Horsepower and Flatheads

[Frank Gooz]

I would like some help, PLEASE. I have read many post about swaps from one flathead to another flathead. Of the same size/length. It seam that some have said that a later year 230 has more horsepower then an earlier year 230. I just picked 230.  Is this do to compression, camshafts, pistons ?

 

Thanks to all that reply.

Frank

[Andydodge]

The earliest use of the 230 was I think 1942 by Dodge, 6.7 :1 compression, 105 B.H.P with a single barrel carby.....the last 230 car use was 1959 Plymouth with 8.0:1 compression, 132 B.H.P. and a single barrel carby..........I had high hopes for the ex airport tug 230 I was going to build and install in the 41 Plymouth I had..........I had an Edgy Finned head that was supposed to up the CR to 9.0:1, a twin carby intake, split exhaust manifolds, a 1/2 race reground Waggott cam, HEI distributor, and intended to have it balanced  and ports cleaned up..........I had a set of 60 thou over 4 ring pistons but also intended to get some custom 3 ring forged pistons as well..........I was hoping to get somewhere around 180 BHP.......but sold the car & engine like a dope........lol.........heres a pic of the mocked up engine on a stand............the Montana Mopars boys would be the guys to speak to re hopping up flatheads as they give Bonneville a go with their mopar flatheads.............but pistons/cam/carby/compression all help...........lol...................andyd   

[greg g]

There may have been some cam changes over the years, but since all the various Horspower rating were pulled at 3600 rpm, it doesn't seem that cam grind changed that much or the peak torque and Hp rpm numbers would have moved around a bit.  However if you look at the specs over the years, every time compression went up, so did hp.  More squeeze, more timing advance, better gas, more power.

 

http://carnut.com/specs/gen/ply50.html

[greg g]

My engine is a 56 230 flywheel hp was 125 at 3600.  Mine is .030 over, balanced, .040 off the head, .010 off the block Working comp ratio estimated by machine shop at 8.7  to q.  Stock cam, single exhaust, dual Carter's on Fenton intake.  Rear wheel hp on chassis Dyno was 127 at 3300 rpm.  Runs fine on 87 gets 18 to 20 mph on the road with od on, 16 to 17 around town.

[47 dodge 1.5 ton]

Very nice information. Do you happen to know what compression readings you have in PSI? 

[greg g]

I can't recall it's been over 15 years.  When I get it out of storage, maybe need to put the gauge on her.  My old 2i8 was down in the 90s. 140 to 150 rings a bell but not sure.

[James_Douglas]

On 4/19/2021 at 2:43 PM, greg g said:

My engine is a 56 230 flywheel hp was 125 at 3600.  Mine is .030 over, balanced, .040 off the head, .010 off the block Working comp ratio estimated by machine shop at 8.7  to q.  Stock cam, single exhaust, dual Carter's on Fenton intake.  Rear wheel hp on chassis Dyno was 127 at 3300 rpm.  Runs fine on 87 gets 18 to 20 mph on the road with od on, 16 to 17 around town.

Hey Greg,

 

8.7 to one on regular with normal timing and no detonation? Maybe on the coupe, but I have 8 to 1 with a stock cam and no way I can run regular with the 5000 pound Desoto without it pinging on the hills. Even when the engine was new. I have run a single carb manifold set up as well as a Edmund with two carters. Same result.

 

I personally CCed the cylinder heads and checked the piston height. So I know mine is at 8 to 1. I suspect that you may not have the compression ratio you think you do. If you do, then I need to take lessons from you on how to not get detonation above 8 to 1 on regular gas with a flathead six !

 

James.

 

 

 

[greg g]

Taking the machinest's word on it.  Timing set by vacuum, initial at idle is 5 degrees btdc she checked with timing light at apx 500 rpm.  I believe the dist is out of a 54 Dodge pickup.  The dist number is in the car, the car is in storage so the advance curve might be a bit different.  Also using the thinner one piece solid copper head gasket.

I did have an Edmunds head on it that was supposed to be 9 to 1 and ran 87 with that also.  But it had issues and was removed in favor of the milled stock 56 head.

[greg g]

James, I have had several 6 cylinders in the mid 60 to mid 70s of several brands that had compression ratios in the 8.4 to 8.7 range, all ran on regular gas. AMC flatheads,and overhead, .Ford and mopar, GM straight and v6 . The one I did have that was fussy was Volvo 164 it liked high test but I ran ii on regular and a blend of self restraint.  Luckily not a lot of steep long grades around here.

[Sniper]

Best improvement you can do to gain HP on the flathead is ditch the direct drive mechanical fan.  Those things are known HP robbers.

[HotRodTractor]

1 hour ago, Sniper said:

Best improvement you can do to gain HP on the flathead is ditch the direct drive mechanical fan.  Those things are known HP robbers.

This is true. I added a mechanical fan back into the P15 and its a noticeable difference in power - but the car works so much better in stop and go traffic, and I no longer have issues when I get off the interstate and get an immediate temperature rise to the point of the car stuttering if I hit a red light at the end of the ramp. I know this means I need a better electrical fan setup as it is apparent that what is in the car just doesn't cut it for my driving style. 

It still runs down the interstate at 80mph with no issues, but its a noticeable drop in power when trying to get there with the mechanical fan. 

I've been looking to see if I can adapt a more modern flexalite fan to the factory water pump. Its tight in there and I don't believe I have room to do a fan clutch since the radiator is already moved forward for the 25" engine install. Its pretty tight just adding the fan back in. 

[JBNeal]

Everything that I have read has pointed me towards 8:1 CR, 2bbl carb, split exhaust manifold for a definite bump in hp, as these improvements were noticeably done on later big truck flatheads...running a PCV setup with a 180°F thermostat helps keep engine compartment fumes to a minimum and reduce sludge formation, which kinda helps sustain those hp improvements ?