New weber carb in a 258 issue
- Thread starter mkbakker
- Start date
superj
Well-known member
the regulator is set at 30, or 3.0? i would set the fuel pressure on that to around 2 or 2.5. in my weber experience, even 3 lbs was too much.
but since it does 30 seconds and dies, you probably have a vacuum leak with the high running. cap every vacuum line until you get it so it runs on its own and then you can add in the vacuum advance on the distributor and work in the other stuff, from that point on
but since it does 30 seconds and dies, you probably have a vacuum leak with the high running. cap every vacuum line until you get it so it runs on its own and then you can add in the vacuum advance on the distributor and work in the other stuff, from that point on
Bounty__Hunter
Super Moderator
Sell it and get a Motorcraft 2150. Cut your losses.
superj
Well-known member
it could be the cto but you should always redo your time when you do any thing with fuel delivery on a vehicle with a carb. just put a vacuum gauge on the line going to the dist and set it as high as possible by setting your mixture screws and then your distributor. you will have to do it a few times to get it perfect because as you set one, the other changes slightly, but its very easy. once you have it as high as possible, turn the mixture screws back a half inch on the gauge. then your carb will be set as well as possible, and so will your time, for your engine.
Dragon5126
New member
the weber once properly set up is the best bet as it wont flood on steep angles
Dragon5126
New member
An explanation is required here. It isn't simply a vehicle with a carb, it is also any vehicle with a vacuum advance distributor. Anything that changes the vacuum on the lines to your carb and the distributor NEEDS to be measured and adjusted for the highest vacuum, and then the timing needs to be reset. The vacuum changes the timing at the distributor, (a forgotten fact with current technology vehicles) so when the vehicle is set properly at idle the vacuum is highest and the timing is at full advance. When vacuum drops, timing starts to retard, to compensate for engine speed. As such the vacuum needs to be removed from the distributor, the vac line plugged so as not to affect the engines running, and timing set to the engine's specs. and the line reconnected.
69jeepcj
New member
I think further explanation is needed here: The above is completely correct WHEN you are running full manifold vac to the dist and NOT ported vac. Ported vac works the opposite of full manifold vac, it will have 0 or little vac at idle and vac will increase as load is applied up to a point then will start to drop off just like full manifold vac. full manifold vac starts high and stays there up to a certain point then begins to drop off. Most 76-86 cj,s are running ported vac from the factory. I would use a timing light to set timing and a vac gauge to adjust the carb to highest vac.
Dragon5126
New member
You need to remember, the vac advance only is functional at idle range engine speeds, once the throttle opens, and the engine speeds up, the timing advance set by the vac advance drops off to compensate for the increased engine speed. When an engine uses a distributor set up for systems with ported vacuum the Distributor doesn't have a vac advance, it has a centrifugal advance ( or more correctly, retard). Of all the 76 -80 258's Ive worked on, Ive yet to run into one that didn't have a standard vac advance from the factory. From 80 forward there were no rules in place due to constantly changing emissions nonsense between Canada, the US and the PRC (people's republic of Commiefornia).
Which reminds me their idiot governor stated today that if is Elected they would build a wall between them and they US... Was that an admission or a Freudian Slip?
Dragon5126
New member
that fuel pressure is on the high side by about 28 pounds
69jeepcj
New member
I have to totally disagree with you dragon on the vac adavance. vac advance is indeed used and active up the point centrifugal takes over, which is usually around 2500- 3000 rpms. cruising, vac advance is in play, vac advance is affected by load which affects engine vac, centrifugal is affected by rpm. Ported vac has little to 0 vac at idle, and the vac advance begins once the throttle is opened up to the point centrifugal takes over. I have several write ups from a former GM engineer that helped design these systems and he is still active on another forum. I know vac advance very well.. A lot of people don't completely understand vac advance, it is a mystery to many. I agree the fuel pressure is very high. I could forward you those write ups if you would like? they are a little confusing but once you get it, it makes total sense. most 70,s-80,s systems were ported from the factory. Rules was the reason for the change from standard manifold vac to ported
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Dragon5126
New member
You can disagree all you want, but the fact is I learned auto mechanics on vac advance distributors and have been working on them when they were the high tech distributors, and the best thing on the market. I cut my teeth on the cars that most here only see on TV.
In your summary of the vac advance distributor, you are neglecting the fact that once the engine hits 2800 rpm the weights spin out and turn the rotor forward advancing timing beyond what the vac advance is capable of setting. This is why when Ethyl was no longer available in the pumps we retarded the timing to prevent blowing the heads off our blocks. The bottom line is Vac advanced is ONLY in use at idle and in deceleration, to prevent engine damage. any other time the engine runs at a locked ignition timing due to the weight throw out point in the distributor. Your suggestion for the change is missing the main reason for the change itself, the lowering of octane which resulted in faster burning fuel. Which in turn reduced available engine vacuum to start with. Ive spent way too many hours reprofiling the advance characteristics of street and strip distributors to not know the hows and whys of this. I do suspect that you don't quite grasp the minimal difference between straight manifold vacuum and ported, as we have always had both, the biggest difference being the head design, which changed the manifold design needs. As an example the wide open intakes used on early straight sixes ran ported, where the later long runner designs such as used in street eights used straight manifold vacuum, and open manifold designs require ported vac since the ability to generate vacuum fast is almost impossible.
In your summary of the vac advance distributor, you are neglecting the fact that once the engine hits 2800 rpm the weights spin out and turn the rotor forward advancing timing beyond what the vac advance is capable of setting. This is why when Ethyl was no longer available in the pumps we retarded the timing to prevent blowing the heads off our blocks. The bottom line is Vac advanced is ONLY in use at idle and in deceleration, to prevent engine damage. any other time the engine runs at a locked ignition timing due to the weight throw out point in the distributor. Your suggestion for the change is missing the main reason for the change itself, the lowering of octane which resulted in faster burning fuel. Which in turn reduced available engine vacuum to start with. Ive spent way too many hours reprofiling the advance characteristics of street and strip distributors to not know the hows and whys of this. I do suspect that you don't quite grasp the minimal difference between straight manifold vacuum and ported, as we have always had both, the biggest difference being the head design, which changed the manifold design needs. As an example the wide open intakes used on early straight sixes ran ported, where the later long runner designs such as used in street eights used straight manifold vacuum, and open manifold designs require ported vac since the ability to generate vacuum fast is almost impossible.
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