Jeep Wrangler Forum banner
  • Hey everyone! Enter your ride HERE to be a part of JUNE's Ride of the Month Challenge!

1 - 5 of 5 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter · #1 ·
Well I am wondering if anyone may have an idea as to why or even that the 3.8l had cast iron cam, crank and piston rods? I am doing my first ever engine rebuild and can not believe what I see. Could this be part of the reason that it gets dismissal gas mileage? I know that its a jeep, so I do not expect to see 30+ mpg's. So at this point I am going to replace all 3 for sure even with the low budget.
 

·
Registered
Joined
·
664 Posts
What did you expect them to be made out of ?

Cast iron is cheap, that's why they used it. The only reason to go to forged steel is if your building for a LOT of HP, the weight savings on a cast to forged crank is negligible (350 chevy cast crank 54lbs, forged 51lbs) and at a cost of $300 more. Rods and cam are going to be even less of a weight saving. The only other thing you could do (if they even make them) is goto aluminum rods but they are normally strictly race parts as they work harden very quickly and are thrown out after a few passes at the dragstrip. You could probably buy a forged steel crank and have it lightened but for the extra cost it wouldn't be worth it.

The weight savings over cost involved will still only give you a few 10ths (if that) mpg extra. It's a Jeep, they have the aerodynamics of a brick, lots of driveline drag and you may be pushing an oversized tire, lower gears, extra weight with bumpers and a winch.

Even NASCAR still uses forged rods, crank and cam.
 

·
Registered
Joined
·
664 Posts
If I'm not mistaken, the cam should be steel...either cast, then machined, or forged, then machined.

Pat
Not sure on the jeep, but factory run of the mill small block chevy's still used cast iron cams and cranks, I've broken a few of them.
 

·
Registered
Joined
·
664 Posts
Double post.
 
1 - 5 of 5 Posts
Top