ok, i know it is a longer stroke, and 400 crank etc. but why doesnt the piston extend beyond the head if it goes down futher????

i really dont know here guys.. confusing the hell outta me- someone explain this????

Steve

WOOHOOOOOOOO this was my 700th post!!!

[This message has been edited by fb305svs (edited September 28, 2000).]

 

over once wonderd that my self, it realy simple. you obviously increas the strock. now you can use a 400 con rod (5.56) with a stock 350 pistion or use a 350 rod (5.7 inch) with a costom piston the has the wrist pin located higer up in the piston casting. i hope that clears it up if not feel free to email me with any more questions

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when the green flag drops the bull$hit stops

350,performer RPM intake ,650dp, 700r4, headers, 3inch exhast

 

but the shorter piston skirt (or relocating the wrist pin) would take up the extra length of the stroke- yes no???? damn i am having a hard time with this... i wonder if vader has one of those neat diagrams like that cam one he posted a bit ago

Steve

 

the only thing i can tell you to think of is a 327( 4 inch bore 3.25 stroke) and a 350 (3.48 stroke) both have the same con rod but difernt pistions and stroke. just know this, it all works out in the end.

------------------
when the green flag drops the bull$hit stops

350,performer RPM intake ,650dp, 700r4, headers, 3inch exhast

 

hehe well, it obviously works out in the end.. havent heard too many guys with 383's complaining about knicking up there pistons and heads...

j/k yeah i dunno.. it puzzled me but i drew a diagrsam and that helped

Steve

 

The compression height (distance from the center of the wrist pin to the top of the piston) of an average 350SBC piston is about 1.56" The stroke change from 3.48 to 3.75 places the piston (3.75-3.48)/2=.135" higher in the bore, and of course .135 lower as well. The stock 400 had 5.565 rods instead of 5.7 rods. 5.7-5.565=.135" Coincidence? Not even. If you use the 5.7 rods then of course the compression height has to be less (about 1.43"), which places the wrist pin closer to the top of the piston, or as stated above 'higher'.
If I get really bored I'll draw something up for you.

I should also add...
Keep in mind the stroke is found by the distance from the centerline of the crank to the centerline of the rod journal TIMES 2. Most people (even I have) forget that the distance from the centerline of the crank to the center of the rod is not 3.48", its only 1.74" on a SBC.
This making more sense now?

[This message has been edited by madmax (edited September 28, 2000).]

 

i see it has been explained, but should be pointed out almost no one wastes the money on a 400 crank anymore. this is a common misconception.

 

if i am getting really bored? nah i figuered it out, i drew my own little diagram.. retty puzzleing, but when t comes dow to it, it is simple... thanx guys!

Steve

 

u mean people buy after market cranks hat have the 350 journal size with the 400 stroke right???

Steve

 

yes, most people buy brand new cranks with the same journal size as the 350. the stroke for the 383 is obviously going to be 3.75 just like the 400. since 400's weren't made at the time of one peice rear main seal engines your better off buying the new crank then cutting the 400 crank and buying the adapter. also hard to find 400 cranks now compared to a few years ago.