weber/edelbrock 500 very poor fuel consumption

ihatesissycars · Post by **ihatesissycars** » Wed May 02, 2007 7:33 pm

It could well be the WOT settings are bang on and you need to set the light/part throttle stuff which at the mo is too rich. This is funnily enough how mine started out, changing to a mallory dizzy improved it no end too.

V8cortina · Post by **V8cortina** » Thu May 03, 2007 5:51 pm

ihatesissycars wrote:It could well be the WOT settings are bang on and you need to set the light/part throttle stuff which at the mo is too rich. This is funnily enough how mine started out, changing to a mallory dizzy improved it no end too.

Thats what I'm thinking, at full throttle, it pulls like a train and there is no hesitation, as I don't drive like a looney (all the time!) and the car is a daily driver, I was thinking of leaving the WOT settings as they are and just change cruise calibration, something like .083 jets and 067x049 rods, I need to get a kit and I'll have a play

sidecar · Post by **sidecar** » Thu May 03, 2007 6:58 pm

V8cortina wrote:
ihatesissycars wrote:It could well be the WOT settings are bang on and you need to set the light/part throttle stuff which at the mo is too rich. This is funnily enough how mine started out, changing to a mallory dizzy improved it no end too.
Thats what I'm thinking, at full throttle, it pulls like a train and there is no hesitation, as I don't drive like a looney (all the time!) and the car is a daily driver, I was thinking of leaving the WOT settings as they are and just change cruise calibration, something like .083 jets and 067x049 rods, I need to get a kit and I'll have a play

Hi,

If you use the method that I was shown by V8 Developments you can work out how any combination of jets and needles will compare.

Standard is 86 mains and 65x52 rods.

That gives 21 thou gap on cruise (86-65=21)
and gives 34 thou gap on the step (86-52=34)

A small change in the gap size is noticeable.

83 and 67x49 gives 16 and 34. 16 is very lean, my motor was a flat as fart at 17 cruise. Also I can't see such a needle in the kit that is 67x49, there is one that is 57x49 and one that is 67x55.

I run my motor at 19 and 31, and the difference between 19 cruise and 21 cruise (standard) is noticable in terms of MPG. (I run 86 jets, and 67x55 needle).

You can use needles from other kits e.g. 68x57 part number 1436.

The whole problem is that when you find a good cruise number the power step will be wrong or vice versa....its a bit of a pain but thats life!... I guess that the secondary jet could help out here.

You can probably tell that I spent ages fiddling with my carb!

HTH,

Pete

Paul B · Post by **Paul B** » Fri May 04, 2007 11:13 pm

Alley Kat wrote: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.

All the info is already in the forum, as mentioned above. My motor is a basically stock 3.5 in a brick shaped 1000kg Morris Eight, with auto box, and I got average 25 to the gallon on a recent 350 mile trip to Wheels day and back, two up. Part of that was done at 85-90 on the motorway. I get a fair bit less squirting round town.

Last years Wheels day I had a Weber 38 dgas on an Offy manifold, with home made adaptor, and got 23 mpg.

One thing I did find was I had a leaky needle valve when the carb was put on brand new, which made it guzzle fuel and sooted the plugs to buggery.

Last mod I made was putting the accelerator pump back to the centre hole, as I have a hesitation when you press the throttle at lower rpm. it 'seemed to cure it.

I've also modded my ignition advance so I get a full mechanical 36 degrees from tdc at 3500rpm. Stock gives a piddling 26 degrees.

36 is probably a bit too much really, as I had to tweak it back a bit last week when driving it hard.

JSF55 · Post by **JSF55** » Sat May 05, 2007 1:39 pm

I've just had a good session fiddling with mine, the nearest i can find to ideal is 83 jet with 63-47 needle. i'm temeted to go with sidecars 86 jet 67-5 needle as the top end seems very flat ? i've also found the throttle linkage fouls the guide for the outer sleeve, and the the kickdown doesn't have enough stroke from the carb oooeeerrr.... john

Paul B · Post by **Paul B** » Sat May 05, 2007 3:02 pm

JSF55 wrote:I've just had a good session fiddling with mine, the nearest i can find to ideal is 83 jet with 63-47 needle. i'm temeted to go with sidecars 86 jet 67-5 needle as the top end seems very flat ? i've also found the throttle linkage fouls the guide for the outer sleeve, and the the kickdown doesn't have enough stroke from the carb oooeeerrr.... john

I have mine adjusted so that the secondaries don't open fully at wide open throttle. Don't think it needs it, maybe even benefits by not over carbing it? I'd love to get some performance readings on mine to see just how it is running, how fast etc.

