Budget for a 3.9 rebuild

Leadvagas

Well-known member
Jun 10, 2010
232
2
Leadville CO
Just looking for thoughts on a project. I am getting ready to go through a 3.9, planning on $2K plus or minus. I already have heads that are ready to go, so no cost there, just short block. Back ground, 95 D1, sat for the better part of 6 years ran when parked but was weak. Truck shows 200K miles, bought it for storage as a tow away with a melted down T-case. Replaced the case and drove it home, and off and on for the next couple years. I plan on a few up grades, cam, dizzy (Pertronix or HEI). I plan on using the truck as a back up to my diesel D1. Also I am not putting many labor dollars into this, I will pull, assemble, install etc.
 

wrldky

Well-known member
Apr 21, 2004
410
7
Raleigh, NC
Just finished a rebuild on my 4.0. It cost $3500. However I put $1500.00 in flanged liners and the machine work to have them done. Plus I had a machine shop reassemble the engine for $700. I took advantage of the $$ to pound price and sourced a lot of stuff overseas.
 

ozscott

Well-known member
Mate I just rebuilt the top end of my 4.0 D2 4.6. Attention to detail to ensure mating head and block surfaces are even and clean. I had heads crack detected. All ok. I had new valve stem seals installed. Mine was a very low k motor so no other head work required. I got a set of ARP studs for the 4.0/4.6 LR motor (ie where the coarse thread goes fully into the block and bottoms out...dont worry about old threads where they pulled out as those kits were for the Buick motors). Dont follow intructions in box for 4 increments up to 100 ft lbs of torque on the nuts. The updated instructions online at ARP are for 70 pounds. I did 3 even increments up to 75 pounds and used Elring Klinger composite (read stock) gaskets. I used Three Bond RTV Red silicon in a very small amount on valley gasket ends (rubber) and on rocker cover gaskets (rubber). I used Loctite 515 flange sealer (very small amount painted on with stiff brush) on the steel gasket that goes between intake manifold and upper plenum. I flushed block whilst there. I cleaned off piston tops carefully and vacumed out - do not blow with compressed air. In mine there was zero evidence of liner shift but there was a head gasket leak from each end where the water jackets are. I did an oil flush and new oil after the re-build, but if your bottom end has been reconditioned then you can just use assembly fluid and and fresh oil I suppose.

Cheers
 

ozscott

Well-known member
Oh...dont forget to be very careful with inserting steel bolts into alloy threads...and if needs be use a tap or better still thread chaser to clean out threads for head studs/bolts. Then use degreaser and blow out and then finish the hole cleaning with CRC brake cleaner and blow out so no residue.

Cheers
 

jymmiejamz

Well-known member
Dec 5, 2004
6,008
361
35
Los Angeles, Ca
Mate I just rebuilt the top end of my 4.0 D2 4.6. Attention to detail to ensure mating head and block surfaces are even and clean. I had heads crack detected. All ok. I had new valve stem seals installed. Mine was a very low k motor so no other head work required. I got a set of ARP studs for the 4.0/4.6 LR motor (ie where the coarse thread goes fully into the block and bottoms out...dont worry about old threads where they pulled out as those kits were for the Buick motors). Dont follow intructions in box for 4 increments up to 100 ft lbs of torque on the nuts. The updated instructions online at ARP are for 70 pounds. I did 3 even increments up to 75 pounds and used Elring Klinger composite (read stock) gaskets. I used Three Bond RTV Red silicon in a very small amount on valley gasket ends (rubber) and on rocker cover gaskets (rubber). I used Loctite 515 flange sealer (very small amount painted on with stiff brush) on the steel gasket that goes between intake manifold and upper plenum. I flushed block whilst there. I cleaned off piston tops carefully and vacumed out - do not blow with compressed air. In mine there was zero evidence of liner shift but there was a head gasket leak from each end where the water jackets are. I did an oil flush and new oil after the re-build, but if your bottom end has been reconditioned then you can just use assembly fluid and and fresh oil I suppose.

Cheers

So basically you did a head gasket job, and not a rebuild of the top end.
 

ozscott

Well-known member
Yep another helpful post mate. The OP must be getting a lot out of this. You drop a little gem or advice (or a turd depending on how you look at it) and move on.

To the OP do your own research but if you jump on Aulro there is a lot of good advice and good success with studs versus stretch bolts. Torque to yield bolts are probably fine on good castings with a factory machine putting them in all at the same time with precise torque thenot precise 90 plus 90 turning. However for older motors or motors with suspect casting thicknees near bolt holes studs allow more reliable builds and no torsional twist on the hole. They also offer more precise torquing specs given the fine thread that the torque is applied to.

Cheers