Flat Head Mods= What HP????

[55 Fargo]

Gents, have asked this ?, on a few other related threads.

What HP can one expect from a modding these flat head 6s.

Here is what I hope to do with my sezied 251, rebuild,shave head .060, have cam reground to higher-perf specs, split dual exhaust or headers, single 2bbl Holley Webber carb, electronic ignition. What HP, could I develop, out of an engine such as my plans, the factory is about 115 hp, hope to get 150 to 175 hp is that possioble.....Fred

Here isa pic of my current engine in my 47 Chrysler Coupe, it is a 218 Canadian stroker, shortest stroke of all Mopar flat head 6s, which 3 3/4, a 251 is 4 1/2 stroke.

Edited August 18, 2009 by Rockwood

[Andydodge]

The best the factory got for the 230 was 140hp from 57-59 and that was with 8:1 compression and I think a 2 barrel carb........so I am hoping that with my 230 with an 9.5:1 Edgy Finned head, twin carbs, split exhaust, balanced, S10 HEI dissy, low restriction mufflers, engine driven fan removal, lightened flywheel,minor intake/exhaust porting, me leaning forward when driving and a good 50knot tailwind that I may, hopefully see the high side of 170-180.......maybe.......lol........andy(the optimist)d

[55 Fargo]

That's not bad Andydodge, Earl Edgerton is currently work on a "hemi head" for a flat head 6, wonder what kind of HP that will develop.

I am hoping to get to 140 to 150 HP with my plans, nothing radical.

I figure a 150 hp engine, tied up with a 3 spd trans, and 3.73 rear end, should be a lot better off the line than a 98 hp 218 long block I have now. Even with the 218, I can keep up with city traffic off the line no problem, don't think I would be able to do as well if it were fluid drive.

I have driven a fluid drive Chrysler once, it was neat, but what a dog off the line...................Fred

[greg g]

Fred if you are only going to run a single carb, and you want a holly weber or carter weber, keep in mind that most of these carbs were put on enginse between 1400 and 2400 cc.s Your engine will be in the 4.0 liter neighborhood. So when you source your carb, you need to keep that in mind. I know the a lot of Jeep 4 liter guys used Weber barbs, so that one might be a good starting point for your needs.

As far as HP, if you can pick up 10 to 15% you're doing good. What I just looked at says the 251 in desoto and chrysler made their most hp in 54 ad were rated at 117.

The 59 Plyymouth 230 made 132 Dodge was rated at 135. Seems the ratings don't make much sense. Of course the 251 made a lot more torque, and torque is what gets you going.

I know my moded 230 is significantly more responsive engine than the 218.

[BeBop138]

My 265 bored 40 over--410-260 cam--head shaved 65 thou and decked about 5 thou-- balanced---split exhaust-- HEI---Moose intake and a pair of Carter-Webers---hope to get 160 to 170 HP. Get the rest of the zip with gearing---good luck......Lee

[greg g]

Over on the hamb, there is a guy trying to get 200HP out of his flattie. Quite an extensive list of postings regarding his efforts. He was at 170 last updates. but was having trouble pulling more than 4700 rpm, thus limiting his peak HP.

[BeBop138]

Over on the hamb, there is a guy trying to get 200HP out of his flattie. Quite an extensive list of postings regarding his efforts. He was at 170 last updates. but was having trouble pulling more than 4700 rpm, thus limiting his peak HP.

Greg, Hudson on the Inliners was getting 6000 with his 230 in a tractor. 200 ponies is a tall order, I still want to street mine. Doing what I have done is more of a challange to do as much as I can and still street it and doing what most people don`t do----hop up an old inliner, especially a flattie........Lee:D

[Andydodge]

Maybe I am the Optimist........how about 150-160......lol.......andyd

[55 Fargo]

Did an update showing my current engine