1969 302 max Bore?

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gt350son

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Dec 1, 2008

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Jan 27, 2011

#1

• Jan 27, 2011

• #1

I have a 1969 block that needs to be bored over to .060 but my local machine shop says I should get a different block. Now I've heard that the 1969 blocks have thicker cylinder walls and was wondering if the 1969 block can handle running with a 0.060 with little to no issues? I've heard that if they do have issues its usually cooling.

 

woodsnake

15 Year Member

Jan 16, 2007

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Hicksville, NY

Jan 27, 2011

#2

• Jan 27, 2011

• #2

Your machine shop is right. While it is physically possible to go that far over on your block, you are setting your self up for failure. For longevity purposes, I think you will be money ahead getting a better block to work with, and only going .030 or .040 over for a performance build.

 

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gt350son

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Dec 1, 2008

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Jan 27, 2011

#3

• Jan 27, 2011

• #3

Thanks for your reply. Guess I'll be looking for another 302 block.

 

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Pony66

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Jul 23, 2010

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Jan 27, 2011

#4

• Jan 27, 2011

• #4

Id listen to the machine shop. I was in your shoes last year. I found a good builder in my third block. I watched craigslist all summer and found several people giving away 302s. I ended up using a 70 302 and put all my 1966 289 heads and stuff on it. It runs great and I got some free Cobra valve covers off one of the engines.

 

PoppyMod

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Jun 27, 2010

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Severna Park, MD

Jan 28, 2011

#5

• Jan 28, 2011

• #5

gt350son said:

I have a 1969 block that needs to be bored over to .060 but my local machine shop says I should get a different block. Now I've heard that the 1969 blocks have thicker cylinder walls and was wondering if the 1969 block can handle running with a 0.060 with little to no issues? I've heard that if they do have issues its usually cooling.

Click to expand...

Hi,
If you need that much "clean up", I'd go for a different block too.
Boring .040 is about the max, I would ever go. As someone else mentioned, it's starts to get a little thin and the 302 blocks are just too plentiful.
Good Luck!

 

Realmongo

I prefer to be called "Evil Genius"

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Oct 10, 2001

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Jan 28, 2011

#6

• Jan 28, 2011

• #6

Ford's literature says not to overbore beyond .030".

 

PoppyMod

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Jun 27, 2010

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Severna Park, MD

Jan 28, 2011

#7

• Jan 28, 2011

• #7

Realmongo said:

Ford's literature says not to overbore beyond .030".

Click to expand...

While, no doubt they do make that recommendation (for conservative margins of safety), there are numerous real-world 289/302 blocks being bored .040 over without any problems. I, for one, am running an original 5 bolt bored .040 over and running a 331 stroker kit. It makes 400 RWTQ at 4400 Rs and runs 190-200 deg in our MD summers, and has been for a number of years.
But, at .060 over the walls are just too thin and the blocks too plentiful.

Happy Motoring!

 

69gmachine

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Dec 2, 2004

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Southern Maryland

Jan 28, 2011

#8

• Jan 28, 2011

• #8

I've never heard anyone having a problem at .040 over, but I've had first hand experience with overheating at .060, and that was with an early block as I built the engine around '79 or '80 with a junkyard core (it was actually a 289 block IIRC). I had to pull it out and start all over. Very demoralizing. Occasionally a block has enough meat in it to hold up to .060 over, but as Poppy said, there are so many cores out there, why waste the time and money?

 

iskwezm

10 Year Member

May 24, 2005

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Rowland Heights,California

Jan 28, 2011

#9

• Jan 28, 2011

• #9

Im not sure about longevity of a .060 over block, but i do know i built mine in high school and it there were no issues.The motor lasted about 14 years till i melted a piston.The block itself is still fine and is in another car 21 years later.I dont who has really bored a block or who is repeating what they read or heard. But i wouldnt do it again.

 

Realmongo

I prefer to be called "Evil Genius"

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Oct 10, 2001

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Jan 28, 2011

#10

• Jan 28, 2011

• #10

I'm sure it has a lot to do with core shift. The original 5.0 out of my '84 had so much visible core shift, I did not even consider using it again. It gave me the good excuse to go get a roller engine out of a 1988.