Inliners International Forums General Discussion MOPAR Flatheads: how much can they take?

I'm wondering what the “outer limits” of flathead performance are. Does anybody know of a supercharged or turbo'ed installation? What do you think the max HP might be? Also, (probably not the way to max hp.. how fast has one turned(RPMs).. the valves can't hit the pistons, but I guess at some point a part of the rods can sure hit the block!

Leif

I think Rusty O`tool is supercharging a flattie--he comes on here and the Chrysler forum---try there also....Good Luck!!

Look at the 2004 Bonneville pictures to see a supercharged Chrysler 8 (inline flathead) in a '34 Airflow.

God's Peace to you.

d
Inliner #1450

Leif,

Many years ago, I scattered a couple of Moderately built '50-'51 flathead Ford sixes, when I began to rev 'em over 5,000 rpm on a regular basis. Below that "magic number" they seemed to be pretty robust.

In a supercharged version, I believe the power could be increased, while keeping the engine below critical rev limits. Speed would be gained with the correct gearing, negating the need for higher RPM.

I'd imagine MOPAR sixes would be less prone to self distruct, as they LOOK more robust(to me). However, I doubt if they could withstand RPM in the over 5,000 range, for long, either.

Even the mighty Hudsons were seldom revved much over that figure.

I'd like to see some good research and figures on this subject, myself.

I have GOT to get to Bonneville and see some of the Inliners run! That straight-eight, blown Chrysler had to sound awsome!

I wonder though all that added pressure would the lower end react the same way that it would to high rpms?
I suppose it's the long stroke of these engines that limit their rev potential....really the piston speed could be robbing power at serious rpm...I dunno...my plan is to spin my 237 hard as it has the shortest throw of any of the mopar sixes...

I have a 230 in a pulling tractor. It is a balanced engine with a X drilled crank. It can turn 6000 with no problems. It did it for 3 yrs. It is in retirement now. If you have never heard a flattie turning 5 or 6 you should. It is a sweet sound.

Frank Kleinig's Hudson 8 once held on to over 7,000rpm... and lived...

I have the story somewhere. Kleinig was running it in a hillclimb, the biggest hillclimb in Australia at the time, at Rob Roy in Victoria. It was about 1948 or so.

Kleinig was a demon at hillclimbs. In road races he wasn't so ferocious, but as a bundle of energy released suddenly for a furious run up a hill, he was held in awe.

The gearing was such at this climb, however, that he was forced to make a gearchange some 80 yards or something before the finish line. His mechanic, Clive Gibson (who tells this story) told him to hold the gear over the line because he was under pressure from another competitor.

He did, it did and the whole thing survived.

The top line Hudson race engines here had a low pressure oil pump and a squirter system that sent a stream of oil out in the path of the dippers on the ends of the rods. With this they avoided losing lubrication through the oil not closing into the 'trough' carved by the dippers as they rotated.

Hmmm... somewhere I have a photo of the car...

Hey Ray;

Ya think that 'story' has been told a lot over the years?? :p

Well, Clive's the one who tells it...

And Clive has a habit of keeping on talking. But when Clive tells a story, you can pretty well bet it's a true one.

That wasn't the pic I was looking for, either. The one I wanted showed the car with the inside front wheel about a foot off the ground. I think it's in the State Library archives.

There's no doubt that this run pictured was far from a winning one!

I don't think it's a question of how much the bottom end can take so much as the amount of time spent there and whether the engine is actually making any power there...(with port flow restrictions and so much piston ring drag)

That's why I was thinking turbo or supercharger. You could overcome the bad ports and low CR that way. I know the Model A Ford guys use modern pistons and rings to get rid of the extra drag. It seems like especially with a turbo, any engine can he boosted beyond its ability to take it.

uncommon engineering is making 600plus HP from their blown hudson 6's.lots of mods though,to keep the bottom end together.but i think a turbo or blown flathead of 200-300 cu in should make 250-300 streetable HP without too much trouble(next project??)with around 10-20lb's of boost

If I where to get a mopar 8 I might try it....
or if anybody wants to fab up and sell a nice stud girdel that may help....please excuse any spelling errors...

