010 Location: Temecula, CA Posts: 4,093	Re: valve recession I would too, .030" isn't much.

04-17-2024, 12:13 PM	#4
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,907	Re: valve recession The bring a seat back to the correct width, cut the seat to 45 degrees. Then cut the bottom of the seat to 60 degrees and the top to 30. As you are cutting, check to make sure the width of the seat that is at 45 degrees is in the center of the valve face. Do a light lapping of the valve to the seat. Just to the point of having a uniform grey ring on the valve. Some mechanics will cut the seat to 46 degrees which provides a sharp edge at the top of the valve face and, it is thought, a better seal. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

04-18-2024, 07:49 AM	#6
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,159	Re: valve recession Sponsored Links (Register now to hide all advertisements) it depends on how recessed the other valves are and as has be mentioned- the form and width of the seats I have seen them cut so deep that the mushroom on the valve stem was almost gone and the keeper resting on the tappet with the top cut to narrow it the seat almost under the gasket. Take some pictures.

04-18-2024, 12:00 PM	#8
johnneilson Senior Member Join Date: Jun 2010 Location: 34.22 N 118.36 W Posts: 1,057	Re: valve recession Typically having a valve low will not cause too much trouble other than limiting port flow It should be noted that removing material from the seat will never raise the valve up Replacing seats is an option but there can be complications if not done properly So, if you have late model valves already I would look for a larger valve to replace the offending one or two This allows for the seat to be corrected and get the valve raised back up John __________________ As Carroll Smith wrote; All Failures are Human in Origin.