Valve grinding question

[walt jones]

When Model A valve seats are ground should a single angle grind be used or a multi angle grind to narrow the seats ?

[Tom Wesenberg]

I would never grind valves without the seats having 3 angles.

[Russ/40]

A multi angle job is necessary to get the proper seat width. That being said, its a very forgiving engine, and excessively wide seats just need redoing sooner.

[Fullraceflathead]

I would keep the width no bigger than the original Specs. If you run extra wide seats you are increasing the chance for carbon to potentially build up on the seat. Once this happens the exhaust valve can burn. Remember the valve spring pressure in the Model A is realatively light by today's standards. Valves can stick easily too if not set up with proper stem clearances and kept clean, no heavy carbon or gummy old gas build up.
Strictly from an Air Flow point of fact. The three angles and proper seat width will flow more air at lower lifts too.

[Patrick L.]

A valve job should consist of at least 3 angles. The purpose of the 'top' and 'bottom' angle is to set the seat to the correct width [ .080-.090" exhaust, .060-.070" intake] and center the seat on the valve face. I use a plain ole pencil to check those.

[BILL WILLIAMSON]

Sponsored Links (Register now to hide all advertisements)

If you're not well versed doing these angles, get a seasoned machinest to do them.
Bill W.

[noboD]

Originally Posted by BILL WILLIAMSON

If you're not well versed doing these angles, get a seasoned machinest to do them.
Bill W.

With a Neway seat cutter, gives much better finish and is more accurate.

[BRENT in 10-uh-C]

Interesting read guys!! Not sure I am understanding your positions though.

Actually what I have learned thru my son's racing efforts is the valve seat angles really does not have anything to do with the width, ...it is done to aid in air flow over the seat. Theoretically if you cut the valve at 45 and the seat at either 44 or 46, you will see a tight width there too. That is why it was never recommended to run the same angle of seat and valve.

And matter of fact, performance technology today has gone away from the typical 30-45-60 degree seat angles that most folks are familiar with. Taking that even further, most hi-performance shops that do head work do not even use an air-flow bench any longer. (Thus the reason a SuperFlo system can be purchased so cheap these days) Technology has moved to using a wet-flow bench that actually uses a dyed liquid flowed with air to represent the air & fuel mixed. What they have proven in some engines is the shape of the seat can cause turbulence that causes the fuel to fall out of suspension with the air. Surprisingly enough, some smaller engines actually fall off in gains with a 3-angle valve job. Adding to this mindset, the shape of the valve head, the port, etc. etc. all factor in on this. Personally I did/do not have the time nor $$ to spend on having a block wet-flowed to find out if a 3 angle is actually worth the extra effort on an A/B block however if you want to study up on this yourself, follow what the Briggs & Tecumseh garden tractor puller engine builders (-not JR drag racing engine builders) are doing. Again, based on what questions I had asked back then, it is very possible that a typical 3 angle job does/did not create any additional performance gain on a 'typical' restored Model-A engine. Just more food for thought ...that once digested eventually muddies up the water!

[Patrick L.]

Someone just had to go beyond what we were talking about. We , I thought, were talking about a long lived reliable valve job on a Model A or some such similar low performance flat head motor.
Talking about modern technology and high performance engines is a different conversation. Thats a good conversation to have, I just didn't think it applied here. JMO. Sorry to get involved.

[H. L. Chauvin]

FWIW: On Valve Grinding Jobs:

Several persons in the past have published numerous Model A and Model B dynamometer performance test which indicate increases in A & B engine horsepower.

A few years ago, in talking to several persons who published these tests, I found that not all individual tests were printed and published.

In speaking to Mr. Ron Kelley several times, (advertised in MARC magazine), he stated that through careful dynamometer testing, he found that the most "inexpensive" and "easiest" method to improve Model A/B/ engine H. P. performance was to make a few modifications on one's next "valve grinding" job, to try to "increase" fuel/air mixture flow entering the combustion chamber, for example:

1. Remove any built up carbon on top of engine, around valve seats; and,

2. Remove and round off the sharp angle and the tiny metal lip on the circumference and bottoms of the valve's valve seats; and,

3. Remove and round off the sharp angle on the circumference and tops of the valve's valve seats; and,

4. Feel for sharp angles in the intake and exhaust ports and "slightly" round off these sharp angles in said ports with a Dremel tool stone; however, be careful and do not remove too much engine cast iron in ports such that one causes the water jackets to leak; and,

5. With a Dremel tool, sooth out the interiors of the intake manifold at both the engine and at the carburetor.

6. Insure that the carburetor to intake manifold gasket has a large enough opening and is centered to allow unobstructed full flow at this gasket joint.

