Stroker 392 Crankshafts

Discussion of the 331-354-392 HEMIs.

Moderators: TrWaters, 392heminut, scottm

DavidBraley
Posts: 163
Joined: Sat Jan 30, 2010 7:40 pm
Location: Fort Collins, Colorado

Stroker 392 Crankshafts

Post by DavidBraley » Fri Oct 01, 2010 12:02 pm

Some of the more knowledgeable people here mention that a 5/8" arm is a safe stroking length in a 392. But what exactly does this mean when they say a 5/8" arm? Does it mean the crank has a 4.525" stroke (stock 3.90" + 0.625" = 4.525")?

Have people gone more? And if so, what's possible with a steel rod? I know from other engine builds that one of the concerns is with the total length of the cylinder. It's not safe to let too much of the piston skirt hang out the bottom.

Sorry for my dumbness. Thanks in advance for reading this.

David
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law

DblAdigger
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Location: SoCal

Re: Stroker 392 Crankshafts

Post by DblAdigger » Fri Oct 01, 2010 9:22 pm

Yes, a 5/8 "arm" is a 4.525 stroke. Bless our old welded stroker cranks. A 5/8 was about the limit with the aluminum rods of the day and there were no steel aftermarket rods...then, not that anybody would even think, back then, of running any steel rod. Conventional wisdom, at the time, was that you need the aluminum to absorb some of the shock. I do know of a fellow racer that built 1 or 2 with 7/8 arms and ONE attempt at a 1.00 arm. Those 3, however, were all dry blocks...'cause they were WAY into the water jackets. Today, with a well designed steel rod, AND NO BLOWER, a 5/8 might be a doable deal.
Chuck Stevens
Some people can break a cannon ball, in a sand box, with their bare hands.

DavidBraley
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Joined: Sat Jan 30, 2010 7:40 pm
Location: Fort Collins, Colorado

Re: Stroker 392 Crankshafts

Post by DavidBraley » Mon Oct 04, 2010 4:35 pm

Thanks for the reply!

Now if I can just find a block.... :roll:
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law

392heminut
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Joined: Sat Nov 30, 2002 2:16 pm

Re: Stroker 392 Crankshafts

Post by 392heminut » Mon Oct 04, 2010 10:06 pm

DavidBraley wrote: Now if I can just find a block.... :roll:

Do you have someone in your area that could pressure test the water jacket of a block and could you go to Albuquerque to pick one up?
Owner of the Poor Man's Hemi Cuda

DavidBraley
Posts: 163
Joined: Sat Jan 30, 2010 7:40 pm
Location: Fort Collins, Colorado

Re: Stroker 392 Crankshafts

Post by DavidBraley » Fri Oct 08, 2010 3:13 pm

Hi 392heminut,

I just sent you a PM.

David
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law

392heminut
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Re: Stroker 392 Crankshafts

Post by 392heminut » Sun Oct 10, 2010 12:33 pm

Sorry for the delay, been out of town. Got it and responded! :)
Owner of the Poor Man's Hemi Cuda

dan miller
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Re: Stroker 392 Crankshafts

Post by dan miller » Sat Oct 16, 2010 3:51 pm

It's my understanding that a .750" and/or longer stroker is doable, but that a .625" is pretty much the "sweet spot". Any larger, and friction eats up power at high rpm, and the breathing ability of the heads starts becoming an issue.

Danny

Powerflite
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Re: Stroker 392 Crankshafts

Post by Powerflite » Tue Jan 04, 2011 5:47 pm

But most, if not all of the people "back in the day" that were using stroker cranks didn't bother with running water in their motors so they could cut up the water jackets without concern. My question is what is the largest stroke that a stock motor with uncut water jackets can take? Did the 5/8" stroker require a lot of massaging?

DblAdigger
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Location: SoCal

Re: Stroker 392 Crankshafts

Post by DblAdigger » Tue Jan 04, 2011 9:17 pm

It's not the crank stroke that is the problem, it's the big end of the rods. Although we always used bulky aluminum rods and had to do alot of grinding, I can imagine a steel rod with the shortest possible rods would only require minimal clearancing with a 5/8 arm.
Chuck Stevens
Some people can break a cannon ball, in a sand box, with their bare hands.

budmspeeco
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Joined: Tue Dec 21, 2004 5:35 pm
Location: South Houston, Texas

