Hot rod flathead 6?

[sixbanger]

I just got a spitfire head its looks great but after finding out that the head is 2" too long for my 50 dodge I want to find the 25" long block for it and build my 22 dodge rat rod with it. My question is just how radical can these engines perform? I want to shave the bottom of the head, have a cam regrind and a duel carb setup. If done right can these engines be a respectable responsive hot rod engine?

[Andydodge]

Sixbanger.......these engines are never gunna turn 8 second 1/4s, but with a finned head/milled stock head, 2-3 extra carbs, exhaust headers/split manifold, decent ignition, a good balance job, hot cam, etc.......they might give a flathead ford of similar specs a run for its money.......eventually my 230 will be finished, at present the build is stopped due to lack of funds to proceed.........hopefully soon.........heres where its been at for the past 12 mths..........lol............one day soon........also a pic of the crappy engine bay at present........andyd

[Frank Elder]

Even a 15 second 1/4 would be optimistic.

[Robert Horne]

I just got a spitfire head its looks great but after finding out that the head is 2" too long for my 50 dodge I want to find the 25" long block for it and build my 22 dodge rat rod with it. My question is just how radical can these engines perform? I want to shave the bottom of the head, have a cam regrind and a duel carb setup. If done right can these engines be a respectable responsive hot rod engine?

You can always see alot of information on dyno tests on many V8s. It would be very interesting to see dyno tests on different variations of our flathead 6s.

[tinlizzy]

Good luck on finding a dual intake for the 25" block. I think you will have to go to a fab'd one from our local guy rusty hope to get an intake.

Lots of 230 stuff but not much on the spitfire from what I have seen. Olddaddy made me a dual for mine and did a good job. I have yet to mount it but it's ready. I have mine in a 48 pilot house. I am thinking of using a 2 barrel carb instead of the single for an added boost.

Lee

[greg g]

You might want to also contact member moose, as he builds intake and exhaust items for your engine. He has a 25 inch flat 6 in a model A bodied car,so he can speak to many of your issues.

Also a late forum member had a 25 inch chrysler motor with an automatic behind it in a model A coupe bodied roadster modified hot rod. I can attest that it was a fairly zippy vehicle. He only added Dual carbs and home mede header style exhaust, and did some milling as modifications.

The Spitfire head is no different from any other Chrysler head except for the logo.

These engines respond the same as other engines to modifications. higher Compression, better breathing and a different cam grind will help performance. However since they are long stroke engines, they like to make torque as opposed to HP. So modifications should be limited to those improve things in the 1800 to 3400 rpm range.

You can mill the head, deck the block, modify intake and exhaust, and probably have an engine that makes maybe 140 to 145 HP when all is said and done. Much more than that is unlikely and would make a less than reliable street motor. There was a guy on the HAMB that was trying to wring 200 HP out of a 265 motor. I believe he got to about 175/180 on the dyno but he is building a motor for drag racing. With his modifications, he was having to look at oiling system modifications, and other iternal stuff.

You should also consider balancing the engine, and lightening the flywheel.

[Robert Horne]

Found a few dyno tests.

[moose]

You might want to also contact member moose, as he builds intake and exhaust items for your engine. He has a 25 inch flat 6 in a model A bodied car,so he can speak to many of your issues.

Also a late forum member had a 25 inch chrysler motor with an automatic behind it in a model A coupe bodied roadster modified hot rod. I can attest that it was a fairly zippy vehicle. He only added Dual carbs and home mede header style exhaust, and did some milling as modifications.

The Spitfire head is no different from any other Chrysler head except for the logo.

These engines respond the same as other engines to modifications. higher Compression, better breathing and a different cam grind will help performance. However since they are long stroke engines, they like to make torque as opposed to HP. So modifications should be limited to those improve things in the 1800 to 3400 rpm range.

You can mill the head, deck the block, modify intake and exhaust, and probably have an engine that makes maybe 140 to 145 HP when all is said and done. Much more than that is unlikely and would make a less than reliable street motor. There was a guy on the HAMB that was trying to wring 200 HP out of a 265 motor. I believe he got to about 175/180 on the dyno but he is building a motor for drag racing. With his modifications, he was having to look at oiling system modifications, and other iternal stuff.

You should also consider balancing the engine, and lightening the flywheel.

I'll back up everything Greg just said, with some changes... My A has a 23" 230, and moparsled on the hamb also had a 230. I do have a 25" in my Chrysler, and I've made parts for them too.

Same idea with making them run stronger though. Just depends what parts you find or want to pay for. In a light car like a '22, it would be very helpful to lighten the flywheel, so that it can rev quicker. I've got a heavy truck flywheel in my A, and it seems like its being held back by all that extra weight.

Electronic ignition would also be a great addition. Bring the compression up, open the exhaust a bit, and throw on a couple more carbs--you'll get moving for sure...

[49wayfarer]

I recently purchased a 250ci Chrysler Spitfire engine (4.1 liters); if I split the intake and exhaust manifolds and run two small turbos from a 2.2 liter engine w/ twin carbs (as a pull through system)

How do you think these engines would respond to forced induction?

[greg g]

check the web for turbostude. similar engine design, likely similar results albiet 194 vs 250 cu.

