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MG MGB GT V8 Factory Originals Technical - Appalling mpg
|Just bought a V8 roadster, 3.5 Rover engine with edelbrock carb. Although I do admit to having my foot to the floor on most occassions, I've just posted 12mpg on my first tank of petrol! Surely I should be getting more than that? Do I need to get the engine tuned at all?|
|12 mpg in London rush hour traffic might be a litle high for a standard engine - on the other hand,if yours is tweaked (and the carb not perfectly matched ) 12 might not be such a bad figure.|
Try new air filter, plugs, cap,rotor,coil and new right foot and see what you come up with then
|Once recorded 12mpg on a factory V8 where the whole tank was used pottering round Solihull, typically get 18/19 with mixed driving, 27 on regular motorway commutes.|
Check the timing and operation of the centrifugal and vacuum advance mechanisms, an adjustable timing light and the specs for your dizzie setup makes this easy.
My 4.6 with Holley (not the most economical) turns in 18/20 with mixed driving (traffic jams and motorways). May be worth a rolling road session. If near Woking I can recommend a rolling road.
|Echo most of the others.|
Check the vac advance works, strobe light at idle, suck the tube and make sure the timing advances.
Check cam timing. It has been known for people to time the cam by aligning the keyways not the timing marks.
Mark the front pulley using a protractor (10 degree intervals should do), remove rocker cover and rotate engine till you spot where max lift is and compare to the cam spec. You should get enough info even without a dial gauge as the sprocket teeth are in 16degree increments.
I'm in Putney, so Woking is just a few miles and half a tank down the A3 for me. Would appreciate a recommended rolling road.
Ian Smith of GRL 01483 725759
East side of Woking.
|The American 4-bbl carbs are cool looking but boy do they suck gas if your foot's the least bit heavy. My 4.2 with a Carter 400 gets only around 15 in town and 19 on the highway, and that's if I stay out of the secondaries altogether (easy to see, using an A/F meter, if you're dipping into the 2ndaries). If you avail yourself of the secondaries and accelerator pump, fuhgeddaboudit. A big cam doesn't help either. I can lean the carb out to give just a tad better mileage but if I do that there seem to be a couple of soft spots in the performance band. I've played around to no end with the timing and my conclusion is that the Rover just isn't all that sensitive to timing because it makes little difference performance- or economy-wise. I think the bottom line is, the Rover V8 just loves the taste of gasoline; I also have a Land Rover Discovery 4.0 and the rate at which that thing consumes fuel is only exceeded by the Space Shuttle. The only good thing in all this is that gas is cheap again.|
Gas maybe cheap again in the US, but it certainly isn't over here!
|Not sure I understand correctly.|
If you have an AFR reading and it changes when the secondaries open doesn't that mean your carbs not set up correctly?
What AFR does it read?
I wouldn't of thought you needed the secondaries until high load above 4500rpm.
|You live in London, drive a V8, "my foot to the floor on most occasions," and you want to worry about fuel consumption as well? Come on!|
This thread was discussed between 13/02/2002 and 15/02/2002
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