MG V8 Conversion help required - 3.5 - Eddy 500 etc

V8Paul · Post by **V8Paul** » Mon Apr 18, 2011 12:59 pm

Hi,

I've done a lot of searching on the forum to try and help with my issue but I can't seem to get any nearer to solving it. I'm not sure if this is the correct section but I wondered if anybody could shed some light for me please...

I'm running a Rover 3.5 with 9.75 pistons, mild cam from reel steel, standard heads.

Ignition wise I did have a mallory dual point with RPI's amplifier unit which I have since swapped for a standard new 3dm8 type with vacumn advance and the side mounted amp. 6v ballast resisted lucas coil. Magnacor leads.

Fuel wise I have a stock replacement solid state pump, inline fuel regulator and the Edelbrock 500. It's been jetted/rodded as per RPI's recoomended spec.

Now the issues...

The car has never really run very well (bit flat) always smelt strongly of unburnt fuel, I took it to RPI on one occassion where they 'set it up' by running it down the road a few times. And this resulted in the fitment of the amp box, some adjustment of the Mallory to stop the advance coming in too early and leaning out the idle mixture. Ran OK.

I took it on a track day a couple of weeks ago and towards the end of the day it developed a hessitation and misfire. More of a stutter and loss of power on cruise and through acceleration although misses heavily as you build the revs up and hold them in neutral. Would still rev up, albeit not smoothly..it also misses on idle

I have checked the plugs which are all evenly coloured, look slightly light deposits. Swapped the leads out and the coil and eventually replaced the mallory with the new stock dizzy. (anything else I should be checking?)

I've now arrived at the fuelling. I have taken the top off the Edelbrock to check the bowls and floats, bowls had some fuel in them and floats were gapped as per eddy manual. Jets didn't look blocked as far as I could see.

What would you guys start checking now? Would love to get it running right as the weather is there now and the car is stuck in the garage!

Any help appreciated..

mgbv8 · Post by **mgbv8** » Mon Apr 18, 2011 5:11 pm

Is the carb new / in good condition?
Are there any petrol stains showing on the side of the carb near the accelerator pump piston?
What type of solid state fuel pump (make and model if you can)
And why a fuel reg? Does this pump do more than 5-6 psi?

Just need some basic background so we can get some idea's together.

Also, do you know what the jets and needles are in the primary and what jets in the secondary?
Also, what colour springs are in the pistons, and have you got the vac advance connected. And if so, which of the two ports have you connected it to?

Perry

Eliot · Post by **Eliot** » Mon Apr 18, 2011 6:14 pm

Invest £200 in a wideband lambda sensor and go and take a few datalogs. Then you will be able to see exactly what is goining on with your fueling - rather than guessing or just spending money on random performance parts/solutions without actually getting any results.
You could of course go down your local dyno and get the same data, but thats going to cost £50 - which is 1/4 of the cost towards a tool that you can use for the rest of your life to diagnose and tune all manner of vehicles.

V8Paul · Post by **V8Paul** » Mon Apr 18, 2011 7:51 pm

Perry,

The carb is two years old (I bought it new) and has only covered say 5k mies.

Maybe some petrol stains collecting in the mainifold, thought it was a touch of oil but it's too golden.

Not sure on the model of fuel pump but i can check, i think it's the MGB Hive pointless. Maybe SU.

Fuel pump just makes that PSI on idle but I can't measure it once i'm driving as only have inline gauge. I was concerned about fuel flow rate but seems strange that it's only just started to misfire/run rough.

Not sure which jets are primary and which are secondary... the metering rods you can remove from the top of the carb were changed to ones supplied by RPI but that was 2 years ago so I can't remember the numbers. The jets are all stock.

Vac advance is connected to the timed port on the left as you look at front of the carb. The pistons have the silver springs fitted (standard).

Not really up for buying a wideband sensor etc, I'd rather get it running right then get it on a rolling road for setuo

CastleMGBV8 · Post by **CastleMGBV8** » Tue Apr 19, 2011 12:13 am

Paul,

When you swapped back to a Lucas 35DLM8 dizzy did you remove the ballast resistor? and you need the lucas DLB198 12v coil, I'm surprised it runs at all with your set up.

You really need to recurve the Lucas dizzy for optimum performance 10 - 12 deg at 1000RPM and all in 34 degrees by 2800-3000 RPM with the vacuum advance disconnected and plugged permanently, the edelbrock provides far too much vacuum for the Lucas dizzy.

