Why do some Big blocks have HP on the tabs

[ACUDANUT]

 I have been through my share of them and I never found anything special about those with the stamp or those without. 

[Ghoste]

I don't think it has anything to do with the blocks but rather the internals.  For assembly plant and warranty use more than anything else.

[ACUDANUT]

 What kind of internals ?

[Ghoste]

Camshaft, connecting rods in some cases.  Maybe intake side comes into play as well if it was of any value for assembly. 

[Nacho-RT74]

springs with dampener, double timming chain set, windage tray, HiPo camshaft, 4bbls intake, HiPo exhaust

[oldschool]

as far as a used block is concerend,i would rather have one that is not an hp block.the hp just means it got the snot beat out of it.a regular one would be my pick.

[TylerCharger69]

I'm not sure how much truth there is to this....but a few people told me that the "HP" blocks were not only different by the internals  (connecting rods, camshafts, pistons, etc.) but the blocks were decked .050 to raise compression ratio.  How much truth there is to that....i don't know.  But it seems to me that the HP stamping would mean more than just internal component differences.   Someone is sure to chime in with facts and opinions.

[Ghoste]

The blocks were no different and they weren't decked to raise compression.

[oldschool]

The blocks were no different and they weren't decked to raise compression.

  the only difference is the HP stamp.....

[Ghoste]

Taken without permission from the website for 440 Source...


"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. we 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."

[Nacho-RT74]

I'm not sure how much truth there is to this....but a few people told me that the "HP" blocks were not only different by the internals  (connecting rods, camshafts, pistons, etc.) but the blocks were decked .050 to raise compression ratio.  How much truth there is to that....i don't know.  But it seems to me that the HP stamping would mean more than just internal component differences.   Someone is sure to chime in with facts and opinions.

mmm and what about the pushrod lenghts ?... I don't think so