340 Mopar

I bought a pro street. I have no build sheet for the engine. Was told is puts out 750 horse. Has Eldelbrock alum heads 6600 performance series, 2- 925 Demon carbs, 671 blower. Engine looks and sounds very good. Short of pulling engine and having it dynoed, what other choice do I have. Also 340 block was produced 1-20-1970,with block I.D. being 2780930-340-8, what does the last 8 mean?  Thanks  

Sounds like you have a nice ride. I would find a company near you that has a chassis dyno. This way you can dyno the engine in the vehicle and find out your rear wheel horsepower.

As far as your engine goes, I found the following info on Year One's website:

340 "LA" Engine, 1968-73 • 4.04" bore x 3.31" stroke
The 340 should be considered the "Hemi of the small block family". Why? Simply because the 340 was designed from the outset as a performance engine. Look at the stats: high compression, big valves (2.02 intake, 1.60 exhaust), forged and shot-peened crank and rods, etc. These engines were built to perform well and stay together doing it. A testament to the 340's power potential is the fact that Chrysler installed the beefy A-727 Torqueflite automatic behind it instead of the usual 904, the only small block to receive such an honor. 340 development peaked with the 1970 6-bbl version available only in the limited-edition AAR 'Cuda and T/A Challenger (which were Dodge and Plymouth's entries into the SCCA's Trans-Am road racing series). Considerably underrated at 290 horsepower at 5000 rpm (not coincidentally, Chevy's Z/28 302 and Ford's Boss 302 were also rated at 290 horsepower), by turning it higher, which it was more than willing to do, resulted in much more power. The 6-bbl 340s had beefier blocks with thicker main webs to go along with the forged crank and rods. The cylinder heads were also unique to the 6-bbl engine. Chrysler relocated the intake pushrods, which allowed a much larger intake port opening and thus more flow. The valvetrain was adjustable, and induction chores were handled by three Holley 2-bbls on an aluminum intake manifold. In late 1972, with factory performance nearing an end, the 340 got a cast crankshaft and heads from the 360. But as far as small blocks go, the 340 is legendary.

Now, as to your specific question about that last digit. That info was a little tougher to find but I had remembered reading something about it before. I checked my sources and found it at 440source.com. Here is what they had to say about it:

While we are on the subject of casting numbers, often there will be what is known as a "tooling revision number" or a "dash number" after the casting number. A 1968 440 block, for instance, might read 2536430-12, or sometimes there will just be a space, such as 2536430 12, or sometimes 253643012. While 2536430 would be the casting number, the 12 would be the tooling revision number, which indicates how many times the tooling (core molds) have been reconditioned back to the proper specifications or modified to include improvements. After so many "pours" the tooling gets worn and needs to be reshaped or reconditioned. So theoretically, higher numbers will be later dates and have any casting improvements incorporated into them. The only problem with this theory is that engines were produced in such volume that many many different sets of tooling were used concurrently to meet the necessary output. So while some may have lasted for quite a while, (in which case you will find later dates with earlier revisions) some got worn quickly or damaged and needed to be revised after a short time. So while in some cases, parts with later numbers may include some improvements the earlier parts may not have, on a practical level, it means nothing as far as the quality of the piece. In other words, don't waste your time looking for an early or late tooling revision number. Blocks, heads, water pump housings and many other cast parts have revision numbers as well.


Hope this helps.  
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Frank the Crank
www.amberlightgarage.com

Thanks for the reply, was very helpful.  

Frank "the crank" Thanks for the reply. This was very helpful.