weber/edelbrock 500 very poor fuel consumption

[V8cortina]

I have just fitted a rover 3.5 V8 in a mk5 cortina, the engine is rebuilt to stock spec and is fitted with an edelbrock performer manifold and weber/edelbrock 500 carb with 10" edelbrock air cleaner.

fuel consumption is dire to say the least, does anyone know what size rods and jets would sort this out? I've set the base idle mixture and backed off the accelerator pump to the outermost hole, I need to get a jet kit (haven't yet) but if I can find out which sizes will be best suited to a stock engine then maybe i can save on buying the whole kit of stuff that I won't use.

My last V8 powered cortina had again a stock 3.5 but with a holley carb and I was getting near 30mpg, this one is nearer 10 and thats just cruising at 60 down the motorway.

I don't mind sacrificing a bit of performance, this car is my daily driver and I drive 80 miles a day to work and back so it needs to be good(ish) on fuel.

Please help me before I put the pinto back in!!!!!

[Eliot]

Give chris crane at rpi a call - he should know one of the top of his head.
All edelbrock carbs have a default factory calibration of "rich as hell". have you taken a look at you plugs..

[katanaman]

There are already quite a few topics relating to this, here is a couple.

http://www.v-8.org.uk/forum/viewtopic.php?t=829

http://www.v-8.org.uk/forum/viewtopic.php?t=631

I am sure if you have a search there will be more.

[V8cortina]

have you taken a look at you plugs..

no but i expect they'll be as sooty as hell, what sort of mpg is realistic with one of these carbs fitted to a stock 3.5 in a car as light as a cortina?

I bought it because of all the sales blurb about it being the best around for economy and performance and that it comes "calibrated for a stock 3.5" yeah right!, should have stuck with a holley!!!!

[katanaman]

whoever told you it came jetted for a 3.5 lied unless they have specifically re-jetted it as it comes out the box for something more like a ford 302. No carb comes jetted from the maker for any specific engine as that's impossible. Even someone else's settings could be out for your specific engine so some tuning is always going to be needed.
Is it a better carb than a holley 390? I would say yes but I guess it all comes down to personal preference and application. If both a holley and a webber are jetted properly you should get better low down performance from the 500 and the 500 has a higher BHP ceiling although a 3.5 would be unlikely to get near this on either of the carbs.

[V8cortina]

I've just emailed rpi, hopefully they can send me the correct rod and jet sizes

[V8cortina]

Give chris crane at rpi a call - he should know one of the top of his head.
All edelbrock carbs have a default factory calibration of "rich as hell"

Chris emailed me back and said its more than likely an ignition problem, I'm not convinced as I don't get this problem with a holley

[sidecar]

Give chris crane at rpi a call - he should know one of the top of his head.
All edelbrock carbs have a default factory calibration of "rich as hell"

Chris emailed me back and said its more than likely an ignition problem, I'm not convinced as I don't get this problem with a holley

Ignition and carb both need to be setup to get the best MPG but I agree with you that it most likely your carb. My 3.5 is in a replica cobra which is fairly light but not very aero dynamic, I can get may 18-20 mpg, it was A LOT worse before I leaned up the carb. The other thing is the you will knacker your bores, rings and oil if you leave it running rich.

RPI's settings were way too lean for my motor.

The carb is easy to work on...give it a go!

Regards,

Pete

[Eliot]

Give chris crane at rpi a call - he should know one of the top of his head.
All edelbrock carbs have a default factory calibration of "rich as hell"

Chris emailed me back and said its more than likely an ignition problem, I'm not convinced as I don't get this problem with a holley

He's probably not in the mood for answering questions - as bad mpg isn't an ignition problem. No reason not to ensure everything is sound though.

Get a rod/jet kit. You can probably go 1 or 2 stages leaner on the low/mid settings and probably 1 stage on wot and still be pretty safe.

I dont think you will see 30mpg (unless its on the back of an AA truck) but 18-20 seems fair.

[ian.stewart]

May be the carb is too big for your application, even a 390cfm is probably too big for a 3.5 unless you are using above 6000rpm.
You may be having fuel atomisation problems associated low air speed thru the carb, then, oh its not responding, and pumping more fuel in with the accellerator pump trying to get the engine to react????

[sidecar]

May be the carb is too big for your application, even a 390cfm is probably too big for a 3.5 unless you are using above 6000rpm.
You may be having fuel atomisation problems associated low air speed thru the carb, then, oh its not responding, and pumping more fuel in with the accellerator pump trying to get the engine to react????

Some people do reckon the to webber 500 is too big but the primary chokes are smaller than the primaries on a holley 390 which is the carb that the same people suggest fitting. The secondaries on the webber are mechanical but do have a sort of vacuum flap so if the motor can't create the required vacuum in the manifold they won't be fully opened.

I've not worked on a holley but from what I've read they are a lot more tricky than the webber. At the end of the day if you want MPG don't fit a V8! All JMHO!

Regards,

Pete

[ihatesissycars]

I had an Edelbrock 500 carb in mine on Rpi jetting and it was rich as branson to begin with! It will need fine tweeking but with a calibrationkit you should be able to get it very good. A wideband lamba meter would be a good investment to get it spot on.

The 500 carb is a suitable size for the rover v8, even the 3.5 as it has very small primaries and on my 3.9 it could take full throttle from 1200rpm in 5th without problem.

[Alley Kat]

See Paul B's post, he gave info about the parts RPI sent. You may be able to save cash and get them separately; the std Edelbrock kit is £55 and doesn't include some of those parts anyway. Think Paul said £18 delivered or something.
I may have a std kit for sale but prob best get the stuff Paul had anyway.

As said the 500 has smaller primaries than the 390, mine gave better mpg round town on my 3.9. On a mixed run London crawly cr*p and 90+ cruising it gave 19mpg. Like Gav I found it very tractable, top gear pootling to flat out.

[V8cortina]

May be the carb is too big for your application, even a 390cfm is probably too big for a 3.5 unless you are using above 6000rpm.
You may be having fuel atomisation problems associated low air speed thru the carb, then, oh its not responding, and pumping more fuel in with the accellerator pump trying to get the engine to react????

it perfoms fine and goes like stink, no flat spots or hesitation but I should get more than 10mpg when cruising @ 60mph with very very light throttle, all I'm doing is taking the slack out of the throttle cable, pretty much, and its drinking fuel, you can also smell the "richness" with the window down, definately not right.

With a holley 390 on a stock 3.5 years ago, i was getting 20-25mpg and good performance (in a cortina), the reason i chose the weber is because of all the sales blurb stating that you get the best of both worlds with it (performance and economy)

[katanaman]

I think going by the comments above everybody else agrees with the sales blurb. Get it set up right and all will be good.