SLROC Forum

Needing help and advice with a standard 3.5 V8 running on an Edelbrock carb. Engine starts and runs but lumpy, doesn't always like to restart, set the timing as per a V8 but no idea if it is right or wrong with this set up. Does  anybody run a similar set up or could help with getting this to behave nicely? Thanks

The timing should be ok as factory (6 degrees) at least to get it running. Is the dizzy in good condition? Bob weights attached? Vac advance free?

After that do you know that the needles are correct for the engine? If its an edelbrock 500 its quite a big carb for rovers, even for a 4.6

Engine had a Mallory ignition system fitted along with the Edelebrock when I extracted it from the very crusty and rusty Defender it had previously been fitted to. Before removing it I did get it fired up ( hadn't moved in more than ten years ) and it sounded fine then. The only difference I have made is that the fuel pump is external and not in the tank as before have also fitted a pressure regulator.

hi buddie,

I run an edelbrock 500 cfm on my 4.6 they are generally very reliable carbs as once the correct jetting has been properly installed all you have to adjust is the idle mixture and speed, I would check the carb over visually first before attempting to open it up have you blocked off the vacuum ports? when looking at the carb from the front of the car you will see 3 ports you should have your dizzy vacuum advance on the left one and the other two blocked off unless your centre diff is a vacuum operated effort in which case use the right hand port for that. when running the engine try spraying wd40 or damp start around it to see if it has any traceable vacuum leaks ie, carb to manifold or the airhorn (top half of the carb) to carb body, if no joy there or any obvious draw through gaskets take of the air horn and check the float chambers are clear of debris and that the float height is correct 7/16" from memory is about right. The fuel pressure should never exceed 5 or 6 PSI so not a great deal of pressure is actually required you could check your lines and filters are clear, maybe worth checking the stand pipe on the tank? a quick guide would be to remove the fuel hose at the carb and run the pump if there is plenty fuel look no further, if it ran well in the previous vehicle its probably something simple, have you looked at your ignition for stray arcing around the cap or coil connections? try starting it in the dark and opening the bonnet difficult starting and rough idle could be something really simple like that and not even carb related......anyhows I've waffled enough hope this is of some help.

Stu. 

Ok I will try your suggestions, tank, pump, fuel lines and pressure regulator are all new so there shouldn't be any debris in those parts. Vacuum take off is the far left one looking at the carb, everything else is blanked off. Will try setting the timing again with a strobe and possibly lift the top of the carb next.

Set the timing with a strobe today, idle speed was a liitle bit erratic so not easy. However it starts easier and will restart better. However the plot thickens as with the engine running at 1200rpm adjusting the idle speed to slow it down causes the revs to start to fall away even after the slightest adjustment has been made then it conks out. My guess would be fueling but I have reached an area of inadequte knowledge know so I need more advice please

Hi buddie,

Have you checked over the ignition system? As I mentioned previously stray arcing in the ignition can cause roughness and erratic running aswell as difficulty starting, have a look at all connections on you coil and your distributer damaged plug leads or king lead, a crack in the distributer cap? Or damaged rotor arm? Is it on points or electronic? Did you have a look under the bonnet whilst running it in the dark? Sometimes the stray arcing through a damaged ignition component can be very hard to see in day light. Hope this helps 

Stu

So latest update. Ran the engin in the dark and there doesn't appear to be an wayward sparks. Set the timing with a strobe, took the carb off and blew it through with a high pressure airline and checked everything else. Engine starts and runs well from cold but as soon as it warms through it will no re-start happily. A couple of drops of petrol into the carb and it fires up. Earlier this afternoon it was running fine and fairly smoothly although still very reluctant to restart. Went back just now to have another attempt to make run it better and once it was warmed through the idle speed is very erratic slow then fast, no amount of twiddling with carb settings makes any difference. At this point the coil is to hot to touch. It's a newish coil but does this sound like it is causing some of the problems?
A quick run down of the ignition / fuel system is

New alloy tank
Red top facet fuel pump
Fuel regulator set to 6psi
Edelbrock carb ( already on the engine)
Mallory distributor ( already on the engine)
Ignition set to 6 btdc
Coil and ballast resistor both replaced during the build
Standard 3.5 V8

Any advice or help  will be greatly appreciated as I just need it to work!

Hi,
Couple of thoughts. 6 psi is more than enough fuel pressure for a Rover V8, but doubt that excessive fuel pressure is the root cause.
Idling fast and then slow when warm does sound like an air leak?
If you can set the timing to just short of pinking on full advance under load ....... on my last V8 this was about 36 to 38 deg BTDC ...... a figure I got when I phoned Real Steel http://www.realsteel.co.uk/

As an aside does your engine have wee pipes coming from the exhaust manifold that lead back to the air intake? If so GEMM 4x4 have the blanking plugs that let you bin it. I had it and HT leads just rested on all the metal pipes. Not good.

Hope you progress.
Harry

Thanks for your reply. No pipes anywhere aside from the vacum advance for the dizzy and will have another look at the timing. Checked everything  out and can't find somewhere that it could be leaking air.
At the moment I'm wondering if part of the problem is the coil with it being to hot to touch. However that doesn't explain why it won't start when hot but will do with a drop of petrol fired down the carb.

As a long distance, keyboard expert I would suspect a fuelling/air leak issue. The fact that it requires extra fuel down its throat when warm suggests it is running lean, which is 'covered up' by the choke when cold starting.

Mebbe, perhaps ? 

Hi
The could should be warm ......... not too hot to touch. Have you the correct coil for the ballast resistor and is it all wired correctly? Now That I think about it, I had a hot coil problem and it was a 4cyl one not a v8 one (DLB101 rather than DLB198). I had converted to electronic, ditched the ballast resistor and after a false start got the right coil.

Thanks again for replies. Just wondering if I should re-route the fuelline as I'm wondering if it is fuel vapourising when it gets hot? Presently it comes into the engine bay along the bulkhead into the pressure regulator and across towards the carb and above the exhaust manifold. That might explain it starting with petrol lobbed down the carb. Also look at changing the coil as it is getting to hot to touch. It is wired up correctly and is apparently the correct one but I'm running out of things to try

You can get hot fuel vapourisation problems from the ethanol in modern fuels.  If so, a return loop back to the tank as in an injected engine might help.

So I spent some time re-checking the timing and adjusting the carbs, engine was running good and even re-starting when hot, I was a happy bunny Then it all went pear shaped again and started to run rough, no adjustments made any difference until I replaced the new coil ( which had been getting to hot to touch) with the one that was on the donor vehicle when I got it.  After that it ran smoothly and without problem apart from a slight flat spot which all but went when I reset the timing. Job done then..............................but not quite. Engine was running really nicely this morning in the workshop but then started running rough again and the coil once  again was to hot to touch.

What coil should I run? The ignition is a Mallory distributor with points and near the coil I have a ballast resistor fitted. Any advice as ever gratefully recieved.