School me, 3.79 strokers

-
I gotta sympathize with U Rumble
Like when the trans am honchos got all upset about our 4 1/4 x 3 3/4 "5 liter" AMC
block said 360 on the side just like it should have
stroke should have been around 2 3/4 - what's an inch- just a typo
cross ram looked stock
picky picky picky
heads had raised ports
picky picky picky
and roller cam
picky picky picky
back then the foundry guys could shave the cores and do a short run with a factory part number
The did it for the 6 cyl Indy project too block with thicker deck and cylinder walls
actually easy as there was 252 "Mexican" Block that had a larger bore similar to the much later 4.0 Jeep
so they shaved the core for the deck and used the mold for the larger bore but shipped unbored under 3 3/4
limit to make class was .010 over
bottom end was plenty strong with 1/2 inch bolts- we did not use studs- and filled in webs already
210 inches 1,200 Reliable HP
someone mentioned ruling against MOPAR - Indy ruled against the AMC 6 with a maximum fuel rule we were using rich to cool the motor
 
Thanks Wyrm.... it’s the nit pickers and the resto Nazi’s that ruin it for me to the point I don’t go to meets anymore. For them it’s hotta be a perfect car or they just swarm you repeating the same thing over and over again making themselves a menace on purpose for there own joy. You really can’t miss it.
 
I didn’t see one for the LA but only the RB and Gen3 HEMI
 
These 3.79 cranks are a great piece and very strong. They can make great power and torque with the right combination of parts. The 8 bolt Hemi style flange is the one minor downside I found for small block builders with existing flywheels or flex plates. I believe the intent of the hemi style flange was to allow swapping with the big block parts flex plate or flywheel parts that were available for racing.

Callie’s use to make small block cranks and likely still do on custom order if not listed in their catalogue.

Here is a list of cranks Mopar sold in the early 1990’s with 2.500 main journals and standard small block rod journals. This was well before the the 4.00” stroke cranks were released. 1993 catalogue list and displacement chart pictured below.

0389904D-583F-4004-8B12-085FD2465FAC.jpeg
21360D01-FD77-42EC-8E6E-B57B3167CD9D.jpeg
 
The dragon slayer I have found are no longer available.

As said, Molnar makes a nice one, when using a 6.400 rod, it’s gives a nice ratio and the pistons come up lighter.

They are available in 6 bolt crank flange.
 
Lots of interesting information, I am kind of wondering why the 3.79 has faded out of popularity verses the 4.00? I would not think it is because of options offered to other manufactures. An example would be the Chevy 383 (3.75 stroke) remains very popular, even though he 4.00 seems to the more prevalent with the Ford crowd. If the 3.79 worked well, why the shift to 4.00?
 
Does Ford have a stock crank @ 3.75 for the small blocks?
 
DrEamer said:
Lots of interesting information, I am kind of wondering why the 3.79 has faded out of popularity verses the 4.00? I would not think it is because of options offered to other manufactures. An example would be the Chevy 383 (3.75 stroke) remains very popular, even though he 4.00 seems to the more prevalent with the Ford crowd. If the 3.79 worked well, why the shift to 4.00?
Click to expand...

Well, post 17 gives a very good discussion of why no one should be using a 4 inch stroke in anything. Unless you have enough cylinder head to feed it. And they don't. There isn't a head capable of actually doing the job that has OE architecture. Period. Doesn't matter whose name is on it, what the claimed flow numbers are.

I've built my share of 400 inch small blocks in all three varieties. Built many Chevys that were over 420 inches. They are all severely RPM limited or the cam to make them pull and make power is horrendous. You can easily see this on a dyno. Since most guys don't dyno, they think just because the valves ain't floating they are still making power.

When you are induction limited, longer strokes and the lower Rod to stroke ratio is a killer.

If, and it's a big if, you can get enough induction on them, then it's ok. As I've posted several times lately, the 632 Chevy with the right induction will make power well past 8000. 20 years ago, that would have been unheard of.

