stphers
Well-Known Member
THAT'S ALWAYS A GOOD SIGN !!
Zenith carb baseline settings source?
- Thread starter dang
- Start date
Did you do your smoke test?
Tonight. I'll try to get a video of it...
I guarantee you have a vacuum leak I just went thru this exact same issue and plugs. I too had improvement when I covered the inlets took my carbs off and found the plastic base plates cracked and the gaskets kaput. I recommend new plugs as they are very difficult to get cleaned with that soot level. My journey was 6 months then removed carbs and all became apparent.
Ran a smoke test and found leaks where the choke assemblies used to be mounted. I caused my own problem, but I think this is the way these carbs ran on my coupe for years. Strange. Anyway, I plugged the holes and the motor didn't pop or spit at all but still has a misfire. My friend came over that is really good with carbs even though he hasn't worked on Zeniths before. He ran a smog shop for years so he understands how all the systems work together. The motor runs smoother if we restrict the air flow to the front carb and the richness adjustment doesn't seem to be very effective compared to the rear carb. We took the carb apart and everything looked good but stopped last night before doing much more so we'll try again tonight.
You probably ran your previous car rich to compensate. Make sure the mix screw is the correct one, is in good condish, and the passage is clean. Try swapping screws to see if it makes a difference. How far out from fully closed are they when running?
Could be too much air coming through the secondary. They are tricky to set up right; nearly closed plus preload setting on the gate or it will bind. Try covering up just the secondary of the front and see. You may feel very strong suction when covering with your hand; shouldn't be that much air coming through it.
We started about two turns out on both. The rear carb changed as we turned the mix screw but the front didn't change until we got way out, over four or five turns, so we thought it might be allowing air in at that point. It runs with a heavy miss, like on four or five cylinders, and when you restrict the front air inlet it runs a lot better but still somewhat rough. It runs rough but like it could be adjusted out. My friend wants to bring his vacuum gauges over because he says you can learn a lot from them. We'll also double check that all cylinders are firing, etc.
oh, brilliant !
I posted this on my build thread but after checking every system out again on the motor we both agreed that it sounded like it was missing on at least one or two cylinders. We had been concentrating on the carbs, then moved to dwell, timing and finally checked the wires and plugs. TWO out of the six brand new Bosch spark plugs were bad! I pulled 20 year old plugs out of my tii parts car and the M30 motor fired and ran very smoothly. Baaah! I'm frustrated and relieved at the same time. I've had enough of the motor for now so I'll go back to it and fine tune once I start driving it...
Ugh! I just bought a set of NGK plugs after reading the plug threads but second-guessed myself when I saw you using Bosch. Maddening for you, but I leaned a lot watching you & everyone attack your troubles. Small consolation, I know.
My mechanic friend says he only buys NGK or Nippondenso.
I’m jonesing to try that smoke machine! Right now, I just run 101 gas to smooth things out b/c I’m scared of the Zeniths, but $7.50/gal is too expensive in driving season. The damn Street Outlaw idiots & their fanboys here will pay stupid money at the only source, so drop in oil has only dropped 50 cents, & you can’t buy it on Friday or Saturday b/c they have a virtual party around that pump (also has ethanol racing fuel)—they don’t part the sea of Mustangs for an old green BMW. Feel like I’m in junior high & can’t get the salt from the bully table.
This is the one I bought on eBay. It works great and is exactly what I expected after reading reviews. Two common things that the reviews agree on.... One, the power cords should have a disconnect so you can spin the canister without the wires twisting, and two, burning mineral oil (or any oil) stinks! It's not so bad when you're using it but you have to put everything in a sealed container when you're not using it so it doesn't stink up the garage. I've used it way more than I expected.
Stinger Automotive Smoke Machine Leak Tester for EVAP Vaccum Systems Exhaust Etc | eBay
Included with the Stinger Pro 2 are a universal threaded EVAP port adapter, an EVAP valve removal tool, a 1/4" quick-connect air hose fitting, and a smoke hose plug for added versatility and ease of use.
www.ebay.com
This is the one I bought on eBay. It works great and is exactly what I expected after reading reviews. Two common things that the reviews agree on.... One, the power cords should have a disconnect so you can spin the canister without the wires twisting, and two, burning mineral oil (or any oil) stinks! It's not so bad when you're using it but you have to put everything in a sealed container when you're not using it so it doesn't stink up the garage. I've used it way more than I expected.
Stinger Automotive Smoke Machine Leak Tester for EVAP Vaccum Systems Exhaust Etc | eBay
Included with the Stinger Pro 2 are a universal threaded EVAP port adapter, an EVAP valve removal tool, a 1/4" quick-connect air hose fitting, and a smoke hose plug for added versatility and ease of use.www.ebay.com
Thank you. Smell is key as my garage is still below our bedroom & wife has a nose like a bloodhound. PB Blaster was banned & replaced by Kroil 5 mins after a quick spray on one bolt.
This is the one I bought on eBay. It works great and is exactly what I expected after reading reviews. Two common things that the reviews agree on.... One, the power cords should have a disconnect so you can spin the canister without the wires twisting, and two, burning mineral oil (or any oil) stinks! It's not so bad when you're using it but you have to put everything in a sealed container when you're not using it so it doesn't stink up the garage. I've used it way more than I expected.
Stinger Automotive Smoke Machine Leak Tester for EVAP Vaccum Systems Exhaust Etc | eBay
Included with the Stinger Pro 2 are a universal threaded EVAP port adapter, an EVAP valve removal tool, a 1/4" quick-connect air hose fitting, and a smoke hose plug for added versatility and ease of use.www.ebay.com
For posterity, there’s an identical looking one with a “Smoke-Tek”label on Amazon for $25 less.
DQ, I’d be very interested in the table settings as you say if not too much trouble. I’m sure other would as well. I’ve spent time with the tech manuals but start to gloss over after a while.