SU advice for 4.6 ltr

dangermousehouse · Post by **dangermousehouse** » Mon Nov 24, 2008 9:06 pm

Hi everyone,

This is my first post.........so be gentle.

I have recently bought a 1985 range rover fitted with a rebuilt 4.6 ltr rv8.

I'm looking at replacing the stromberg carbs for su's, but not really sure where to start with needle selection.

The engine is fairly standard, with T sleeve liners, 3.5ltr heads, ported air manifold, 1986 efi camshafts (high torque/low profile) and compression ratio of 9.35 to 1.

The rangie is mainly used offroad (outback Queensland) so has to remain simple so I can fix it myself (hence no efi etc etc).

Anyways if anyone can help, that would be great.

Cheers

RoverP6B · Post by **RoverP6B** » Tue Nov 25, 2008 2:19 am

G'day dangermousehouse,

I might be able to help you here.

I have a 4.6 running with twin SU carburettors in my 1974 Rover P6B.

SU HIF6 carburettors will be the ones to go for. In my case, I started with BBW needles, but these proved to be too lean, so they were polished or carved if you prefer to suit.

I can give you a lot more details, so just let me know.

Ron.

minorv8 · Post by **minorv8** » Tue Nov 25, 2008 6:44 am

I believe I used BCA needles with uprated 4,6 engine.

dangermousehouse · Post by **dangermousehouse** » Tue Nov 25, 2008 10:30 am

Hi,

Many thanks for the replies.

P6B, any advice would be really appreciated. Engine is a Bruce Davis (sydney) and I'd like to get the best out of her! Plus, I am planning a trip to Cape York next year, so need to get it right to avoid expensive recovery

MinorV8, did you have to modify the BCA needles?

RoverP6B · Post by **RoverP6B** » Tue Nov 25, 2008 11:50 am

Hello dangermousehouse,

As your 4.6 like mine is a non standard factory issue, no needle will be perfect at all points. For that reason, my needles were custom modified to suit the entire system. Ward at Graeme Cooper Automotive set them up for me, put the Rover on the rolling road, full diagnostic equipment and carved the needles to suit..absolutely brilliant. (There are some pics of my car and engine in the "My car section" of the forum.)

I can tell you that the BCA needles do have a very rich top end, which may well suit your Range Rover, being a much heavier vehicle than my Rover. Given that my BBW needles were carved, they are now closer to BCA than their original specs.

The type of air cleaner and filters that you intend to use along with your exhaust system will also influence the needle selection.

As far as the SU HIF6 carburettors are concerned,...set your float levels to 60 thou. Remove the standard butterflies complete with poppet valves and replace with solid ones. Fit new yellow graded 8oz springs. Being in a Range Rover, use a 20W-50 engine oil in the dashpots.

I use flame traps between each rocker cover and carburettor. The engine breather is situated behind the air cleaner, venting the lifter gallery.

Glad to help where I can,
Ron.

minorv8 · Post by **minorv8** » Tue Nov 25, 2008 3:35 pm

The BCA needles were not modified. I had solid butterfies but don´t recall which springs I had. I have since replaced the SU´s with Edelbrock 500 which give better all round performance.

dangermousehouse · Post by **dangermousehouse** » Tue Nov 25, 2008 5:29 pm

I'd heard the edelbrock 500 was a good set up, but also heard that it wasn't too good offroad (at funny angles). What type of car/truck did you fit this to?

G'day P6B. Thanks again for the info'. Sorry about time delay, I am currently working out in Brazil.

I think I'll have to find a decent tuning guy up here in FNQ, as I have a snorkel etc.

What kind of dizzy would you recommend. I've been reading about the 'pointless' type. Are they the go?

One more thing..........will the SU's fit on the Strommie manifold flanges?

Thanks again

minorv8 · Post by **minorv8** » Wed Nov 26, 2008 5:18 am

My car is a road car so no steep or funny angles like off raod cars face.

SU´s and Strömbergs fit in the same manifold, no problem. Depending on the age of the carbs, you may have to modify the linkage as there has been various linkages throughout the production. I never liked the std linakge so I modified mine to make it smoother. I can take a pic to show how it was done.

As for points vs. pointless, I believe off road people want things to saty basic so good points dizzy is guite good. You tend get more precise and stronger spark at higher revs but I doubt this is an issue with off road use. It is easier to repair a points dizzy in the mud (basically points, condenser and coil) than a dead pointless dizzy.

I use Mallory Unilite which has behaved quite nice. Only issue was a few years ago when the module died in a local cruising event and I had to be towed away. Since then, I have a new spare module with me but naturally have not had issues since

I think any electronic dizzy will do as long as you are prepared to carry a set of spares in case somehting dies.

RoverP6B · Post by **RoverP6B** » Wed Nov 26, 2008 6:52 am

The cast aluminium elbows which run between the carburettors and the air cleaner box are different in both length and diameter for both types of carburettor.

Those for the SU are a larger diameter, allowing better air flow.

I have read that fitting the airfilters directly onto the carburettors delivers less engine power and torque compared to using the elbows with air cannister,..the round one being the best. A good 3" inlet is also necessary to ensure that there is no impedance to air flow for the 4.6.

Ron.