The Dodge Challenger Message Board

How much can you over bore a 440 hp block. I have a number matching motor that my machine shop said it might not be good. he said thay had to cut the the pistons out they were rusted in so bad.the block had water in it for years. I would hate to trash a numbers matching block. any thoughts.

Depends on which year your 440 block is. If I'm right it's as following:
thick wall design blocks (till mid '68) overbore max at .060
thick wall design blocks with stiffening ribs (mid '68 till mid '72) overbore max at .060
thinn wall design blocks with stiffening ribs (after mid '72) overbore max at .030

Not sure about the years I mentioned, but I'm pretty sure someone else can make it sure for you.

Hope this helps.

The block is 1970. Has any one ever had a block sleeved ? What are the Pros and Cons?
thanks

The modern method of sleeving blocks where a seat is left at the bottom of the bore for the sleeve to sit on is a safe and reliable way of saving a block. The head holds the top of the sleeve of course.

The whole 440 family is a 'thin wall' design and any more than 40 thou overbore (on any mopar engine big or small) is asking for trouble unless you have the wall checked for thickness.

Even a standard bore is slightly flexable so the more oversize you go the more important it is to use a deck or torque plate to finish the bores.

Hey, I will check that once again. I read about the overbore a couple of weeks ago in a Big-Block performance book i have. I will copy the lines to the board this weekend.

It may be possible to go 60thou (or more!) over but that does not mean it is very desirable. The blocks to watch out for are the '76-78 blocks which are even thinner. They do not like any more than a 20thou overbore!

To keep the car numbers matching I might consider going 60 thou over if this is a pure street driven car. If more than one or two bores need sleeving the costs can be too high to make it worth while.

You have to weigh up all of this and compare it to cost of replacing the block with a better one. Sometimes costs have to be the deciding factor with these things.

But cheer up! I have seen blocks like that cleaned up with only a 40thou overbore! Fingers crossed for you.

Dave, did you read that article in Mopar Action recently about overboring (early vs late) big blocks? made for some very interesting reading! If you didn't I could dig it out for you.

Did they have an opinion on bores more than 60thou over? I have heard that at 60thou there is so much flexbility in the bore that you can actually make less power than a standard size bore.

I stopped getting the Mopar magazines a few years ago. Part of a range of cut backs so that I could afford petrol for the Challenger. I made the wife give up a few things so I had to show willing as well!

It was not so much the cost of the subscription. It was that every time I read one I would want to buy something for the Challenger or change the way I was going to do things.

Next time I see American Auto Mags tent at a show I will try to get any Mopar Action 'Tec Specials' from the last few years to make up for it.

Dave, email me your address and I'll photocopy the article and post it to you.

Here's that article I meant. (out of Big Block Mopar Performance written by Chuck Senatore)

...The 440 Block - Though any 440 block will physically work, there are a few year-to-year variations that are worthy of a closer look. There are three different 440 blocks that you will encounter in your junkyard. The first type will be found with casting dates from mid-1965 until mid-1968. These first series are a thick-wall design and will make a good starting point for your engine. The next series goes from mid-1968 up through 1975 and are the same as the earlier blocks, but have additional stiffening along the outside in the form of cast-in ribs. These blocks are the best to use. The third series of blocks will be the 1976-1978 blocks which have a thinner cylinder wall design. These thin-wall blocks still have the external stiffening ribs but they don't have as thick a cylinder wall as the earlier blocks. This isn't really a problem but keep the overboring on these to .030" or less. This does not mean that these blocks should be avoided. On the contrary, many killer engines have been built with these later blocks as they still have the same bottem end strength...

...Selecting overbore size - Make sure the overbore you have selected won't leave the cylinder wall too thin. If you have acces to a sonic checker, make sure that the cylinder walls are at least .080" thick after boring. This is considered a minimum and any thicker is better, especially for performance use. All the thick wall blocks can be safely bored .060" over. Some of the early 400 blocks can actually go .100" over but sonic check first. The later model thinn-wall blocks should be limited to a .030" overbore. If the water jackets have been filled with cement, the overbore can be increased. Even the thin-wall blocks can go .060" over with no problem if the block has been filled. This a race-only modification. Also remember to check the inside diameter of the head gasket that you you plan on using to be sure that it will accomodate your desired bore size. Don't forget to make sure that there are piston rings available too.

"make sure that the cylinder walls are at least .080" thick after boring. This is considered a minimum and any thicker is better, especially for performance use"

That was the infomation I was looking for Hans. Thanks.

It sounds like Nick might be able to save his block. If it is stock or close to stock anyway.

Reading between the lines I think what they are saying is go 60thou if you have to but the thicker the cylinder wall the better.

I still think going that far in a much higher than stock power engine is probably pushing your luck a bit.

I agree with you, that you can better overbore it in a safe way instead of bore it at the max. Not so funny when you spend lots of $$ to build a 600hp 440 and it will crack because of a big overbore.

Thanks for all the info.