Stroking

jwillburn119 · 07-29-2005, 06:36 PM

hey guys... im putting my engine back together... and i am wondering if how stroke works... if my pistons are already at the top of the deck... how is it possible to put more stroke on the crankshaft without raising the piston out of the cylinder...

and if i bought stock speed pro pistons and scat... stock length connecting rods... would they work with a stroked crank if it had the same journals?

Wicked · 07-29-2005, 06:45 PM

When you increase the stroke, you have to shorten the rod or move the piston pin up in the piston.

Wickd GT · 07-29-2005, 07:12 PM

When you stroke the rod becomes longer example a 3.40 cranck and the rod becomes 5.400 rod, nut the compression hight in the piston goes up, meaning the piston pin now is further in the piston so it would not put the piston out of the deck, but you can use a smaller rod 5.135 I think thats what it is.

Edgar

jwillburn119 · 07-29-2005, 08:11 PM

but wouldnt that leave the same compresion ratio at the top? or is it getting more downstroke?

jwillburn119 · 07-29-2005, 08:12 PM

because if you shorten the rod, you get the same stroke?

jwillburn119 · 07-29-2005, 08:14 PM

Quote:

Originally Posted by jwillburn119

because if you shorten the rod, you get the same stroke?

or would you get the same upstroke and longer downstroke?

Italian LX · 07-29-2005, 08:41 PM

Quote:

Originally Posted by jwillburn119

but wouldnt that leave the same compresion ratio at the top? or is it getting more downstroke?

Your compression ration increases. Even if your combustion chamber is the same size, you're still compressing a larger amount of air in there; therefore, increasing the ratio.

jwillburn119 · 07-29-2005, 08:47 PM

so i get more downstroke... causing the cylinder to fill more... but still push it up the same height...

i understand... you have to change both at the same time... longer crank shorter rod... to get more downstroke displacment... but keeping the same upstroke... thats hard to understand... but i got it

what is the stock conecting rod hieght?
and the stock journal diameter if anyone knows?

Italian LX · 07-29-2005, 08:53 PM

Quote:

Originally Posted by jwillburn119

so i get more downstroke... causing the cylinder to fill more... but still push it up the same height...

i understand... you have to change both at the same time... longer crank shorter rod... to get more downstroke displacment... but keeping the same upstroke... thats hard to understand... but i got it

The downstroke and upstroke are increased the same amount... the laws of physics won't allow any different. When you increase the stroke, you are taking in more air and compressing that same amount of air in the same size combustion chamber which equals more power.

Wicked · 07-30-2005, 08:56 AM

Quote:

Originally Posted by Wickd GT

When you stroke the rod becomes longer example a 3.40 cranck and the rod becomes 5.400 rod, nut the compression hight in the piston goes up, meaning the piston pin now is further in the piston so it would not put the piston out of the deck, but you can use a smaller rod 5.135 I think thats what it is.

Edgar

All depends on who you buy your stroker kit from.
Think about a 393 poor mans stroker.
It uses a 351W block with 351 crank offset ground from 3.5inch to 3.85 inch stroke. It then uses the stock 351 rods and a shorter 302 piston(which moves the piston pin up closer to the deck).

Some strokers use short rods and lower piston pin. Others use long rods and raised piston pins. Example: Long rod(6.0inch) versus short rod(5.7inch) chevy 350.

You have to be careful not to get a kit that put the piston pin intersecting the oil ring groove as it will cause excess oil consumption for a street driven car.

07-29-2005, 06:36 PM	#1
jwillburn119 Senior Member Join Date: May 2005 Location: temple, tx Posts: 240	Stroking hey guys... im putting my engine back together... and i am wondering if how stroke works... if my pistons are already at the top of the deck... how is it possible to put more stroke on the crankshaft without raising the piston out of the cylinder... and if i bought stock speed pro pistons and scat... stock length connecting rods... would they work with a stroked crank if it had the same journals? __________________ Whats in your WALLET?

07-29-2005, 06:45 PM	#2
Wicked Friends Join Date: Dec 2004 Location: Pell City, AL Posts: 1,371	Re: Stroking When you increase the stroke, you have to shorten the rod or move the piston pin up in the piston. __________________ 2001 Cobra 'Vert Procharged and Intercooled 455rwhp/441rwtq Work Car: 2005 Honda Odyssey 400 whp Turbo V6, 6-speed, full cage, H&R Suspension, Brembo Brakes

07-29-2005, 07:12 PM	#3
Wickd GT Friends Join Date: Dec 2004 Posts: 1,645	Re: Stroking When you stroke the rod becomes longer example a 3.40 cranck and the rod becomes 5.400 rod, nut the compression hight in the piston goes up, meaning the piston pin now is further in the piston so it would not put the piston out of the deck, but you can use a smaller rod 5.135 I think thats what it is. Edgar

07-29-2005, 08:11 PM	#4
jwillburn119 Senior Member Join Date: May 2005 Location: temple, tx Posts: 240	Re: Stroking but wouldnt that leave the same compresion ratio at the top? or is it getting more downstroke? __________________ Whats in your WALLET?

07-29-2005, 08:12 PM	#5
jwillburn119 Senior Member Join Date: May 2005 Location: temple, tx Posts: 240	Re: Stroking because if you shorten the rod, you get the same stroke? __________________ Whats in your WALLET?

07-29-2005, 08:47 PM	#8
jwillburn119 Senior Member Join Date: May 2005 Location: temple, tx Posts: 240	Re: Stroking so i get more downstroke... causing the cylinder to fill more... but still push it up the same height... i understand... you have to change both at the same time... longer crank shorter rod... to get more downstroke displacment... but keeping the same upstroke... thats hard to understand... but i got it what is the stock conecting rod hieght? and the stock journal diameter if anyone knows? __________________ Whats in your WALLET?