excessive carbon build up in 3.9 rover v8

[jeanmarc]

The engine is out of a 1985 rover sd1 vandum plus. It was bored out and new liners achieving 94mm bores where fitted. The engine was fully rebuilt, the cam was a rc87 and compression ratios 9.35:1. I decided to opt for a edelbrock/weber 500cfm card and manifold.
I normally would have gone for a holley 390 but because of advice went for this carb. the engine did 4000 miles and had 3 oil changes over a period of a year and a half. Fuel cosumption was about 30-33 mpg ( the car is a hawk weighing about 900kg) The heads where removed in order for another pair to be fitted . I discovered alot of carbon build up , normally associated with short run town cars. There was way to much crap in the engine to leave it like that , so I stripped the whole thing cleaned it up had it rehoned new rings where fitted, also swapped the cam for a R.Steel typhoon. The engine is now back together and I have done a further 100 miles. I have changed the oil again and it was black.

This worries me, the engine does not breathe heavily I have checked the timing , static is set to 10 and full mechanical to 38(no pinking) the bob weights are all ok the dizzy is the type with the amp mounted on the dizzy. my carb is jetted 080 on primaries , needles are 6252 and secondary jets are 095, springs are orange. rpi recommend thier own a&r amp instead of the opus unit also the magnecour plug leads. I have oem plug leads(lucas) and the same coil that came out of the vandum plus . I find the spark to be good if I disconnect the coil lead , the spark from the coil will jump an inch and a half to the side of the car, on crank over.

For some reason the car pulls better when its cold then when its hot it tends to go flatish at about 5000 rpm when hot. If I stand next to the car when its running the exhaust gas really sting my eyes and smells rich. I believe either the mixture is way to rich or the fuel is not being burnt properly i.e bad spark.has anyone any expierence with the weber carb? is this combo of jets and needles to rich?

cheers for your help Jean-Marc

[eliot]

Without the Edelbrock jetting sheet to hand, those numbers dont mean a lot to me right now. You can usally go at least 1 or 2 stages leaner in the part/midrange and then do plug chops or purchase/borrow a wideband to dial in the WOT (secondaries) - but I would stick my neck out and suggest you can go at least 1 stage leaner on the secondaries (assuming you are starting from the factory jetting) - the pamphlet will show you the factory settings. Edelbrock tend to ship them rich, I guess to cover themselves.
Worth checking that your floats levels are correct and not emptying themselves down the venturi - again its in the pamphlet.
Take a read through this:
www.telusplanet.net/public/gilesij/Volvord/edelbrock_1.htm
(note, he uses a narrow band lambda - for the money nowadays, you are better of getting a wideband)

Edited to add:
The link above includes the jet/rod combinations, I assume you are using a 1404 (500cfm), the chart for you carb is here: www.telusplanet.net/public/gilesij/Volvord/1404.htm
I cant see your combination on the chart.

>> Edited by eliot on Tuesday 27th December 11:32

[jeanmarc]

thanks for your response, I know the chart and have tried with no luck to find the 080 6252 combo and I know that edelbrock do an 080 primary jet.

My carb is indeed a 1404. Float levels where checked sometime ago and found to be good. I shall read up on the links you sent me.

cheers Marc

[eliot]

It was after learning all about this stuff, that I realised that evertime you make a change in one place in the correct direction it will go in the wrong direction somewhere else. It all depends on how much patience you have. I went EFI very shortly afterwards, very satisfying to change the mixture using a laptop whilst driving along instead of stopping and taking it to bits - even though rod/jet changes on the edlebrock are quite easy.

Have you any idea what your plugs look like?

[jeanmarc]

I have removed them a few times to check and they are normally black(sooted) , I still have to do a proper test concering the plugs.

Marc