Please excuse me if this has been sent before. I sent this with Outlook Express and did not see it in my mail, so will send it again. HP engines were discussed earlier in this thread. This was George Reihl's responce to a server question about 300 engines. I have no idea where he got this information or the accuracy of it.
Since you asked I went out to the garage and measured -- the HP stamp is
slightly larger than the S 41 stamp -- I'd guess one font size. The S 41
stamp and the date code stamp are the same size.
By the way, HP blocks are a different casting blend than standard blocks --
higher nickel content. HP blocks also were heat treated for stress relief.
HP blocks were built in batches, separate from normal blocks, so they were
not pulled out of the production line for performance modifications. HP
blocks sat in a group in the warehouse until they were pulled for the
production line, which is why the date stamp on an engine can be much
earlier than the car's build date.
You are correct in the way the Chrysler blocks are cast. All 413 blocks, and
others, are cast out of the same material with high chrome and nickel
content. More than the other car manufacturers blocks & heads contain.
Blocks and heads coming out of the foundry are
cooled then reheated for
stress relief. Then sent for the initial machining. They are checked for
sand holes, discarded if any, then final machining and checked again. Any
blocks or heads not up to par are sent back to the foundry for remelt.
When blocks and heads are found to be perfect, after machining, some are
destined for the "premium" line. Generally for high performance, marine and
industrial use. From what I have been told
by some of the "old timers", is
that on the premium engines, final machining is done with "new" tooling to
keep close tolerances. "Used" tooling is the used on non premium blocks.
After all machining is done, the blocks & heads are sent to the assembly
line. The 300 engines, Pistons, bearings, crank, etc. are carefully
assembled. All of the high perf. engines then get a precise balance job. I
have been told, plus or minus 2
grams, other engines get as much as 20 gram
balance.
With the high performance engines, they get a flame hardened forged
crankshaft to .060. This is what makes a H.P. engine along with the
camshaft. N.Yers. and Imps do not get these engines and their cranks are not
hardened. After the precise machining, crank, camshaft, etc., then the "H P"
is stamped onto the block along with the date of engine assembly.
All 413 blocks have the same casting numbers along with the various shift
codes when they were cast. Exception to that rule is the "motor home"
blocks. They are cast special because of the extra cooling passages cast
into them and also the heads. Motor home blocks and heads should never be
mixed with regular engine components. But their cranks are hardened
Other non premium blocks will have the "diamond", "maltese cross" and
other
stampings associated with "under sizes" incorporated into the blocks.
Re: undersize crank, oversize rod bearings, oversize lifter bores, and
sometimes oversized main bearing bores. On GM engines, one can find "shims"
under the main bearing caps because of oversize line boring. Never will one
find these marks on a premium "Chrysler" block.
All 413 blocks are not the same. That goes for all the other "H.P."
engines that come out of the Chrysler foundry and machine shops, 318, 340,
360, etc.
In all of my years, Chrysler builds the best engines.
George Riehl>
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