Turbocharging with a stock carb

[41/53dodges]

Has anybody turbocharged a flathead using their stock carburetor? I would like to leave the intake manifold untouched and use the factory carter BBR-1 carburetor with a blow-through setup, running about 7LBS boost. anybody see any issue with this?

[greg g]

Carb is designed to operate at one atmosphere. Pressurizing it would probrably case a lot of leaks and likely overpower the acc pump and its check valves. If you loook att supercharged Kaisers,there carbs are mounted in a box so that when boosted the air pressure is equal inside and outside the carb body.

At low boost,acarb upstream of the compressor (like a s charged Graham Paige) would be much easier to deal with. I think tthe Graham and Kaiser ran 5/6 lbs boost for about a20% pop of HP

[Kudzuking]

The carb will have to be modified to hold pressure, particulaly the throttle shaft, that's the major mod. pretty sure you'll have to make a hat for it, along with everything else. Paxton did have a system where the carb was sealed in a box so it was always sealed against the atmosphere. Turbocharging isn't that hard, but you have to match the turbo to your engine /trans/rearend ratio to make sure it spools at the right time, I would read up on it before selecting a turbo, Turbonetics has some good info on the subject.

Edited December 20, 2012 by Kudzuking

[40P10touring sedan]

B&Bs are known to be leakers to start with...adding pressure will only heighten that effect.

True, the 54 kaiser, running a Mc Culloch supercharger and a 225ci flathead 6, had a boxed carb, but those are hard to find and costly.

Add that the supercharger supposedly takes 30ish HP to run so any HP gained via that would be a possible wash out given a 25% increase from it's use{use the naturaly aspirated oem engine HP numbers and add 25%...isn't much}. Also, "that SC" can't be ran as a blow thru system because the impellor is oiled...the gas in the air going thru it would wash the oil off of the impellor and cause early/increased wear....the carb has to be downstream.

Alot of the newer/smaller SC's are the same way- dry and set up for FI

...but you weren't talking about an SC...

The turbo type you'd be looking for would be off of an inline 6 diesel...low reving like the flathead 6 engines are and roughly the same Liter capacity...I'd even suggest a TBI in place of the oem carb and some kind of aftermarket ignition to run with it{accell/mallory had add on FI/TBI systems}. An adaptor plate could be made to mount the turbo to the oem single exhaust manifold dump and plumbed up to the fuel input of choice. I've always liked the GM cross fire twin TBI set up...could be used for a twin carb aftermarket flathead 6 manifold.

[40P10touring sedan]

...Let me add that I once owned an 86 GLH turbo with a lil 195hp 2.2 turbo and that car was a blast. Could beat a V8 mustang{LX or GT} in the standing 1/4 allllll day long....go past 1340 feet and that gap started changin in a hurry. I'll always remember that car....and the dreaded wheel hop it had.

Folks say that youd need a set of forged pistons and a forged crank for a turbo flathead 6...pistons you can get...a crank, not so much! I think it could be done with cast pieces but that's purely speculation on my part due to a lack of anyone having actually done it and lived to tell us about it. The flathead's lack of high reving would be another issue...once again though, finding a purpose built turbo built for low reving would fix that. Installing the proper sized exhaust {1 1/2"?} would keep it breathing well enough, and setting a waste gate correctly would be essencial....the GLH turbo hit 5psi all day long but peaked just at 7psi....5-6psi is enough I think.

I've got a chrysler 265ci 6cyl to play with, so a TBI{s} roughly set for 4 Liters should fit my bill...a smaller motor would require less unless your an overkill kind of person. If I could nail down the TBI{s} and sensors for mine I'd do it in a heartbeat as a bare bones system- crank/ign trigger{HEI dizzy tach sensor lead?}, O2 sensor, amibient air temp or map sensor and I think I'd be good....just haven't put it all together yet.

[greg g]

don't the industrial engines have forged crankshafts?

[40P10touring sedan]

don't the industrial engines have forged crankshafts?

