The LA Motor "Block"

-
340BABY

340BABY

Well-Known Member
Joined
Mar 14, 2012
Messages
54
Reaction score
44
Location
Northern Michigan
(Small Block Mopar) I get asked a lot of questions about the LA block so I thought I would answer it on line. First off there is a lot of opinions out there and there is defiantly many ways to skin a cat. "PETA" people are rolling there eyes right now, LMAO. OK, this is what I have learned about the LA block after 30 years of racing them. The Ritter Block and the R blocks are the best choices for all out racing "Period." Now if you are looking for a good stock block to build 600 to 700 Horse Power out of then I would look for 1970 - 1972 360 block, I know, I just made half of the forum grasp there heart like Fred Sanford, but like we say up North "Let me splain." When they stated developing the 360 in 1969-1970 they did not have a mold built for the 360 yet, so they used the 340 mold until 1973 castings. This make the 360's from 1970-1972 years a small bore 340, thick walls, and 2.81″ diameter main journals makes it the best choice. If you are going to race it with over 500 hp I would use block filler, do not put in 4 bold main caps, just buy a main girdle. I have used girdles up over 900 horse power with NO PROBLEM. I have built over 25 SB engines that made over 600 HP with Hardblock, and a Girdle and have never had a block failure. In my opinion it comes down to Heat treating the block "heat relieving", Good Machining, balanced rotating assembly, good selection of parts, "DO NOT CUT CORNERS" Not overfilling the Hardblock, a girdle and a tri metal head gaskets. Be clean and take your time and check everything during assembly. I also use Herb McCandless oiling Mods for small block mopar, it works great. I hope this helps, now this is my opinion and we all know what opinions are like, so I will say it like this "This is my opinion and treat it as such" happy racing.
408 - 360 - tunnel ram.JPG
 
Last edited by a moderator:
Where can one find the Herb McCandles oiling mods?
Thanks!

I’ll add to tour check list, sonic check the block!
 
I agree, but I don't think anyone will gasp over the early 360 block....that's been a known 'winner' for ages. Since no real improvements were made in later years, the early 360 remains the one to get.
 
Do you know what Bob Glidden did for his SB mopars the couple of years he ran them?
 
The early 340 and 360 thick block thing is a myth. You still need to sonic check them. I've seen thick ones and I've seen some that wouldn't go .040".
 
Early late etc !!
I can tell u a 74 ( 318 ) blocked weighed 10 lbs more than a 1985 318 block took it work used a UPS scale could not believe 10 pounds could be removed in such a small package.
 
I'm with RRR, all my potential .060 over blocks sonic tested. Better safe than sorry putting money into a block that won't work.
 
Last edited:
RustyRatRod said:
The early 340 and 360 thick block thing is a myth. You still need to sonic check them. I've seen thick ones and I've seen some that wouldn't go .040".
Click to expand...
Exactly. My ‘89 roller cam block sonic tested good for 4.070 bore. Checked by Brian at IMM.
 
It's not a myth, or a hard fact, but rather a general guideline. We all know there are good and bad cores on a block-by-block basis. Your odds of getting a thick wall are better in an early block than any other years.

As for weight, it's a mathematical conclusion....before I bored my block, I calculated it would lose 10lbs.. After boring, I weighed it and it had lost 10lbs. It's just the weight of cast iron....
 
gregcon said:
It's not a myth, or a hard fact, but rather a general guideline. We all know there are good and bad cores on a block-by-block basis. Your odds of getting a thick wall are better in an early block than any other years.

As for weight, it's a mathematical conclusion....before I bored my block, I calculated it would lose 10lbs.. After boring, I weighed it and it had lost 10lbs. It's just the weight of cast iron....
Click to expand...
Pretty common knowledge
With all American V8s !!!
I have a 90 over 1968 318
With partial fill !!! It contradicts all info we were ever told
Hensley Performance in TN sonic tested it and bored with torque plates
 
I've bored specific 318 castings to 4.040 and threw std 340 pistons into them. Some will, some won't.
They also opened up more coolant passages in the later decks and heads fyi

The smog heads weigh more too.
Look at all the outer edges of the heads at or near the head bolt flats over the years... they changed too.
 
gregcon said:
It's not a myth, or a hard fact, but rather a general guideline. We all know there are good and bad cores on a block-by-block basis. Your odds of getting a thick wall are better in an early block than any other years.

As for weight, it's a mathematical conclusion....before I bored my block, I calculated it would lose 10lbs.. After boring, I weighed it and it had lost 10lbs. It's just the weight of cast iron....
Click to expand...

That's just not true. In fact, as the casting process went through time, it got better and more consistent, with the advancement of modern technology. If you find a thicker block from earlier castings and it sonics good on both the major and minor thrust surfaces, you just got lucky and found a good one. I've gone through some early blocks with a sonic tester. Found a few that seemed "thicker" and most were right in line with everything else. There is much more consistency in newer castings as the years go by. Up into the later LA years and into the Magnum runs, they really got consistent with cylinder thickness block to block.

All of this started when people began the rumor that the 360 was somehow cast on the same molds as the 340 and that's just a myth that's been passed down through the decades. It just ain't so.

I had one of the crappiest years ever of a 360 "you'd figure"...a 1977 cast block. I had that block tested and it could have gone 4.100 with room to spare and it was even on all sides of the cylinders. All I went was .070 as I was building a 416.

You spout all the nonsense you want, but you're just as full of **** over here as you are on the .org site. It might mislead someone.
 
The part about the 360 being made on the 340 pattern was in a MP book at one point. I'm not gonna go try to find it, but that's one place I read it.
 
gregcon said:
The part about the 360 being made on the 340 pattern was in a MP book at one point. I'm not gonna go try to find it, but that's one place I read it.
Click to expand...

I know. Larry Shepard later came out and said that info was incorrect.
 
Just for kicks, here it is from my circa 1981 Direct Connection book, along with my hand notes from the same era when I made a 373" small block. That was high-tech back then....the extra cubes that would put me over the edge into the crazy zone of horsepower.
DC 374.jpg
 
You must log in or register to reply here.
-

Back
Top