my 1930 coupe has a great running engine but I would like to have a little extra power. looking for advice . I have a model b head . should it be milled and if so how much ? also also thinking about a b carb or would two tillotsons be better ? also have an old Mallory yL dist but would prefer to keep the original Thanks for any info STEVE
model a high comp head
- Thread starter sfowler
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Terry NJ
Well-known member
It's probably a good idea to take at least.020 off to flatten it. You should probably buy a new Snyder's 5.5 instead. Carbs are a matter of cost, effect, and maintenance. I prefer one carb to to a multiple setup. For the almost stock look, I stick with a "B" carb. BUT, I recommend that you "Port and Polish" your manifold. First, you'll have to bore out the main (Carb) runner) from 1" to 1.250"+ (To 1.300") For a Distributor, again the "B" seems to be a good choice. But you have to change the cam cover because of the different timing position. If your engine is out of the car and the flywheel is available, and you know a shop with a big lathe, have them take a few lbs off of it. This allows the engine to spool up a little faster. Good Luck!
Terry
Terry
I agree with Terry in post 2 above. You will get as many opinions as there are Model A owners. What I have found is that the 5.5 head mentioned and a touring ground cam does it all. I have had the 2 carb setup and it ran strong but I never knew if the two carbs were in sinc or not. I guess with a model A carb they can't hardly be out of sinc. I don't like my lightened flywheel as I am not trying to beat anyone of off the line. The heavy flywheel is said to wipe out the rear main bearing faster and therefore a lightened one is better for longevity, but at 81 years old I don't plan on the engine imploding in my life time. The heavy one seems to give a strong steady pull when going up a grade. Advice is to stay close to stock, Henry and his boys knew what they were doing. Jack
Fred A
Well-known member
Steve seems to be considering a B head on his A. The B head is a better designed chamber in an era when owners were still likely to add turpentine and other hydrocarbon solvents to the still antique blend fuel. It is still a low compression head. The cost of a B water pump and a resurface goes a long way toward that of the bargain Snyder's 5.5 offering. A single downdraft V8 carburetor is long used to give a good low cost boost but is a visually obvious change. I have run many. The B cam retains most of the garden tractor note of the exhaust with a good gain from improved Ford spec lift and timing. Since the Ford fours are some of the most expensive power out there, a light flywheel in any usual type is a great way to trim some dead weight that is tough on the center main, a weakness in Model A design. So called light flywheel is hardly light, but compared to the stock anchor. Track the continuous march to Ford flywheel reduction over the next decade. Driving and market expectations went a long way to slow some very basic improvements. The public was enamored with the extreme slow idle along with old Henry, probably gave the engineers heartburn. Another Opinion: Fred A
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thanks much for all the info . I will put snyders 5.5 head on my list . drove the A last night with my GPS and it went 50 MPH on a smooth flat roadway but not really comfortable . It liked 40 to 45 MPH much better and wasn't working so hard plus less vibration. I am planning more road tests before deciding on any modifications . the brakes work well and I always plan ahead and watch for other cars. I have a complete set of 1932 front brakes and wonder how much they might help stopping . STEVE
We are in the process of adding strengthening to the inside similar to the 6:1 heads. I just started machining some.
Tod
Terry NJ
Well-known member
I notice that no one has actually mentioned the original weight of the flywheel, it's 63 lbs. I've shaved mine down to 55 to 57 lbs. This is in an era where the average flywheel
on the roads is less than 30 Lbs. It drains hp to get this mass spinning. The need for speed is due to modern roads and traffic patterns. To get around Trenton NJ, I have to go about 4 or 5 miles on I 195. Whats it like in a almost stock mod A? Exciting, very exciting!
Terry
on the roads is less than 30 Lbs. It drains hp to get this mass spinning. The need for speed is due to modern roads and traffic patterns. To get around Trenton NJ, I have to go about 4 or 5 miles on I 195. Whats it like in a almost stock mod A? Exciting, very exciting!
Terry
Arlyn Bieber
Senior Member
6-1 Snyder's head, B cam, B carburetor, CW crankshaft, large intake valves, 28# flywheel, and a 36% Mitchell overdrive with 3.78 rear end is the way to go. This works great in my heavy slant window sedan.
I agree with others about the full-weight flywheel. After running a lightened flywheel for a couple years, I went back to a full weight flywheel on the same motor/car/etc. (only change was the flywheel and a new clutch) and it made a huge difference. Felt like another 10 HP when climbing hills.
However, unlike the others, I am not a fan of the high compression heads. They change the torque curve noticeably, and as long as you keep the RPMs up, they will serve well. However, if climbing a steep enough hill that the RPMs fall off, then the high compression head loses to the stock head every time.
With the stock head, the car could climb the hill to my house (about a mile long, kinda steep) in 3rd gear. It would go down from 50 to 40 MPH and then just dig in and stay at 40 MPH all the way up the hill. After swapping to the high compression head, it feels stronger at 50 MPH, but on that same hill, the RPMs fall off, then it gets below 40 MPH and then it really falls flat. I have to downshift and go the rest of the hill in 2nd gear, real slow.
As soon as I have a good excuse, I am going back to the stock head.
The trick is with the valves and the cam grind. The touring grind cam and bigger valves gets more air into the cylinders and gives you a lot more for your money and effort. It feels like another 10-20 HP all across the RPM range.
However, unlike the others, I am not a fan of the high compression heads. They change the torque curve noticeably, and as long as you keep the RPMs up, they will serve well. However, if climbing a steep enough hill that the RPMs fall off, then the high compression head loses to the stock head every time.
With the stock head, the car could climb the hill to my house (about a mile long, kinda steep) in 3rd gear. It would go down from 50 to 40 MPH and then just dig in and stay at 40 MPH all the way up the hill. After swapping to the high compression head, it feels stronger at 50 MPH, but on that same hill, the RPMs fall off, then it gets below 40 MPH and then it really falls flat. I have to downshift and go the rest of the hill in 2nd gear, real slow.
As soon as I have a good excuse, I am going back to the stock head.
The trick is with the valves and the cam grind. The touring grind cam and bigger valves gets more air into the cylinders and gives you a lot more for your money and effort. It feels like another 10-20 HP all across the RPM range.
Railcarmover
BANNED
A carb synch tool is vital to getting the most out of dual carbs...the heavier the flywheel the greater the balancing effect (less vibration) and more stored kinetic energy ( smoother power transfer). Counterbalancing the crankshaft is the key to running a lighter flywheel.In theory,a high compression head should help torque rise,not hurt it...porting intakes and improving fuel and exhaust flow is critical...it's how Ford and his trimotor aircraft engineer maximized the A engine during development.
Charlie Stephens
Well-known member
In my opinion it should be milled just enough to clean it up. Attached are pictures of a Model A police head that, in my opinion, has been milled too much. The first picture shows the relief intended for piston clearance has been removed. It might be OK but you would need to check your piston to head clearance carefully. The second picture shows a crack probably because it was milled to much. Several places on the head will have this cracking problem.
Charlie Stephens
