4.6 short block with 3.9 stuff

[stuee]

Just browsing the net and saw discovery automotive has 4.6l short blocks for $4200 (curretn special). Having read previous posts it sounds like it is possible to transfer the rest of the equipment from a 3.9l motor (in this case out of a 97 disco) with a mild head job ( not that type ) and computer tune thrown in for good measurment.

If this is the case why were we quoted $9-10 000 by another rover specialist when we were originally enquiring about this upgrade. Is it that lots of things that are generally worn need replacement or what?

I am still leaning towards a gen 3 conv but if this could be had for $6g (with most of the work done by myself) then it may be a cheaper option.

[Soundsgood]

I am running a 4.6 from Graham Cooper with 3.5 heads and carbies. Goes well and was a reasonably easy conversion. You van do a lot more if you want to spend the money.
Bruce

[Soundsgood]

I am running a 4.6 from Graham Cooper with 3.5 heads and carbies. Goes well and was a reasonably easy conversion. You van do a lot more if you want to spend the money.
Bruce

[PeterO]

I am running a 4.6 short from ULR melb $4,000 did the rest myself had heads shaved 50 thou to try to recoup some compresion. The shorts come in with no cam so its a short short but all your other 3.9 stuff bolts on you will need to buy or make a crank spacer to get you balancer to do up. Also be sure to buy new head bolts or a stud kit. You can chose which cam you want to run and then decide if you are going to have your chip upgraded or swich to an aftermarket ECU.
Do a search for RPI Engineering www.rpiv8.com lots of good info there.
Cheers Peter

[stuee]

When I searched the forum I found a link to the RPI website faq page on conversions using 4.6 short blocks. I am still trying to figure out if its worth the money. You really need a custom computer ($2g up, not fond of megasquirt), a new cam ($250 second hand???)etc etc. I am starting to see now where it all adds up. I will have to look into it further, but now I've researched it more it doesn't look that good anymore.

[PeterO]

Just a chip upgrade at around $600 will give you very good preformance without spending the $3 to 6k for a motec or something equally as expensive. This is all I did to mine and I am very happy with it. Its an auto and the preformance is greatly improved on the 3.9. I drove it for a short while without the ECU upgrade and can honestly say the chip made a big difference. If you want a race car then Motec would be the go but my guess is you want a reliable 4X4 with more tourqe than revs so a chip upgrade would be enough. The RPI site is great for all the how to bits but you must remember they are building Morgan race motors and the like so some of their stuff is a bit to much aimed at big revs and light cars.
Also I would recommend you have your heads tidied up and the guides machined to take decent valve stem seals. Cost me $400 with the shave.
Never buy a secondhand cam a new one is about that price. Buy rover lifters not holden and check out your rockers and shafts, if worn replace.
Decisions decisions best of luck with it
Peter

[justinC]

Stuee,
I agree with peterO, and as regards local ECU upgrades, try Bruce Davis Performance on (02) 96791179.
I have them supply all my ECU's for 14cux and TD5, excellent mapping for australian pump fuels. UK has more choice at the pump than us, and better quality.
I had a 3.9 disco remapped recently by them, and even after the new high lift cam and head work/ port matching etc, the single biggest improvement was the ECU upgrade. Made it idle and start better, run cooler, I can dial in more advance, and fuel bill stayed roughly the same, except the owner likes to fang it more now....= more fuel!
$650.00 fitted and set up is a pretty good deal for local product, with the addition of a good high flow exhaust and port matched manifolds, it is reasonably cheap to get good performance from a 3.9
JC