3500 crank

[Joseph Upson]

If it has the wide seem line it's steel even if you can't find the last 4 digits of the steel crank part number on the crank snout. I don't remember what they are but they're posted. More importantly they probably only used the cast iron crank in the early engines as I have only seen one in a picture on this forum side by side with the steel version and it had the characteristic thin seam line on the front throw.

I recall the debate I had some time ago here after noting that my crank looked funny compared to what I was used to a cast crank looking like. I called GM parts direct and was given two part numbers for the 3500 crank the difference being the cost and the shipping weight of the crank, my numbers matched the heavier more expensive crank and along with the pictures confirmed it was the steel version. It proved that just because GM didn't say it, it doesn't mean it isn't so.

Forged or not, it should be considerably stronger than the iron crank and lets not forget the benefit of the larger diameter throws for increased bearing load distribution and further stiffening of the crank to make high rpm safer. The fuel cutoff at least for the 3900 was bumped up to about 6400 rpm and thats with a heavier reciprocating mass. I don't see any cause for concern with the crank.

[ForcedFirebird]

7484 is the designation number on the snout.

[ForcedFirebird]

Also notice the 7484 crank is almost completely machined, whereas the older 981 cranks are almost completely cast (except in the journal areas). Even this process would make it much stronger even if it was iron because it is closer to being "billet" - or machined out of a large piece of stock, rather then being molded to shape.

[34blazer]

I took a bunch of pics... here:

http://www.3500z.com/Gallery/main.php?g2_itemId=741&g2_page=2

http://www.3500z.com/Gallery/main.php?g2_itemId=741&g2_page=3

the crank is just sitting in the block, if you need any pics of different spots just let me know.

from where i sit, its cast. thanks dave

[ForcedFirebird]

from where i sit, its cast. thanks dave

The casting markas are the same as a forged GM crank, it's hard to tell until someone can talk to them and get a solid answer.


Either way it appears to be much better built then the predessesor.

[ForcedFirebird]

from where i sit, its cast. thanks dave

If your judging by the sound, all the literature I can find on the subject says a steel crank will ring and a nodular iron will thud. Just because the outside appears to be cast doesn't mean it is, look close at your forged 60* rods - they appear to be cast.

[34blazer]

If your judging by the sound, all the literater I can find on the subject says a steel crank will ring and a nodular iron will thud. Just because the outside appears to be cast doesn't mean it is, look close at your forged 60* rods - they appear to be cast.

in that case hopefully someone can verify with a definite answer. because im unsure im gonna do some research on how to actually determine the testing. i just dont want to go out and buy 2 or 3 3500 cranks to find out they are cast, because id like to have a crank to support my hp goals.

[Joseph Upson]

in that case hopefully someone can verify with a definite answer. because im unsure im gonna do some research on how to actually determine the testing. i just dont want to go out and buy 2 or 3 3500 cranks to find out they are cast, because id like to have a crank to support my hp goals.

I don't see what all the fuss is about, all of the 3900 engines get a steel crankshaft, the difference between the cast 3500 crank and the steel 3500 crank is clear and distinctive visually especially when it comes to the seam on the throw. The 3500 steel crank also carries the same part number as at least the 06 3900 steel crank and to my knowledge the only reason the part number may have changed is because the press on crank trigger wheel changed in 07 I believe on at least some vehicles.

My 04 and 05 3500 engines both had steel cranks with the last 4 digits of the steel crank part number visible by removing the balancer bolt with the balancer in place. My 3900 crank does not have the number in that location but it is identical to the steel 3500 crank in the picture I posted. I highly doubt your concern is warranted, just make sure the crank looks like the one posted in the picture and you can't go wrong.

[34blazer]

i understand what you are implying, my main concern is will it hold up to 600 hp? if it was forged id feel alot better, and possibly raise the bar a little more. i asked a few times in the past if anyone pushed the 3x00 past the 500hp threshold and didnt get much of a response. so this is new territory to me. when i had my buick, i wasnt hard to find out that the factory turbo 3.8 could handle well into the 500hp range. when i build mine i still bought a forged crank to bolster the bottom end, which my goal was in the 600hp range as well. so thats why im asking, but i dont want to create a ruckus.

[Joseph Upson]

i understand what you are implying, my main concern is will it hold up to 600 hp? if it was forged id feel alot better, and possibly raise the bar a little more. i asked a few times in the past if anyone pushed the 3x00 past the 500hp threshold and didnt get much of a response. so this is new territory to me. when i had my buick, i wasnt hard to find out that the factory turbo 3.8 could handle well into the 500hp range. when i build mine i still bought a forged crank to bolster the bottom end, which my goal was in the 600hp range as well. so thats why im asking, but i dont want to create a ruckus.

Probably the most productive route to getting a definitive answer would be to take the crank or at least the specs to a reputable machine shop preferably someone with race knowledge and have them assess it. I doubt however given the quality the crank has over stock iron 3800 cranks that it should be a concern.

I believe your efforts would be better placed in the main caps because the 60 degree angle will allow for more stress on them than the 90 degree block of the 3.8 would.

[34blazer]

Probably the most productive route to getting a definitive answer would be to take the crank or at least the specs to a reputable machine shop preferably someone with race knowledge and have them assess it. I doubt however given the quality the crank has over stock iron 3800 cranks that it should be a concern.

I believe your efforts would be better placed in the main caps because the 60 degree angle will allow for more stress on them than the 90 degree block of the 3.8 would.

with cross-bolted mains, im pretty confident they can handle some serious power. if curtis made 470 some hp on his stock mains and crank, im pretty sure the 3x00 bottom end can handle above and beyond that number.

[TurboGTU]

If you dont cut it down..the larger jurnals will help with intergrity. RPM will kill a crank not just raw power. Lightening the rotating mass can help too.

I say it can hadle the power.

[Superdave]

bringing this back from the dead..

i found this article: http://www.carcraft.com/techarticles...to/index1.html


also asked some local guys and they seem to agree that the 7484 crank is infact forged steel. They said that the parting line gives it away.

[SappySE107]

The parting line was what I was going by. Its wide

[El_Diablo]

thats what i went by when i bought my block, lol