Max bore size

[nrubino]

What is the max bore size on the 360 LA block and the 360 Magnum block?

Thanks, Nick

 

[JBurch]

Ask 10 people and get 10 different answers...........MOST LA blocks , .04 is about max, the first 360's (71 to 73) are cored the same as 340's and theoretically should go out .100 over. Core shift does have an influence on all of this; as an example, I had a mid 70's block that soniced at .120 with a standard bore down one whole bank.

Magnum blocks have as I understand it have less core shift, though are some what thinner walled cylinders, therefore .03 is about the limit.

Others I am sure will have much to say.

 

[moper]

Keep them at .030, or the smallest bore that allows for a good ring surface. If you plan on more than factory stroke, or power levels beyond 1.5hp/inch then you should have the block you want to use sonic tested to verify the integrity of the cylinder walls. Core shift is terrible in Mopar blocks and that makes the "same as 340s" go out the window, but it seems to be less prevalent in Magnums and later LA 360 blocks.

 

[RustyRatRod]

Till you hit water. I'm gonna stop short of saying this is an unintelligent question.....because if you're asking because it's already bored and needs it again, then it IS intelligent.

However, if you're askin because you just want a bigger hole, then.....well......I won't say stupid question, but unintelligent. Lemmie splain.

Bore size ALMOST has ZERO to do with power output comparatively speaking. People who go around talking about "she's bored out" just sound stupid as hell. Don't be them.

I don't know, Dave......what do you think? All things being equal between two engines, does a .030 over motor make 1% more power than a standard one? I don't think so.

At any rate.......like I said, if you're askin cause it needs boring and you wanna know the limit, best thing to do is sonic test it as has been said. If you're trying to add power, stroke it.

 

[moper]

I'll gladly trade wall thickness for bore diameter. I'll make more power that way.

 

[rumblefish360]

Sonic check the block I. Question for the answer. That answer may not be the same answer on the next block. If a big bore is desired, check into a MP race block. Some models got to 4.125+. If this is not enough....... Big block time.

I myself will keep as much cylinder wall as possible for strength. The less the cylinder moves, the better the ring seal for making power. There is a very little gain in going .030 over bored. But there is a gain.

 

[moparlover]

also if it's a factory resto car and you absolutely positively must use the block (numbers matching) and it's already maxed out you can get it sleeved as needed. will cost extra.

 

[DartVadar]

Only go as big as necessary to clean up the bores. What my grandpa told me, he's been doing this for a looong time. My LA block is .30 over because thats what was needed to clean everything up.

 

[Bakerlite]

Bore it though to the water jackets.... then back it off half a turn...

 

[fratzog lover]

Haaa! Good one, Baker.

 

[FrostyMopar]

Make sure you can get pistons the correct size before you get any machining done.

a lot of manufacturers go straight from stock bore to +.030" on their budget line of aftermarket pistons. so in that situation a freshly machined +.010 or +.020 block isn't very useful.

 

[swinger340]

i'll gladly trade wall thickness for bore diameter. I'll make more power that way.

x2. I pass on 340 blocks all the time that have already been bored .030-.040 and have a ridge. No thanks. After its cleaned up @ .060 or more there is a good chance (not always) that the cylinder walls are now thinner than id like. I have seen some 360s fine @ .070 over and others where .030 is about it. Every block is different. As others have already stated, important to get it sonic tested. Otherwise just a shot in the dark.