What did this 340 come out of????

[Super Blue 72]

If you can look at the front driver's boss pad and it reads "340R" then it is a low compression engine, "R" for Regular fuel.  More than likely you have this designation, my guess... these #s on my block are VERY light.  Don't disturb the paint too much here (like by sanding/scaping) as it may take away some of the #s!

If it says "340HP" then it was a high compression version, but doubtful as we are playing with the '73 year and they didn't have the "HP" versions then.

[mrbill426]

In 33 years who knows what's happened to it.  As far as I know, some '72 340s had a forged crank.  Color, again, who knows what's happened to it.  The only thing for sure are the #s on the block. 

Here's a link about the forged vs cast crank.

http://www.carcraft.com/tipstricks/3027/index5.html

Our '72 340 has a forged crank from the factory; it was built in April '72.  The numbers on the head boss are almost totally gone from being very lightly stamped in the first place, but all the other numbers on the car, transmission, and pan rail match so it must be all original.

 

['Cuda Hunter]

  Is your 72 Cuda?  What color is the engine? 

[Challenger6pak]

It would make sense for Chrysler to use up the forged cranks that were left over from 71 instead of tossing them.  Maybe mid 72 production ended up being when the changeover was made. 

[mrbill426]

It would make sense for Chrysler to use up the forged cranks that were left over from 71 instead of tossing them.  Maybe mid 72 production ended up being when the changeover was made. 

Yes it is a '72 and except for the carb, Legendary interior, and water valve (which I have found an NOS one to replace the generic one) it is all original down to the factory A/C.  1972 was the last year that steel cranks were used in (some, not all) the 340s.  My factory parts book has a Tech Bulletin that says the cast cranks replaced the forged cranks on April 11th with engine # HM340R-3911-800.  The #4 counterweight on the cast crank will have a raised "CDF" on it indicating what foundry it was cast at.

 

[Super Blue 72]

  Is your 72 Cuda?  What color is the engine? 

Sorry if this question was directed to someone else but all '72 340s should be blue. 

My engine is original and never taken apart and is blue but under the drivers valvecover where the paint is flaking off there was orange paint.  For all I know they could have replaced that valvecover or maybe it was a left over '71 as my car was made on 8/17/71.  Not sure.  But they should be blue engines for '72.

[mrbill426]

Sorry if this question was directed to someone else but all '72 340s should be blue. 

 

Yep, mine's blue too.   

['Cuda Hunter]

 Cool.  thanks alot. 

[4Cruizn]

1973 barracuda had a blue engine also . . but they were also balanced differently as one was balanced internally and I beleive the 73 was externally.   

[mrbill426]

1973 barracuda had a blue engine also . . but they were also balanced differently as one was balanced internally and I beleive the 73 was externally.   

 
Yep, forged crank= internal balance, cast crank= external balance.  Different vibration dampers and converters too; NOT to be mixed.

[bb71challenger]

I always heard that the factory used up their supply of high compression 340's early in the 72 model year. They were still painted blue but were really left over 71 340's, is this true?

[mrbill426]

Not sure about that.    While ours does have a steel crank, it has the lower compression (8 to 1?) pistons   
I found a brand new set of +.020" forged ones to replace them with though 

 

[Green Drop Top]

1. All 1968-1973 340 engines, regardless of compression, head style, or crank type were considered "HP" engines
2. Engine color for 1970 was Orange
3. Engine color for 1971 was orange, then switched to blue sometime in March/April of 1971
4. All 340's 1972 and later were blue (I would not even give this one the "never say never with Mopar" beinfit of the doubt) they were ALL blue!
5. Forged cranks were used from 1968-1971 and well into the 1972 production year before the switch to cast cranks. I've never seen a factory 73 engine with a factory forged crank.

[HP2]

Yep, forged crank= internal balance, cast crank= external balance.  Different vibration dampers and converters too; NOT to be mixed.

Unless somewhere along the line someone had it internally balanced in order to use other 340 parts.

[Super Blue 72]

I always heard that the factory used up their supply of high compression 340's early in the 72 model year. They were still painted blue but were really left over 71 340's, is this true?

That was always a question that I had when I got my '72 Challenger and was kind of hoping too!  The build date was 8/17/71 and from what I understand August (8th month) is the month they started the new model year so this is a very early '72 car.

On the front driver's side engine pad just below the head, there are VERY light stampings, I think if my memory serves me right it says somehing like "HM 340R"  The "R" stands for "Regular Fuel" as opposed to Premium fuel, so this means for at least my individual car that it's NOT a high compression engine.  I could be wrong.  As far as I know, this is the only way to tell if it's a high or low compression engine from the OUTSIDE without actually taking the engine apart.  I could be wrong and would love to find out if there is another way to tell this.

This does NOT mean that there weren't some '72 cars with high compression engines.  Just that my car was not.  It does have a '71 Rallye gauge cluster though from the factory so left over '71 stuff could've made it to '72 cars, like engines even IMO. 

Only thing is that since the change in compression was a federally mandated item, I wonder if they had to be more compliant as far as letting leftover '71 stuff go into '72s?