.060 Over 340....Your Thoughts?

-
K

kend

Well-Known Member
Joined
Jul 29, 2012
Messages
89
Reaction score
10
Location
GA
Anybody have problems going .060 on a '73 340 block?
 
toolmanmike said:
Are you already .040 over?
Click to expand...

No, going for max horsepower with the cubic inch increase.... :D

Seriously, the engine sat for 30 years with water in it and will need 2 sleeves unless the pits in one of them will clean up at 60.
 
Cubic inches doesn't give power. Thicker walls produce power. If it has to go .060 over, and are planning big power, you should sonic test it. I've done several, but also had two blocks fail sonic in the process.
 
Of course you will be sonic checking it before even using it im sure!! I'm with these other guys, only bore as much as you have to, but if you have to go .060 over, it is still in tolerance!!
 
Thanks for the responses guys but I guess I need to add that I was joking about the cubic inch thing, hence the smiley face. Nobody in these parts has a sonic tester and it's a stock build so I'll let'er rip. Thanks again!
 
Why spend a lot of money on something that is that questionable. .040 is about max for a high horsepower 340. Get another block or sleeve it. Sonic check would be mandatory on a .060 . Find a good machine shop that has the correct tools to be doing quality machine work. It is cheaper to go out of town if necessary to find one than to scatter a bunch of parts, but it is your money. If you have to ask what you should do, you have already answered it.
 
I didn't ask what I should do I was simply looking for info and opinions on going 60 on a 340 block, I can make up my own mind from there. "Stock build" indicates it is not a high horsepower 340. Thanks for your input.
 
Sorry. When I read in your post "No, going for max horsepower with the cubic inch increase.... " I read that as high powered. Not a stock rebuild. You're right - if you don't care about the power output, and only are worried about will it hold water and cylinder pressure, you can roll the dice with cheaper stock parts. Worst case it splits a bore. Middle of the road cases are overheating, lack of wall integrity, loss of ring seal. Best case it's fine. Odds favor the middle or best case, but personally I don't like any odds...lol.
 
kend said:
I didn't ask what I should do I was simply looking for info and opinions on going 60 on a 340 block, I can make up my own mind from there. "Stock build" indicates it is not a high horsepower 340. Thanks for your input.
Click to expand...

This does not matter. Pushing the limits of cylinder walls to get those last CID for any reason is "not a reaon." Power doesn't care if it's "street" power or "race" power. CID does not gain you much, and thin, flexible cylinder walls will lose your power

Some of these guys have given you good advice here. Take it and think about it.
 
moper said:
Sorry. When I read in your post "No, going for max horsepower with the cubic inch increase.... " I read that as high powered. Not a stock rebuild. You're right - if you don't care about the power output, and only are worried about will it hold water and cylinder pressure, you can roll the dice with cheaper stock parts. Worst case it splits a bore. Middle of the road cases are overheating, lack of wall integrity, loss of ring seal. Best case it's fine. Odds favor the middle or best case, but personally I don't like any odds...lol.
Click to expand...

Dude, read the rest of the post and take note of the smiley face. Again, the first part was a joke. Geez.

Looking for someone to tell me what to do is one thing, asking for information is another. Two completely different things. And I wouldn't have bothered asking the question if I didn't think there was a lot of good info here, I've learned my share that's for sure.
 
My 72 block went .060 over. It was done when I was young and stupid. After having a lot of issues not related to the block I had it checked as I was redoing quite a bit to the engine and I wanted a good foundation. It checked out OK. If I had it over to do again I would have it checked first or use a 360 block....

Bottom line, check before you bore.
 
I had a 060 340 for a few yrs, mild build, and it made good power and ran fine. It did seem to run hotter than my similar 360 build in the same car with all the same cooling stuff, so the bore was my best guess at what caused the heat build up...

Joe
 
Bracket raced a .060 340 for many years...bought it used and disassemble....started with X heads on it..replaced them with w2 heads.....still have the block in the shed...

even poked a hole in number 1 cylinder with a long bolt in a short hole...sleeved it and continued to race it.....

sonic test????
 
One of the best engines we ever had was a .060 over 73 340. That thing was a champ. Finally broke a rod bolt and scattered. We bored that poor thing over .080 just to see how far out it was. Must have been a solid casting day that day. It was too thin at .080 over but it was plenty strong at .060 every where we sonic checked it. I believe that one came from Hemsely Racing back in the day.
 
My .060 over 340 always ran Hot! when i sucked a valve (because i was stupid) i found out why. The valve stem when threw the cylinder wall. There couldn't have been .010 to .015" wall thickness.

It ran just fine, just wouldn't run in the heat of the summer. found a stock block, bored it .020 over, put it all back together and heating problems were gone.
 
grimreaper said:
What wall thickness would be acceptable with a sonic check?
Click to expand...

All you "sonic check it" guys don't have an answer for this? I'm curious myself, why sonic check it if you don't know what's acceptable?
 
What is and isn't acceptable maybe known with a sonic checking.
Are all 340's able to be overbored .040 or greater?
 
You must log in or register to reply here.
-

Back
Top