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Author Topic:   377 pistons
DirtDobber
Dirt Maniac

Total posts: 114
posted February 28, 2005 06:05 PM  
When building a 377 with a 5.7 rod and 350 crank are the pistons listed for the 377 combo the same as a stock 5.565 rod 400 piston??
I am looking at the specs for the two pistons and they appear to be the same. But mathematically they donít add up?? Whatís the deal??

400 = 3.75 stroke 5.565 rod - say 1.555 compression height = 10.87
350 = 3.50 stroke 5.7 rod with the same 1.555 compression height = 10.755

Am I thinking right??

sdhnc29
Dirt Forum Champ
Total posts: 934
posted February 28, 2005 08:41 PM  
Yes they are the same piston. I assume your talking about compression ratio, when you say they don't add up. If this is true, then your difference comes simply from the different stroke cranks.

Steve

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780
http://www.hendrensracingengines.com

awkwardjeff
Dirt Forum Champ
Total posts: 562
posted February 28, 2005 09:07 PM  
I assume the 10.87 and 10.755 is DECK HEIGHT.

Your math his off because when you measure deck height it's measured from CRANK CENTERLINE......that is 1/2 of the stroke, so the 350 crank is not 3.50 it becomes 1.75 then the 400 crank is not 3.75 it becomes 1.875......so the math looks like this

400= 1.875 stroke + 5.565 rod length +1.555 compression height = 8.995 deck height

350= 1.75 stroke + 5.7 rod length + 1.555 compression height =9.005 deck height

that looks much better....about 9 inch deck is the normal place.....that is why your deck height was over 10.....Only half the stroke to figure deck height.

DirtDobber
Dirt Maniac

Total posts: 114
posted March 01, 2005 06:55 AM  
Thanks guy's!!
awkwardjeff That is why I could not get the 9 inch deck. I wondered where I was wrong...
Jason

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