Would like to know how to improve on a 1941 Pontiac flat six(239)! Not just power but [FONT="]reliability also. [/FONT]
I know nothing about the Ponty specifically, but flathead sixes in general are a little different from V8s in that they dont usually suffer from breathing woes around the valves. Hence porting and relieving are pretty much a waste of effort in a street engine. Raising the compression seems to be the best bang for the buck mod you can make, probably around 0.060 off the head, but you would want to check how much valve clearance there is first (use clay). A twin carb manifold and twin outlets in the exhaust manfold will make a difference, but you'll probably have to fab them, I would'nt think there'll be too much speed gear for a Ponty. That's about it really. If you want to get really involved, you could have the cam reground for a mild grind, but you have to remember that flatties dont like to go much over 3500-4000 revs unless you do some magic with the lubrication system, particularly in regard to the crank.
Aught to run like a watch, as long as you keep it maintained and don't expect it to be a racecar. Improving on it would be called transplanting a 1955-1978 Pontiac V8; a 55-57 manual bell may even bolt up to your existing transmission (although you may find yourself needing to replace that shortly after). Performance parts were made for these back in the day; an aluminum head and dual carb intake should turn up with time, patience and money. With a 12V conversion it may be possible to adapt an electronic ignition to the stock distributor. I'm not sure what else you can do, because it will call for finding parts for other motors and seeing what can be adapted.
There was actually one famous souped one, in a lakester that still exists...HRM published a very scanty tech article on what was done. I think a mild cam grind and higher compression would be the most practical steps...dual carbs with SMALL modern carbs like Falcon or something, perhaps, but would likely require fabrication, as would headers. Remember that this engine is small and has limited breathing, and will never be a fast machine if it's dragging around a big car, but it can certainly have adequate performance so you can cruise the highways and get away from lights without being ticketed as an obstruction... I think a good, careful rebuild would be your best improvement, with attention to ring sealing and good valve seat work, with minor cleanup of bowl area. Forget anything like big carbs or very hot cam pointed at high RPM output--there ain't gonna be much to get, and that's largely useless on the street anyhow. Probably Edmunds or somebody made heads and manifolds, but those would be really damn scarce--they probably sold about two back in the day.
There's was a Saltflat racer in Hop Up that was kool, I'll scan it in and post when I get home... Mine's a '51, but not much changed for ten years (something to do with the wars maybe) Anyway heres's what I done so far: Bored it 30 over, shortened the stroke, put in a 3.55:1 rear end and pressure seals in the tranny. The dual intake is a Edmunds custom, I'm working on the linkage for the two Strombergs they're 18" apart. As for the exhaust I'm planning straight pipes. Parts are a little hard to find, but if I can be of any assistance, send me a PM
I'd suggest re-gearing the rearend or maybe swapping out the axle. There are after maket adaptor kits available, depending on your budget. You're going to need to find the reference axle number and tranny number to find a good match and correct gear ratio! If you have a shop manual it should give you the location of these numbers and ratio charts.
I believe that Pontiac center sections up through '56 will fit your rear end, so gear ratios better suited to highway cruising are available. Also, Hot Rod magazine had a hop up article on Pontiac sixes sometime in 1950.
Yeah--the rear is likely indestructible. I think your trans is a slightly strange selector type, and while it should be utterly reliable behind this engine, i think it is the place to focus. I believe your rear is likely a ratio in the low fours, not what you want for cruising but good for low speed pep with big car/little engine...SO, rather than changing to a high gear, consider tossing the trans in favor of something like a T-5 with overdrive--you can have your cake and eat it too, with low gears at low speed and high gears in OD at cruise. For the rear, just checkitout for leaks and replace seals if you find any.
My 41' Poncho has a rearend out of a 56' in it now. It will cruise comfortably at highway speeds, but take-offs aren't quick.
Wait a minute isn't a T-5 and Ford transmission? If Misterwakko is going to swap out the tranny...I'd suggest checking with his local transmission shop, give the reference information. Before doing anything
T-5s come in both Ford and GM bolt patterns, but either one would require a homemade adapter plate for use in a '41 Pontiac. If you go hunting for a different center section for your rear end, pre-'57 Olds should be the same, and most automatic cars had either 3.08 or 3.23, while the '49 and newer standard shift cars were mostly 3.64, with a few 3.90s as well.
Well if its a 41 it might still have steel pistons in it my 48 had an earlier motor like yours and and the steel pistons tend to seperate at the ring grooves. Mine came apart at the top ring last year. If your going to rebuild it mill the stock head as an aluminum is next to impossible to find Ive been looking for two years with no luck. And balance the entire bottom end including the pressure plate they are supposed to be balanced but mine had to be welded on one side and drilled on the other to balance it! Edmunds dual intakes are around from time to time I put one on mine with a split manifold its not fast but with the carbs, a cut head and the split exhaust its noticibly better! I think you can get a petronics ignition even for the 6 volt check with an auto parts store. If you want a split manifold I can split my spare one for ya but would want a core back if its good. Good luck Dave
Best bet is find a shop manual, if you don't already have one. CPR has web site\company with parts for Pontiacs 1926 and up: www.pontiacparts.net Try searching for Pontiac Oakland Club International web site it use to be (www.poci.org) and had tons of info...only draw back was to get the real detailed stuff like tech articles, you had to join their international club. Not sure if their still around?!?
My 41 is a 26 series, stock standard gear is a 4:30. There was a 4:10, and 4:56. The "economy" gear was a 3:90. 37-46 are differant than 47-56 rear ends, but the whole assembly should swap over, plus alot more gear ratios available. On my 55's the auto car came with 3:08's and the manual car had a 3:64.
When I was a kid we always looked for old Pontiacs to grab the rearend gears for our '50 Olds 88s. Same housings more or less, Pontiacs had the drag race gears in them. Plenty strong enough for a six.
This is one I'm using. Run it as is. It's a bit of work but you can split the exhaust manifold. Maybe a little extra hp and sure sounds cool. -stick
A black engine doesn't look too bad, but the correct blue-green paint is available from Bill Hirsch auto if you didn't know and would look better IMO. I got some for the 55, real nice engine paint.
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