MSD Ignition or Weber Carb Issue?
- Thread starter CESLAW
- Start date
Jac's right, the strangest things will rear up and strike when you least expect them. I was visiting a fellow forum member at Texas Speedway one weekend and he developed symptoms exactly like those you are describing. We changed out the PV, not much improvement, so we went on a search. I suspected electronics, so the first thing he did was take the top off the switchbox in the interior of the racer and found that all the vibration had loosened a contact on one of the switches. He fixed that, and it was a minor improvement, again.....but still the car was practically unable to get going from a standing start. We started to be suspicious of the dizzy and so he went to a friend's pit where an extra dizzy was available. We took his out, put the new one in, and it was no better. As he was watching the VOM, I "fiddled" with the wire to the distributor where there was a rather secure looking splice. He mentioned how the needle was jumping all over the place. In the end, all it took was a more secure connection in that line to the dizzy, but we spent hours figuring it out.....
Here's hoping it's something simple as that for you!
Doug
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flatchat(Chris)
Supporter
Oh yeah ! and disconnect the tacho ---I've seen faulty tachos give similar symptoms as well.
Hopefully we are getting closer to closure now :sad:
Hopefully we are getting closer to closure now :sad:
RichardH
AKA The Mad Hat Man
Reet - latest info.
Been to inspect! a couple of local garages and have decided to take the beast to one for investigation. They are happy for me to be on hand and assist, which means I learn and it keeps the cost down.
They can perform a 'proper' leak down test, Have a Dyno on hand for final tweaking when its running again and a machine shop in the rear (hopefully not necessary). They do lots of engine tweaks (ECU re-programming) and NOS kits and appear genuinely interested in the car, rather than it just being another motor to earn money on.
It is being collected next Wednesday - so a week of comparative quiet on here from me
- here's hoping.....
I will keep you informed of what we find.
Whilst I think about it - two vacuum tubes were not connected, and left open on the Holley - one of which is immediately in front of the Choke mechanism and the other is on the Throttle body - which one operates the vacuum secondary? Or is it neither? I suppose what I am asking is can I block both, or is one necessary to operate the carb, and if so where can I connect it to on the engine (Inlet manifold), as I cannot find that it has ever been connected?
Been to inspect! a couple of local garages and have decided to take the beast to one for investigation. They are happy for me to be on hand and assist, which means I learn and it keeps the cost down.
They can perform a 'proper' leak down test, Have a Dyno on hand for final tweaking when its running again and a machine shop in the rear (hopefully not necessary). They do lots of engine tweaks (ECU re-programming) and NOS kits and appear genuinely interested in the car, rather than it just being another motor to earn money on.
It is being collected next Wednesday - so a week of comparative quiet on here from me
- here's hoping.....I will keep you informed of what we find.
Whilst I think about it - two vacuum tubes were not connected, and left open on the Holley - one of which is immediately in front of the Choke mechanism and the other is on the Throttle body - which one operates the vacuum secondary? Or is it neither? I suppose what I am asking is can I block both, or is one necessary to operate the carb, and if so where can I connect it to on the engine (Inlet manifold), as I cannot find that it has ever been connected?
Neither of those vacuum ports operates the secondaries, Richard, and yes, you should block off both. It is possible that one provides the vacuum signal for the dizzy, so if that is the case I'd plug the one on the metering block and use the port on the carb's base for that purpose. The "Jerry rigged" way to block the one on the metering block would be to put a screw into that piece of tube directly in front of the choke mechanisn, but the one on the base may also need to be sealed up. Any decent auto parts store ought to have an assortment of plugs (nipples?) to seal up the vacuum ports, so that ought to be an easy fix, as well as much more secure than the old "....banana in the tailpipe trick" (if you've never seen "Beverly Hills Cop", you won't understand that one, sorry).
Anything left open to atmospheric pressure will be interpreted by the Holley as a vacuum leak and WILL affect the operation of the Holley, so get all of the unused vacuum ports sealed up and it will work much better.
Sounds like you've found a garage full of gear-heads! Good on ya...they'll undertake this sort of project as if it were their own car and you'll be on the roads again.....as we say down here in Texas, "Yee-Haw!!"
Doug
RichardH
AKA The Mad Hat Man
woohoo - car gone in today to be looked at....
here are the results of the compression test and leak-down test - all good.
mind yu - we did find another problemette - whilst moving the distributor cap around, we noticed this.........
That wont have been helping things either. New Disty cap on order for Monday.
here are the results of the compression test and leak-down test - all good.
mind yu - we did find another problemette - whilst moving the distributor cap around, we noticed this.........
That wont have been helping things either. New Disty cap on order for Monday.
I do not have time to check this whole thread, but on the ignition side of the question--use your timing light on each plug wire as if it were cylinder no. 1 and see if it lights up like it should. If yes, you know you have fire at each cylinder.
On the Weber issue, I have 4-48 IDAs and love them. Balance the air first. Completely warm up the engine. Tune the idle mixture jets for max RPM. Success of all this depends on correct jetting, etc. for your engine spec, cam spec, etc.
Good luck.
On the Weber issue, I have 4-48 IDAs and love them. Balance the air first. Completely warm up the engine. Tune the idle mixture jets for max RPM. Success of all this depends on correct jetting, etc. for your engine spec, cam spec, etc.
Good luck.
Ron Earp
Admin
Richard,
What is your repair budget? The engine appears to be relatively low spec based on the pictures-iron heads, etc. You could get an aluminum headed 302 here from the US for not very many beans. Knowing how expensive parts/labor is for US engines over in the UK sometimes getting a new one might be a viable alternative. Just throwing it out there.
