4 Bolt 360

[Lasalles]

Hi everyone i have a 360 with 4 bolt mains and am wondering why.Its a 1970(cast in block) and the number goes something like this 3418498.?.360
Here in Oz they are all 2 bolt mains.What have i got????

[pishta]

If Im not mistaking, the TA blocks (340 TA on block, cant miss it) had provisions for 4 bolt mains (2,3,4) but not factory caps. My book is misplaced so I cant look it up. A 4 bolt LA block sounds rare indeed. There was no meat for the additional bolts in the main webs, so it was not an easy retrofit. Anyone elaborate on this?

[tsteiner61]

Interesting. You may have something rare there. The Mopar engines book says that the 3418496 casting's first year was 1971. I have read many times that this casting was based off the 340 casting, and you can overbore it as far as you would a 340 (4.07+) and still be good. However, every 360 with that casting number I have seen has been a 2-bolt. There is the off chance that someone other than the factory put both the holes and the caps there. Mopar does sell 4-bolt mains for the 360. Best of luck finding out.

[mr_340]

Are the outer bolts splayed (at an angle relative to the inner bolts)? If so these are aftermarket caps. Either way I'm sure that they were added unless there is a special Aussie block like the Pherd boys. It's a good block. Enjoy.

[Dart 65]

I dunno about that block. All of my literature states that the first year for the 360 was 1971. Could you have a block that was cast in late 1970? Sure it's possible. My books aren't specific enough there. But the four bolt main thing is still an issue. Check the heads. If they have AAWJ 360 stamped into them, then you have yourself a 340 six pack engine. Also, if that is the case, the pushrod holes will be angled away from the intake ports. This modification necssitated use of an off center rocker arm. Another way to tell is to look at the lifter valley. If is has extra webbing that you don't see on a regular LA motor, that is another way to tell the 340 six pack. If you don't see these things I mentioned, don't be bummed out. You would therefore have a hopped up 360 which is nothing to be disappointed in. Keep us informed.

[Lasalles]

The block has 12/6/1970 cast in.The guys in Oz tell me it must of been converted to a 4 bolt.I can say whoever did the conversion did a damn good job.
Oh i also brought the block bare with a crank that is a 360 and didnt even realise the difference.I though they all must of been 4 bolt blocks lol.
Thanks for the help guys
Oh i forgot to add this,a quote that someone found from Chrysler "the use of 4 bolt mains is generally overrated and not necessary in most cases.Dont try to add them to a production block and will not make block any stronger when done"
Hmmm now am i meant to beleive i ahev a weak block????
Anyway its still a 360 just a little different from the others.Not bad for $180 virgin bore but.

[tsteiner61]

No, you actually have an excellent small block to start almost any performance buildup you wish. I could've had the exact same block casting about a year ago, but passed because at the time I didn't realize that short of a 340, it is the best block you can have. As for the 2 bolt vs. 4, I read in High Performance Mopar that the reason 4 bolts MIGHT weaken the block is because the extra bolt holes shift stress onto the main web which is traditionally one of the weakest parts of any Mopar small block. With that block and good main caps, you should be good to AT LEAST 450hp, so have fun.

[Lasalles]

Well 450hp would mean heaps of fun.I suppose it all looks well for my plan of a 400 stroker crank.
Do u know u guys could have bought the block for $90 US for what i paid in Oz dollars.
Not bad hey