I've done a good few full throttle take offs and it doesn't seem as impressive as it once was, but then I don't have the kick down cable connected so it auto-changes up at 4000 rpm or thereabouts. Apparently with the cable connected it will wind up to 5000+ before shifting. That might be a plan next time I get the chance to play.

JSF55 · Post by **JSF55** » Sat May 05, 2007 3:49 pm

I was thinking of going of the pedal like ur's if i dont think i can get the full stroke on the carb linkage ! i pulled a couple of plugs and for the first time they weren't black !!!

sidecar · Post by **sidecar** » Sat May 05, 2007 8:31 pm

JSF55 wrote:I've just had a good session fiddling with mine, the nearest i can find to ideal is 83 jet with 63-47 needle. i'm temeted to go with sidecars 86 jet 67-5 needle as the top end seems very flat ? i've also found the throttle linkage fouls the guide for the outer sleeve, and the the kickdown doesn't have enough stroke from the carb oooeeerrr.... john

83 with a 47 power step needle is very rich (36). My motor is tuned and runs a typhoon cam but still needed leaning off on cruise and the power step.

This might all change as I've found out that the middle of my baffles have been hammered flat to get the car through the SVA test!. I making a new set of baffles at the moment.

Regards,

Pete

JSF55 · Post by **JSF55** » Sat May 05, 2007 9:39 pm

I got a 60 mile trip tmrw, i'll do a fuel a plug check when i get back, it might give me a much better idea, flat baffles to get through sva ??? new one on me !!

sidecar · Post by **sidecar** » Sat May 05, 2007 10:08 pm

JSF55 wrote:I got a 60 mile trip tmrw, i'll do a fuel a plug check when i get back, it might give me a much better idea, flat baffles to get through sva ??? new one on me !!

Tell me about it!

Here is a post with a pic on the cobra forum:-

http://autos.ninebean.com/cobraclub/vie ... highlight=

JSF55 · Post by **JSF55** » Sat May 05, 2007 10:54 pm

Oh dear, ur not having much luck as an aside, the X pipe or crossover is supposed to reduce exhaust noise as well, but probably damn impossible to do a cobra? john

JSF55 · Post by **JSF55** » Mon May 07, 2007 9:55 pm

Well my trip went fine, fuel was about average 20ish to the gallon, did a few other mods on the car today and decided to pull the carb to change the jets, saves dropping them down the manifold, lol, i decided to check the float levels...... thats where my problem lies, it blackens the plugs on tickover, not on a run, so i think checking these would be well worth it, john

Alley Kat · Post by **Alley Kat** » Mon May 07, 2007 10:03 pm

Float level +/- is quite nice & generous if I remember, they're not anything like as sensitive to float level as the 390.

JSF55 · Post by **JSF55** » Mon May 07, 2007 10:17 pm

Cheers bill, i've reset them right anyway, john

V8cortina · Post by **V8cortina** » Sat May 12, 2007 7:30 pm

Bit of an update, I've got myself a jet and rod kit from rpi.........

Float heights were miles out so I've re-set them, got a fuel pressure gauge on it now and fuel pressure is set to 4 psi, a bit on the low side but performance is not affected, just doing that made a big difference on economy.

as for carb, first of i tried .86 19 31 (0.86 jet 67x55 rod). Performance not affected and getting around 20mpg and engine runs so much better.

Today I fitted .83 jets and put the standard rods back in (65x52), performance still the same!

Will give it a good blast tomorrow and whip some plugs out, if they're nice and tanned then I'll leave it like that, if not I'll go back to 86 19 31

Cheers everyone for the input

I will put a post up and let you all know how i get on.