HP - when was it used and why?

[matthon]

I am looking for information on the "HP" or "HP2" stampings, which are, for example, found on the front pad of the 383 in the pic below.

Information I have found from reliable sources is listed below, (reliable sources include the Barracuda Data Book, Galen books, and information I have received directly from Chrysler, including my IBM build card, a letter, and other documents):

- For all 1967 and older engines (including Lo Performance 1968 engines), you have to date the engine prior to the scheduled production date of the vehicle.

- For all 1969 and newer engines (including Hi Performance 1968 engines), a (full or) partial serial number is stamped on the engine block.

- All 1968 HP V8 engines are stamped on the top rear of the block near the oil sending unit.

- Engine numbers without the following symbols indicate "standard cylinders and crankshaft bearings".
HP = High performance (includes all 1967-78 440's w/HP2)

- I have also received a letter from Chrysler with my build card, and the letter includes:
H = 383-4 HP 8-Cylinder

-The data book for 67-69 Barracudas also lists the 383 multiple times as 383 HP, never without the HP.

Note: The information above groups all 67 engines with all 68 Lo Performance engines, which could be interpreted as the HP was not available in 67, but the data book lists it for all years 67-69.


Does anyone know when the HP stamping began?

On what engines?

In what models?

Did you have to (or could you) specify an HP engine, and if so was there a corresponding code?

What does the HP stamped on the engine stand for, Hi Performance or High Performance? And is there a difference, (I've seen it listed both ways).

Was HP ever stamped on the heads?

What is the difference between HP and HP2? And was there an HP3?

Why would Chrysler list my engine as 383-4 HP if there is no HP stamped on the block? (definitely the original block)


I've done some research on this, and found a few variations of the 'facts' to where I could answer most of the questions, but nothing definitive.
It seems everyone has their own version of what the reality was, and some appear to be just wrong.

Any help would be appreciated, something concrete to refer to would be great.

 

[340-4spd]

There were alot of variables like carburation, exhaust manifolds, available trannies and drivetrain packages, etc. but I believe the most common differentiator was the 268 cam found in the HP b/rb engines.

 

[crackedback]

The 2 designates second shift.

So HP would be built by first shift; HP2 is second shift.

It's not anything else. No 6 pack, special, nothing, just a shift difference.

There were 350hp 440 for example that were not stamped HP because they weren't considered HP. The 375hp and six pack engines got the HP stamping

 

[cudamark]

The 2 designates second shift.

So HP would be built by first shift; HP2 is second shift.

It's not anything else. No 6 pack, special, nothing, just a shift difference.

There were 350hp 440 for example that were not stamped HP because they weren't considered HP. The 375hp and six pack engines got the HP stamping

X2 and I would add the following answers to your other questions.....The HP was stamped only in the block on '67-78 383, 400, and 440 engines. The VIN will tell you if your car came with one from the factory. The A-body big blocks were all considered HP even though the horsepower was rated a little lower than other body styles. The block photo you posted is a '71 model year 383 High Perfomance with a March 25th build date.

 

[cudamark]

There were alot of variables like carburation, exhaust manifolds, available trannies and drivetrain packages, etc. but I believe the most common differentiator was the 268 cam found in the HP b/rb engines.

Plus the valve springs, higher compression pistons, and high flow exhaust manifolds. some had dual point distributors also.

 

[EL5DEMON340]

they could have forgot to stamp the HP, only heads that i know of that had the HP were the 67 915's with the bigger 1.74 exhaust valves, they would be stamped on the ends.

 

[demon seed]

Over the years, many years, I've heard so many stories about the "HP" stamp on 383's but more so on 440's that nowadays I just roll my eyes around. I know for a fact that the blocks on the 68-70 440's were for all intents and purposes the same and the only time I've come across a 440 that should and did have the HP stamp is one that had the heavier 6 pack rods in it. Hell I'm not even sure if that even makes sense.:read2:

I guess what I'm trying to say is don't get caught in the HP legend.:angry7:, it may not mean a whole hill of beans nowadays.

I wonder if I took my metal stamps and stamped those 2 440's sitting in my garage with "HP" on the pad I could ask an extra $500 for them, see what I mean.

 

[340-4spd]

I wonder if I took my metal stamps and stamped those 2 440's sitting in my garage with "HP" on the pad I could ask an extra $500 for them, see what I mean.

For a whole engine, if you could fool a potential buyer into believing the 265 grind was an HP cam then yes, you could get away with it. Just a block, why bother?

 

[demon seed]

For a whole engine, if you could fool a potential buyer into believing the 265 grind was an HP cam then yes, you could get away with it. Just a block, why bother?

Hey I could put any cam you want in that HP stamped block. Where does it say that it should only be a 265 grind.

 

[cudamark]

Over the years, many years, I've heard so many stories about the "HP" stamp on 383's but more so on 440's that nowadays I just roll my eyes around. I know for a fact that the blocks on the 68-70 440's were for all intents and purposes the same and the only time I've come across a 440 that should and did have the HP stamp is one that had the heavier 6 pack rods in it. Hell I'm not even sure if that even makes sense.:read2:

I guess what I'm trying to say is don't get caught in the HP legend.:angry7:, it may not mean a whole hill of beans nowadays.

I wonder if I took my metal stamps and stamped those 2 440's sitting in my garage with "HP" on the pad I could ask an extra $500 for them, see what I mean.

The blocks ARE the same between HP and non-HP....it was the added goodies that got the HP stamp on the block. If you're doing a complete rebuild, you're going to changed those parts anyway.