[BeBop138]

I just got a spitfire head its looks great but after finding out that the head is 2" too long for my 50 dodge I want to find the 25" long block for it and build my 22 dodge rat rod with it. My question is just how radical can these engines perform? I want to shave the bottom of the head, have a cam regrind and a duel carb setup. If done right can these engines be a respectable responsive hot rod engine?

My modified 265 and T-5 tranny with 3:50 gears pushes my 52 Windsor along very nicely. Here is a pic also of the intake Moose made for my engine..........Lee

[55 Fargo]

My modified 265 and T-5 tranny with 3:50 gears pushes my 52 Windsor along very nicely. Here is a pic also of the intake Moose made for my engine..........Lee

Very cool BeBop, how or what could you compare your hopped up 265 to, any idea how much HP you are now pushing out.

I have a 251 sitting here at home, and possibly someday it will be hopped up for my 47 Chrysler Coupe, I could use a little more ooomph, that my current old engine is pushing out.

[BeBop138]

Very cool BeBop, how or what could you compare your hopped up 265 to, any idea how much HP you are now pushing out.

I have a 251 sitting here at home, and possibly someday it will be hopped up for my 47 Chrysler Coupe, I could use a little more ooomph, that my current old engine is pushing out.

It is a 54 engine and I think stock they had around 115HP----I would like to think I have 145-150HP. It doesn`t give you a set you in the seat feel, but it keeps up with the Big Dogs---much more pull. The tranny and gears make a big difference also. Hey we do this mod stuff just because we can and it is different than just doing another V-8:D...................Lee

[thrashingcows]

..... Hey we do this mod stuff just because we can and it is different than just doing another V-8:D...................Lee

That is why I abandoned my 331 Hemi plans for the Desoto....vintage Hemi's are cool...but when was the last time you were at a show and saw a hopped up flat head six?

[Gary Manes]

Love that yellow. Would never have thought I would, but it looks really nice.

How did Hudson get all that power out of their sixes used in the Hornets? They tore up NASCAR, and could out run the Olds "Rocket Eight."

These are the first comments I have read recently about the 265. I do not plan to make mods except perhaps for a more efficient carburetor, but it sounds like they have pretty good power without them. The '54 car was quite a bit larger (125" wheel base) than the '48 (121"), so this one I am planning to buy should give me what I want, and the automatic won't lose all that power through the fluid drive like my '48.

Nice discussion!

[martybose]

I recently purchased a 250ci Chrysler Spitfire engine (4.1 liters); if I split the intake and exhaust manifolds and run two small turbos from a 2.2 liter engine w/ twin carbs (as a pull through system)

How do you think these engines would respond to forced induction?

My first thought is that you'll find that the turbos are too large, since you'll never turn a flathead at the RPM that the original application did, but it might be fine anyway, just maybe a little lazy off of idle.

Marty

[Tim Keith]

I think the flathead would do okay with a turbo but only for short bursts at WOT. Turbos can run cooler than superchargers, but any major power increase can lead to overheating during sustained driving. With the large gasket surface the head gasket might fail. If the fuel management is okay there ought not be melted pistons, the same issue with any turbo motor. I'd limit boost to five pounds using a small turbo to build some mid range torque - 2500 RPM. The goal might be like a small turbo diesel where the boost is at lower speeds. The oiling system of the L-head is decent. Turbos don't load the cranks bearings to any significant degree, it is piston speeds which kill L-heads. Boost the torque a little at lower speeds and have fun with it. You might want to read Corkie Bell's 'Maximum Boost'.

Edited February 16, 2011 by Tim Keith

[49wayfarer]

My first thought is that you'll find that the turbos are too large, since you'll never turn a flathead at the RPM that the original application did, but it might be fine anyway, just maybe a little lazy off of idle.

Marty

These turbos are off a little diesel engine that had a 3000 RPM rated speed.

[greg g]

Coupel things the stock low compression lends it self to forced induction, as long as you keep the boost moderate maybe 6 or 8 lbs max. The long stroke and bottom end should be OK with that. Back inthe 30's and 40's Graham Paige used a centrifigal engine driven supercharger on their engine which was almost the spitting image of the MOPAR design.

Their set up added 20 hp to the stock engine. A british motor magazine did a test comparing the two set ups and found that the supercharged engine was only slightly noiser and the the 20 hp added significantly to the cars performance, shaving nearly 4 seconds of the 0 to 60 acceleration, the super charged car showing the run in 21 seconds. Whoo hooo.....

If you do a turbo, what will you do for induction. Fuel mixtures when compressed don;t like the added heat which negates part of the benefit from the forced air. The Graham mounted the carb on top of the charger and the compressed everything. Most modern applicatioins use fuel injection and add the fuel to the already compressed charge at the port. Studebaker and ford used Paxton blowers at one point and put the whole carburetor inside a pressure chamber so the pressure inside and outside the carb was equal.

Lots of stuff to think about but anything can be done but will the gain be worth the effort?

Remember diesel engines are basically a constant air pump with speed/power controlled by the Fuel injector mapping, where as with a gas motor you need to deal with throttle position, air and fuel.

Perhaps the small trubo blowing through a throttle body type FI unit would make the most sense for this type of system.

Edited February 16, 2011 by greg g