The V8 Owners Forum -

Hi All,
I'm nearly finished locating the donor parts to fit a Thor injection system on my 3.5 P6. After much thought the mega squirt v3 looks the best option to drive it. Has anyone on here done the conversion ( whether in a P6 or not)? I had thought about just putting a 4.0 lump in it but the engine came from a very late P6 ( VIP engine) and only has 50k on it at the most so seems a shame not to use it.
Thanks

Is the reason you chose the Thor bonnet clearance? Dunno how well it will work on a 3.5 - has it ever been tried? Can't think of any problems using MS with Thor - but you will need at least an MS2 to drive the stepper motor idle.

Would be well worth fitting later heads too.

Dave,
I had bought a spare setup for a LPG conversion on the 4.6 Range Rover we have so it seemed logical to just use that as it looks a better set up all round over the GEMS. Now you mention it, it'll sit lower than the GEMS plenum as well. It also gives you the opportunity to get over Kickdown cable and throttle cable attachment at the engine, as the Throttle body has a double cam for throttle and cruise control. I've been speaking to Phil at ExtraEFI about the MS3, as I'd like it to go fully sequential and there's still a few more bits I need to get. I'm going to stick with a 3.9 cam, but I'll have to get that in and run up before taking the carbs off - don't fancy losing a cam lobe on a couple of attempts to get the MS working. As you said - the EFI heads are well worth it - and they're off having guides and a skim. The plumbing will be interesting as the throttle heater and thermostat are two points in mind at the moment. The P38 has a 'remote' thermostat, so I should be able to connect it and 'copy/ modify' the Range Rovers water layout. One of the things that is puzzling me though is whether or not there's a proper vacuum take off on the Thor plenum - (the small one I know is available but I'll use that for the MAP sensor as I did for the LPG conversion). The P38 has a pump for the brake and so no servo. I could use an electric vacuum Pump, but that would have to be on a switch to ensure it keeps the vacuum available, and of course a tank. So if there is a vacuum take off point that will help greatly. All in all a lot of work but the cars getting a full restoration anyway so I might as well do it all at the same time. Hopefully start early next year. So if anyone out there has done this conversion ... all suggestions or advice will be gratefully received
Thanks

I have a complete Thor EFI set-up here which I was going to try on my SD1 (with MS) - but got put off the idea by others saying I'd loose the top end poke. Seems it was designed for bottom end on a 4x4. The Vitesse unit loves to rev.

They do look pretty, though.

It would be good to see some dyno figures using Thor against Rover inlet on the same engine. Rather than just rely on hearsay.

Wouldn't bother with the throttle heater.

As for vacuum anywhere after the throttle plate should do. Looking at this photo, the lefthand side (opposite end to tb) looks like there's some convenient taps, probably emissions stuff.


the fuel rail is "dead headed" i.e. no return to the tank. I've read that you can fit a hot-wire rail (and therefore fuel pressure regulator) on the thor.

As Eliot says, there are some places you can pull a vac from.

The major drawback with the Thor manifold is access to injectors / rocker covers. There ain't any without removing it!

Chris.

Dave, Eliot - thanks for your replies;
I don't know about the top end performance of the thor, but if you give it enough on the go pedal it moves the Range Rover on pretty smartly, personally I've always found the SU's run out of steam at the top end so anything extra will be a bonus, when you think the engine was de-tuned for our market. as for adding to the torque - great news - I'll look forward to that, along with the proper fueling of each cylinder (':D')
ref the Plenum picture: I looked at these too, one is quite loose ( the bottom one in your picture) it seems to be just a plug in a rubber grommet, the one above it is for the engine breather hose, and interestingly there's a small outlet ( plugged, just below this) which accepts the MAP sensor hose nicely. So looks like a definite area to try. You're correct he lack of return for the fuel will have to be addressed, I figured that I could tee off the main fuel supply with a smaller diameter hose to run back to the tank as a fuel return? If that won't do it then I could just fit a pressure reg. The fuel rail is a nice bit of work and as both the plenum and inlet manifold for the GEMS and Thor are different castings - I might have a problem fitting a different rail. I can't see that the bosch injectors will be too stressed looking after a litre smaller engine?
Thanks again
Joe

Chris,
Oh yes the rocker covers - guaranteed to start leaking about 6 months after the build and, as you know, can't get to the inner two bolts to give em a tweak.
I had a problem with condensation that I traced to the LH ( as you look at the front of the engine) R/Cover , the plastic shuttle in the breather hose/ rocker cover was completely bunged up with burnt oil.
But I've also had to get hold of P38 rocker covers to make sure I can connect all the breather stuff up.
Thanks

As a matter of interest, is your P6 a low compression one?
My very first RV8 was a high compression P6 - and that certainly wasn't lacking at the top end.

However, I wasn't comparing the Thor to SUs - but to the earlier plenum set-up as used by the Lucas EFI, etc.

Hi Dave,
from memory I think its either 9.25 or 9.35:1, can't be sure without getting out the gunk and having a clean up first!
I figure I may loose a bit with the composite head gaskets but may gain a bit with the new heads? That's maths and never my strong point. I'm quite looking forward to it as its been ages since I skint my knuckles in a P6 engine bay - now if I can just finish working on the camper.....

Basically, half way through the P6 run they reduced the CR as 100 octane petrol was being phased out - and mags of the day commented on how much performance was lost. It wasn't until the SD1 engine revisions they got (most) of it back. Be interesting to get a good version of each on a test bench, as I suspect the factory wasn't too honest about the respective figures. I looked after several P6 3500 for friends at that time, and they all showed a big difference in performance between high and low compression versions.
If changing to composite gaskets, you could have the heads planed to retain the original CR - that's what I did with my Vitesse unit.

ThatV8sound wrote:. You're correct he lack of return for the fuel will have to be addressed, I figured that I could tee off the main fuel supply with a smaller diameter hose to run back to the tank as a fuel return?Joe

You cant just return the fuel like a carb setup - you need to fit a pressure regulator on the return. It maintains a pressure in the rail by bleading fuel back to the tank.

If you could get a hose tail welded into the thor rail you could use any aftermarket FPR - btw they are also typically referenced to manifold vacuum too.

I'm not sure about the Thor, but some use electronic pump control to do the pressure regulation - rather than a return system with vacuum regulator.

Thanks for the info,
I'll have to trawl through the RAVE manual to see what the 4.0 and 4.6 thor fueling set ups are with regard to the pressure, I know there's definitely not a return line on the Range Rover.
As for the heads, I don't know what the amount will be taken off to get them flat - minimal I expect ( hope). I have asked that the inlet manifold has the equivalent taken off so that it sits properly in the valley, the inlet manifold gaskets are not the best fit around the inlet tracts. Talking of gaskets - what do you think are the best composite make for the 3.5? I was going to get some from real steel, but in the interim, the set I have here don't have the water jacket seal which is on the elring ones I got for the 4.6?

Dave,
you've got me thinking about compression ratios, just check this logic for me will you?
Original and present CR is 9.25:1 with tin gasket and 36cc heads.
When I put on the later heads, with a composite gasket, the composite gasket will make up for the reduced head volume (more or less according to the articles on here), so as no other measurements have changed ( head skim is just to get em flat - so minimal), my CR may be the same or slightly higher?
Or have I missed the point
Thanks