Over bore: How far is too much ?

[Canadian Dart]

I have a question, regarding a 360 build up. The engine casting date is
12-4-75. Basically a 1976 engine.
I've heard that a 360 engine after 1974, has a thinner cylinder bore, and should only be bored .030 over. I'm considering a purchase of a 360 build with a .060 over bore.

Does anyone have any experience with a 360 bored .060 over ?
My plan is to race. The engine will be coupled to a 727 transmission and a
8 1/4 rearend.

PS. I may have placed my last thread in the wrong forum#-o

 

[MopaR&D]

.060" is a bit on the big side but the only way to be sure is to take the block to a machinist and have the cylinder walls sonic checked. Personally I wouldn't run a block with more than a .030" overbore without having it checked.

 

[needsaresto]

THin wall,thick wall,it's an urban myth really. Any block from any year could be either depending on the casting process and core changes.

Have it sonic checked like said.

 

[JR]

THin wall,thick wall,it's an urban myth really. Any block from any year could be either depending on the casting process and core changes.

Have it sonic checked like said.

100% correct! Dates should only matter if you have a super rare car or you are going for a 100 point restoration where you are anal about factory pant drips. I have a 1976 360 in the garage that is 40 over and it was my daily driver (driven very hard) for about 7 years with no problems.

 

[moper]

Brfore sonic testers were en vogue if the bores were bad enough, it went .060 over. The safe overbore by Mopar I think is .040. But it's been done a bunch of times. If you know this engine or it's owner and know it to be reliable, it's worth getting. If you dont know him but trust him, it's still an ok situation. If you were going to stick a 4" arm in it (or it had one already) then it must be sonic tested. For a stock stoke, I'd say if it's got some miles it's probably fine.

 

[70aarcuda]

have drag raced with two 360 blocks that were bored .060,,,one is currently in use...

the other died from a rod going out the side...but had ran for 7 yrs with w2 heads on it...

neither were sonic tested.

 

[fishy68]

Every block is different. I have a 73 360 block that's safe going .060 over. My machinist even said he'd take it .080 over for a stock street engine. On another note he said he just had a 360 block go through that had bad core shift and one side was fine for .060 and the other side was only good for .020 over. You never know where they are so if your building a high hp engine, especially a stroker have it sonic tested.

 

[Canadian Dart]

Thanks for all the response's on this overbore question. I have spoken with a couple of passed buyers. They all say good things about the builder.
I will post more information when I transplant this baby into my 68 Dart.

Good day eh!