Found that other picture of Kleinig with his Hudson Special at Rob Roy Hillclimb, I believe it's 1948:

Terrific!

I think that's during it's Amal carburettor period...

Four motorcycle carbies all in a line, and as you can see the exhausts sweep over the top of the head to the other side to give room to move.

Leif, seeing as you liked that one, I've got a little treat for you (I know Geoff wouldn't mind and I don't think John will either):

:

So you can see how it was all set up. Note also the brake cable/chain arrangement and other things. This car had a Mathis front axle mounted in an MG N (large touring car) chassis.

Hudsonator revs his hopped up 230 Plymouth 5000 RPM. Mind you, this is in tractor pulling so it is only a few minutes at a time.

I'm still working on the McCulloch blown 265. But this is not an all out horsepower project. I plan on keeping the pressure down to 5 pounds or so which should give me about a 1/3 HP increase over the stock 120, or 160HP total.

About the same as a stock 318 2 barrel or slightly less.

Hudsonator also claims that the limiting factor to flathead horsepower is the engine's ability to reject heat.

His engine after a run is practically red hot from head to oil pan while the rad is cool.

His competitors with newer OHV engines, finish a run with the engine cool and the radiator hot.

This indicates that the stock cooling passages etc are simply not designed for high horsepower levels.

One reason old timers used aluminum heads on hot flatheads, is that aluminum disperses heat better than iron giving a cooling advantage right where the engine is hottest.

Incidentally I don't believe Uncommon Engineerings horsepower claims. So far as I know the only engine they ever got to run, scattered after about 10 seconds.

Every engine has its built in limitations. You may be able to get a 50% HP gain and retain enough drivability and reliability for daily road use. Or double horsepower for short bursts as in racing.

The highest horsepower flathead 6 Chrysler car engine was the 120HP 1954 Windsor.

A 50% hp gain would be 180 total, a doubling would give you 240.

I believe either of these would be possible given a sufficient investment in time, talent and money. But to go substantially farther would be impractical if not impossible.

For another perspective on this, look at some of the centrifugally blown engines offered in the US in the 1930s.

Auburn replaced their 150HP V12 with a supercharged straight eight of the same horsepower. Graham replaced a 120HP straight eight with a supercharged 6 also with the same HP as the engine it replaced.

For a 6=8 and 8=12 equation, the HP increase from supercharging would have to be 1/3 to 1/2.

These were both conventional inline flathead engines, with centrifugal blowers belt driven off the crankshaft.

The supercharger did nothing at low speeds which is good because it prevented knocking and damaging the engine.

At medium to high speeds when the conventional engine was running out of puff, the supercharged engine came into its own.

Thus they could tune the engine for economy, smoothness, and low speed pulling power and at the same time, the supercharger gave them the high speed performance of the most sophisticated performance engine.

The supercharger was simple reliable and had no adverse effects, they even figured it improved economy and low speed running by "homogenizing" the incoming mixture even when it was not providing pressure.

It has seemed to me for a long time that the centrifugal blower and the flathead engine is a marriage made in heaven. The blower overcomes the built in drawbacks of poor breathing and low compression found in the typical flathead, while keeping the virtues of simplicity, smoothness, economy and excellent low to medium speed pulling power.

Very nicely put Rusty! Also a centrifugal blower on a flat head seems very "American'. European cars of the period nearly always had a roots blower and while there were flatheads (side valves) they we mostly confined to basic transportation.
I do think it is possible to improve on the past performance measures with modern materials in the bottom end, but the heat you mention is another matter. Good food for thought!

Leif

For extra cooling of a real high performance flathead a finned aluminum cylinder head would be a must.

In addition, an oil cooler and high volume oil pump would help a lot.

The guys a Motor City Flathead (V8 Fords) found that much of the over heating problem was caused by casting sand left in the blocks. I don't know much about the Mopar engines but suspect that it wouldn't hurt to check for sand in the water passages. I know this won't change the design but it could help.