Supercharging a Model A

G

GeneBob

Senior Member
I have been playing with a supercharger on my engine for most of the year. I have learned a few things that I thought I would pass along just because it was interesting.
The starting point was a recently rebuilt original engine with a Specialty Cams 340 cam, a Lion III cast iron head, electronic ignition, the Weber carb adapter manifold, a Snyders' cast iron exhaust header, electric radiator fan and electric water pump. The supercharger produced 4 psi of boost with peaks of 5 or 6 psi on occassion. The fan and pump were installed to free up the fan belt to run the supercharger. I live north of Denver so the altitude was around 5000 feet.
1- I had a problem with my front pulley coming loose before I put the supercharger on. This only got worse with the additional load of the supercharger. I even added a second 1/4" key to drive the pulley. I think the longer heavy 5/8" v-belt may have been the problem?
2- Tuning the carburetor required adding a fuel/air ratio meter since the supercharger hid issues from the tried and true old methods. I tried the Weber, an Autolite 2100 and finally ran a Stromberg 97. The Stromberg performed better before adding the supercharger as well.
3- The supercharger pressurized the crankcase causing me to think more about why. My conclusion is that the pressurized intake ports pushed air past the valve guides and into the crankcase. Remember, flatheads engines do not have valve guide seals in stock configuration.
4- The compression test at the end of my little experiment showed 100 psi across all 4 cylinders cold so I don't think piston ring blowby was a problem.
5- The supercharged engine produced considerably more heat than the un-supercharged engine did. Although this engine ran hot before adding the supercharger.
6- Wow! The supercharger added at least 20% and probably closer to 30% to the horsepower output of the engine.
Now that I have returned to normally aspirated, the engine runs smooth but I am disappointed with the performance.
If I return to supercharged, or if anyone is considering it, I will make some changes to the engine. I am looking into what it would take to add valve guide seals and how to run a serpentine belt instead of the heavy V-belt. Possibly changing the attachment of the front pulley to the crankshaft.
If anyone else has experience with running a supercharger, I would be interested in their lessons as well.
Have fun!
 
All that you need is to bolt on one of these era "Bat Super-Chargers"....for more speed, more power and economy:

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"Experience a new sensation" :D

Brad in Maryland
 

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GeneBob said:
I have been playing with a supercharger on my engine for most of the year. I have learned a few things that I thought I would pass along just because it was interesting.
The starting point was a recently rebuilt original engine with a Specialty Cams 340 cam, a Lion III cast iron head, electronic ignition, the Weber carb adapter manifold, a Snyders' cast iron exhaust header, electric radiator fan and electric water pump. The supercharger produced 4 psi of boost with peaks of 5 or 6 psi on occassion. The fan and pump were installed to free up the fan belt to run the supercharger. I live north of Denver so the altitude was around 5000 feet.
Click to expand...

I would expect you saw a greater improvement in performance because of the blower in your area than would be seen at sea level. In my youthful days, I was involved in drag racing where we traveled to Bandimere in late July. Thick, hot air was not our friend and were glad to have a 'belt-driven tunnel ram' (blower) on our TAD Comp Eliminator engine. Still, we were off by a 10th.

I will add some thoughts/questions below.

1- I had a problem with my front pulley coming loose before I put the supercharger on. This only got worse with the additional load of the supercharger. I even added a second 1/4" key to drive the pulley. I think the longer heavy 5/8" v-belt may have been the problem?
I would have thought a 2nd key would have corrected the problem, so it was apparent that harmonics were present. I wonder how much a counter-weighted crank could have helped??

2- Tuning the carburetor required adding a fuel/air ratio meter since the supercharger hid issues from the tried and true old methods. I tried the Weber, an Autolite 2100 and finally ran a Stromberg 97. The Stromberg performed better before adding the supercharger as well.
Based on your comments below in #5, I would say you were lean when using a 97. If you were wanting an era carburetor, I would have thought a 94 would have been a better choice just because of the power valve alone.

3- The supercharger pressurized the crankcase causing me to think more about why. My conclusion is that the pressurized intake ports pushed air past the valve guides and into the crankcase. Remember, flatheads engines do not have valve guide seals in stock configuration.
While that is possible, I doubt it. I would suspect compression loss by the rings either due to ring choice or bore roundness.

4- The compression test at the end of my little experiment showed 100 psi across all 4 cylinders cold so I don't think piston ring blowby was a problem.
This is where a leak-down test would have confirmed your suspicions.

5- The supercharged engine produced considerably more heat than the un-supercharged engine did. Although this engine ran hot before adding the supercharger.
As stated above, I suspect the engine was lean in certain RPM ranges. Theoretically, you should have been able to push more air & fuel to compensate.

6- Wow! The supercharger added at least 20% and probably closer to 30% to the horsepower output of the engine. Now that I have returned to normally aspirated, the engine runs smooth but I am disappointed with the performance.
I'd say you will want that performance back very soon! ;) Thanks for sharing!!


If I return to supercharged, or if anyone is considering it, I will make some changes to the engine. I am looking into what it would take to add valve guide seals and how to run a serpentine belt instead of the heavy V-belt. Possibly changing the attachment of the front pulley to the crankshaft.
If anyone else has experience with running a supercharger, I would be interested in their lessons as well.
Have fun!
 
