model A engine with 2 stromberg 97 carbs
- Thread starter FrankWest
- Start date
mike657894
Well-known member
the amount of air/fuel delivered by the original carb has to pass through a about 1 inch venturi. that limits the rpm to 2800 by restricting air. so when you put on a downdraft twin carb setup you are removing the bottle neck created by the original equipment. the power is not gained by the direction the air is moving but by the amount you can move with the strombergs.
Mikeinnj
Well-known member
Frank,
The addition of larger intake manifold ports and carburetors on a stock Model A engine will not increase it's power or efficiency.
Performance and power gains are the result of a combination of modifications to an engine, with each mod complimenting the others.
They usually involve increased compression along with larger valves and a hotter camshaft profile as well as a larger manifold port size and an increased fuel and air supply as well as larger exhaust, a hotter spark etc.
Think of an engine as a compressor. Here are some combinations of modifications and the actual horsepower.
gainshttp://modelaparts.net/dynosheets.htm/dynosheets.html , compliments of Pirano's website.
The addition of larger intake manifold ports and carburetors on a stock Model A engine will not increase it's power or efficiency.
Performance and power gains are the result of a combination of modifications to an engine, with each mod complimenting the others.
They usually involve increased compression along with larger valves and a hotter camshaft profile as well as a larger manifold port size and an increased fuel and air supply as well as larger exhaust, a hotter spark etc.
Think of an engine as a compressor. Here are some combinations of modifications and the actual horsepower.
gainshttp://modelaparts.net/dynosheets.htm/dynosheets.html , compliments of Pirano's website.
FrankWest
Well-known member
Is it dangerous to a stock engine to try to run it at a higher rpm.
Mikeinnj
Well-known member
Frank,
I do not know if the owner had made any modifications to his engine.
If he only added the manifold and carb's to an otherwise stock engine he would see a very small gain in HP as compared to adding a combination of the modifications I previously mentioned, and then seeing a significant gain in HP.
Mike
30 Tudor and Coupe
Junior Member
I ran a dual downdraft manifold and carbs on mine many years ago when I was in High School. It looked impressive, really roared when you opened them up but I did not notice any power improvement, went back to the stock setup.
Chuck Sea/Tac
Well-known member
When multiple carbs are used, the jets are changed(smaller) because you're right. You can only pump so much gas into any engine, until you reach "saturation"
Synchro909
Well-known member
OK, I'll bight. The short answer is - it depends on how high the revs are. I know others are going to disagree with me but I don't think a stock engine should be driven at any more than 45 mph MAX! The main bearings will take it for a while but their life will be shortened by more and more the more you drive at a higher speed, especially the middle one.
Back in the day, 45 mph was a break neck speed and above what most people were happy/able to do. I held my stock engine to about 42 mph and the bearings lasted about 8,000 miles before they broke up. I've walked away from cars when the seller said that he drives at a speed I consider too fast based on that EXPERIENCE.
There, that can of worms is open!
FrankWest
Well-known member
Funny...Like those guys that have fire shoot out!
FrankWest
Well-known member
Not to mention that these are 85 years old engines..And definitely should not be subjected to over stress...unless you don;t mind destroying your original engine.OK, I'll bight. The short answer is - it depends on how high the revs are. I know others are going to disagree with me but I don't think a stock engine should be driven at any more than 45 mph MAX! The main bearings will take it for a while but their life will be shortened by more and more the more you drive at a higher speed, especially the middle one.
Back in the day, 45 mph was a break neck speed and above what most people were happy/able to do. I held my stock engine to about 42 mph and the bearings lasted about 8,000 miles before they broke up. I've walked away from cars when the seller said that he drives at a speed I consider too fast based on that EXPERIENCE.
There, that can of worms is open!
It is funny that for the longest time ford was producing 60 hp v8's? I often wondered why.
model A was 40 hp
model B was 50 hp
Original v8 was 65 hp 1932 and early 1933 I believe then they got it up to 75hp late in 1933 and 85hp in 1934
then they went back to 60 hp v8's...Why Hi-ways were being built and used, right.
Some of the straight 8 cylinder cars produced 100 hp, right.