 

[cudamark]

they could have forgot to stamp the HP, only heads that i know of that had the HP were the 67 915's with the bigger 1.74 exhaust valves, they would be stamped on the ends.

Really? I've had at least a dozen sets of the heads over the years and didn't see any HP stamped into them. Where exactly were yours stamped? On a machined surface or just into the rough casting?

 

[demon seed]

The blocks ARE the same between HP and non-HP....it was the added goodies that got the HP stamp on the block. If you're doing a complete rebuild, you're going to changed those parts anyway.

Exactly my point cudamark, It's like trying to pull teeth to get a diffenative answer from the people that are supposed to know, what constitutes all the internal goodies that merits the HP stamp. Is it 915 heads with the 1.74" exhaust valve (the head they called the Magnum), valve springs with inner dampeners, which cam out of 3 possibles is it, which carburator, dual point ignition, exhaust manifolds or just all of the above. Maybe the people that did know are looking up seeing dirt instead of blue sky go rest their souls.:read2:

 

[limelite70]

The maltese cross on your block means it had a internal problem.

Broken rings, bad bearings. Had to turn the crank ,etc.

 

[cosgig]

Maltese cross= .001 undersized crankshaft main journals...Maltese cross+"X"=.010 undersized crankshaft main journals

 

[Alaskan_TA]

The various engine stampings are discussed in the factory TSBs. As a general rule, they appear in one of the first TSBs issued for Chapter 25.

I do not have them available for all years, but since a 1971 engine was shown above, here is a link to those pages from the Chrysler, Plymouth & Imperial set;

http://www.hamtramck-historical.com/images/TSBs/1971/71-25-1_page5.jpg

http://www.hamtramck-historical.com/images/TSBs/1971/71-25-1_page6.jpg

http://www.hamtramck-historical.com/images/TSBs/1971/71-25-1_page7.jpg

For Dodge or other model years go to http://www.hamtramck-historical.com/library.shtml & find the model year that interests you & find the TSBs in the grid menu, then look at Chapter 25 for those I have.

 

[EL5DEMON340]

Really? I've had at least a dozen sets of the heads over the years and didn't see any HP stamped into them. Where exactly were yours stamped? On a machined surface or just into the rough casting?

they are on the "915" big block 1967 440 HP heads with the larger 1.74 exhaust valves, most 915 heads had the smaller 1.60 valve but the hi perf GTX ect had the better 915 big valve head, they were usually stamped on the ends like the alt mounting hole area.

 

[340-4spd]

Plus the valve springs, higher compression pistons, and high flow exhaust manifolds. some had dual point distributors also.

Right, basically all the things supporting (or supported by?) the bigger cam.

Hey I could put any cam you want in that HP stamped block. Where does it say that it should only be a 265 grind.

Wasn't this was about the "factory" reasons or differences for the HP-stamped blocks? Like I said in my first reply to this post, it all centers around what cam the engine was built with before it left the factory.

Basically the HP stamp is just a way to easily tell the higher rated engines with the 268 cams. Nothing to do with the block itself and nothing special or magic - pretty simple, really.

 

[mcode]

Seems like I read 50 years ago or so, (yeah, I'm that old), that the HP just indicated
the fuel required, regular or hi-test.

 

[340-4spd]

Seems like I read 50 years ago or so, (yeah, I'm that old), that the HP just indicated
the fuel required, regular or hi-test.

That would be true to a certain extent, because the higher compression engines would require higher octane.

 

[matthon]

So did the car you ordered and the engine in it dictate if it received an "HP" engine?

For example, my 67 A body came with a 383 that was not stamped HP, but yet it received an HP engine?
I've heard of A body BB cars with the HP and without.

If I ordered a 68 Road Runner with a 383, that would be an HP engine as well, based on the car and engine combo I ordered, correct?

And in either case, HP may or may not be stamped on the engine, yes?

I'm not looking to make a big deal about HP engines, or HP2 engines, or the lack of the designation- I am trying to figure out what customers would, or could order, and how the factory workers new what to mark HP, or if that was random, and how they knew what engine to install on what car?

I find this stuff very interesting, and it makes me wonder 'where are the assembly line workers today?'
I'd like to pick their brain.

 

[340-4spd]

Car manufacturing operations were alot different 40 years ago than they are today. More manual labor, less automation and quality control. That's why today you can only get a select few trim combinations, tighly integrated with their corresponding powertrain packages. Back then if you knew the right guy in the sales dept. you could special order literally almost any package combination you wanted and have it custom built right on the assembly line. That led to alot of things like recordkeeping snafus, low-production runs and year crossover anomalies that makes genralizing about what came with what or what was available when more or less an art and a science.

There were alot of mostly followed package rules and a some pretty hard and fast rules. If the HP block is all you are talking about, one of the few things you can be just about absolutely sure of is an HP block left the factory with a 268 cam. Beyond that it's gonna be pretty variable along certain guidelines. There were even some things fleet managers could order from the factory like cop car builds most people never even heard about, including the dealers.

 

[grumpuscreature]

Went to work in a C/P dealership in 1969. All I know about it was that the 335 horse 383s, 375 horse 440s, and 390 horse 440s were stamped HP on the identifier pad. This started in '68 and the A body big blocks were rated lower because of different exhaust manifolds. That and insurance rates.

 

[matthon]

Interesting.
The information you guys provided probably explains why a 67 A body with a very late build date has HP stamped on it.

So the letter I received from Chrysler with 383-4 HP 8-Cylinder is not the same as the HP stamping on the blocks, but it does mean High Performance.

I didn't think there would be a magic answer that solves everything, I thought it would be, well, what it is.

Thank you FABO.