If I was going to supercharge my Model A, I am not, I would consider adapting a small engine turbo charger, even one for a motorcycle. With an innercooler the integration could get complicated real quick. The advantage is that you are utilizing the exhaust heat that normally gets thrown away and there is no additional load on the crankshaft. I think that a different cam grind may be needed.
 
nkaminar said:
If I was going to supercharge my Model A, I am not, I would consider adapting a small engine turbo charger, even one for a motorcycle. With an innercooler the integration could get complicated real quick. The advantage is that you are utilizing the exhaust heat that normally gets thrown away and there is no additional load on the crankshaft. I think that a different cam grind may be needed.
Click to expand...

Neil, I would think the biggest drawback to a turbo on a Model-A is the engine is very low speed so the lag (-slow spool-up) would make it a slug to drive. Especially if an aftercooler were used. Also, a detriment with a turbo would be the siamesed exhaust ports of a Model-A engine block. Because of this, a blower on a Model-A engine actually helps overcome the exhaust's restriction.

Additionally, to enjoy the benefit of the turbocharger, the transmission gearing really needs to be very close ratio-ed where the turbine can stay spooled-up thru a wastegate with little RPM drop the exhaust pressure will remain high when the transmission is shifted to the next gear. I think every time the Model-A transmission was shifted to a different gear, the RPM drop would make the performance feel very sluggish while waiting for it to return to the horsepower band. Just my thoughts, ...others experiences may vary.
 
I have been kicking around the ultimate A engine. A Burtz with EFI and a Turbo. I've already got the Burtz approved by the wife since it's "necessary" for the AC she wants. I figured the Turbo would be easier to package without any drive problems.
As far as the small engine turbo considered above you need to remember the A has 200 cubic inches and less than 1/2 the compression of a current engine. Most of those turbos were designed for 1.6-2.0 (up to 122") and 9+ compression. I'm thinking one sized for 289"-350" will be ample. Also Valve seals are designed to keep excessive oil from getting into the guides. If you are getting enough air past the guides to pressurize the crankcase you need new guides.
 
I tried a turbo on Elvira (28 tudor), that was OEM for a VW Jetta. It gave me about a 20% seat of the pants performance gain. I used a motorcycle slide carb., which ran well right out of the box ($50 on Amazon). Built my own manifolds.
However, those cheap turbos were designed for an EFI setup, and they are not properly sealed for the vacuum seen when the throttle is closed, and it sucked oil through the turbo's seals. Smoked a bit. Actually, quite a bit. I bought the turbo new, on ebay, for $89, including a nice waste gate. Was fun to listen to it spool up. Decided to remove it and not stress the engine. That wimpy crankshaft is not really made for much extra power output.
 
Brent,
I failed to mention that the crankshaft was balanced (by Model A standards) and insert bearings were installed as part of the rebuild. I have always suspected the pulley is suffering from a torsional harmonic but there is no way to check without removing the engine.
I find it hard to believe that the valve guides would allow enough leakage to cause the smoke I saw from the oil filler cap. These are the modern valve guides, not the split type. However, with 100 psi compression, I don't know what else would cause the pressurization; other than maybe a crack in the block and I really don't want that to be true.
Is there another path to pressurization that I am not thinking of?
Maybe a leak down test would answer this question too. I think a leak down test is in my future.
BTW, I used the air/fuel ratio meter to chase out the lean conditions in my driving. It was actually looking pretty good when I got it tuned in. The first Stromberg 97 was causing me to chase my tail so I replaced it with a new one that tuned in quite well.
 
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Brad in Germany,
Oh, if I had only known sooner about the BAT! I too could enjoy snappy acceleration and better fuel economy!
 
Not sure what is going on with the Ford Model A engines in this vehicle, but maybe something like this would work:

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Brad in Germany
 

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Brad in Germany said:
Not sure what is going on with the Ford Model A engines in this vehicle, but maybe something like this would work:

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Brad in Germany
Click to expand...

That's the Mancilas brothers dragster. They never ran the twin engined car but ran a single engined turbo charged roadster at the 1/4 mile drags. Eddy Mancillas now runs a similar engine in a dragster, and it is really fast, exceeding most OHV banger dragsters in mph an e.t. Eddy still has the twin engined car but only occasionally shows it. Eddy is the son of one of the original builders.
 
I ran my OHV Cook with a Buick turbo on the Bonneville salt flats. There was no noticeable turbo lag. It originally put out 6 lbs. of boost, when I jacked it up to 10 lbs. it overheated and froze up. The last run, in our 4 ever 4 Club's lakester was 167.45 mph, on methanol. I now have a bigger turbo, hotter cam and more compression but because of rain there have been no race meets to test it on, wish me luck!
 

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I have been looking into using a Holley Sniper EFI on my banger. I wonder how that blower and the Sniper would work together? Pretty good I expect.
 
I notice that on the turbo charged twin engine dragster they used a constant velocity SU carburetor, I doubt that was for no reason. I would think that almost any motor would benefit from a constant velocity carburetor, after all countless millions of motorcycles can’t be wrong.
 
Having changed a bad head gasket on a Model-A, I would think that a supercharger would be hard on the head gasket.
 
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