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#1
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Strokin basics
Please feel free to correct me if I'm way off base here.
Strokin any motor is done by crank and ovebored pistons? |
#2
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"stroking" an engine is increasing the stroke. This is accomplished with the crankshaft as the crank is what is moving the rods and pistons as it spins the crank is what has the stroke built into it.
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#3
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vettekilla;
man please keep it all in the same thread so we aint gotta go chasing you all over the forums trying to answer your questions.its easier for everyone replying if you keep it together,we can all contribute and elaborate on one anothers train of thoughts,and information. now this obviously doesnt apply if your question isnt related to your original thread/post made...then by all means create a new thread. |
#4
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strokin an engine is basically in the crank. with chrysler it is done with keeping the stock lengthed rods and using a different placement of the wrist pin in the piston. sb example is the 4 inch crank from MP. stock cranks being 3.31 (340) and 3.58 (360). they each use the stock 6.123 inch rod and custom pistons with the wrist pin relocated. big blocks have a similiar design worked out.
boring a block increases cubic inches but does not add stroke. stroking an engine adds cubic inches and stroke, stoke being the distance measures in a firing cycle for a particular cylinder.
__________________
Sapporo Man |
#5
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The stroke is the is the distance the piston travels from TDC (piston all the way at the top) to the bottom of its travel (all the way down in the bore) Stroking the engine is increasing this "distance" Every engine has a "stock " stroke 318's & 340's share the same stroke, the reason a 340 is 22 cubic inches "larger" is due to the bore size. a 360 has a longer stroke and a larger bore . Engine cubic in. size is determined by the bore X stroke. (this is not complicated math!) Stroking an engine, is acomplished by using a crankshaft with a longer stroke. The piston has to have the wristpin moved up in relation to the top of the piston,otherwise just putting in a longer stroke crankshaft would cause the piston to be pushed too high in the bore and it would hit the head! (the engine would not even run) So, to "stroke" an engine you need a longer stroke crank & the correct piston to go with it. Note: This information pertains to all piston engines not just mopars!
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#6
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Stroke is measured from the center of the main to the center of the rod throw. ie, 1-1/2" would be a 3"stroke since 1 revolution will cause the throw to move up 1-1/2" and down 1-1/2". This is why when you stroke a motor say 1/2" the piston will only go 1/4" farther up in the bore but will also go 1/4" farther down in the bore for the total of 1/2". This is also why the piston pin is raised and the skirt is shortened on stroker pistons.
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#7
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There's also some slack in both the "up" and "down" distance predictions.
The entire 1/2 of stroke increase frequently shouldn't be removed from the compression distance, because the original piston was not as tall as it should be for best compression and quench. "Adjusting the CD up a bit will result in "tightening up" the quench distance to where you want it to be: about .040" total. With a closed chamber head this means total of deck clearance and gasket thickness. The entire 1/2 of stroke increase doesn't always have be removed from the skirt length, because the original piston may have cleared the counterweights by more than needed. The new skirt length has to clear the weights @ BDC by 1/16" or so, don't take off any more than that. |
#8
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BTW: yes, it's a lot of new ideas to take in and make sense of. Anyone who tells you this is not a complex subject doesn't understand it.
I learn something new pretty frequently, and I've been doing this stuff for 40 years. |
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