cyko83

i'm trying to find out about the different types of crankshaft. there are a couple that i'm looking at, most of them have different main's or strokes. well my questionis whats the better choice for a crank. i'm looking for one that will give me more torq. oops i forgot, the crank i'm looking is for a 350cid. can any one help me out

Sonix

iTrader: (1)

A crankshaft won't give you more torque, it has nothing to do with the output of the motor - unless you use one with a larger stroke, to increase the displacement of the engine.

You need one with "350" mains, ie, large jounals. (not small 327 journals, not 400 journals etc).

A 3.48" stroke is the norm.

A 3.75" stroke would give you a 383 stroker motor, and would mean you need "383 pistons".

What kind of power output and RPM band will the motor see after it's complete? If it's not too exorbitant, then a cast iron one should do fine. If you're planning on going above 6000RPM regularly, a cast steel or forged steel one would be a good idea.

cyko83

well i'm trying to go for 6500 rpm rang with a forged crank. what about if i put a 6.0 rod lenght or a 5.7 rod lenght? what would happen??

5678TA

i would go with a 3.75" stroke and a 6.0" rod.. brings you to a 383, assuming its .030" overbored.. the 6.0" rod will help reach that 6500rpm and with less piston speed= more power.. the larger stroke will give you that extra torque as well..

sixpackmtrspts

a 6 inch rod also gives the piston more dwell time at the top of the cylinder allowing it to fill more with air/fuel. the longer rod also reduces friction since the angle isnt as severe as with a short rod, which results in more power and less piston and cylinder wall wear. a 3.75 stroke in a 350 block makes an excellant street engine and decent strip engine.

when looking for a crank, the manuf will state what rods to use, this will be the shortest rod you can use, you can use longer however, (ex if they say its uses a 5.7 rod you can use a 6 in rod no problem).

if your just satrting out your buildup and are gonna us e a stroker crank i would suggest getting a complete rotating assembly from a supplier like jegs, summit etc. these will come with everything you need for a rotating assembly.

doc

If you exceed 6000 RPM as routine, then you should get forged crank. As the others have said aboe, longer strokes develop more torque. So basically, you should be looking at a 350 stroked out to a 383, or like I did a 395. Also, you have the option of 5.85" rods, not just 5.7" or 6.0".

cyko83

ok thanks for the info but does any one know how much will it cost me to balance teh crank ?? also is it better get one thats internal balance or external balance. one more quetion, if im going to make it into a 383 stroke do i need to change the heads on it ??

iroczracer07

iTrader: (2)

The crank is just a weight. What you want to balance is the rotating assembly. With the 383 you will make more torque, but the heads will determine how much overall power you can make. So yes, I would change the heads. Engine Quest sells 180cc Vortec heads that would probably work well for a street/strip combo without breaking the bank. Dart is another popular choice for low buck heads. And internally balanced cranks are better than external. I'm gonna catch a lot of flak for my next comment, but before anyone goes judgemental, this statement is from John Lingenfelter. 86 up 305 & 350 roller cam blocks are externally balanced, so changing to an internally balanced set up will improve upon it. Just don't forget to get the adapter to convert the roller cam block from a 1 piece rear main seal to a 2 piece unit.

cyko83

hold on...... is the vortec heads for LS/LT intakes, cuz i have a TPI system in.

iroczracer07

iTrader: (2)

You can get an intake that would allow you to use the Vortec heads on your T.P.I. motor without any other changes.

cyko83

if i get the vortec heads, does that mean i have to swap out the headers to??

SheldonZ28

iTrader: (1)

Nope,

Vortec heads are the same as a SBC heads, with different intake ports and intake bolt patters.

Besides that,everything is the same, you can use your regular rocker covers, rockers etc.
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Here is a complete 383 rotating assembly for a 1pc rear.

Forged pistons
Forged rods
Cast steel crank etc.

http://store.summitracing.com/partde...0&autoview=sku

iroczracer07

iTrader: (2)