Thread: What HP would you guess???

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These are some beautiful built flathead motors with blowers that look like they would make some serious HP and lbs. Anyone care to guess what they would make?

Chevy37
This one is "expected to dyno at 340 hp" according to Hot Rod Magazine. Note that it has a lot more sophisticated components than does the ones
in your pictures.....

It's amazing that they can force enough air through those flatties to make that kind of HP.

Just remember that the crankshaft on those flatheads had 3 main bearing journals and that the bearing shells on the conrod bearings floated between the conrods and the bearing journal on the crankshaft. True that the crankshaft is forged and is a work of art. But forcing to much boost on a flathead is asking for a bit of flex.

I recall a buildup in a Hot Rod annual by a guy named Cotton Mather who claimed 550 HP from a blown flathead and I vaugely recall a cover picture of a flathead in the Fall of 1955 claiming 400 HP from a flathead at a time when a lot of folks were keen to install some late model OHV engine. It may be possible that a few flatheads with ARDUN heads and running fuel could have made over 500 HP but as Southerner said how long did they last? What is often ignored is the attention to beefing up the bottom end using a steel girdle around the bottom of the block and historically that sort of thing may have been behind the redesign of the Ford V8 in 1954 emphasizing the Y-block with the deep block around the crank bearings. Still having only three main bearings is a weakness, not to mention the siamese middle exhaust port. You have to remember that the average street rod in 1955 probably only had dual exhaust, finned aluminum (8.5:1 ?) heads and a two pot intake manifold and all of that probably added up to 120 to 130 HP using a stock cam. The cam was harder to change in a flathead because you had to add adjustable lifters and adjusting them required removing the intake. Among my H.S. friends most ('41) Fords had only dual exhaust, shaved heads and steel pack mufflers and that probably produced 105 HP, so even a Studebaker OHV V8 looked pretty powerful and Olds 88s were king of the road with '50 Mercs and '52 Hudson Hornets a close second, but it was clear that the OHV V8s produced a lot more power in stock form than an expensive fully built flathead. Still Pep Boys sold a lot of dual exhaust kits for flatheads and Smithy Mufflers must have made some money too.

Don Shillady
Retired Scientist/teen rodder

Right on Don , I remember the Ford mercury Flathead put out 98 HP in stock form, so adding all the go fast goodies in those days gave you about an extra 25 to 40 HP. And in the light roadsters of those days you really feel that. You would probably know. That a lot of us only saw the outside of the cars, we very rarely saw iny interior shots because there was no interior !!!! Just a couple of seats, the dash and maybe some material to cover the inside of the doors. You hardly ever saw things like rag tops on roadsters. But what the heck everybody still had a real lot of fun. It was real hands on experience then.

Better get back on line with the thread, motor number to seems to show the best traditional supercharged flathead look because it follows a theme of using parts commonly available in that era, I am noting things like carbs, GMC Blower, Offy heads and a gilmer drive. What tends to put me off motor number 3 is there is a lot of modern stuff that seems to clash with the flathead look.
My pick on motor number 2 is 4 lb's boost and 165 HP tops for a long lasting street motor.

Southerner Your real close as that motor susposedly put out 188 at 5 lbs boost. I've got a good friend that both of us took apart our first motor when we were living in vermont at 11 years of age. It was a 40 ford that was sitting in a field. The owner said go ahead and work on it. To make a long storu short we got it running after taking the motor apart and sure enought the farmer sold it. Well Vick became a engine builder and he has a 37 ford with a 53 merc flattie thats putting out 215HP w/0 a blower and thats with a .060 overbore and sleeving all cylinders plus Ardun heads and 2 97's with a unknow cam.

Chevy37, see if you can get some pictures of that ARDUN-Merc, not many of them running around!

Don Shillady
Retired SCientist/teen rodder