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Tech Q&A - Modified Vehicles


I enjoy driving my '30 Coupe and touring with the "Colonial Virginia Model A Ford Club." I usually operate at sustained highway speeds up to 50 mph. In order to reduce strain on my engine, I am considering changing my stock ring & pinion gear, and engine head to allow operation at fewer RPM. Do you have a recommendation for a high speed ring & pinion set-up in combination with a head that has a higher compression ratio? My engine has a stock bore and I am considering a ring & pinion gear with a ratio of 3:54 to 1, and a Brumfield head with a compression ratio of 5.9 to 1. Is there anything further that should be considered when making this modification?

The 3:54 with Brumfield head is about the best combination you can get .... unless you want to put in an overdrive. I have a 3:54 with high compression head on my Phaeton and I like the combination. I have also added a "B" cam which moves the power curve to the higher RPM range. It gives the appearance of more power but not really, just more power at higher RPM. It gives the extra power when climbing hills where it is needed.

If you are fighting highway traffic and want to drive at 60 mph with out putting the strain the engine, I would put the Mitchell Overdrive in. Its been extremely dependable for the folks around here. But you are looking at about $1800. The difference is when you need to maintain 60 mph your engine is only turning at about 40 mph. It really saves the engine. It also helps to have about 25 pounds taken off the flywheel. These are the main things you can do to increase power and reduce engine stress. -- Les Andrews, 1998 Technical Director


I have a 29 A standard coupe, car looks to be 30, but engine is a 29, ?? and a Riley 2 valve OH conversion head, with a Mallory magneto for this car. The exhaust valves remain in the block as original, with two valves for each cylinder in the head. Now the hard part. What kind of carburetion and exhaust should this be set up with ?? Dual up drafts, or ?? Exhaust-- I have no idea. Cooling modifications? I would like to restore the car to original except for the engine modifications, but I think it should be set-up properly to look and run like a true "Hot Rod Model A". The Riley head came from Montana, and I am told it was a competitor for the Miller-Offy OH conversion that ran at Indy in ?? 1929, 30, 31. I have seen a Miller head also but I don't know where it is today. Any ideas on parts, literature, a Photo (lots a luck) would be helpful.

What you have is a Riley Valve In Head overhead valve conversion first made in 1929 by George Riley. I am mailing both of you a copy of magazine that has all the answers you will need to get you project started. I applaud you for trying to restore the car and keeping the engine as you found it. These original Riley two port heads are worth about $4000 complete.

There were about three versions made in the old days and one new version is back on the market today. These were the best heads ever made for the Model "A" and "B" engines. Powerful (about 80 HP) but not so much that they would damage the engine like so many other OHV. The head is an "F" head . . . meaning the intakes (2 per cylinder) are in the head and the exhaust (1) are in the block. All the parts are Model A : water pump, valves, springs, guides, keepers, exhaust manifold. the Intake manifold is special, but a Model "A" speed manifold can be made to work. Strongly suggest that you join the Secrets Of Speed Society (SOSS) to learn more. There is so much information that it has taken us 8 years to get the whole story out.

-- Charlie Yapp, Executive Director and Editor of the Secrets of Speed Society, PO Box 957436, Hoffman Estates, IL 60195-7436

Last Updated: 01/20/2009