The V8 Owners Forum -

Hello!
This is my first post so please be kind.
I have an MGB with a 4.6L Rover V8
Just had a rolling road session (Tuesday)which showed 314ft lb torque and 282hp
It was running very lean at 20:1 which is a bit worrying.
Carb is Edelbrock 500 with base calibration.
Now the guy with the rolling road (brand new Dastek dynamometer) hooked up a pipe from his box of tricks to one of the vacuum ports and as a result concluded that the carb was a bit on the small side and suggested I get a bigger carb.
So now Ive ordered a 600 Edelbrock and calibration kit from V8 tuner and was wondering if anyone else was using one and what would be the best rod/jet combination for starters.
I do a lot of track days and have had a high rev missfire and susspect that this could be caused by the leanness (is that a word?).
Just wondering have I done the right thing or should I have stuck with the 500.

Thanks
Mark

I'll be interested in this one as my new engine is a 4.6 and I was going to continue using my Weber 500 as I thought it should be ok with the right jets and needles.

First time ive ever heard an edelbrock running lean. Do the plugs confirm this?
A 500 should be plenty for a 4.6

Mebbe I'm missing something but can't see how a bigger carb (potentially more air) would help with a lean condition. People run the 600 on 350's, the 500 is meant to suit a 5 litre-ish.

Sorry I didnt mean that the bigger carb would sort the lean problem.
It was the suction through the vacuum pipe.
Apparently the line on the graph from the dyno should have been straight, indicating that the carb couldnt draw enough air if that makes sense.

Mark

Would it even run at 20:1?

An edelbrock 500 should be ample for all but the most mental of rover v8's. And, 285bhp is a stonker of a power figure! What else has been done to it?

Hey sorry to drag this off-topic - is your 4.6 standard or modified in anyway (barring the obvious )

Haha, good timing with that question ihatesissycars

Great minds

Its a 4.6 with top hat liners, 4.0L pistons, Big valve heads DJE, 10.8:1 CR, piper 285, MGRV8 manifolds, Mallory Magnetic dizzy. port matched edelbrock performer inlet.
Edelbrock 600 should arrive tomorrow.

Mark

I used to use an edelbrock 500 a while back now and although it is an exellent carb for road use it could not cope with demands for racing it would lean out badly no matter what jetting it had , i changed to a holley 600 and problem solved.

Thanks Darren
I will fit the 600 and set it up the best I can.
A return to the same rolling road should be interesting.
Will post results.

Mark

mgbloke wrote:Thanks Darren
I will fit the 600 and set it up the best I can.
A return to the same rolling road should be interesting.
Will post results.

Mark

Please do.
I assume the the flap in front of the secondaries was opening up - you would need to look down the bores whilst at full throttle to see.

Eliot wrote:

mgbloke wrote:Thanks Darren
I will fit the 600 and set it up the best I can.
A return to the same rolling road should be interesting.
Will post results.

Mark

Please do.
I assume the the flap in front of the secondaries was opening up - you would need to look down the bores whilst at full throttle to see.

Funny that you should mention the flap, I just took mine off last night and took the car for a spin. I thought that the flap was too crude to do any good but I was wrong. It is possible to drive the car without the flap but if you floor it below 3k is bogs down to the point that the engine actually quit running! (Rv8 3.t with an Edlebrock 500)

I've put the flap back now
Pete

I have checked that the secondaries are opening fully and the flap seems free enough but I never actually checked the flaps operation while running.
From the dyno figures I cant see this being a problem.
Horsepower was about what I was expecting with torque surprisingly higher than expected.
Air fuel ratio started at 15 and got worse as the revs went up.
With this setup it actually drove very well on the road with no sign of hesitation, smooth as could be.
The torqu curve was all over the place apparently due to it leaning out.
Torque peaked at 3581rpm while hp peaked at 5430rpm
Not expecting much in the way of more power with the bigger carb but as it is regularly driven flat out on the track I need to get it set up right.

Mark

full throttle under load and 17 to one fuel ratio and leaning out further to 20 to one I would expect it to be melting plug electrodes and pinking like the proverbial not running "smooth but the torque curve all over the place".
Infact as was said before with rover heads and 20 to 1 will it run at all? the HE heads on the 80s jag would run on medium throttle and load with 19 to 20 to 1 but that was a special megga swirl leanburn design with very high compression and ultra fast burn ultra compact head.
Are you sure of this guys AFR meter????
Sorry but I am a little suspect of the numbers, not necessarily the symptoms and the cure.
Mike