360 Bore

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Depends on the sonic testing of the block, but if you couldn't have it sonic tested I would stay in the .020 range with .030 being the absolute maximum.


Chuck
 
Yeah but that .010 could be the difference between a split cylinder wall and a block that holds up. According to Mopar, the '71- '74 360 blocks were cast with the same casting cores as the 340 so it can be bored like a 340 to 4.10 but it is highly recommended that the block be sonic tested. I'm building a 360 stroker that's been sonic tested and bored to 4.06 but that was not my intent. I only wanted to go as little as possible to clean up the bore and have a straight cylinder because the thicker the walls the better. When I got the block it was already .020. Too many guys get caught up in the cubic inches game.
 
o no i know i was going to say to have it sonic tested. becasue 360's can go kinda high since people are using them as strokers
 
.030 is listed IIRC as maximum fatory allowable on anything newer than 1980. .040 is no big deal for stock and mild builds. If you plan to make more than 400hp, or really work it (pulling/towing, racing, whatever, then .030 is always the safest bet. 318s can go .090 if they pass sonic. You'll never see a factory 360 block that can go safely to .090. Different casting cores=different thicknesses. smaller than .020 may be hard to find pistons for too. .030 is normal.
 
Might not hurt to pour the block with Hardblock. Done correctly it can help stiffen the cylinder walls. But it's debatable on how much to pour, especially for street applications.
 
Locomotion said:
Might not hurt to pour the block with Hardblock. Done correctly it can help stiffen the cylinder walls. But it's debatable on how much to pour, especially for street applications.
Click to expand...

sounds interesting and i cant seem to find much about "hardblock" anywhere

can anyone help me here..
 
It's possible that it's not a good idea for the street, especially filling the block a lot. But that's why I said it was debatable. I've seen discussions on it but don't recall the details.

I didn't see any negative affects in my race engine and I've heard that there isn't much water movement at the bottom of the block regardless of application. The closer to the deck you get, the more important the water flow is for cooling. I just never tried it on the street.
 
I have heard from a fella or 2 that they would hardblock about half. They were saying something about filling it up to the frezze out plugs.
They claim no problems on there street rides.

I'd imagine, a great cooling system would be of great use.
 
On the street, you have to run an oil cooler if you're 1/2 filled. And it's more than just dumping it in. Do it wrong, you get air pockets, and the block is junk (no way to get it out...). Personally, there is no reason to fill a block that is not going to be raced as it's primary use. Find a better block, or sacrifice the single digit horsepower that staying smaller on the over bore might give you. For anything to 450hp, figure .030 over and run it.
 
You can get by with a half fill on the street bacause most of the heat generated in combustion is in the head so it will still receive plenty of cooling. But as Moper stated it would be best to add an oil cooler because the lower half of the cylinders will not have any coolant to help maintain oil temps. Also as Moper stated it isn't just a matter of pouring it in and letting it harden. I have my 340 half filled and the block has to be leveled so one deck is completely level. Have a cylinder head and head gasket ready then pour in the block filler. I tapped on the block in various places with a hammer to release any trapped air then bolted on and torque down the head. Then do not disturb the block for 24 hrs. Then repeat on the other side. The main reason I used the stuff is my motor is .060 and right at 14:1 so I believe it was necessary. If my motor was only 10 or 11:1 or less I wouldn't have done it. If you don't get it right you will make the block junk and it is in there for life. You can't get it out.


Chuck
 
Like what Chuck added too...the mains and heads need to be bolted and torqued in place while it hardens...So the order of operations is align hone/fit caps as needed, the rough bore and square deck, then hard block, then finish hone w/ torque plate.
 
moper said:
.030 is listed IIRC as maximum fatory allowable on anything newer than 1980. .040 is no big deal for stock and mild builds. If you plan to make more than 400hp, or really work it (pulling/towing, racing, whatever, then .030 is always the safest bet. 318s can go .090 if they pass sonic. You'll never see a factory 360 block that can go safely to .090. Different casting cores=different thicknesses. smaller than .020 may be hard to find pistons for too. .030 is normal.
Click to expand...

I am considering to purchase a 360 block that has been bored 060. over for my 68 Dart; and you mentioned something about "IIRC" and maximum factory allowable on the bore for any block newer than 1980 to be .040.

I've read a book by "Jim Szilagyi" (How to build Big Inch Mopar small blocks) and he stated on page 17, something about "any block after 1975 were made lighter to improve fuel economy. And that this change effected the cylinder bore on the water jacket side. Plus to have the block "Sonically checked" could provide more information.

What or who is IIRC, and where did you find the information about 1980 blocks ? I'm new at this engine stuff, and I want to be absolute sure before I purchase this 360. Thanks
 
Remember fella's it's only .020 for a .040 over bore or .005 for every .010, see it's a hole and when a hole gets .040 bigger it's cause .020 has been removed all the way around.lol

My 360/410 stroker is .040 over.
 
"If I Remember Correctly"...lol. I recall reading that for a bunch of engines that were used thru the 70s. I recall where but I think it was a rebuilder's guide the machine shops have/had. In any event, Jim while very bright, is generalizing. They were cast with a better iron, but the castings were made thinner. But it had nothing to do with the reality of Mopar castings... They suck. As most manufacturers' were at the time. They suffer from core shift.. which means when the cores were first set for the block molds, the sand cores were not placed perfectly and the result is bore centers that were off in any direction of the compass. Every cylinder has two thick directions and two thinner ones. They should be oval if you cut the decks off and looked straight down. but if you dont have the mold centered in the spot, one thin side gets really thin, or one thick side gets thinner, etc. That is core shift and every block I've ever tested except one had it to some degree. (In case you're wondering, I do own a really good sonci tester and know how to use it) So you want certain minimum thicknesses for strength and for heat dissipation. The factory stated small oversizes because the really bad blocks get really thin at larger overbores. I've had to sleeve two blocks because one or more cylinders were too thin to run the power level my customer needed. The other holes were fine, but one or two int he 8 were badly shifted and that left the thin side on one at .080" before boring, and the thick side (called the major thrust of the cylinder) was around .120" thick. So by cutting it out a sleeve was isntalled to correct the bore center and we were good to go. I am leary about buying any .060 over block. I will bore them to there after testing, but buying a fresh one thats .060 over isnt a big deal. Buying a running engine at .060 over and partially thru it's service life leaves no room for rebuilding. While not often, I have done 2 +060 4" arm small blocks that are fine. (both of them required sleeves to get all 8 thick enough) For a stock stroke, 060 over isnt a big deal but I'd want it all brand new at .060 over. Not used or bare at .060 already.
 
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