Ron
What is your repair budget? The engine appears to be relatively low spec based on the pictures-iron heads, etc. You could get an aluminum headed 302 here from the US for not very many beans. Knowing how expensive parts/labor is for US engines over in the UK sometimes getting a new one might be a viable alternative. Just throwing it out there.
Ron
Ron Earp
Admin
Heads on Richards motor are alloy & its Holley carb,---- 'somebody' ----cross pollenated his thread with Chucks MSD/Weber thread!!!!!
Man, what kind of a**hole would do that??? Wow.
My bad.
RichardH
AKA The Mad Hat Man
Well!!!! An interesting day today. The new distributor cap and rotor arm and plugs came yesterday, so it was fit everything, static timed the car, adjusted Holly float bowls on car and try it again.......
No change!
not starting, fireing back in carb or exhaust pipe.
so we re-stripped the carb, just in case i had forgotten anything, checked it all and blew it out with an airline. Refitted it, reset float bowls and tried again.
With judicious juggling of the idle mixture, tickover idle adjust and playing with the throttle, we managed to get it running for about 10 minutes - It wouldnt go over 550-600RPM and wasnt firing on all cylinders. Looking into the carb (a bit dicey with the occasional blow-back) it looked like the main jets werent working correctly - more dripping than spraying.
What we believe is happening is that the fuel is being restricted so that it only runs by pumping the throttle pump on the side of the carb, not on main jets, the fuel is only being drawn into the cylinders in varying amounts, which is why it only runs on a few cylinders, occasionally blows back and occasionally fires in the exhaust. The fuel pumps (red tops) were running at 3PSI, so that was increased to 6 - as per Holley recomendations - still no joy. As all the main jets were clear and there is no adjustment, it is a bit confusing as to why there appears to be fuel starvation and, of course, why it has suddenly changed over winter. One thought, after we had finished for the night, was the fuel filter.... I have known them to "jelly" over a winter, so thats a check for tomorrow. It is the only thing at the moment, that I can think of, that would allow good fuel pressure, but low flow to the carb. I cannot think that it can be the carb now. Tiz really weird.
No change!
not starting, fireing back in carb or exhaust pipe.
so we re-stripped the carb, just in case i had forgotten anything, checked it all and blew it out with an airline. Refitted it, reset float bowls and tried again.
With judicious juggling of the idle mixture, tickover idle adjust and playing with the throttle, we managed to get it running for about 10 minutes - It wouldnt go over 550-600RPM and wasnt firing on all cylinders. Looking into the carb (a bit dicey with the occasional blow-back) it looked like the main jets werent working correctly - more dripping than spraying.
What we believe is happening is that the fuel is being restricted so that it only runs by pumping the throttle pump on the side of the carb, not on main jets, the fuel is only being drawn into the cylinders in varying amounts, which is why it only runs on a few cylinders, occasionally blows back and occasionally fires in the exhaust. The fuel pumps (red tops) were running at 3PSI, so that was increased to 6 - as per Holley recomendations - still no joy. As all the main jets were clear and there is no adjustment, it is a bit confusing as to why there appears to be fuel starvation and, of course, why it has suddenly changed over winter. One thought, after we had finished for the night, was the fuel filter.... I have known them to "jelly" over a winter, so thats a check for tomorrow. It is the only thing at the moment, that I can think of, that would allow good fuel pressure, but low flow to the carb. I cannot think that it can be the carb now. Tiz really weird.
Back to basics - recheck your firing order as it has all the classic syptoms ! Frank
What's the chance it could be stale fuel?
We've had a problem over here the last few years with the 'new' unleaded in that it only has a limited shelf life. Stale fuel symptoms are very similar to yours. This occurs frequently with lawnmowers, weedeaters and anything else laid up over the winter as well as cars that are off the road for any length of time. Stale fuel can be revitalised or permanently preserved by adding about 20% Avgas or any other leaded fuel that you can get your hands on.
Edit Firing order
302: 15426378:
351: 13726548
I believe aftermarket cams use the 351 firing order. If in doubt pull your valve covers and see what order the valves are working.
We've had a problem over here the last few years with the 'new' unleaded in that it only has a limited shelf life. Stale fuel symptoms are very similar to yours. This occurs frequently with lawnmowers, weedeaters and anything else laid up over the winter as well as cars that are off the road for any length of time. Stale fuel can be revitalised or permanently preserved by adding about 20% Avgas or any other leaded fuel that you can get your hands on.
Edit Firing order
302: 15426378:
351: 13726548
I believe aftermarket cams use the 351 firing order. If in doubt pull your valve covers and see what order the valves are working.
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That's what it does......Hard (impossible almost) to start, will only run like crap and only on choke unless REALLY hot. Spits back, no revs etc
Richard, there are two common but very different firing orders, what order are you useing, and what cam have you installed ? Frank
RichardH
AKA The Mad Hat Man
its a comp cam 260 grind cam.
firing order - cant remember and the manual is at the garage - we are using the "standard" 302 firing order. Can you tell me what the two different firing orders are - and I can check tomorrow. It hasnt been changed over the lay-up period tho - only it might have today when the disty cap was changed.
firing order - cant remember and the manual is at the garage - we are using the "standard" 302 firing order. Can you tell me what the two different firing orders are - and I can check tomorrow. It hasnt been changed over the lay-up period tho - only it might have today when the disty cap was changed.
See firing order details in my post # 195