Re: Stroker 392 Crankshafts

Post by budmspeeco » Tue Jan 04, 2011 10:40 pm

Why are you contemplating a crank with such extreme stroke lengths? Are you really going to use one of such humongous proportions? Have you never heard that bigger is not always better, (Ask my wife LOL) especially if you are up against a limit of capability/spending? A $1,000.00++++ for a crank, $$$$++++ for different rods, pistons, heads good enough to control and use that much breathing, bigger cam, valve train to let it in and out, adequate intake/exhaust system, and on and on. GET A PLAN within your range of ability and budget, and stick to it. If you don't know, ask RELEVANT questions. Dreams are nice, but the reward of finishing will be far more gratifying than "What I might" have finished or "What I might have" planned to get. Look at some of the prices of the finished killer motors for sale, especially on the Hemi, H.H.s or eBay. They ask that much to recover just PART of what was spent, not counting their time and effort. I would like to compete in the Engine Masters Challenge but it ain't ever gonna happen so I don't email a jillion futile questions to our esteemed fellow hemi lover who HAS done it except take me with you next time. Everyone has heard the old one IF HAVE TO ASK THE PRICE YOU CAN'T AFFORD IT. Wake up!!!!!!!!!!!!!!!!!!!! Buddy "PS" - I just wanted to start the new year out with a bang.
'48 anglia

phil
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Re: Stroker 392 Crankshafts

Post by phil » Sat May 21, 2011 7:22 am

which company make a stroker crank for the 392

Rob
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Re: Stroker 392 Crankshafts

Post by Rob » Sat May 21, 2011 9:56 am

Why not simply put the 4" LA crank in it? Since those cranks are a bolt in for the poly engines, won't they work in the Hemis too?

DavidBraley
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Location: Fort Collins, Colorado

Re: Stroker 392 Crankshafts

Post by DavidBraley » Sat May 21, 2011 11:32 am

phil wrote:which company make a stroker crank for the 392
There where several companies making stroker cranks for these engines back in the day. I think Velasco? (spelling) might have been one. I'm sure any of the smaller custom crank companies would make you one, but it's going to be spendy. I'm sure george, mart, or 392heminut will have more thoughts.

Rob wrote:Why not simply put the 4" LA crank in it? Since those cranks are a bolt in for the poly engines, won't they work in the Hemis too?
Um, I don't think I've ever read that an LA crank will bolt into a poly, but I could be wrong. I do know that the bore spacing for the 331-354-392 is 4.5625", and the bore spacing for the LA is 4.46". That alone would be a deal breaker.

I would love to find something close to a 4.5" crank for my project at todays BBC crank pricing. :wink:

David
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law

Rob
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Re: Stroker 392 Crankshafts

Post by Rob » Sat May 21, 2011 12:18 pm

Nope, read this.

http://www.1962to1965mopar.ornocar.com/poly318.html

Gary Pavlovich is a well known Poly guru. He says the LA cranks will interchange with simply turning down the counterweights. Seems he's built some. In that article it also says the 4" stroker cranks interchange into the poly. That's what got me to wondering about the cranks going into the Chrysler Hemis. Aren't the blocks the same dimentionally as the polys? Course, it would require custom pistons. There's even a 4.250 stroke crank for the LA motors now. That could make for some big early Hemis......IF the cranks will fit.

Rob
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Re: Stroker 392 Crankshafts

Post by Rob » Sat May 21, 2011 12:24 pm

....and I'm not debating the bore spacing. They are clearly different.....but that article clearly says they have used the LA cranks in the poly blocks. If they can fit in the poly blocks.....I'm thinkin they'll fit in the hemi blocks.

Rob
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Joined: Thu May 05, 2011 10:15 pm

Re: Stroker 392 Crankshafts

Post by Rob » Sat May 21, 2011 12:35 pm

....and check this article out. It clearly says in the text if you read it that the cranks are the SAME.

http://www.moparmusclemagazine.com/tech ... index.html

Here is an excerpt:

"A few more facts are in order here. All of the '56-'66 poly motors have the same rear block-face bolt pattern as the later LA motors and can share the same crank. However, only the '62-'66 polys came with the same crankshaft as the 273/318/340 motors, the crank that accepts the popular '62-and-later aluminum case TorqueFlite transmissions. The '56-'61 poly motors use a crank with an extended flange, mainly for use with the old-style, cast-iron case TorqueFlite transmissions, so you may want to use a '62-and-later crank."

According to that, they will ALL interchange, but the 56-61 used an extended flange. I am like you. I don't understand how in the world the LA crank can fit, but here we have two seemingly solid sources that not only say they do, but have done it. Tell you what I'll do. I have two 318 LA engines. I will remove any question. When I get my 331 on the stand and torn down, I will get the crank out of one of my 318s and see what's what. It may be a little while. How's that?

