Hemi vs chevy big block - Team Camaro Tech
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post #1 of 15 (permalink) Old Sep 19th, 01, 08:20 AM Thread Starter
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What is the difference between these two engines and why are hemi's so expensive and legendary?
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post #2 of 15 (permalink) Old Sep 19th, 01, 09:26 AM
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The main difference is in the combustion chambers. A hemi has hemispherical (hence the name) combustion chambers which are much more efficient than conventional combustion chambers found on other engines. If you search the net, I'm sure you can find some pictures and a better explanation than I can give you.

The reason that they are legendary and expensive is that they produced alot of power and are somewhat rare. The same reason that the Chevy sb302 is so expensive and hard to find.
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post #3 of 15 (permalink) Old Sep 19th, 01, 09:46 AM
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Info Cameron gives is true, but, they are not as rare as they once use to be. Chrysler is reproducing them again, but, they may as well as be rare due to the price for a complete assembly.

Hemi wrote the book on making power, and due to its combustion chamber shape, makes it very efficient, all other things being equal.

It is the King!! Just listen to a Hemi and anything else at the starting line of your local drag strip, The Hemi's STILL pumping iron at the big end!!!!!

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post #4 of 15 (permalink) Old Sep 19th, 01, 10:59 AM
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The hemi's ports were huge by large - made for high rpm racing. From stoplight to stoplight, the Dodge 440 would beat it but get it on the strip and forget about it. The high RPM's is where the hemi heads really come into their own.
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post #5 of 15 (permalink) Old Sep 19th, 01, 01:36 PM
 
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There are a whole bunch of the old pre 426 hemi's out there that came out of Dodge's, DeSoto's and Chrysler's. But the only prob. is that each car model made their own engine line and the parts don't interchange all that much.

If I remember right they ranged from the little 241 Super Red Ram Dodge up to the big Chrysler 392. The little engines are down right "cute", kinda cute like the little 215 B/O aluminum engine.

The Chrysler line was 331, 354 and 392 I think. And a very interesting bit of info is that there are more early "elephant" heads around then blocks b/c the engines put out more power then the engine valley/main web casting area could hold together.

I remember looking at a pic. in one of the early rod mag's that showed a AA/FA setting on the track w/ all eight pistons hanging down where the pan used ta be!!!

There was a recent story done in either HR or CC that had a (I think) Toyota hemi in a very small hot rod that they said was just about as good a modern copy of the little 241 hemi that could be made!!

I again wish I could afford ta play w/ the little jewels!! pdq67



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post #6 of 15 (permalink) Old Sep 19th, 01, 09:42 PM
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I heard that on the Hemi motors, instead of using head gaskets they glued them to the block.
Is this true?
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post #7 of 15 (permalink) Old Sep 19th, 01, 11:32 PM
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once you get past all the technical things that make a hemi so great, there is also the feeling one gets in the gut when just looking at one..they are just flat out cool looking.huge by large valve covers with plug wires disappearing into the middle...cross ram intake or big single holley or 8-71 huffer....ahh...better than looking in playboy..and i am a die hard chevy guy!!!

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post #8 of 15 (permalink) Old Sep 20th, 01, 01:50 AM
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Check out the article in October HRM titled Hemi Heroes. The article tells a lot of the story about the early days of the Hemi.

There is also a "Spotters Guide" that describes all those early hemis PDQ 67 is talking about. Chrysler made a 331, 354 and 392 Hemi. DeSoto made a 276, 291, 330, 241 and 345 Hemi. And The Dodge Red Ram Hemi's were the 241, 270, 315 and 325 Hemi.

BTW - the 426 Hemi is the heaviest gasoline engine I've seen weighing in at around 725 lbs.
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post #9 of 15 (permalink) Old Sep 20th, 01, 04:38 AM
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I've seen aftermarket hemi heads for ford 429/460... Only if they made them for chevy....
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post #10 of 15 (permalink) Old Sep 20th, 01, 05:42 AM
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So thatís why they call them elephants
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post #11 of 15 (permalink) Old Sep 20th, 01, 06:13 AM
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there is a place called ARAO racing or something like that... I read about their small block chevy 4 valve heads... they have similar chambers to the hemi (not quite the same) and also have a central spark plug that pokes through the valve covers like the hemi. It does just look very top fuel to see plug wires coming out of your valve covers!
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post #12 of 15 (permalink) Old Sep 20th, 01, 02:45 PM
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No, Hemi heads weren't glued to the block - they used ordinary steel shim head gaskets. I built blown fuel Hemis in '61 and '62 for my AA/FD - the old long-stroke 392 - Marine block, Moldex crank, Carillo rods, iron Marine heads, KB-machined 6-71 blower, Hilborn/Enderle injector, Joe Hunt Vertex magneto; bulletproof as long as we kept it at 65% or below. Sat BEHIND it in those days....

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post #13 of 15 (permalink) Old Sep 20th, 01, 02:47 PM
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Boodlefoof
I think the style is a pentroof(?) combustion chamber. Has better warmup and gas milleage than full hemi design. Kinda the best of both hemi and wedge designs.

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post #14 of 15 (permalink) Old Sep 20th, 01, 03:13 PM
 
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I've read/heard that the early Hemi's are still used as industrial stationary engines at oil well sites and irrigation stations where it costs too much to run an electric line for an eletric motor.

I'm sure that down Texas way in the oil fields you can probably still pick used ones up that are in good rebuild shape real to fairly cheap if anybody wants one.

Oh, and thx. Eric for posting the sizes. I have that info. buried somewhere so can't lay my hands on it!!

I think you can stroke the little engines to get some more cube's out of them just like the big ones so can come up w/ a real powerful "small sized" Hemi that's about the same size as a small block, but heavier. Of course the crank and stuff would be custom, -- so expensive!! But the WOW factor would be fantastic!! pdq67.



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post #15 of 15 (permalink) Old Sep 21st, 01, 07:05 AM
 
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A company called Arias used to make hemi heads that would bolt to a big block chevy. Don't know if they are still made.
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