Did this on my last engine which performs well ..... 1930 Town Sedan .... average 20 mpg in stop & go traffic ........ modifications include a B distributor, a B carburetor, a Police head, a Stipe 330 cam, and a 3.27 to 1 ring & pinion gear set.

[BRENT in 10-uh-C]

Originally Posted by Patrick L.

Someone just had to go beyond what we were talking about. We , I thought, were talking about a long lived reliable valve job on a Model A or some such similar low performance flat head motor.
Talking about modern technology and high performance engines is a different conversation. Thats a good conversation to have, I just didn't think it applied here. JMO. Sorry to get involved.

No not necessarily Patrick. The entire conversation started out as whether a single angle, -or multiple angle seat should be used. Tom then suggested it be a 3-angle seat. You then mentioned what those angles should be. Others followed suit. The topic then turned to "why" a 3 angle job was needed. Again, as I said above, I am not sure I understand your thoughts and positions on this as it counters what I have been taught by some top notch motorsports engine builders. More than a couple of them have offered thoughts that multiple angle valve jobs on a low rpm flathead application likely would not find a gain in performance. So it begs the question, does anyone know for sure if one shape is superior to another in a 'typical' driver Model-A application, -or is it speculation based off of a totally different engine configuration and application??

[Bruce Lancaster]

I understand the '26-7 T's came with radiused seats...in effect continuous set of angles.
Somewhere I have a KRW seat reamer connected with that. Radiused seats have been a fad in race cars from time to time.

[Tom Wesenberg]

I've never given a thought to power increase in connection with the 3 angles. # angles are needed to establish the correct width of contact between the valve head and seat. How far you grind the top and bottom angle will determine where the seat contact area meets the valve. I want the contact area just slightly out from the middle of the valve, as the valve will expand slightly when it gets hot.

There was an International tractor shop near me years ago that only ground one angle and never cleaned the grindings out. I would never have had them do my work. Maybe they worked that way to get repeat business.

[ursus]

I have always understood that the ideal contact area for the seat was a compromise between rate of flow and the rate of heat transfer between the valve and seat. Supposedly, the 3-angle grind helps to achieves this optimization.

[Patrick L.]

Originally Posted by Tom Wesenberg

I've never given a thought to power increase in connection with the 3 angles. # angles are needed to establish the correct width of contact between the valve head and seat. How far you grind the top and bottom angle will determine where the seat contact area meets the valve. I want the contact area just slightly out from the middle of the valve, as the valve will expand slightly when it gets hot.

There was an International tractor shop near me years ago that only ground one angle and never cleaned the grindings out. I would never have had them do my work. Maybe they worked that way to get repeat business.

The width of the seat and its location on the face does make a performance difference. The number of angles can also make a difference. I've gotten fancy in my younger days and used up to 9 angles, but, I don't really do that kind of work today. Easing angles and edges thru out the intake system changes flow and sometimes adds [ or distracts] from flow.

We had a fella that claimed to be an expert auto machinist come to work for us a long time ago. He believed that just one WIDE angle was needed and his theory was that the valve needed to 'guided' back into seating itself. He didn't last long, he also would hone king pin bushings one at a time. When he warped one too many valve covers from use of the impact wrench it was time for his tool box to head down the road.

[Tom Wesenberg]

I just pulled this picture up from the internet, for anyone interested.

Google "images of 3 angle valve job", and you can stay busy reading all day.

[Terry, NJ]

When I first saw this thread, this AM, I was tempted to comment, but then I thought better of it because of all the comments regarding the 3 angle seat. I was taught that valve seats had to be 3 angles and I was just being lazy and cheap for not bothering to do it right. I say "cheap" because my Hall Detroit valve seat grinder didn't come with 30 and 60 degree stones, only 45. So I did my best job of grinding them i knew how. The seats at 45 deg. and the valve faces at an interference fit of 46, or is it 44 degrees? Whatever makes the contact at the at the top of the valve seat, lap them to a 1/32 ring and call it done. I had far more trouble with grinding the valves for a proper gap I use a chop saw and a VEE block and I got impatient and took too much off a couple of valves and it sounds like a cement mixer. It runs fine, just noisy!
Terry

[walt jones]

I would like to thank all who responded with comments to this question. You have helped make a good learning experiance for me.