Rob
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Re: Stroker 392 Crankshafts

Post by Rob » Sat May 21, 2011 12:52 pm

I see what the deal is. the 318 poly is the bastard child. It has the same bore spacing as the LA engine, but different from all the rest. That's strange.

DavidBraley
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Location: Fort Collins, Colorado

Re: Stroker 392 Crankshafts

Post by DavidBraley » Sat May 21, 2011 1:12 pm

Thanks for all that info Rob, it's interesting for sure. It seems like the term "Poly" is being used generically. The "Spitfire" was the early version of the Poly engine based on the Chrysler Hemi block design:

http://en.wikipedia.org/wiki/Chrysler_S ... _V8_engine

David
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law

Rob
Posts: 208
Joined: Thu May 05, 2011 10:15 pm

Re: Stroker 392 Crankshafts

Post by Rob » Sat May 21, 2011 2:15 pm

DavidBraley wrote:Thanks for all that info Rob, it's interesting for sure. It seems like the term "Poly" is being used generically. The "Spitfire" was the early version of the Poly engine based on the Chrysler Hemi block design:

http://en.wikipedia.org/wiki/Chrysler_S ... _V8_engine

David
Now that is interesting. I've also seen the early polys called Windsors. Too bad that the LA engine didn't retain the Hemi bore spacing, ain't it? LOL

mart
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Re: Stroker 392 Crankshafts

Post by mart » Sat May 21, 2011 5:44 pm

There a *lot* of confusion about the so-called "Poly" engines. There were three completely different "Poly" engine families that have little if anything in common with each other. The Chrysler Poly was based on the early hemi and most Chrysler hemi parts will either interchange or can be made to work. Then there was the Dodge Poly, which was based on the Dodge Red-Ram hemi and uses mostly Dodge hemi parts. But the so-called "A" series" Poly which the "LA" series wedge engine evolved from, was originally a Plymouth engine and completely different from either the Chrysler or Dodge Pollies and was based on the the '57 313 and 318 Plymouth Poly. Modern-day "LA" stroker cranks can definitely be modified to work in the older 'A" series 313 and 318 Poly engines, because the "LA" evolved from the original Plymouth "A" series - the but they won't work in the Chrysler or Dodge Pollies.

mart
=================

DavidBraley
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Re: Stroker 392 Crankshafts

Post by DavidBraley » Sat May 21, 2011 6:58 pm

I sometimes daydream of someone casting an early Hemi style block and heads with the BBC bore spacing. Slightly longer rocker arm shafts, a custom set of valve covers and oil pan, and you have an engine that looks just like an early Hemi, but instead with access to tons of crank and rod choices. Even the 4.25" second gen 426 Hemi pistons could be made to work.

I know that the Hemi gods at HotHeads, and Dan Miller (RIP) have already prototyped a 392 block with siamese bores that will go to something like 4.3" bore. EDIT: I was partially wrong about who is behind this new block, it's "Veteran nostalgia racer Claude Lavoie and legendary Hemi engine builder and tuner Gene Adams". But the stock bore spacing still leaves you needing a stroker crank that costs over 3 grand.

Just daydreaming. :roll:

David
Last edited by DavidBraley on Mon May 23, 2011 11:14 am, edited 1 time in total.
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law

Rob
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Re: Stroker 392 Crankshafts

Post by Rob » Sat May 21, 2011 9:32 pm

Awesome info here. Thanks yall. All I got to say is I sure am glad I will be happy with ouly 300 HP. LOL

johnny5
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Location: St Charles, MO

Re: Stroker 392 Crankshafts

Post by johnny5 » Wed Aug 10, 2011 9:42 pm

There's a local place close to me that markets custom cranks for pretty much anything. If I get brave enough I'll call them and ask just how much a low or high deck crank will cost. If they can sell a batch then then price will definitely be lower.......

DHEMI
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Re: Stroker 392 Crankshafts

Post by DHEMI » Thu Aug 11, 2011 9:17 pm

One thing I haven't seen addressed here is rod angle.Lot's of shivvies are made into 383 engines,but the rod angle is really bad.Why go to a big stroke if the rod is trying to push the pin end into the cylinder wall at an extream angle? It'll work but why take a chance?

johnny5
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Location: St Charles, MO

Re: Stroker 392 Crankshafts

Post by johnny5 » Thu Aug 11, 2011 9:56 pm

even the worst early hemi stroker combo has a better ratio than a sbc. if you go with off the shelf 6.8" rods you have a 1.60 ratio and a good skirt on the piston. it's a personal preference of the engine builder. outer limits are probably 6.535 rods on a 4.375" crank in a low deck - not so good 1.49 ratio.....

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