As far as I know...the marine ACE engines had forged cranks and not the industrial nor auto...

[Rusty O'Toole]

Pretty sure they all had forged crankshafts. I would worry about the pistons, they seem to be a weak point even in stock engines. A more modern piston from Ross would be a better bet than stock ones.

The McCulloch VS57 was said by the manufacturer to be good for a 40% increase in rear wheel HP with 5 pounds boost. If you keep the boost down to 5 pounds or 7 at the most, and do not over rev the engine, no mods should be necessary. Other than the pistons.

[40P10touring sedan]

Pretty sure they all had forged crankshafts. I would worry about the pistons' date=' they seem to be a weak point even in stock engines. A more modern piston from Ross would be a better bet than stock ones.

The McCulloch VS57 was said by the manufacturer to be good for a 40% increase in rear wheel HP with 5 pounds boost. If you keep the boost down to 5 pounds or 7 at the most, and do not over rev the engine, no mods should be necessary. Other than the pistons.[/quote']

Hey Rusty, yeah, by cast I would mean newer available 3 ring pistons, not the oem 4 ring drop ins that love breaking the top ring land off during "casual" use. Doesn't keith black make "better" grade pistons too...purely for reference sake. "Silv-o-lites" are out there but hard to find.

[Kudzuking]

Unless your going to put a lot of pressure on the motor I would think the cast crank will do, I would have it checked tough, i would invest in the forged pistons and keep the compression low, 8:1 or so, increase the exhaust side and don't worry about porting and intake flow, keep the pressure at about 5 lbs, no special cam needed, high duration and large overlap will hurt the turbo performance by beeding off or wasting the pressure, you don't want the intake valves to be even close to opening while the pressure is built up. I would use as large an intercooler as you can and remember this turbo flat six isn't gonna make the big numbers because of it's rpm limitations. The most important factor is selecting the right turbo for the rpm limitations, it will have to spool early, but not to early otherwise you'll be just cruising around and building boost. There are a couple of books on turboing and the Turbonetics site has a wealth of info, there's also a site called turbomustangs that has a ton of info and people that have been there,done that. I used to hang out there when i was building my single turbo Dodge Dart. Here's a couple of pics of the turbo Dart

Edited December 28, 2012 by Kudzuking

[greg g]

believe Egge in Ca also makes pistons to order.

[Tim Keith]

Pretty sure they all had forged crankshafts. I would worry about the pistons' date=' they seem to be a weak point even in stock engines. A more modern piston from Ross would be a better bet than stock ones.

The McCulloch VS57 was said by the manufacturer to be good for a 40% increase in rear wheel HP with 5 pounds boost. If you keep the boost down to 5 pounds or 7 at the most, and do not over rev the engine, no mods should be necessary. Other than the pistons.[/quote']

I think this is generally true of most engines. If the oiling and cooling system is adequate almost any motor can tolerate some boost, as long as the air/fuel ratio is correct. Even the best built turbo motor can quickly melt pistons when its run too lean. According to Corky Bell's book Maximum Boost most of the pressure on the crankshaft bearings comes after TDC, which is not a problem - unless its run at high RPM. When there is pre-ignition with boost there is a problem. Aim for mid range boost where a flathead starts to run out of torque, don't target for high RPMs. When the boosted flathead is running too warm the head gaskets could fail.

[41/53dodges]

ah, thank you guys for all the tips! just to clarify a few things, I already have a turbo laying around, one out of a 1.8 litre subaru, and those were supposed to make boost around 2200 RPM factory. I bought it for $10 just to dick around with, the engine was toast, as were about a half dozen others in that same yard (all from the same family, died of no oil...) the turbo was siezed, so it was just a nifty paperweight. turns out, the same dipstick that ran it out of oil put RTV in the compressor turbine, so evidently it never ran for most of it's life if at all! so, now I have a perfectly good turbo laying around, some spare manifolds, and now a perfectly good holley 1904 glass bowl to go with it! so, this project is a "why the heck not?!" thing.