I have a series 2 with Weber’s that spits back thru the carbs and on occasion will backfire thru a venturi. As I have a electronic ignition I had the timing checked at a local shop with a lift. The timing is set at 4 degrees before TDC. The carbs have been balanced and the Idle is at 800± RPM. The compression on the front 5 cylinders is at 115 PSI. # 6 is at 125 psi. Any one have any thoughts on what I am doing wrong. The car has less than 60,000 miles. I have some gauge issues but that is for another time.
Thank you
when was the last time it ran right and under what settings and equipment?
Can you describe when they spit back? user full load? partial load? tickover? then we will ask what jets you have and model of webber (DCOE 45 or 48? plus choke size. 36, 38 ??)
Have you checked valve clearances? That is a fundamental place to look.
All,
Thank you for your reply. I greatly appreciate your help. I feel that I am quite capable for most things on the car, but this has me baffled.
The Stromberg’s were giving me tuning problems but the car ran OK at that time. Once I installed the Weber’s I needed to install a vacuum port. That I thought was beyond me so I had a mechanic do that. At that time the electronic ignition was installed by this mechanic as well. then the spitting started. the mechanic is not around for me to review this with
I will check the valve clearances, but thought that if anything they would wear and increase clearance which to my way of thinking would keep the valves closed longer and minimize the issue.
The Weber’s are 45 DCOE I will have to check on the jet size. The spitting occurs at idle and increases under load at higher RPM (not under load) it occurs intermittently.
Thank you,
Fred
valve clearance decreases with wear. the idle circuit on Webbers accounts for most of the mixture up to about 1500 rpm from memory. let use know what idle jets you have. also, do you know how many and what position the Progression hole drillings are
http://240260280.com/Tech/Carbs/Weber/DCOE%20Theory%20Operation%20and%20Tuning.html
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Phil,
The Idle is .55 the next # is 8
The main is 1.65
and the air is 1.90
Thank you for your offering to help
Fred
What size choke?
07714 759198
Air correctors have nothing to do with low speed operations.
Hummmm. could that just be a coincidence?
Phillip
Not sure where you came up with 4 BTDC as a timing setting. The Webers do not behave like Strombergs. They do better with a larger amount of initial timing. I was running 17 BTDC and limited total to 36 BTDC. As they do not use vacuum advance or retard, should be straight forward to check the distributor. If you are using a emission distributor from 1968-1971, it will most likely have to be recurved to limit the total advance. Do no hook up the vacuum retard if your car is so equipped. A Triple SU carb car will backfire with a timing setting of 4 BTDC. Of course, once the timing is squared away, then jetting the Webers properly is next. Every engine is different so some mixture measuring equipment is the best way to get the proper settings.
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Dick,
thank you for your reply. I will reset the timing next weekend and give it a go, The distributor is new and not the original one.
Thank you,
Fred
Fred can I be honest here?
You are never going to get this car running properly unless you take it to a rolling road/dyno setup and have it tuned properly by someone who understands Webers. There are simply too many permutations and combinations here.
Thank you,
I understand, however first thing for me is to get it better than it is now. I will try and adjust the timing and see where that gets me. I have not found a Weber shop on Long Island anyone have a recommendation? A Weber shop and rolling dyno would be over the top.
Thank you all for your replies.
Fred
Is Marcovetzi-Wentz racing located on LI?
Hi Fred, I too have a 69 with webers. Note, I have the standard ignition. First, set the idling advance to 10deg. btdc You can play with that later. I have two cylinders at 10psig above the other four. After much struggling I bought a ‘synchrometer’ (on ebay I think). It is a flow meter with a rubber adapter that fits to the weber choke. Use this, adjusting the idle speed screws to get the intake flow as even as possible across all 6 cylinders, generally at 700/800rpm. Next is the idle jet setting. That controls much of the low speed operation. My idle jets are 55/F8. Typically, back the screws out 1-2 turns, then adjust to get fastest idle speed. That should do it, OR , like me not quite a magician, buy a Colortune. from England. Install the spark plug in each cylinder and adjust until a blue flame appears. I was just amazed at the performance, smooth operation, and control. Hope this works for you.
Duncan
Duncan,
Thank you, I have the syncronizer and the colortune, I will reset the timing and start from there. This has been a story of too many moving parts to be certain where to start. The timing to me is the issue. once that is adjusted I think that I will be fine.
Fred