cams and computer upgrades?

[adam big lad]

Hi i'm currently rebuilding a 3.5i and i've had work done to the heads now it's time to do the cam and computer anyone have any info on these where to get done and what to get done??? Thanks adam

[bigbad]

easy upgrade is the 3.9 cam but really the options are endless. Lots of info on here http://www.v-8.org.uk/forum/index.php

[adam big lad]

hi thanks for the reply i've got a 3.9i motor which i took out because i had too many problems with it is there any thing else i can take of it and put on the 3.5??

[bigbad]

what sort of problems, engine problems or efi problems? I am just about to fit a 3.9 to my 110, but will be keeping the strombergs and LPG

[adam big lad]

the 3.9i is not that good of a engine i've done two sets of head gaskets and now i think it's cracked the block i'v done a bit of research on rover engine's and the 3.9 and 4.6 aren't that good of a engine the 3.5 is a much stronger engine

[RRV839]

i think that you will find, and i havnt 100% confirmed this, but the 3.5, 3.9 and 4.2 are 'virtually' all the same engine, the heads are very similar if not the same on the earlier v-belt 3.9's the later having different ports and valves i beleive, , the blocks are nearly the same the main difference is the crankshaft and a few other sublte differences, they all use lucas electronics and are of the same basic design that they were back in the 60's when buick designed it, with the addition of electonics etc and other minor upgrades.

The 4.6 is quite a different engine using block liners to strengthen the block after boring out for capacity increase and have differnt main bearing caps etc the heads, are ery similar to the older ones with valve and port changes also the injection system is different but still lucas on earlier model then later bosch and the block was changed again and new intake manifolds were put on (thor type) the 4.0 are a pretty reliable unit more similar to a 4.6 then the earlier engines but without many of the problems associated with a 4.6.

As for the cams, if you do the reaserch you can get casm made with whatever lift and duration you want, or if you want one out of the box, look around over in the uk, the postage isnt too much and they have alot more support for them over there.

As for computer, powerchip do an easy plug in chip which boost power fairly nicely (brings a std 3.9 up to 150kw) for around $600 i think, or you can look into aftermarket systems which usually start at around $1000 depending on wether you want a basic one and if it comes with a loom and if you want, fan control, aircon control and other outputs to run things but take into account you need a dyno tune which can be up to $300

[Hobie18]

When you previously replaced the head gaskets did you have the block tested for hardness. I had the 3.9 rebuilt late last year due to a head gasket issue. When we got the heads off, the mechanic mentioned that they had been machined incorrectly which means that the gasket had previously been done. What we found was that the block had lost its hardness so that when the new gasket was fitted by the previous owner it was just a matter of time until the threads let go and the gasket went again - about 18months after I bought it.

The block had to be re heat treated twice to get it back to the correct hardness. All liners were replaced as 5 were slipping, new pistons, upgraded torque cam etc. We didn't modify the heads because at that stage we thought it was going to be a simple rebuild although they were fully rebuild as many of the valves weren't sealing. The rebuilt motor is going nicely. Haven't touched the computer.....yet

[bigbad]

An experienced engine builder on one of the UK forums stated that most of the engines that head gaskets failed on were using stretch bolts which had lost there elasticity and were not retaining the heads, he recommends either the earlier type bolts or preferably a stud kit.

The later 4.0 is the same capacity as the 3.9 but has a stronger crank and crossbolted mains, the block is the same as the 4.6.

[RangingRover]

The 4.6 is quite a different engine using block liners to strengthen the block after boring out for capacity increase

Please explain what you mean here? All rover V8s have steel liners inserted into the bore, if they didn't the motor would be lucky to last half an hour (alloy block).

And as commented by Hobie18, 3.9s have been known to drop liners too. Agreed 4.6s have a history of doing it often - although very often the liner hasn't actually dropped, simply the aluminium between the back of the liner and the water jacket goes porous, and water work its way up between the liner and block, then into the cylinder. This is more prevalent in 4.6s due to the larger bore leaving less material in this area, but I have seen a 3.9 snap the nose off a starter motor after being hydraulically locked by a leaking liner.