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The 440 overbore question

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Yib-Yab

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I have a 1977 440. One of the cylinders is messed up enough that im gonna have to bore it. Ive read about there being a .030 overbore limit because of "thin cylinder walls". Ive also read of this being a myth and that through out the years the cylinder wall stayed the same. If they did however never get thin, how much can i overbore?
 
Bore as little as possible. Is it standard now? 440 source. Com has an excellent thread called "everything you wanted to know about blocks". They say there is no such thing as a thin-wall block, but there are definite variation in lower bulkhead strength from mains to cam tunnel. You could also just sleeve the one hole. I don't know which is more cost effective, but if you bore it you can get more than the 7 1/2-1 compression you likely have now.
 
I Am doing this to a 75 440. Its currently at the machine shop. It as been bored .30 over If you can go 30 and clean it all up I would do that. More bore = less times you can rebuild it. So I had to get new pistons. Bought an engine kit from Summit. went from 7.5-1 ish to Approximate compression ratio 9.37:1 with a 88cc head This is the kit I purchased. FEM-CSMHP815-300 If you decide to sleeve the engine and use the old pistons. I would check into a Hughes Whiplash cam. Its made for the low compression 440's.

Piston specs from the kit I bought.

Bore (in):4.350 in.

Bore (mm):110.490mm

Piston Style:Flat top, with four valve reliefs

Piston Material:Forged aluminum

Compression Distance (in):2.061 in.

Piston Head Volume (cc):+7.00cc

Wrist Pin Style Press-fit

Wrist Pin Included:Yes

Pin Diameter (in):1.094 in.

Piston Ring Thickness:5/64 in. x 5/64 in. x 3/16 in.
 
Last edited:
:popcorn::popcorn2:I'll be interested in reading what some of the more knowledgeable folks on here have to say.
Yep, 440Source says there's no such thing as thinwall 440's, only differences in core shift in castings over years.
 
Don't know bout the 77 440 but I did have a 76 400 block that went .040 over and it got stroked to a 451 a few years back. No issues with it.

My 73 440 is also at .030 over but I've not assembled it yet.

Regardless, I wouldn't want to push past .060 at the absolute max and even then, overheating may become an issue
 
I have been reading a lot about this recently as I just dropped off my 440 with the engine shop recently. I just watched a pretty good 10 or 11 part series on YouTube by "Pete's Garage" of a stroked 440 build. He talked about wall thicknesses when discussing choosing a block. He said the same thing as Moparedtn mentioned above. Chrysler did not design any "thin-wall" blocks, but mentioned the cores that form the cylinder walls could shift on some blocks causing thin walls. He just suggested taking some measurements on the block to see how aligned the cylinders are with the block and other cylinders (he didn't seem too worried about it). He also did a nice job of showing the changes the factory did in the later years to strengthen the blocks by adding ribs here and there.

I also read somewhere that max boring recommendations were +.060" on the earlier blocks, and that they reduced it to .040" on the later blocks. I apologize, but I don't remember the year it changed. It was somewhere in the 70's though. I want to say maybe '74 or '75?

Yours being a 1977,.... I would say you are safe to go +.030" over standard bore. I believe standard bore on a 440 was 4.32", so +.030" would bring you to a max bore of 4.62" (just confirm it hasn't been bored before). Any more than that and I would suggest doing more research.
 
the factory service pistons were limited to .040" over. some people have been successful at .060". i'd bore is little as possible; .020" or .030". it's my understanding that the later '76-'78 blocks were not made of as good a quality iron as the'75 and under and this is why the engine manuals wanted over bores limited to .020" on these blocks. there's a lot of opinions and published "info" on this and for me I just revert back to what the factory states. the best thing to do is just sonic test the block if over bore is a big concern. keep in mind that not all the so called "good castings" will have perfect bores. I think because there are so many variables in core shift/casting there just aren't any firm rules on this. sometimes you just can't inspect and measure enough.
 
