Engine Replacement Project for Disco 1

Knightspirit

Well-known member
Sep 22, 2019
145
42
Mount Shasta, CA
I know there are other threads regarding this - but I thought I would start a new one rather than bumping an old one forward.

I am planning on rebuilding a replacement engine for my Disco 1 in the background while still driving my existing rig. I am currently at about 165K and the usual knocking - which I am pretty sure is the liner slipping (louder warmed up and at idle). I imagine I can still get 20 or 30K more out of it before it blows.

I have been looking for the unicorn red block 4.6 from a P38 to buy - but no luck so far (please PM me if you know of one for sale). I see several complete 4.0 blocks on Ebay (GEMS) that I can buy with shipping for about $1000 so that would be another option. I understand that the 4.0 can be upgraded to the 4.6, so that might be the easiest way to go. What I am unclear about is what gets changed in that process - is it the crank or the rods?

I have not ever rebuilt an engine - so this will be a bit of a project for me. Most of the hard stuff is of course done at the machine shop - so really it is an assembly issue, so I will need to make sure I have the right tools and techniques at my disposal. I'll need some advice from this forum for sure! I am hoping that I can come in under $4K all said and done.

I would be interested to hear from anyone who has done this - particularly the 4.0 to 4.6 upgrade - and any advice that you might have before I pull the trigger on buying the donor motor.
 

Lake_Bueller

Well-known member
Aug 11, 2004
2,029
45
53
Beloit, WI
If you decide to go with a 4.6 and want to do a complete rebuild, I have a complete kit from Turner Engineering in the UK with top hat liners, new pistons & rings, crank, etc, etc, etc.
 

Knightspirit

Well-known member
Sep 22, 2019
145
42
Mount Shasta, CA
If you decide to go with a 4.6 and want to do a complete rebuild, I have a complete kit from Turner Engineering in the UK with top hat liners, new pistons & rings, crank, etc, etc, etc.
PM me on the price!

I would prefer to go with a 4.6 but I haven't seen any that were GEMS available. Advantage of using the 4.0 is I can get one pretty cheap, and can use the pistons for a little more compression - but I am concerned that I might not be able to source a 4.6 crank and rods easily. Could maybe get them from UK...
 

terryjm1

Well-known member
Jan 23, 2011
523
69
I found this thread - it has exactly what I wanted to find out - and should be a great resource for anyone wanting to do this:


Looks like a 4.0 donor motor is the way to go.
Wow, what a great thread! Thanks for sharing! I’m going to do the almost exact rebuild, but will not be changing the liners as I have a relatively low mileage 4.0 that is in good shape that came in a 96 D1 rusty parts rig. I was even lucky enough to be given a 4.6 crankshaft still in standard spec with the connecting rods which also measured/weighed within standard specification.