strokers???

allcarfan

The Answer Man

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May 22, 2004

#1

• May 22, 2004

• #1

ok...

There are all kinds of 302 based strokers...317s, 331s, 347s, etc.

Im a little confused though. Some 331/347 kits have the same rod lenght, different pistons, and different crankshaft sizes. While others have different length rods, different crank sizes/stroke, and different pistons.

How many different ways can a 331 and a 347 be made? what are the different rod lengths, piston sizes, and crank strokes??

 

3

3spd on floor

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May 22, 2004

#2

• May 22, 2004

• #2

basically there is an infinite number of ways to make a strocker combo. For a 331,you need a 3.25 inch stroke crank, 3.4 inch for a 347. From there you can use any combination of pistions and rods that will give you an 8.2 inch(i believe its 8.2 for a 302 block) total throw distance (distance from crank centerline to cylinder deck). The formula to compute this is half the stroke plus the rod length plus the piston compression height. Most strokers use a 5.4 inch rod, but there are some that use a 5.325. Also, you can make a 331 using 289 rods (5.109 inches???). The only thing that limits the combinations are that the manufactures only make so many different length rods and pistons. If it fits the 8.2 inch requirement, it will work, provided adaquet clearance is made for everything.

as a side note, in general, a longer rod is better, but requires a shorter and possibly less stable piston.

did i touch on everything?

 

brianj5600

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Sep 19, 2003

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May 22, 2004

#3

• May 22, 2004

• #3

Dart blocks can be bored up to 4.185, which means even more displacement. Or the same with less stroke.

 

allcarfan

The Answer Man

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May 22, 2004

#4

• May 22, 2004

• #4

crap.

looks like i have to sell my pistons or my crank.

THanks guys

 

3

3spd on floor

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#5

• May 22, 2004

• #5

what pistons and crank do you have? why do you need to sell them?

 

ratio411

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Apr 21, 2002

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May 22, 2004

#6

• May 22, 2004

• #6

allcarfan said:

crap.

looks like i have to sell my pistons or my crank.

THanks guys

Click to expand...

Why?

 

allcarfan

The Answer Man

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May 22, 2004

#7

• May 22, 2004

• #7

I have two 347 crankshafts (both 3.4"), 5.4" connecting rods, and pistons for a 331 (with a 3.25" stroke crankshaft). So, I will have to sell either the crank and go with a 3.25" crank to make 331ci, or sell the pistons and get 347 pistons for use with my 3.4" crank and 5.4" rods for 347ci (which is what i want.)

right?

 

ratio411

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May 24, 2004

#8

• May 24, 2004

• #8

Yeah, sounds like you need shorter pistions.
What is the compression height of the ones you have now?
I am curious, although common sense tells me that they wouldn't short enough. They would have to be spec'ed for 5.5" rods to work with your crank.
Dave

BTW: It might be possible to mill the top of the pistons shorter. Some pistons are made with plenty of 'meat' for custom work. If the pistons are advertised as 'lightweight' or 'race', then this is unlikely, but street pistons are usually bulky. Something you might check into. You would need to mill about .075" from the top of the piston.
Another thing to check into is: What pin diameter is the piston set-up for? What pin is the rod set-up for?
You may be able to get some of the difference made up with an offset bushing/smaller pin combo. This would not take up all the difference, but would allow a much smaller milling from the top of the piston...
In the end though, nothing beats the 'right' parts.

 

allcarfan

The Answer Man

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May 24, 2004

#9

• May 24, 2004

• #9

Dave,

With all of the machining and what not, wouldnt it make more sense to sell the pistons that I have and just buy some new ones? Seems like the most cost effective and efficient way to 'build it right.' The pistons are advertised as light weight, so there probably isnt a lot of meat on the top of them. Since I have two 347 cranks, I can sell one of them and sell the set of pistons really cheap (both sold seperately) - and just pick up a new set. This is probably what I am going to end up doing.

Worst case scenario: Sell both 347 cranks and buy a 331 crank.

Thanks for your help....again.

 

ratio411

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May 25, 2004

#10

• May 25, 2004

• #10

Yeah, that is kinda what I was getting at...
You have options, but selling the extra crank and pistons is probably the way to go.
I was curious about the piston height because with a shorter rod they might go with that crank. In that case you could sell them as a set.
Just a thought.
Dave

 

allcarfan

The Answer Man

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May 25, 2004

#11

• May 25, 2004

• #11

Well,

I decided to go ahead and sell the pistons. $747 set of pistons and i cant even get $300 for them...sheesh. I also decided to step down from Forged to some KB Hyper pistons. I will be 100% NA, so I think these will be sufficient for my application. Thanks for everyone's help.

Shane

 

ratio411

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Apr 21, 2002

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May 25, 2004

#12

• May 25, 2004

• #12

BTW:
After thinking about it, I would really like to know the specs on those pistons.
I might be interested in buying them.
I intend to build a 306 in the near future and want to use long rods, so a shorter piston is in order.
Thanks
Dave