v8 with su carbs. gets to approx half throttle then dies

Hi there landy lovers,have just converted my old diesel 90 to a v8 and it wont run properly. half throttle then it dies out?
Here is the list of whats been done.
1 Removed v8 from range rover,was efi but changed inlet manifold and fitted su carbs to eliminate all the horid black boxes
2Fitted all new o sils and gaskets etc,etc + rpi convertion kit
3Brought new facet fuel pump 4-5 psi model,Fitted
4Both carbs checked and cleaned,by a profesional
5Fuel filters in place
6 all electrics seem to run fine,new coil fitted.and if it was electrical surley it would'nt run at all?
7The engine was preassure tested before fitting it and all work was under taken by a professional.He works on the movie sets and done most enginering work for band of brothers,007,judge dred + loads more, this is why i paniced when he scratched his head.
This is my last hope for some kinda diagnosis or it goes to the mincer.

sounds like the carbs are not correctly set, are dash pots filled with oil

yes dash pots are filled.
im baffled.this has been fustrating me for nearly 4 months now and ive not even got a spare vehicle.
the carbs and inlet manifold came from a donor wich had been sat for approx 4 yrs but my helper said he took them apart and everything looked clean and tidy+he reset them to factory settings

sounds like carb issue, but ignition modules do play up, where are you

Could be the wrong needles in the carbs, I'll have a look whet they should be and you can check.
If you give me the number etc off the tags on the carbs I'll tell you what needles are in them and what they are off.

Or the needles may not be seated propperly in the pistons or they could be running weak.
With SU carbs the mixture can be fine at say 3000 and way too weak at 4000 or vice versa depending on the profile of the needles.
pipes might be on the carbs wrong. Make sure the crank breather pipes are on or blocked off.

Just checked me manual and it only goes up to 1987 for Range Rover V8. That lists the 3.5 V8 as having a single HIF44 SU which is only inch and three quarters
Would check the needles though, cheap to buy richer ones and easy to fit and instant difference.

Im in west sussex,will sort profile now.As for numbers i will have a look tomorrow and post it.
Thank you so much for the next lead in my problem

batfink001 said:

Im in west sussex,will sort profile now.As for numbers i will have a look tomorrow and post it.
Thank you so much for the next lead in my problem

Click to expand...

Sorry to misslead you but my manual dont cover Land Rover after 1987 so I cant find the info.
V8 engines sup a lot of fuel and if you have weak needles in it will show. With it being a hybrid engine now you will have to experiment.
The Rover P6 V8s used BAK, or BBV, or BEP or a KO needle in the carbs. I dont know which was the richest though.
You could get hold of two old needles and doctor them.
You can either use emery paper to thin them down or file a flat on the back of the needle. Bit at a time mind as you cant put it back once filed off.
Consider the needle to have three stages for simplicity, the top third is tickover, the middle third is cruising and the bottom third acceleration.
As yours runs ok at idle and cruise then file a bit off the bottom third and see how it goes trying a bit at a time till it goes best.
I used to do this on my race Minis, you can really tell the difference if the needle was too thick, it lets more fuel in.
Either get two new needles and experiment with the old ones or vice versa, Burlen Fuels site will give you more information.

have yu spoken to RPI?

Ive never played with carbs before,will i be baffled with it if i take them apart?:doh:
Also ive just brought su workshop manual. hopeing this will enlighten me to how they work.

Many thanks for the info. i will have a look tomorrow
Have spoke to rpi this morn holly said its running rich and only needs adjustment, not sure how to do this properly and without a gauge to balance it,it makes it harder.

contact jimattrill and look here

At a complete and utter guess Fuel pump issue should run quite a volume for full throttle any issues there then it would die out but again utter guess you need to find out if its ignition fuel then go from there. does it start easily after dying? is there too much fuel or not enough? Or ignition dying under load? many questions

It has been known for non mechanics to plumb up the fuel lines wrongly aswell giving similar issues as described. A guy was driving a series through Dunstable on his way to france he moved there he has the same probs a few years back

Your carbs should be like this.
No 7 is the mixture screw and it screws in to richen and out to weaken , simples. If the engine speeds up then you are going the right way, if the revs drop then turn it the other way with regular little blips on the throttle to clear it's throat.
No 6 should be connected to the crankcase breather or blocked off, the other two are fuel in and overflow pipe.

Thank you so much people
Fuel pump is brandnew and i will be replacing the fuel lines on wed.
Also wil make sure hoses are corectly fitted tom.

Looks like ive alot to look at tomorrow no worries been signed of for a week.