I have a crack free 348 that was standard bore, but it's terribly rusty. I will need to bore it quite a bit to clean it up. What is the normal, safe limit on a 348. While I am here, I would be interested in knowing if there is a plate available to bolt to the top of a 348 block to allow use of a portable type boring bar.
348 Maximum Bore Size
- Thread starter NAIRB
- Start date
CDNpontiac409guy
Banned
NAIRB...
EVERY 348 block ever cast will accept a .125" overbore. I personally think that's a big as you can go, but if I'm not mistaken, there is a fellow in group here that has been running one for a few years now that is STD 409 size ! ( .187" over ).
Bottom line.... don't give it a worry... Your block will be fine
EVERY 348 block ever cast will accept a .125" overbore. I personally think that's a big as you can go, but if I'm not mistaken, there is a fellow in group here that has been running one for a few years now that is STD 409 size ! ( .187" over ).
Bottom line.... don't give it a worry... Your block will be fine
CDNpontiac409guy
Banned
I doubt if anyone here had one, that they would get rid of it !
Just take the block to a competent machine shop
Just take the block to a competent machine shop
Well, since I'm a seasoned machinist myself, and I am tooling up my own machine shop, I was just wondering how they bored them back in the old days before there were rottler type boring bars that set up off of the pan rail around. I'm sure a guy could make a plate, but I just wondered how it used to be done. I'd like to do it myself.
Bore
I would not bore over .060" without sonic testing. Core shift on some of these blocks will leave you with dangerously thin cylinder walls. In my case a .060" bore left me with # one cylinder at .113". For around 60.00 you could save yourself some grief . At .125 overbore this would have left me with a .080" cylinder wall. A little thin for high performance no?
I would not bore over .060" without sonic testing. Core shift on some of these blocks will leave you with dangerously thin cylinder walls. In my case a .060" bore left me with # one cylinder at .113". For around 60.00 you could save yourself some grief . At .125 overbore this would have left me with a .080" cylinder wall. A little thin for high performance no?
Big 348
Yeah CPG, I had a 348 that was bored to standard 409. I don't have the car any more but the engine is still running great. I put 5000 miles on it when I had the car. I think I had the only block you can do that large of a bore on. It was the "655" 348 truck block. Mine was a replacement engine from 1965, I think. Makes for a fairly inexspensive 409 engine. Although the man that built the engine said it was a little more expensive to have the block bored out because of the ammount of times each cylinder had to be bored to reach the std. 409 bore!
Ross
Yeah CPG, I had a 348 that was bored to standard 409. I don't have the car any more but the engine is still running great. I put 5000 miles on it when I had the car. I think I had the only block you can do that large of a bore on. It was the "655" 348 truck block. Mine was a replacement engine from 1965, I think. Makes for a fairly inexspensive 409 engine. Although the man that built the engine said it was a little more expensive to have the block bored out because of the ammount of times each cylinder had to be bored to reach the std. 409 bore!
Ross
Sonic Results .125"
Hey, just for anyone intersted in a little proof of what a .125" overbore will sonic to. (Mine at least ) haha The only problem was the "hourglass" shape of the cylinder from irregularities in casting. Here are the results from mine, these are the thinest measurements of the cylinders at each side...
.145 #1 .144 .169 #2 .180
.147 #3 .183 .188 #4 .180
.153 #5 .180 .211 #6 .175
.190 #7 .157 .193 #8 .185
Jim
Hey, just for anyone intersted in a little proof of what a .125" overbore will sonic to. (Mine at least ) haha The only problem was the "hourglass" shape of the cylinder from irregularities in casting. Here are the results from mine, these are the thinest measurements of the cylinders at each side...
.145 #1 .144 .169 #2 .180
.147 #3 .183 .188 #4 .180
.153 #5 .180 .211 #6 .175
.190 #7 .157 .193 #8 .185
Jim
Old way Boring 348-409
John
What we had register off of Cyl. It had a adj. mandrel that was in cyl about 6in long,Had a heavy plate on that.Thats what you bolt boring bar to. If I remember right you could bore 2 cyl then move and bore two more. Van norn made the one I have. I bet its been 30 yrs sence I have use it. about that long sence I even seen it.
Dale
John
What we had register off of Cyl. It had a adj. mandrel that was in cyl about 6in long,Had a heavy plate on that.Thats what you bolt boring bar to. If I remember right you could bore 2 cyl then move and bore two more. Van norn made the one I have. I bet its been 30 yrs sence I have use it. about that long sence I even seen it.
Dale