I have been searching around to see what the size / width of the 45 degree valve seat should be.
I am thinking of doing a 3 angle job on the seats of the flat head T245. Not finding much info I was going to do a standard size seat width with the 60/45/30 angles.
Then I found this reference to a Mopar Engine Manual.
Anyone on this board know if this is correct and or have done a three angle job?
personally, I think if it meant a lot back then, Dodge would have specified a 3 angle. Perhaps a very small performance gain. I wouldn't worry about it. hal
Typically the Exhaust valve is the one that can burn. Too little contact and it will burn. Too much contact and it doesn't get hot enough to shed its carbon buildup. The extra angles are just to improve flow around the seat and valve.
The Exhaust seat size range is the 1/16 - 3/64 = .0625 through .0468 that's a difference of .0156 to play with.
The factory did specify a three angle seat profile: 60deg, 45deg, and 20deg. The 20deg is sort of an odd angle nowadays, but Neway still makes cutters in this diameter and angle. A more common 30deg would probably be okay.
Here's Fig. 46g from TM 9-1840A Engine and Clutch:
Screenshot 2023-05-03 at 9.00.05 PM.jpeg (145.49 KiB) Viewed 2992 times
“When a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, IT IS THEIR RIGHT, IT IS THEIR DUTY, TO THROW OFF SUCH GOVERNMENT...” -Declaration of Independence, 1776
That's interesting. I went with the 60, 45, 30deg. I wonder why they chose 20 deg. I don't see that gaining more performance. As long as the seat width is good the valves will not tell the difference.
Doing the 60 degree grind was interesting as down in the throat of the intake and exhaust the openings had different amounts of metal/not consistent with the casting. I guess porting would have been in order if this was a racing engine.
I'm not sure of the history of the 20deg angle. The more common 30deg or even 15deg would work, at least as far as defining the upper boundary of the valve contact face. A flow bench would give some feedback as to which angles work better, but I've never seen a flathead block on a flow bench.
The intake and exhaust passages in the block on these flatheads are awful. Lots of obstructions, corners, turns, edges, casting nubs, etc. I'm in the process of doing a port match and polish on the block and head, and it's a lot of work.
“When a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, IT IS THEIR RIGHT, IT IS THEIR DUTY, TO THROW OFF SUCH GOVERNMENT...” -Declaration of Independence, 1776
I don't rev fast enough or have enough carb to even think about needing to port or polish. The rough surfaces keep up turbulence and help keep the fuel atomized and entrained in the air.
And the flow in a flathead is a joke at best. There was a reason for the compromise of the F head in Jeep
Hi All,
This is a timely post since we were playing around with grinding some seats yesterday in what has become the world's slowest engine rebuild!
That 20 deg top cut is weird. From what I understand if the angles differences are 15 deg or less the flow will behave as if the seat is a radius cut. For the last motor we put together we used the typical 60-45-30 cut and back cut the valves 30 deg. The idea was to try and improve low lift flow since that's what would benefit the engine the most. Once we have the deck mowed down .015" on this motor we'll be doing quite a bit of work to restore the valve seats.
We're using Sioux grinding equipment and it's been a learning process. Right now I'm wondering what the best stone is for the hardened exhaust seats. They are specified as "special alloy"... wonder what the heck it is??? The general purpose stone cuts it, but it's slow. We picked up a really nice Sioux 645 valve grinder except it's missing the coolant pump system. There's another project .
ashyers wrote: ↑Sat May 06, 2023 5:28 am
Hi All,
This is a timely post since we were playing around with grinding some seats yesterday in what has become the world's slowest engine rebuild!
There have been some rebuilds here (mine included) that have stretched out for years...
We're using Sioux grinding equipment and it's been a learning process. Right now I'm wondering what the best stone is for the hardened exhaust seats. They are specified as "special alloy"... wonder what the heck it is??? The general purpose stone cuts it, but it's slow. We picked up a really nice Sioux 645 valve grinder except it's missing the coolant pump system. There's another project .
What about Neway carbide seat cutters?
“When a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, IT IS THEIR RIGHT, IT IS THEIR DUTY, TO THROW OFF SUCH GOVERNMENT...” -Declaration of Independence, 1776
just me wrote: ↑Thu May 04, 2023 4:37 am
I don't rev fast enough or have enough carb to even think about needing to port or polish. The rough surfaces keep up turbulence and help keep the fuel atomized and entrained in the air.
And the flow in a flathead is a joke at best. There was a reason for the compromise of the F head in Jeep
"Flathead" and "flow" should not be used in the same sentence!
While I agree that the intake port surface texture contributes to maintaining the fuel atomization, I believe that the port shape is even more important. Bends, obstructions, sharp corners, etc. are all bad news in terms of keeping the fuel in the air, and these flatheads are full of problem areas. Especially so at lower RPMs, where the intake port velocity drops.
“When a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, IT IS THEIR RIGHT, IT IS THEIR DUTY, TO THROW OFF SUCH GOVERNMENT...” -Declaration of Independence, 1776
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