289 / 302 4 Bolt Main Conversion?

J

jabb

Member

Dec 14, 2007

39

0

6

Mar 10, 2009

#1

• Mar 10, 2009

• #1

Hi all,

I was recently reading an article on block selection Engine Blocks which casually mentioned that a 289 hipo 4 bolt main cap could be added to an ordinary block, but didn't go into any detail. A search (forums and google) hasn't revealed anything for a 289, just info on the conversion for 351Ws and chevy 350s.

Does anybody know of a kit for this conversion? Is it really as easy as just getting a 4 bolt cap and tapping the block?

Thanks in advance peeps!

 

D

D.Hearne

New Member

Sep 29, 2000

11,730

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0

south louisiana

Mar 10, 2009

#2

• Mar 10, 2009

• #2

289 Hi-po's never had 4 bolt main caps. 2 bolt only. They did have heavier main caps though than the std motors. The only factory production 4 bolt small blocks were the Boss 302's and a select few racing only 289 blocks. If you want a 4 bolt main block buy an aftermarket or the newer Boss 302 block. There's really no need for one unless you're into serious racing only

 

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HookandLadder

Founding Member

Feb 17, 2001

261

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St Louis

Mar 10, 2009

#3

• Mar 10, 2009

• #3

You can convert th 289 to 4 bolt caps, but you are better off with a later block and an aftermarket like Hearne said. Besides, with the later blocks you can run a longer stroke without running into piston skirt issues.

 

rbohm

Founding Member

Apr 12, 2002

6,698

550

204

tucson,az

Mar 11, 2009

#4

• Mar 11, 2009

• #4

the others are right, there really is not enough material in the web to convert a 289 or 302 to a proper four bolt main configuration. even if you made your own main caps, and used bolts that were small enough to prevent creating stress risers in the block, the gain in strength would be minimal at best. if you want a four bolt main 289/302, then find on old boss 302 block, buy a new boss 302 block, or get an after market block.

a 351w can be converted to four bolt mains though, and there are even kits to do just that. however the only small block ford that can be easily changed over to four bolt mains is the 351c. the main caps are the same thickness and width, you just need to drill and tap the block, and use the 351c four bolt caps for the conversion as the two bolt caps are configuered slightly differently.

 

J

jabb

Member

Dec 14, 2007

39

0

6

Mar 12, 2009

#5

• Mar 12, 2009

• #5

Alrighty I appreciate the input. My application won't need a 4 bolt, just wanted to add one if I could for peace of mind.

 

mrmustangman357

Member

Feb 11, 2007

763

3

18

Mar 12, 2009

#6

• Mar 12, 2009

• #6

the block would need to be line bored and honed as well

 

R

-R-J-P-

New Member

Mar 21, 2020

1

0

0

Arkansas

Mar 21, 2020

#7

• Mar 21, 2020

• #7

My 1967 Shelby GT350 with a 289 had 4 bolt mains and a single 4-bbl Holley believe it was rated at 307 HP.
A few years later, we blew the engine, however, with the help of a friend we procured a new 289 short engine with 4-bolt mains. Was exactly the same except the block was stamped Hencho en Mexico. We were nobody special so I did not think they were that hard to get. Per the other replies, it appears we were very lucky, but back in those days maybe they were not as rare as supposed as Shelby made a lot of cars.
Later I bought a new Boss 302 short block and it too had 4-bolt mains

 

tos

Founding Member

Apr 27, 2001

896

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59

Cincinnati Ohio

May 3, 2020

#8

• May 3, 2020

• #8

Have you considered a main stud girdle? No machining, easy install and distributes stress.

 

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