The Dodge Challenger Message Board

what is the difference between HP marked motors and HP2 marked motors. is there any meaning behind this? i know HP means high performance but why did mopar use HP and HP2 codes?

My block which is #s matching to the buildsheet has the following on the block pad located next to the distributor. F 440 H P then in the lower left corner is a 2 then a diamond. The numbers and letters are stamped crookedly as well. My block was a .010 overbore block from the factory as indicated by the diamond. Instead of 4.320 it was 4.330. The 'internals' were all original including the plain steel head gasket. I dont think all were marked 100% 'correct' from Mound Road. I have heard where some were stamped incorrectly as well. Maybe others can chime in and state what theirs are As far as whats the difference between the two? Not a damned thing! www.440source.com has an informative Chrysler Block tech paper, check it out!

thanks eddie,i found this and pasted it for all to read.it seems that HP or HP2 is the shift workers where on at work at the assembly plant.

"There is absolutely no physical difference between a block with an HP or HP2 stamp and one without."

"All blocks were cast and machined at the foundry, and then assembled at Chrysler's 2.1 million square foot "Trenton" assembly plant in Trenton, Michigan. During assembly, if the engine was given high performance cam and valve springs, or in some cases other items that differed between HP and non-HP engines such as: six pack rods, carbs, etc., then the engines ID pad would be stamped with HP. All blocks originally came from the same place, and there is absolutely no difference in cylinder wall thickness, nickel content in the cast iron, strengthening ribs on side of the block by the freeze plugs (see below for the real story on this,) or any of the other myths you have heard. The number 2, which you may find after the HP, (or in the case of non HP blocks, you may find just a "2" by itself, usually in the lower right hand corner of the ID pad) refers to the shift during which the engine was assembled. In running a factory, one 24 hour day can be divided into three 8 hour shifts. The first shift was considered a "1" however to save time, Chrysler did not stamp a "1", they just left it blank. So an HP2 engine, only means that the engine happened to be assembled on the second shift. There is no advantage to an HP2 block over an HP. I have never seen an HP3, (or just a "3") although Chrysler does allow for it in their documentation, so let me know if you have one or have seen one. Also of note is that non-HP engines usually used the same heads, intake manifold, and many other parts, which is great since it makes it a lot easier to bring a non-HP engine up to the power levels of a factory HP and beyond. But unless you are doing an original restoration, don't worry about finding and/or paying extra for an HP block."

Well I have wondered and enquired about this many times over the years. The second shift thing is what is most quoted and those that "know" insist on it so it must be true right?

However that only works if they are working 12 hours shifts. There is no third shift or any HP3 engines.

For sure the blocks are cast with a night/day shift mark. So the theory of marking work between the two shifts is a reasonable one.

But if it is true then why just the HP engines? That is what gets me.

Good point Dave.

dave-r wrote: There is no third shift or any HP2 engines.

For sure the blocks are cast with a night/day shift mark. So the theory of marking work between the two shifts is a reasonable one.

But if it is true then why just the HP engines? That is what gets me.

dave mine is clearly marked hp2 on my id boss (see photo)

it also has a WT on an angle -what ever that means- beside the F440

but there are hp2 motors,you say there arent HP2 motors?

Danny, some say the WT means "Water Test".

airfuelEddie wrote:Danny, some say the WT means "Water Test".

eddie you beat me to it,your good!! i just found WT in a vehicle identification section for secondary codes in authentic performance by mopar. it does mean Water Tested. cool,now i know all the codes to my ID Boss. the same book also has hp or hp2 as one of the secondary codes!! eddie the diamond emblem=oversize tappets in this book.A=(oversize cylinder bores) p=premium fuel.and many more

Then it must be an A, it's kinda hard to tell, the numbers and letters are really "bad" it's like they didnt stamp it hard enough? I thought it was an "diamond" which in reality must be the 'A' with out the line across, so to me it looked like a diamond, oh well I learned something as well. (BTW, Danny I kept all my original internals )

Was there a .040 overbore in small blocks from the factory?

472 R/T SE wrote:Was there a .040 overbore in small blocks from the factory?

I am no expert. But I have never heard of an piston cylinder overbore more than .010. Also from a manufacturing perspective, it would seem the balance factor would be thrown off due to one piston being heavier than the rest.

Reason I ask is the guy I bought my car from had this to say about the motor.

"I couldn't find any factory markings indicating it was a factory .040 block so I'm not completely convinced it's never been apart before. I know the heads had been off before because the gaskets were coated with orange rtv (yuk!) But yet they were still the original style steel shim gaskets as original. But the rod and main bearings were still dated 1969's . And I was told it was untouched when I bought it in 1999".


He's a Mopar tech and former Mopar Nats Judge. It's not that I don't trust him cause he's an absolute stand up guy, but you mentioned a factory .010 overbore so it intrigued me seeings how I've never heard of it in the first place but only makes sense after I've thought about it. So with your diamond stamp and Bill's explanation I wonder what (if) there's a .040 stamp of some sort? That's not leaving much room for future rebuilds' starting off at .040.

Factory info on HP, HP2 and some other stampings;

http://www.hamtramck-historical.com/ima ... _page7.jpg

Alaskan_TA wrote:Factory info on HP, HP2 and some other stampings;

http://www.hamtramck-historical.com/ima ... _page7.jpg

thanks barry,you always come through. i guess the 2 is second shift and would be placed after the hp or on its own like eddies stamping?

IT WAS A TYPO!

I meant to say there are no HP3 440s.

Sorry for the confusion.

I have a HP2 engine myself.