Possible forged steel crank?

[Fierobsessed]

This applies to the pushrod motors just as well, but Im getting some dirty thaughts about using it in my 3.4 DOHC SC.

I was looking at the new 3500 as a possible donor for more modern and stronger bottom end parts to add to my 3.4 DOHC SC project. I was alittle dissapointed to find that the stroke was 84 mm just like every other 3.1 and 3.4 out there. (I was hoping for some sort of a stroker) But then I stumbled on the fact that the crankshaft IS actually VERY different then that of a 3400/3100.
There are two cranks for the 3500's. One is a cast iron crank with larger rod journals, and the other is a FORGED STEEL crank also with 2.25" rod journals. Even bigger journals then the SBC! It seems like they made a high performance, toss it in crank for us. Well almost it seems. The main journals are the same size as the 3400 as far as I can tell (and the 3.4 DOHC for that matter) so it might just fit nicley. However the reluctor seems to have changed to a 24X reference unit, so it isn't really compatible with our ignition systems. Perhaps something that can be easily retrofitted might do the trick. (Steel welds quite well) But heres some info on the unit I found on beretta.net

CRANKSHAFT

A large-pin iron crankshaft is stiffer than a standard crank. The stiffness added by this type of crank improves the stiffness of the engine, resulting in a quieter, smoother engine. This crank is used in the 2005 Uplander, Relay and SV6.

To further reduce NVH and deliver even more refined performance, the Terraza, G6 and Malibu utilize a large-pin crankshaft made from steel.

Critical specs for the 3500
Connecting Rod Journal Diameter 2.248-2.249 in
Connecting Rod Journal Width 0.863-0.869 in
Crankshaft Main Bearing Journal Width 0.941-0.949 in
Crankshaft Main Journal Diameter 2.6473-2.6483 in

Respective specs for the 3400
Connecting Rod Journal Diameter 1.9987-1.9994 in
Crankshaft Main Journal Diameter 2.6473-2.6483 in

I'm having a hard time finding the journal widths for the 3400... but since the 3500 crank needs different rods it doesn't matter anymore. But hey, its was the only part of my engine I have not found a stronger replacment for so it's worth consideration.

[Kohburn]

what is the connecting rod length on the 3.5 vs the dohc?

thats very very interesting news..

[Fierobsessed]

5.9" as opposed to the 5.7... But Im still looking for better rods then that too... Since small journal SBC rods are not compatible with the large journal 3500 crank. The journals are bigger then a Big block too. So far, I have only found Pontiac V8's had 2.25" journals, but all used 6.625" rods, so thats out of the question. Im still looking. The stock 3500 rods seem to be the only match so far... but Im not giving up on rods yet.

[v6h.o.]

If you check the pushrod performance forum I posted specs on the 3500 crank in the one thread forged cranks.



2.8L crank, 3500 crank and a 3400(3100) crank lined up side by side.

[Fierobsessed]

Bingo! Found compatible rods, The best part is they are already a set of 6. the only thing they need is some narrowing. from .930 in to 0.863-0.869 in. I don't know how this will effect the bearings themselves, but Im betting with simple machine work the 3.5's bearings will be useable.

The rods are meant for a Chevy 4.3 and they are 5.7" CTC.

http://www.nolimitmotorsport.com/prod/CRS570063D

Hey, and I was feeling all smart and stuff about the 3500 crank idea.

Anyway, Going by appearance alone, It almost looks like the reluctor is bigger and can probably be turned off with a lathe and re machined with just the 7 notches we want.

But hey, thanks for the info and pics, you rock.

[Kohburn]

hmm might not have enough material to turn the ring down smooth before notching -

but please do find out - that crank, forged pistons, and a o-ringed head and my 3.4 turbo could be making some sick power

[v6h.o.]

yes the rods on the 3500 are the same as any 60v6 up untill now for width's still the same .859 inch width.

However, Don't mean to rain on your parade, But Like GM already said this crank does not fit into the old blocks due to the excessive size of the rod ends in the old blocks.

Doesnt mean it might not fit without some massaging to the block but... you never know.

Maybe I should fit my 3500 crank and rods into my 3400 block and see..

[bszopi]

Not to rain on your parade even more, but here is a thread from Oct 1, 2003...

http://www.60degreev6.com/index.php?name=PNphpBB2&file=viewtopic&t=4&highlight=3500+crank

So its not something that was just stumbled upon, but it is a subject coming back to life recently...

[Kohburn]

didn't even think about clearance up top.. would explain the rods being .2" longer - had to move the cylinders up away from the crank more

edit: but what about grinding the connecting rod journals down to match the earlier rods? the crank is still stronger than the old one that way

[Fierobsessed]

I am curious about the clearance issues too, I mean Its not even .2 its more like .125" >I I< That much more larger swing room required unless I missed something? And that can only be at the points around the rod big end since the rod movment has not changed at all. Its too bad I dont have a 3.1 or 3.4 laying around that I can spin and look for the clearance issues. I can't imagine a clearance issue that can't just be "dealt" with like every SBC 383 owner does: Little notch here little notch there. I guess I just have to get my hands on one and try it out if no one else beats me to it

Don't you hate when you come up with a great idea, and get that "dude, where have you been? We have already done that years ago."

So, the recipe is still forming. If this crank works out, I will have a forged steel crank (it is "FORGED" right?) Forged 4340 Steel H beam rods, cross bolted mains from a 3100. Custom forged pistons. And I am still working on how I will use the structural oil pan or construct some sort of a main girdle/oil managment piece on the bottom. It's nice to be able to freely fabricate things out of aluminum stock. If you haven't realized by now. I want the bottom end to withstand ANYTHING I can toss at it, short of melting the pistons. Once the recipe is complete, it can be duplicated relativly cheeply since all the research has been done. I love to research, even if it means coming to the same ideas people have thaught about long ago. Case in point.

In the end, I wonder how much can I get out of the 3.4 DOHC. I see people getting good power out of them without even opening the crank case, except to weld in the turbo oil drain bung So imagine the possibilities of a well overbuilt bottom end with those 24 valve heads with there monstrous ports, and a decent amount of boost. If your mouth doesn't water at the thaught... then you don't belong here in a forum dedicated to engines.

So, who will be the first to throw a 2500 crank in a 3500, make a rev happy screamer? I suppose thats been thaught of too Would have a huge R/S ratio.

didn't even think about clearance up top.. would explain the rods being .2" longer - had to move the cylinders up away from the crank more

Actually the block still has a 8.818 deck height, the cylenders went nowhere. But on the 3900 however... they moved outward? I read it somewhere.

[v6h.o.]

I have that 2.8L crank sitting there that was going to go in my 3400, probably still will. with the 2.8 crank and 3500 block it works out to 3.2L's.

[your_I.D.]

Couldn't you just grind the rod journal down to a smaller size. Like SBC. that would give you more clearance and open up a plethora of rod's available.

Or like kohburn said

[SappySE107]

Im pretty sure thats what JBP does, only when you grind it down you can offset it as well. I believe they claim a 3.8 stroker out of a 3400 bore with their offset ground forged crank.

[v6h.o.]

I posted pics and whatnot of the full 3500 if you want in a thread in the pushrod area:

http://www.60degreev6.com/index.php?name=PNphpBB2&file=viewtopic&t=6783

[Scott205]

any idea what a indy or other major engine manufacture would charge for carving one out of solid block of steel or aluminum would run?