Carb tuning - RTFM!

[cliffords]

Craig

I have a vacuum Gage , from my motorcycle engine days.
It is the manometer type one with slots for four cylinders, but you could easily use on just one carb take off.

you are welcome to borrow if you wish.

[craggle]

Cheers David.

I may come and have a look at that sometime over the weekend if you are about.

Craig.

[wilf]

I wonder if RTFM'ing will catch on?

[cobra351w]

Hi,

I thought i'd let you all know of my woes with a Edelbrock Performer 600CFM on my 351W in my Sumo Mk3.

Basically no matter what jetting/needle combination I tried , it would not get past a huge bog at WOT when the secondaries cut in, about 3500rpm in any gear!!

I bought an Innnovate technologies Fuel/Air ratio meter,so I could see what was going on in the headers, this indicated the mixture going from very rich to a very lean, back to a very rich condition through the transient phase

Idle and cruise I could get perfect mixture,

I must have tried every spring /needle/jet combo, ensuring that I did minimal change at a time, still could not crack it.

After several weeks I gave up, looking at other possible causes such as ignition timing/valve timing & vacuum leaks ...all made no diiference or was set correctly.

So I bit the bullet, bought a Holley Street Avenger, standard jetting.

Now this may sound odd, but the engine note sounded completely different at tickover, louder and sharper, on first run out, the engine just took off all the way to 5000rpm, admittedly not perfect, a few flat spots, the mixture was lean throughout, so I upped the main from 65 to 68, and the secondary from 68 to 72...plus changed the vacuum diaphram spring for a lighter one.........now it just frightens me!!


Anybody wanna buy a used Edelbrock 600, I have a complete set of jets as well.!!

[Hawk289FIA]

I hope you won't mind me tagging on a question to the thread, but I'm having problems with my Holley carb as the mixture is running very rich after an engine rebuild (not by me! I don't have the skills for that), but it's been dialled down as low as it can. The garage suggested it goes on a rolling road to have a tune and probably change the jets. Does anyone know of a reliable tuner you would recommend?

Many thanks

Marcus

[Warren]

I think theres a chap called Cheng at Thunder Road Cars, down your way, could be Essex though but well respected.

Have quick search or google him.

Warren

[Terry GD007]

Hi
I have an Edlebrock, I think 1407, that was supplied with my RPI 4.0L Rover engine. This worked OK straight out of the box with the set up that RPI supplies except for one problem and that is a back jarring hesitation when coming back on the throttle after being on the over run with throttle closed. I bought a set of springs, rods and jets and read the manual from end to end and found the original set up to be the best. There is no flat spots in the entire rev range and the transition from primaries to secondarys is imperceptible. I have changed the accelerator pump from one end of the pivot point to the other with no positive effect. The carb sits on an offenhausen manifold with 180 port which I know is not the best but I need the height. There is no vac advance used in my set up. I have lived with this for nearly four years now and have found that the only reduction of the effect is by raising the tick over to 1000rpm. Any ideas?
Terry

[apearce]

excellent thread this, and im tempted to dive in using Wilf's advice, but are we re-inventing the wheel a bit ? I mean, there mst be someone who does this for a living and already owns a vac guage, gas analyser and a box full of jets n rods.... someone like that could sort out my carb which is new out of box and not right at all in an hour or two and i'd save his (or her...?) labour costs in a weeks fuel. Does anyone know somebody like this within reasonable reach of Birmingham ? I know rolling roads but that's not the answer - i want somebody with edelbrock/weber carb experience. Said guy could also probably get my timing right.

Does anybody know such a person nr brum ?

Many thanks, Andrew 07525 041140

[awolbuddy]

Its running ok but there is a slight hesitation when i bury the right peddle and on the over run i get some big bangs and if i'm very lucky, nice flames. I think it needs looking at by someone who knows what they are doing annd i'm in Amersham, Bucks. Can anyone point me in the direction of someone local??
PS very first time i've posted something here,hope i have got it right.

[BenBaron]

Originally Posted by awolbuddy

Its running ok but there is a slight hesitation when i bury the right peddle and on the over run i get some big bangs and if i'm very lucky, nice flames. I think it needs looking at by someone who knows what they are doing annd i'm in Amersham, Bucks. Can anyone point me in the direction of someone local??
PS very first time i've posted something here,hope i have got it right.

I get the bangs also, sounds like it comes from 1 side. 2 possibilitys as far as I can tell, too rich or I have manifold leak...Im gunna check out both when I hav 5 mins