Rover V8 with weber 500 problems

[shiner]

Hi all,

I put the weber 500 carb and manifold on my 3.5 SD1 V8 about a year ago now and never got it running correctly. I changed/downgraded the primary needle and jet to a recommended one by RPI Engineering (i think) but still coud not get it running smoothly, and gave up on it until now.

It idles ok but as soon as I pull away the power just dissapears. I screwed the mixture screws right in and it killed the engine but if I turn them fully out, the engine still runs (a bit fast as expected) but doesn't die.

I thought that the engine should die at both ends of the mixture screw and the mid point between them is the correct place, is this right, if so would that mean I got the wrong needle/jets?

I remember reading that it could be the dizzy and/or HT leads - my dizzy is the standard one from the SD1 but put some new HT leads and dizzy cap in.

I did not upgrade the fuel pump, which was used on the twin SU's. I did not think this was the problem due to there always being fuel in the filter but maybe the pressure is not right?

I changed the weber 500 back to the original SU's to make sure it was not somrthing else as I had changed the head gaskets previuosly, but it ran smoothly, so assuming it is to do with the Weber 500 setup.

Also i have not changed the timing as it worked with the SU setup but would changing the carb effect the timing?

Sorry about long post but thought I should put everything in...

Thanks for the help in advance,

Martin

[DaveEFI]

Not an expert on your carb, but on most of this type the mixture screw only effects the idle mixture.
If you have the correct jets as specified for this engine it should at least run - if not perfectly. Do you know what was the main jet size you fitted?

[CastleMGBV8]

Martin,

The mixture screw should be approx 1 3/4 turns out from fully closed.

Do you have the handbook, if not you can download from the Edelbrock site.

The carb does need properly setting up but it is quite simple, the float level need to be set correctly, they are often way out from straight out of the box.

Rods and jets I used on my 3.5 engine with stage one heads and Real steel hurricane cam, 9.8/1 compression.

Primary rods, 1441 (062 x 052) & Jets 1421 (080)

The main jet on the secondary may need reducing but will only affect running at wide open throttle. you could try 092 jets.

Fuel pump. ideally you want a pump to provide max 5.5psi the standard SU pump is only approx 3 psi. this will also only really affect wide throttle openings buit if the carb goes too lean it can damage the engine.

Is the engine otherwise standard and what air filter are you using?

Kevin.

[kiwicar]

If it runs OK with the SUs but not with the 4 barrel then it is very unlikley to be the electrical system. Some basic checks (I am not familier with this particular carb but follow the basic principles on which they work)
1/ Check the float levels, if you havent set them yourself they will probably be a mile out.
2/ Check the carb is actually idling on the idle circute, as the idle mixture screw seems to be having little effect then it sounds like it is running on the transition (part throttle) circute reset the idle speed on the butterflys and make sure it isn't in transition (cant remember if this carb has a transition slot or some other arrangment for transition).
3/ make sure any filters you have are clean, I would just replace them as a matter of course. are the carb bowles full of crud?
4/ What is the accelerator pump doing? not enough fuel or drowning the thing?
5/ Check on here for other threads for jets and rods for these carbs, I would not trust the RPI recomendation
6/ have a look at the plugs is it runnng lean or rich at idle? set it right on the idle mixture screw. Do a wide open throttle plug chop test, blat up a hill in 3rd (3000 revs to about 5000 revs over about 20 seconds minimum) switch off the engine and coast to a halt look at the plugs, is it rich or lean?
Best regards
Mike

[shiner]

Thanks for the replies.

I have not set the float levels but have been reading the edelbrock manual and is it a case of just bending the float to a specific position?

The filter is a 14" brand new one, and the carb is brand new

I have not checked the accelerator pump - is this a case of putting the throttle down and confirming fuel is being squirting in?

I'll check the plugs again when I get back.

Thanks for help everyone - i'm not clued up on this area so appreciate the help alot,

Martin

[kiwicar]

Hi
Pretty sure it is a case of bending things until the level is correct.
with the accelerator pump you are looking for fuel being pumped in when the throttle is opened (dont need the engine running.
Fuel filter not air filter, sorry I should have been more specific
good luck.
Mike

[Ian Anderson]

Could you have a big air leak?
Start her up and spray eZi start around all mating surfaces - if the revs rise you're sucking in air and need to seal the leak.

Or have you got all correct connectors of the vacuum? Vac brakes port will suck a lor of air if it is not blocked off or connected.

Likewise if you are connecting the wrong port to to vac advance on the dizzy you'll be getting spark in the wrong place!

Ian

[sidecar]

Blowing my own trumpet here but I've done quite a few RV8 lumps with this carb. A setup that works well for the 3.5 lump is 86 primaries, 67-55 rods, silver springs, secondaries around 83. (This is not a great setup for the 4.6 lumps)

This will give you an AFR of around 14.5:1 on cruise, 12.5:1 during acceleration and 13-13.5:1 at WOT.

Have a read of this....

http://how-to-build-a-pilgrim-sumo.wiki ... ing-system

Under the gumph on fuel pumps

[mgbv8]

As Sidecar Pete Say's!! use those settings as a base for your motor with this carb. If it dies as you open the throttle its going to be lack of petrol. Are you sure the accelerator pump is actually squirting petrol ??

It sounds like lack of fuel in the transition from idle to primaries opening.

[Eliot]

Or have you got all correct connectors of the vacuum? Vac brakes port will suck a lor of air if it is not blocked off or connected.Ian

My exact thoughts too.

[shiner]

The fuel filter is new
I have blocked off the all vac ports including the 'big one in the rear' (sorry could not resist that), apart from the one going to the dizzy
so should be able to rule these out.

I will check the following

accelerator pump is squirting fuel out
spray eZi start to check for leaks

As for the jets and rods, I can't remember what I put in (1441 rods, 1421 jets sound fimiliar). I did not change the secondaries or springs tho.

I will update you when I get back,

Thanks for help

[shiner]

Where can I find some eZi start - I have searched for it but all i get is 'hair rollers' and 'Perodua Myvi 1.3EZi start-up'

[Ian Anderson]

http://www.amazon.co.uk/Holts-Easy-Start-300ml/dp/B000X2CR4W/ref=sr_1_1?ie=UTF8&qid=1289292936&sr=8-1

Is one place - I'm sure Halfords or somilar will also have it - also a good motor factors

I just chose the Yank spelling!


Ian

[shiner]

Thanks, yes I tried it as easy start and can get it locally.

[jefferybond]

I used to run an edelbrock 500 on my 3.5. I found it ran pretty well on the stock jetting, although maybe a little rich on light throttle.

I also tried RPI's recommended jetting, and it was far too lean! Didn't run well at all. I think I left the primary jet as stock (.086"), and changed the needle to lean off the light throttle (maybe changed to a 6752). I left the seconardies alone! I also changed the accelerator pump to work of the smallest shot (ie. the hole nearest the end of the lever)

I might also have changed the step up spring to one stage firmer, so that the 'rich step' of the rod came in a bit earlier - this was a very minor tweak though and could happily live without it.

When you say you unscrewed the idle screws as far as they would go, do you mean you removed them completely? (because that's what happens!). The idle screws mostly just affect idle as you would expect, but they can help if you have a stumble when gently applying the throttle. They wont have much effect though, just a fine tuning tweak.

Jeff