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Old 01-09-2009, 08:24 PM   #1 (permalink)
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BBF stroker info

Noting alot of us (so far) are running the BBF and many are asking about building for mud/torque, I thought I'd throw out a bit of info for the masses.


By adding a stroker crankshaft, the following occurs:

1) For every 50 cubic inches added, the rpm at which torque and horsepower peak at will drop about 600 rpm. So, if your 460 horsepower peaks at 6000 rpm, a 545 will peak at 5000 rpm. This assumes not changing anything else in the engine combo.

2) If you wish to maintain the same horsepower and torque peaks when you increase the stroke, you need to add between 12 to 16 degrees of additional intake duration for every 50 cubic inches added in displacement. Respectively, exhaust will have to be increased also.

3) The amount of torque below the torque peak, and at peak, will increase. This is a good thing, especially for street cars.

4) The larger the engine, the faster it will pull rpm. The weight of the rotating assembly is almost the same on all strokes, from a 460 to the 545 assembly, but as you increase the stroke, the engine now has more displacement pushing that assembly.

5) If you keep the same cylinder heads on the larger motor, you need to add overlap by using a tighter lobe separation, usually 1 to 2 degrees for every additional 50 cubic inches, until you get to 270 degrees @ .050" lift. Above 270 @ .050" duration, you need to bring lobe separation wider to limit overlap that is inherent after that duration. BSFC numbers go up needlessly with too much overlap.

The tighter lobe separation angle adds the necessary overlap to feed the additional inches, however, it does close the intake valve earlier. The horsepower peak numbers will be similar, but will occur at a slightly lower rpm with the tighter LSA. It is usually good not to advance the cam as much as usual.

If your compression ratio is "on the edge" running on pump gas, it may be inapproopriate to tighten the LSA because it increases lower rpm cylinder pressures. The tight LSA adds low and mid range torque because of the lower end cylinder pressures, but may not be needed if the vehicle combo is traction limited.
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Old 01-09-2009, 08:37 PM   #2 (permalink)
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i dont know about all that you just posted but in florida we biuld them in our back yard shed im building a 638 ford idt premier block crower 4.750 stroke moters are just big air pumps the more air you move the more power and to make more torque than power you run high duration and lower lift on big er centerline also thats how did it offshore boat moters / on my jeeps 416 windsor im running 308 dur 560 lift on 112 center line and makes 80 ft lbs more than horsepower at peak about 6400 rpm
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Old 01-09-2009, 08:48 PM   #3 (permalink)
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Originally Posted by mightydog View Post
i dont know about all that you just posted but in florida we biuld them in our back yard shed im building a 638 ford idt premier block crower 4.750 stroke moters are just big air pumps the more air you move the more power and to make more torque than power you run high duration and lower lift on big er centerline also thats how did it offshore boat moters / on my jeeps 416 windsor im running 308 dur 560 lift on 112 center line and makes 80 ft lbs more than horsepower at peak about 6400 rpm
get over to my shed and build me some horse power!
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Old 01-09-2009, 08:51 PM   #4 (permalink)
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horsepower costs money how much do you want
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Old 01-09-2009, 08:52 PM   #5 (permalink)
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Originally Posted by IDIeselman View Post
Noting alot of us (so far) are running the BBF and many are asking about building for mud/torque, I thought I'd throw out a bit of info for the masses.


By adding a stroker crankshaft, the following occurs:

1) For every 50 cubic inches added, the rpm at which torque and horsepower peak at will drop about 600 rpm. So, if your 460 horsepower peaks at 6000 rpm, a 545 will peak at 5000 rpm. This assumes not changing anything else in the engine combo.

2) If you wish to maintain the same horsepower and torque peaks when you increase the stroke, you need to add between 12 to 16 degrees of additional intake duration for every 50 cubic inches added in displacement. Respectively, exhaust will have to be increased also.

3) The amount of torque below the torque peak, and at peak, will increase. This is a good thing, especially for street cars.

4) The larger the engine, the faster it will pull rpm. The weight of the rotating assembly is almost the same on all strokes, from a 460 to the 545 assembly, but as you increase the stroke, the engine now has more displacement pushing that assembly.

5) If you keep the same cylinder heads on the larger motor, you need to add overlap by using a tighter lobe separation, usually 1 to 2 degrees for every additional 50 cubic inches, until you get to 270 degrees @ .050" lift. Above 270 @ .050" duration, you need to bring lobe separation wider to limit overlap that is inherent after that duration. BSFC numbers go up needlessly with too much overlap.

The tighter lobe separation angle adds the necessary overlap to feed the additional inches, however, it does close the intake valve earlier. The horsepower peak numbers will be similar, but will occur at a slightly lower rpm with the tighter LSA. It is usually good not to advance the cam as much as usual.

If your compression ratio is "on the edge" running on pump gas, it may be inapproopriate to tighten the LSA because it increases lower rpm cylinder pressures. The tight LSA adds low and mid range torque because of the lower end cylinder pressures, but may not be needed if the vehicle combo is traction limited.
to much info moters are much easer than that
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Old 01-09-2009, 08:57 PM   #6 (permalink)
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horsepower costs money how much do you want
ill take a real fire paint job worth...lmao
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Old 01-09-2009, 08:58 PM   #7 (permalink)
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Mine too! Besides that, Are they hiring where you work?
sorry bud one man operation...i really do work out of a shed!
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Old 01-09-2009, 09:00 PM   #8 (permalink)
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ill take a real fire paint job worth...lmao
i know a guy who wants to get that done maybe we can work something out
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Old 01-09-2009, 10:19 PM   #9 (permalink)
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Originally Posted by mightydog View Post
i dont know about all that you just posted but in florida we biuld them in our back yard shed im building a 638 ford idt premier block crower 4.750 stroke moters are just big air pumps the more air you move the more power and to make more torque than power you run high duration and lower lift on big er centerline also thats how did it offshore boat moters / on my jeeps 416 windsor im running 308 dur 560 lift on 112 center line and makes 80 ft lbs more than horsepower at peak about 6400 rpm
not to be an ass or anything, but ........proper grammar and punctuation is important 'round these parts, ight homie
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Old 01-09-2009, 10:34 PM   #10 (permalink)
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are you kidding me in our parts we do what we have to to get the point across not to be an ass but i didnt know i was still in school or that this was book or legal document got better things to do than be all punctual and shit but on another note if you need motor info i might be able to help you out if you can read what i type

Last edited by mightydog; 01-09-2009 at 10:34 PM.
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