As I’m waiting on my new (old from eBay) Zim valve compressor to arrive, I wanted to see what is being done with the valves in the really old engines. To give you an idea of the old I’m taking about, I’m working on a 1937 Hudson 212ci 6cyl splasher. From what I can tell the 1937 valves are same size intake & exhaust & they were typically ground to 45 degrees. What I’m wondering is if there maybe a reason to do a 3 angle valve job vs the original 1 angle? In searching the internet for information, I ran across Flathead ford, Model T guys as well as the guys with old ford tractors doing 3 angle valve jobs. From what I’ve been learning, 3 angle valve jobs have been done for around 50 years now and the main benefit is to improve the flow of air into & out of the combustion chamber. That has to be balanced with enough surface of the valve touching the seat for proper cooling. Additionally I’ve read of individuals cutting the valve face at 45 degrees and the seat at 46 degrees but not sure it’s a benefit. However I’ve been told the 1 degree of wedging effect will actually help the valve seal “lock down” at its time of rest to help the cooling. Additionally as I was looking at the valve stems, they are huge, thus has anyone turned down the stem of the valve in the intake, (outside the guides)? I know some may view these as hedonistic ideas on these old splashers but I had to ask. I believe these are the valve specs: Head Dia 1-3/8" Overall Length 5-11/32" Stem Dia .373" Type Lock 1 Groove Seat Angle 45° Sent from my iPhone using H.A.M.B.
Greetings corn husker!....when I was in Diesel mechanics class over 40 years ago the pretty sharp old dude that taught me quite a lot believed in always doing a 3 angle valve job with one degree of difference on the actual seat to better allow the valve and seat to " mate" ....
They not only specified seat angle but also the width of the seat. If the seat was ground down it could be too wide, then you would use 2 stones one of a flatter angle, another of a sharper angle, to get the seat to the right size. This is what you call a 3 angle valve job. Really it was doing the job properly to get the right width of seat. I have heard of necking down the valve stem and grinding away the back of the valve but only on racing engines where they wanted to lighten the valve for more RPMS. A waste of time in your engine. Do a straight overhaul and a sharp tuneup and you will have enough power to be getting along with. You might be surprised how nice it runs if you corral all the horses that have gone missing over the years. This has been the experience of friends of mine, who had tired six cylinder cars of the thirties, forties and fifties. They found they had all the power they needed for normal use.
The finishing touch of a valve job was to hand lap each valve with fine compound after grinding them in with a stone. This made a perfect fit and allowed you to see that the valve and seat were a perfect match. They haven't bothered to do this in the typical valve job for years.
Rusty O' Tool explained it pretty well. This diagram should explain it along with the folowing link that I got the images from http://johnmaherracing.com/tech-talk/3-angle-valve-job/ borrowed the drawing from. Most shops normally did a 2 angle valve job doing the contact area (in this case the 45) and then narrowing the seat at the top to get the correct seat width. The third angle (the 60 in the drawing ) allows you to narrow the seat from the bottom and helps both with flow and with keeping the contact area at the correct height in the head a bit easier. The also talk about backcutting the valve face as seen in the second image. That is the 30 degree cut on the valve face after the 45 was done.
Man that is the biggest stem for valve diameter I've ever seen. I wonder if that 45-46 angle was ever proven, or if it just sounded good. One of my old motorcycles use a 30 degree valve angle, they claimed it flowed better at the limited lift it has.
I've chucked the valves in the drill press and polished them before. Prettty tedious but they sure looked nice when I was done.
Truck Y block had 7/16" didn't it? probably filled with sodium, though. The seat is normally cut with 3 angles on all valve jobs, the valve itself might be cut with 3 angles if you're going racing in a class and you need to make a whole bunch of little modifications that might add up to getting slightly ahead of the other guy. I would not bother on an old Hudson engine, at least not one before the early 50s, and then only if it's being buil by Smokey..
Well I'm going to assume that this is a lot closer to a restoation than a Hot Rod Hudson. Agree with Squirrel though in that if I was building a "hot rod " Hudson engine I'd want an early 50's model to begin with. A local Gent by the name of Jack Passenger built and ran som pretty fast Hudson stock cars in the 50's and raced them up into the early 60's.
Indeed there have been a few pony’s which have escaped the corral! Hopefully I can at minimum bring them back home, if not add a few along the way. You are correct, it’s a non modified Hudson engine currently.... while I’d like to add some kick to her, she’ll never hold a candle to a 7X-308 Hudson 6 cylinder, which would be a very cool upgrade! I’d forgotten about polishing the back of the valve, great advice! Definitely planning to do a hand lap on the valves to block. The biggest question I have will be how wide should the 45 degree cut be which contacts the seat? Suggestions? Sent from my iPhone using H.A.M.B.
The factory shop manual should tell you how wide the seats should be. For a stock valve job, the valve face should all be 45 degrees, the seat should be as wide as specified, and centered on the face of the valve. If you do the three angle cut on the valve, you still want the 45 degree face to be a bit wider than the seat--the seat will wear a little over time. Maybe 50% wider than the seat?
How is it possible to have the correct width, and correct height of the valve seat without doing three angles?
The seat will have three angles, no matter what. But you can also grind three angles on the valve, to improve air flow a little bit. Sent from my Trimline
I just checked the factory mechanical Procedural manual & it only states 45 degrees. I believe the entire valve & block seat were a 1-angle valve job not 3 like I’m looking to do. Sent from my iPhone using H.A.M.B.
The 45/46 grind was to make the valve pound itself into a tight seal. This was instead of hand lapping the valves in other words, instead of doing the job properly. It saved time and worked well enough.
Yes, the 'One degree interference rule'. Said to 'lap valves while you drive'! 'We did this in the Porsche shops, but only to Volkswagens/Opels.
The Jalopy Journal
