You can type here any text you want

Is this a turbo crank?

Welcome!

By registering with us, you'll be able to discuss, share and private message with other members of our community.

SignUp Now!

fullahotair

Member
Joined
Feb 26, 2002
Messages
940
I see what appears to be rolled fillets on the main journels, but the journels for the connecting rods do not appear to have the rolled fillets or do they?

Thanks for entertaining my dumb question...


n8
 

Attachments

  • DSC02712.JPG
    DSC02712.JPG
    57.4 KB · Views: 338
  • DSC02713.JPG
    DSC02713.JPG
    46.5 KB · Views: 347
Hard to tell in the photos, but if there are not rolled fillets (grooves) in the rod journals, it is an NA crank.
 
The 2nd pic is of the mains, the first is of the rod journels. I can say with some confidence (based on pictures on the net) the main journels appear to have rolled fillets and are far more distinct than the rod journals. The rod journals however are a little harder for me to tell, since i don't have a N/A or Turbo crank to compare against. Do N/A cranks have rolled fillets on the main journals?


Thanks,
Nathyn
 
The 2nd pic is of the mains, the first is of the rod journels. I can say with some confidence (based on pictures on the net) the main journels appear to have rolled fillets and are far more distinct than the rod journals. .........
Was the crank turned?
 
Not certian of that. I can pull the out the mics and check. The engine was rebuilt at some stage in its life, so it is possible and probalby likely.

N8
 
Not certian of that. I can pull the out the mics and check. The engine was rebuilt at some stage in its life, so it is possible and probalby likely.

N8

Are the bearings stamped/marked?
 
.... The rod journals however are a little harder for me to tell, since i don't have a N/A or Turbo crank to compare against. Do N/A cranks have rolled fillets on the main journals? Thanks,
Nathyn

Best way to check the rod journals for rolled fillets is just use your fingernail. If no indented groove, it is a NOT a turbo crank, or the journal has been turned enough to remove it.
 
I looked at the bearings, and it appears the rod journals were turned .010, and the main bearings appear unmolested, althought i would need to mic that to be certain.

Thanks for all the feedback!

Nathyn
 
Rod Journals:

I know this is an old post; but I've turned cranks 010, and wouldn't have know they were turbo cranks except that's what I started with. The fillets are not very deep; although the compression should impart strength far into the journal. Also; I've never seen a crank that only had the mains rolled.

It's probably a turbo crank.

Joe
 
I had a turbo and na crank side by side about a month ago and the one you have pictured is a na crank for sure. I have two na cranks anyone want to buy one?
 
It looks like a NA crank. Both the turbo and NA cranks have rolled mains but only the 3.8 turbo crank and 4.1 cranks had the rolled mains and rods. Have both sitting in my shop.
 
would somebody be so kind as too take a good pic of an NA & turbo crank side by side for all to see as a handy future reference on this subject.
 
The rod journals (in the above picture) may have been turned and brought the surface level with the fillets, especially if they were "light" fillets to begin with. I have seen some turbo cranks that clean up almost smooth at .010" and some that could have gone .040" before ever hitting the bottom of the "gutter" (aka rolled fillets) If you are not building a ten second race car, a NA crank is fine. If you tune the engine correctly, I think a NA crank would even work in the tens just fine. But, with the cost of forged cranks as low as they are, why risk it?
Now....what is the best rolled fillet? A deep one or a shallow one? If it is deep, wouldn't it potentially impact the molecules more and in theory cause cracks at the sub molecular level? It is, after all nodular iron. Is that why some people join the DOTC club? (Drive Over The Crank Club):confused: Do we need to measure the gutter depth before choosing a crank? Do we need to rockwell the gutter, too? Do we...............:p ;)
 
Back
Top