IMO, if you are using a production head, the stroke limit should be the 360 stroke. And you should try and get as long a rod in it as you can.

Over that stroke length, you need at a minimum a W2 head. And it needs some work. Or a W5.
 
The 400 M Cleveland has a 4" stroke which fits the small blocks with a little work although I think the offshore iron has pretty well replaced that conversion
Agree with YR- get as long a rod in it as you can
If you are going for HP/ cu in then YR is spot on
If you are trying for a broad hp curve then you want to max out whatever head you are using at an as low rpm as possible- so build it big
you do not loose too much at higher rpm but pick up midrange
We ran two dragsters with the same heads one 4" stroke the other 4 1/4 extra 50 cu inches won (also 1/8 bigger bore)
The heads will determine the HP in any case- at a higher RPM for the smaller motor no matter which head
racing best head wins
 
rumblefish360 said:
I call my 360 crank in a .030 over 340 a 373.

When some A-hole corrects me, for the actual 372, or dead nutz 372.61 I just roll my eyes and say what ever. Only A-holes pick this **** apart as if there is a royal holy dynasty to up hold. It’s just amazing how some assholes freak out because you rounded up or down.

392/394, a matter of a .030 vs a .040 or less? IDK
I get the general idea and I’m good with it. I can always ask a question on actual BxS cid.
I don’t care, saying I have a (LA) 392 is cool.


Edit-spelling
Click to expand...
Good attitude
 
DrEamer said:
Lots of interesting information, I am kind of wondering why the 3.79 has faded out of popularity verses the 4.00? I would not think it is because of options offered to other manufactures. An example would be the Chevy 383 (3.75 stroke) remains very popular, even though he 4.00 seems to the more prevalent with the Ford crowd. If the 3.79 worked well, why the shift to 4.00?
Click to expand...
One reason , 3.79" cranks dont sell like they should is because they don't make the crank journals/pin to the size of thestock mopar rod(2.125") instead they machine it too 2.1" requiring a Chevy LS bearing/ 1997-2013 / clevite cb663p.., which is also a bit thinner. And the piston pin is a Chevy size on the 6" or 6.125" Chevy LS rods. Hence to use a Mopar rod and stock pistons, machine the moparRod on the big end thinner to Chevy witdth. And find correct Size bearings, 2.125", or make your own if you dare to be criticize, see attached photos for the correct material and cut to size and fit to the backside of of the above LS bearing, I don't suggest using valve grinding compound to cause

IMG_20230603_211659143.jpg


IMG_20230603_211707960.jpg
friction/between the copper bearing spacers .025 and the 2.1" Chevy bearing when installed...though that is exactly what I plan to do.
 
Jessearent said:
One reason , 3.79" cranks dont sell like they should is because they don't make the crank journals/pin to the size of thestock mopar rod(2.125") instead they machine it too 2.1" requiring a Chevy LS bearing/ 1997-2013 / clevite cb663p.., which is also a bit thinner. And the piston pin is a Chevy size on the 6" or 6.125" Chevy LS rods. Hence to use a Mopar rod and stock pistons, machine the moparRod on the big end thinner to Chevy witdth. And find correct Size bearings, 2.125", or make your own if you dare to be criticize, see attached photos for the correct material and cut to size and fit to the backside of of the above LS bearing, I don't suggest using valve grinding compound to cause

View attachment 1716098161

View attachment 1716098162friction/between the copper bearing spacers .025 and the 2.1" Chevy bearing when installed...though that is exactly what I plan to do.
Click to expand...

What? I have two 3.79 cranks out in the shop and both are 2.125 rod throws. The smart engine builders turn all Chrysler cranks to SBC LJ so you can buy bearings. Same with those ridiculous big block rod throws. They get turned to 2.200 BBC.
 
What? I have two 3.79 cranks out in the shop and both are 2.125 rod throws. The smart engine builders turn all Chrysler cranks to SBC LJ so you can buy bearings. Same with those ridiculous big block rod throws. They get turned to 2.200 BBC.
 
You must log in or register to reply here.
-

Back
Top