The V8 Owners Forum -

I have a 4 litre Rover V8 fitted with a Webber 500 carb. I have been unable to get it to idle, it sounds like it is running too rich. Have fitted a vacuum gauge, to the RHS port looking from the front of the car, to try and find the problem but am getting wild fluctuations of the gauge as the engine hunts. Have I connected the gauge to the correct port?
Finished the rebuild 3 years ago and could not solve the problem at that time, then just left it! But now need to get it sorted and the car (TR8) on the road. Any help/advice appreciated.

A correctly functioning gauge will show pulses in the intake, as pulses are occurring there.

So whether or not the problem is gauge related, or the gauge is just reflecting the problems is hard to say.

http://autospeed.com/cms/title_Using-a- ... ticle.html

http://www.secondchancegarage.com/public/186.cfm

You might want to get rid of the vacuum advance if you're running with one. Check for any air leaks around the manifold and carb flanges and also check the brake booster diaphram is not holed.

I'm using silver step up springs on mine and the idle is rock steady at 650rpm.

Still struggling with this problem, now about 3+ years.
Car was MOT`ed this spring and is now on the road but problem persists.
Recap, new short motor (Rover 4l from RPI) with their Piper 270/2 cam. Stage 1 heads, new offenhauser dual port inlet manifold with new Edelbrock 1404 carb. Ignition system is electronic Mallory distributor with Hyfire ignition. Car has done less than 100 miles!!!
Have never been able to get it to idle smoothly, have changed jets and needles, now on 83 jet with 6755 needles, and it is still very rich, plugs black. Now it is on the road it is a pig to drive, surging/jerking on light throttle and is very smokey.
In desperation I have taken it to a local garage who believes that the problem is carb. related and the smokey exhaust is fuel washing the bores and not allowing the oil control rings to function correctly.
I fitted a vacuum gauge to help find the problem but it is all over the place!! So now unsure of whether the fluctuating vacuum is a symptom or cause.
I have tried everything I can think of but still no nearer to finding the problem.
Any further suggestions would be most welcome. It is such a shame as there appears to be plenty of power available when I put my foot down.
Many thanks.
Andy.

Sounds like overfueling ? what pump and regulator you got fitted ?

Fuel pump is a Facet red top mounted below the fuel tank at the rear of the car.

Do not know the make of regulator but have tried it at all settings, even 1 psi all with the same result, so I have now removed it.

Also removed and capped the brake servo connection at the manifold, as suggested by a previous reply, just in case the servo diaphragm was holed causing the fluctuating vacuum. But still no improvement.

Think the next step will be to replace the carb. and manifold with an SD 1 set up, or similar, just to prove it is the carb I have (or not).

Anyone have a set up I could buy/borrow.

Thanks.
Andy.

Check the cam timing.

jenand40 wrote:Still struggling with this problem, now about 3+ years.
Car was MOT`ed this spring and is now on the road but problem persists.
Recap, new short motor (Rover 4l from RPI) with their Piper 270/2 cam. Stage 1 heads, new offenhauser dual port inlet manifold with new Edelbrock 1404 carb. Ignition system is electronic Mallory distributor with Hyfire ignition. Car has done less than 100 miles!!!
Have never been able to get it to idle smoothly, have changed jets and needles, now on 83 jet with 6755 needles, and it is still very rich, plugs black. Now it is on the road it is a pig to drive, surging/jerking on light throttle and is very smokey.
In desperation I have taken it to a local garage who believes that the problem is carb. related and the smokey exhaust is fuel washing the bores and not allowing the oil control rings to function correctly.
I fitted a vacuum gauge to help find the problem but it is all over the place!! So now unsure of whether the fluctuating vacuum is a symptom or cause.
I have tried everything I can think of but still no nearer to finding the problem.
Any further suggestions would be most welcome. It is such a shame as there appears to be plenty of power available when I put my foot down.
Many thanks.
Andy.

Surprised it got through the emissions test of the MOT

I have not checked the cam timing, the cam was fitted to the new short motor by a reputable company in Norfolk, I assumed they would have checked the timing?
But thinking on it now, is it possible to check the timing if the head/valvegear are not in place?

If the cam timing was out how would that produce overfuelling?

What air filter do you have and does it have a dropbase ? How close is the top of the air filter housing to the top of the carb ? Ideally there needs to be at least 7cm, but mine seems to work ok with around 6cm.
I assume the carb still has a choke flap - is this working ok ? I have taken mine off completely. What about the idle screws - how far out are they ? Should be around 2 to 3 turns.
I am using 86 primaries with 68-57 rods. The combination you have is much leaner than that.
In relation to the vacuum, I believe you should use the timed port on the left as you look from the front of the car.

Air filter is a 10" x 2", but I have run it without one and it is still the same.

What is a drop base?

Choke flaps are still in place, it does not require choke just a couple of pumps on the throttle and it starts instantly.

Idle screws do not make a lot of difference if I screw them in too far the engine stops, as you would expect.

Jets and rods have been chosen to reduce the fuelling.

Have tried the left hand port for the vacuum and, again, no difference.

I am determined to get this engine running right.

With regard to valve timing, you can imagine the situation where the inlet valve closes too late, and so the piston pushes some fuel / air mix back out into the inlet and up backwards through the carb. That would royally fsck up the air-flow and hence the carburation.

I would check valve timing with a DTI after taking a rocker cover off.

Chris.

Refit a fuel pressure regulator
Compression check them all.
Thoroughly check the ignition timing and make sure you have a good strong spark at the plugs - all the plugs.
When you get it running temperature check the exhausts - set a water sprayer to jet and a short burst of water at the exhaust outlet about 40mm down on all the manifolds.
Even the most tired worn out poorly tuned and badly serviced RV8 usually idles perfectly.

Drop base means base of filter housing is below top of carb, sometimes necessary for bonnet clearance. Anyway, you have tried running without the filter, so this can't be the problem.
Have you read the Edelbrock carb owners manual ? Runs through a number of things to check such as fuel pressure and float levels. Can be downloaded from the net.
As already suggested, have you checked for air leaks around inlet manifold ?

Fuel regulator has now been refitted.

Compression check completed, nearside all 160, offside 160, 180, 160, 150.
Smoke does seem to be more on the offside exhaust.

Ignition timing is correct and ignition system is 100%.

What is the purpose of spraying water on the exhaust outlets?

Carb float levels adjusted today, they were a bit high but have now been adjusted to the correct level.

Have already checked for air leaks, non found, but would that not give lean mixture?