RPI must have a very good mark up on Mallory dizzys to keep recommending them.

V8 Tuner and Real Steel are good suppliers with fair prices and no bullshit!!

Kevin.

V8Paul · Post by **V8Paul** » Tue Apr 19, 2011 8:14 am

Ha it's good that you said that!

I was looking at some sites last night and realised the very same thing! I'm still running for some reason a Dlb120 which i believe is a 12v coil?? With a ballast resistor in place.

Ordered a DLB198 last night!!

How do you go about re-curving the Lucas?

Thanks

DaveEFI · Post by **DaveEFI** » Tue Apr 19, 2011 8:30 am

Have you considered going for a a mapped ignition system? I know you've spent out quie a bit on dizzies, but then so did I. Before ended up with EDIS.

V8Paul · Post by **V8Paul** » Tue Apr 19, 2011 9:17 am

I haven't really considered it given that I just wanted to try and keep the car setup fairly simple. I must be able to get reasonable results with my setup?

If I was to start again I'd build the whole thing differently but I think that's for another winter.

sidecar · Post by **sidecar** » Tue Apr 19, 2011 9:39 am

RPI's jet settings for the Edelbrock 500 is rubbish in my opinion!

(Unless they've changed what they recomend recently their setting was far too lean in the cruise mode)

I'd go for 86 primaries, 67-55 rods, 83 secondaries and silver rod springs.

If you let me know what's in your carb now I will punch the figures into my spread sheet, it will tell me how your setup compares to any others.

V8Paul · Post by **V8Paul** » Tue Apr 19, 2011 9:53 am

How can I tell? Will it be stamped into the jets/rods?

CastleMGBV8 · Post by **CastleMGBV8** » Tue Apr 19, 2011 11:05 am

Yes and you need a good magnifying glass.

Don't forget to remove the ballast resistor and disconnect and plug the vacuum advance, you can try setting the initial advance to 10 -12 deg. and the modified curve should improve it further.

Sidecar's (Pete) the man to recommend the correct springs for the dizzy can't remember what I put in now but you can get a spring kit from Real Steel.

Kevin

sidecar · Post by **sidecar** » Tue Apr 19, 2011 12:00 pm

V8Paul wrote:How can I tell? Will it be stamped into the jets/rods?

The rods have a number stamped on them, 62-52, that sort thing, this is the size of the two diameters of the rods in thou-of-an-inch.

The rods can be removed in about 10 seconds and you don't even get any petrol on your hands!

The jets are a little more work, the numbers stamped on them can be really hard to read, for a 500 carb the jets are usually the 3 series, 383 would be a 3 series jet 83 thou-of-an inch in diameter.

Actually I wrote a load of gumph on how these carbs work, it's on my mates wiki, its titled "Setting up an Edelbrock 500 on a Rover V8"

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

V8Paul · Post by **V8Paul** » Tue Apr 19, 2011 9:07 pm

I'm going to remove the jets and check the rods this weekend.

Which springs should I get for the dizzy then? And how do you go about changing them?

sidecar · Post by **sidecar** » Wed Apr 20, 2011 4:44 am

Checkout the gumph that I wrote on the Lucas dizzy....

http://how-to-build-a-pilgrim-sumo.wiki ... by-members

You can get the springs from Real Steel.

V8Paul · Post by **V8Paul** » Mon Apr 25, 2011 9:10 pm

Thanks for all the advice so far...

Biggest issue was the 12v DLB120 coil running a ballast resistor. A well known 'v8 specialists' didn't even pick up on this, Should have been DLB102 and they sold me that combination!

Fitment of DLB198 with the new Lucas dizzy has transformed the car, starts on the button and even when hot only requires minimal cranking (little fuel evap i feel). Car is currently running about 10 degrees static advance on idle.

The carb now really needs to be setup 'properly. I'm going to order a set of step up springs to trial as I think it's running lean on part throttle. Who stocks them in the UK? I've roughly set the idle mixture by ear, better than it was (way too lean) although car still smells of unburnt fuel on idle so may be a little too rich.

Primary Jet and rod combo is the 6252 rods with .080 jets. Springs are standard. Secondary jets are standard. Accel pump set to middle hole.

Car feels flat on acceleration, slightly jerky on part throttle and off idle. Only eventually feels quick once you're flat out in a gear.

What should I look at swapping first?