Need help building 306

marine_2003

Member

Jun 6, 2005

427

0

16

Lake County, FL

Mar 19, 2006

#1

• Mar 19, 2006

• #1

I am almost ready to build my 306. Can anyone help me. I know that the 306 uses the stock 302 crank, I am upgrading that to a forged crank, and want to use forged pistons and forged rods. I dont know what length rods to use, or what size pistons. I believe that the pistons are .030 over bore. Can anyone help??

Thanks

 

marine_2003

Member

Jun 6, 2005

427

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16

Lake County, FL

Mar 22, 2006

#2

• Mar 22, 2006

• #2

ttt

 

J

jerryD

Founding Member

Mar 16, 2000

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Gladstone, MO

Mar 22, 2006

#3

• Mar 22, 2006

• #3

306 is just a 302 bored .030 over. the rods that you will need, and the stock size is 5.09. the pistons will need to be .03 oversized. crank is 3.25 stroke and i would reccomend NOT getting the forged crank, just a good cast one. reason being is that the block will break/crack before the crank in most circumstances.

 

sunil6784

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Mar 31, 2005

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Boston, MA

Mar 22, 2006

#4

• Mar 22, 2006

• #4

Yup, a 306 is nothing more than a 302 that has been bored .030 over. It uses the stock rod length (5.09" I believe).

EDIT: Jerry beat me to it.

 

Realmongo

I prefer to be called "Evil Genius"

Founding Member

Oct 10, 2001

2,468

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99

Western Mass

Mar 22, 2006

#5

• Mar 22, 2006

• #5

You should do fine with your stock cast crank as the block is only good up to 400 horses anyway. Have it checked, turned/polished and the oil holes chamfered. Your rods are forged. You can upgrade them with ARP rod bolts at the same time you have them reconditioned. .030" is the normal oversize. You can get them to fit on the stock 5.09" 302 rod, or you can get ones made to go onto the 5.4" rod which was used in the 221, 260, 289, and Boss 302 engines.

Check out this site for ideas:

http://kb-silvolite.com/index2.php

 

M

Mike92GT

Founding Member

Jan 23, 2002

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Florida

Mar 22, 2006

#6

• Mar 22, 2006

• #6

jerryD said:

306 is just a 302 bored .030 over. the rods that you will need, and the stock size is 5.09. the pistons will need to be .03 oversized. crank is 3.25 stroke and i would reccomend NOT getting the forged crank, just a good cast one. reason being is that the block will break/crack before the crank in most circumstances.

Click to expand...

I thought the 302 had a 3.00" stroke, and 331 was 3.25 " ? I could be wrong. I agree that the forged crank isn't worth it for a stock block.

 

J

jerryD

Founding Member

Mar 16, 2000

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37

Gladstone, MO

Mar 22, 2006

#7

• Mar 22, 2006

• #7

crud your right. i wasn't thinking. thanks for correcting me.

 

Rick 91GT

Mustang Master

Nov 29, 1999

9,692

95

99

PA

Mar 22, 2006

#8

• Mar 22, 2006

• #8

For the price you are going to pay for that 306 rotating assembly you could build a 331/347 that will hold more then the stock block will...

Just my $.02

 

T

tylerrocks

New Member

Oct 13, 2005

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Big Spring, TX

Mar 22, 2006

#9

• Mar 22, 2006

• #9

Stock stroke is 3.0, 331 is 3.25, and 347 is 3.4. Dont bother with a forged crank unless going aftermarket block. Forged rods are nice but not needed in all applications. I would put money on forged pistons first. However, Hyper pistons could be used in a NA application as long as there was not a huge amount of compression. You'll want 5.090 rods (stock). piston size depends on cylinder bore can be anywhere from 4.0 (stock) to 4.06 (max reccomended). While you can opt for the 5.4 rod the 5.090 by 3 has a decent rod ratio at 1.7; 1.75 being optimal. To find out more about rod ratios and to help decide which rod length you want, this is a great site: http://victorylibrary.com/mopar/rod-tech-c.htm

Tyler