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318 small block ‘X’ block. Give me the dirty little details. #3146836
05/25/23 08:14 PM
05/25/23 08:14 PM
Joined: Jan 2003
Posts: 21,630
San Jose,CA
migsBIG Offline OP
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migsBIG  Offline OP
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San Jose,CA
So long story short, was told this guy has a TA/AAR block and turns out to be a 1979 dated Mopar Performance over the counter block and has been sitting in his shop since the early 1980’s. Now I know a little something about the ‘R’ blocks produced later on, but nothing on the ‘X’ ones. It looks to have a standard bore set of 340 pistons, but the guy will double check the bores when he gets back home tomorrow. The 4-bolt mains look super beefy and dang, it felt heavy like a 440 block.

So my question is:
Are these desirable?
How much hp/tq are they good for?
Is there a value to owning one or just sell it?
Thanks in advance.

IMG_8071.jpegIMG_8072.jpegIMG_8068.jpegIMG_8070.jpeg
Last edited by migsBIG; 05/25/23 08:14 PM.
Re: 318 small block ‘X’ block. Give me the dirty little details. [Re: migsBIG] #3146837
05/25/23 08:18 PM
05/25/23 08:18 PM
Joined: Jan 2003
Posts: 21,630
San Jose,CA
migsBIG Offline OP
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migsBIG  Offline OP
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San Jose,CA
More pics. Also, got this 360 from the shop and it has adjustable rockers for some reason. Not sure what it is?

IMG_8067.jpegIMG_8065.jpegIMG_8109.jpegIMG_8097.jpeg
Re: 318 small block ‘X’ block. Give me the dirty little details. [Re: migsBIG] #3146839
05/25/23 08:40 PM
05/25/23 08:40 PM
Joined: Jan 2003
Posts: 11,704
Portage,michigan
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B3422W5 Offline
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Portage,michigan
Ultra desirable
Come 2 or 4 bolt
Come 3.91 bore, have seen them check good for use at 4.125 bore. But each one can be a bit different. So, to get to a standard 4.04 340 bore, need lots of metal removed and sonic checking, imo, is a must
Beefier bottom end, filled pan rail, etc
Standard 340 type top end, so unlike 59 degree r3 blocks, roller lifters drop right in.
They can take a lot of punishment. They are my favorite LA 59 degree block
I Ran one at 4.100 700 horse years ago, that block is still in use
Virgin block like you have is worth 3k + all day

Last edited by B3422W5; 05/25/23 08:42 PM.

69 Dart GTS A4 Silver All steel, flat factory hood, 3360race weight
418 BPE factory replacement headed stroker, 565 lift solid cam
Best so far, 10.40 @127 1/4
1.41 best 60 foot
6.60 at 103.90 1/8

Re: 318 small block ‘X’ block. Give me the dirty little details. [Re: B3422W5] #3146868
05/26/23 01:09 AM
05/26/23 01:09 AM
Joined: Jan 2003
Posts: 6,133
Melbourne , Australia
LA360 Offline
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Posts: 6,133
Melbourne , Australia
The 360 has 273 style rockers on it. Nothing uncommon there, as they were an alternative to buying roller rockers. Check that it has a solid tappet, rather than a preloaded hydraulic lifter.

The main selling point for the X block is that most roller lifters are a total drop in. Otherwise they're very similar to the early R blocks that came much later. Both blocks were machined with factory type tooling, just the casting had a lot more material where it matter.

You shouldn't have any trouble selling the X block, they're defintely sought after by the 59* crowd.


Alan Jones
Re: 318 small block ‘X’ block. Give me the dirty little details. [Re: LA360] #3146892
05/26/23 09:10 AM
05/26/23 09:10 AM
Joined: May 2003
Posts: 13,184
aZLiViN
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J_BODY Offline
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That casting number was on standard 318 blocks back in that era too. Just not the “X” on the front along with the other cool features.

Re: 318 small block ‘X’ block. Give me the dirty little details. [Re: J_BODY] #3146963
05/26/23 04:47 PM
05/26/23 04:47 PM
Joined: Jan 2003
Posts: 21,630
San Jose,CA
migsBIG Offline OP
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So I talked to the previous owner and was told it was bored out to standard 340 piston size and looks to may be a non-ran engine and just sat in the garage since 1981-1982. The block has 340 mains and he has a time to clean it up when I need something for it.

Re: 318 small block ‘X’ block. Give me the dirty little details. [Re: migsBIG] #3147321
05/28/23 11:03 PM
05/28/23 11:03 PM
Joined: Jan 2003
Posts: 21,630
San Jose,CA
migsBIG Offline OP
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San Jose,CA
Will post more info Tuesday. By chance, how would someone build up a block like this? High compression? Turbo? Blower? Nitrus?

Last edited by migsBIG; 05/28/23 11:07 PM.
Re: 318 small block ‘X’ block. Give me the dirty little details. [Re: migsBIG] #3147700
05/30/23 09:10 PM
05/30/23 09:10 PM
Joined: Jan 2003
Posts: 6,133
Melbourne , Australia
LA360 Offline
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Posts: 6,133
Melbourne , Australia
They're an early race block, they're not siamese bore, so they're not going to handle a bunch of boost or a bunch of nitrous. Having the extra meat around the crankshaft will certainly help.
The builds I have seen have usually been W5 or Indy headed strokers that make around 700hp


Alan Jones
Re: 318 small block ‘X’ block. Give me the dirty little details. [Re: LA360] #3147720
05/30/23 11:18 PM
05/30/23 11:18 PM
Joined: Jan 2003
Posts: 21,630
San Jose,CA
migsBIG Offline OP
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migsBIG  Offline OP
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Joined: Jan 2003
Posts: 21,630
San Jose,CA
Went to get the block today and my back was not up to the chore of moving it and my garage space got loaded up from the weekend, so I have to make room for it. Will bring it home in a week or two when I’m able to accommodate it.

Re: 318 small block ‘X’ block. Give me the dirty little details. [Re: migsBIG] #3147859
05/31/23 04:26 PM
05/31/23 04:26 PM
Joined: Dec 2005
Posts: 11,474
Fulton County, PA
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CMcAllister Offline
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Useless junk. Contact me, and I'll do you a solid and take it off your hands for a fair price. I need a boat anchor.


If the results don't match the theory, change the theory.






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