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FrankWest
Well-known member
I have a 1933 and 45mph seems like 85mph. Unless you totally rebuild your antique car 45 mph is plenty fast in a 80 + year old car.OK, I'll bight. The short answer is - it depends on how high the revs are. I know others are going to disagree with me but I don't think a stock engine should be driven at any more than 45 mph MAX! The main bearings will take it for a while but their life will be shortened by more and more the more you drive at a higher speed, especially the middle one.
Back in the day, 45 mph was a break neck speed and above what most people were happy/able to do. I held my stock engine to about 42 mph and the bearings lasted about 8,000 miles before they broke up. I've walked away from cars when the seller said that he drives at a speed I consider too fast based on that EXPERIENCE.
There, that can of worms is open!
If you want speed, power and heavenly ride these are not the cars for you.
I always remember the ride I got from a gas station attendant when my Buick Skylark 1964 broke down. The guy had a Chevy Impala 1964, super power/ rode like on a cloud...smoother than a Cadillac..Pickup unbelievable and extra quiet. Probably could have done 120 without noticing it. It was like Mike Mercury's Supercar.
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mike657894
Well-known member
i would like to get a little more out of my drive train. top speed wise. my top is 45 but gets there pretty quick and the ride is smooth and feel great like a modern car but is loud on the engine. i think a rear end gear is my most economical and babit bearing safe option.i think i will change it to inserts if i need to rebuild. now the stock rpm is 2800 if thats safe 3200 rpm should be and maybe what i would expect from a two barrel webber set up. i plan to put a 5.5 head as well.
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mike657894
Well-known member
on these cars horse power is pretty cheap. you can get a 25% gain by just buying a $300 head. but horse power is all in acceleration your wheels will only spin as fast as your engine will turn and all the limitations and over wear that go along with that. i have heard that 5.5 compression is the limit of safe for babbit bearings. modern engines are around 10 to 1
mike657894
Well-known member
i think the 3.27 to 1 would be best for me and a 5.5 head as i want to do 40 at a more reasonable rpm.
Tom Wesenberg
Well-known member
I agree. I think those two options would make the most sense for more power and lower engine speed.
I've got the 5.5 head, but still need to buy the 3.27 gears.
mike657894
Well-known member
just found that snyders put out a 6 to 1 head for $325 with some impressive dyno claims. http://www.snydersantiqueauto.com/cast-iron-high-compression-head http://www.snydersantiqueauto.com/Content/uploads/HighCompressionHeadsDynotestnewsrelease-8780.pdf
Mike V. Florida
Well-known member
OK, I'll bight. The short answer is - it depends on how high the revs are. I know others are going to disagree with me but I don't think a stock engine should be driven at any more than 45 mph MAX! The main bearings will take it for a while but their life will be shortened by more and more the more you drive at a higher speed, especially the middle one.
Back in the day, 45 mph was a break neck speed and above what most people were happy/able to do. I held my stock engine to about 42 mph and the bearings lasted about 8,000 miles before they broke up. I've walked away from cars when the seller said that he drives at a speed I consider too fast based on that EXPERIENCE.
There, that can of worms is open!
How can anyone disagree with that statement? It is what you think based on your experience. If you said the stock Model A was not designed to drive over 45 then that would open up the doors.
Mike V. Florida
Well-known member
If your absolute top is only 45 then you have something setup incorrectly in your car. Timing is the #1 reason for the Model A to top out at a speed under 60.
When I first got my car The engine sounded like a can of rocks. I adjusted the bearing clearances, valve clearances, replaced the timing gear that had some rough teeth and after I was done the car would not go over 40. Thinking WTF did I do I called for help. The troops came by and found the timing off a little, just a little and it was like a new car after that.
One more thing, I have found there are a large number of owners that really don't know how to use the spark levers to the best advantage.
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denis4x4
Well-known member
1931 engine, '39 transmission, single 97. BF head, inserts, counter weight crank, Petronix ignition and 3:54 gears. 60 HP at the rear wheels at 3200 RPM. Stock 40 HP number is at the flywheel. Engine was built 25 years ago and still strong. BTW there were more than a few A's pulling 80 HP plus at the speedster reunion.