.055 piston are readily available. The Source article is very informative and the only difference in castings was the support webbing.
 
FrnkNsteen said:
I have been reading a lot about this recently as I just dropped off my 440 with the engine shop recently. I just watched a pretty good 10 or 11 part series on YouTube by "Pete's Garage" of a stroked 440 build. He talked about wall thicknesses when discussing choosing a block. He said the same thing as Moparedtn mentioned above. Chrysler did not design any "thin-wall" blocks, but mentioned the cores that form the cylinder walls could shift on some blocks causing thin walls. He just suggested taking some measurements on the block to see how aligned the cylinders are with the block and other cylinders (he didn't seem too worried about it). He also did a nice job of showing the changes the factory did in the later years to strengthen the blocks by adding ribs here and there.

I also read somewhere that max boring recommendations were +.060" on the earlier blocks, and that they reduced it to .040" on the later blocks. I apologize, but I don't remember the year it changed. It was somewhere in the 70's though. I want to say maybe '74 or '75?

Yours being a 1977,.... I would say you are safe to go +.030" over standard bore. I believe standard bore on a 440 was 4.32", so +.030" would bring you to a max bore of 4.62" (just confirm it hasn't been bored before). Any more than that and I would suggest doing more research.
Click to expand...
--wiered, where I went to school, that would be 4.350, mine is.
 
FrnkNsteen said:
I have been reading a lot about this recently as I just dropped off my 440 with the engine shop recently. I just watched a pretty good 10 or 11 part series on YouTube by "Pete's Garage" of a stroked 440 build. He talked about wall thicknesses when discussing choosing a block. He said the same thing as Moparedtn mentioned above. Chrysler did not design any "thin-wall" blocks, but mentioned the cores that form the cylinder walls could shift on some blocks causing thin walls. He just suggested taking some measurements on the block to see how aligned the cylinders are with the block and other cylinders (he didn't seem too worried about it). He also did a nice job of showing the changes the factory did in the later years to strengthen the blocks by adding ribs here and there.

I also read somewhere that max boring recommendations were +.060" on the earlier blocks, and that they reduced it to .040" on the later blocks. I apologize, but I don't remember the year it changed. It was somewhere in the 70's though. I want to say maybe '74 or '75?

Yours being a 1977,.... I would say you are safe to go +.030" over standard bore. I believe standard bore on a 440 was 4.32", so +.030" would bring you to a max bore of 4.62" (just confirm it hasn't been bored before). Any more than that and I would suggest doing more research.
Click to expand...
.030 bore is 4.350
 
A 0.060" overbore is fine in an old block, and a newer block. If you sonic check it, you can map the core shift. If you weren't aware, the casting#-XX, XX represents the amount of times the cores were replaced. So, supposedly, the higher the number (XX), the larger chance of core shift. My understanding is no number = 0, and goes up to 10. Obviously, the more meat in the walls, the better it will handle heat.
 
Both 440Source and Andy Finkbeiner say there are no such thing as "thin wall" castings. I trust that.

I have a '76 block with the thick main webs. I had it sonic checked then bored it .060 over.
 
69Bee said:
If you weren't aware, the casting#-XX, XX represents the amount of times the cores were replaced. So, supposedly, the higher the number (XX), the larger chance of core shift. My understanding is no number = 0, and goes up to 10. Obviously, the more meat in the walls, the better it will handle heat.
Click to expand...

So you're saying the -7 on the end of the casting number in this picture means the cores were replaced 7 times. Interesting. I hadn't heard that before. Thanks!

3r63G13J65Le5sd5tad6ocd676d65f4b01800.jpg
 
It was said earlier, but if you are gonna have the block out and at a shop anyway, have it sonic checked...last time(6 years ago)we had one tested they charged an extra $120... it wasn't much more cost for the peace of mind
(BTW it was a '78 RV block that went to .030 with meat to spare..)
 
Only way to really know is to sonic test the block. If it is just one bad cylinder, you could have that cylinder sleeved.
 
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