So I got my Weber in and got everything hooked up. I don't have the vacuum advance connected yet. The engine tries to start but dies pretty quickly. Where do I start? Does the vacuum advance have to be connected? If so, where do I connect since I don't have the stock vacuum ports any more?
Thanks

 

Have you tried starting it and giving it throttle? I know my Weber was not tuned properly, so I had to turn in the set screw until it would at least hold an idle, then adjust the idling screws until the RPM's increased. Once they did, I turned out the idle screw so that the RPM's dropped back to a normal level. I did this until the idle screw was pretty much all the way out, meaning, if I turned it out anymore, it would fall out. The throttle was sitting on the bracket. Other than that, if you can get it to run and keep running, search for a vacuum leak.

 

vacuum advance won't matter, and the carb is probably not dialed in, so you could try either getting it to run at a higher rpm, or maybe richening it up a tad

 

Did you just rebuild the 12A?

If it were me, I'd use whatever carb I was using before the rebuild to break the engine in for the first 100miles or so. Just cause I KNOW the carb that was on there worked. Kinda like ruling out one possible fail point.

 

I never used the old carb so I never saw it run before the rebuild. Also, it's half bridge now. I did get it to run and the RPMs read about 5200 but the engine didn't sound like it was idling that high... Could it be possible that it's only firing on one rotor? It didn't sound like a bridge motor at all, just a really slow idle.

 

Check for spark. Lay the plugs on top of left strut tower, and turn the engine over*. Should light up like a Christmas tree on all 4 plugs.



*with the starter motor

 

did you make sure not to take the front pulley off the hub or mark it before taking it off? the timing could be way off and the car still attempt to run, as with the old hubs can be up to 270* off time.

 

I set the flat part of the flywheel to the exhaust side which put the front pulley key way on the 9 o'clock position as was suggested here. The pulley was on the first mark. What would normally be yellow. The distributor rotor was pointing towards L1 terminal on the cap.

 

ok, then you're most likely just having fuel starvation issues, which is fairly normal for a bridged engine on an untuned carb that likely was previous setup for something that was much less thirsty.

 

It was sent with a set of jets known to be good for a bridged 12A. It's a brand new set up from Rotary Shack.
Thanks

 

it is still in your best interest to not put all your trust in that the carb is functioning perfectly for your engine.

carbs always need tweaking, fuel pressure, idle mixture adjustment, idle speed adjustments, and jetting regardless of what anyone sais.

 

there are several reasons why this is more of a starting point, than a finishing point.

the first of which is that bridges are cut by hand, so they are not all the same, and your exhaust and their exhaust might be different as well.

secondly, they are in LA, and you're not. temps are probably close, but humidity and altitude might not be, which matters.

third, is that you don't know what they picked for AFR's, or idle speeds or any of that.

four, fuel pressure and float level also matter, and float level can be super sensitive, 1mm is huge

if you want a for instance, i have a 12A p port, and its setup as close to the competition setup in the manual as i could. i have a muffler, they don't. they were running it at daytona, mine is mixed street/track.
Mazda supplied a jetting chart, and to get mine to run happily on the street, my jetting is quite different than theirs. my engine is different enough.

in summary, i would bet that the main jet is probably close, but due to the climate, and port variations the idle jet, and air corrections are suspect. not a fault of rotary shack, its just physics, and a bunch of minor hardware differences.

 

OK, thanks for the advice. I checked and all spark plugs are getting spark. I will try again now that I have the throttle cable bracket.

 

Oh and another ?.. Where are you guys getting a socket to tighten the spark plugs on housings with the "eye brow"... My socket is too thick. I just remembered my plugs were loose so may be losing compression too.
Thanks

 

Woooohooo... So, I finally got it running. I just needed the throttle cable bracket and some pumping of the accelerator. Once warmed up it stayed running. Oil pressure is good and water temp got up to around 190. Now I need to fix the water temp sender as it is leaking and the oil pan has a bit of oil dripping from the front.

 

Water pump sender was just loose. The oil leak was an improperly sealed OMP block off plate. Now I have a small coolant drip, I think, out of the coolant temp sensor. Ordered one today.

Overall, the car is running ok. It starts after pumping the gas about 10 times and may take a time or two to stay running. I guess that's the price we pay for chokeless Webers. Once it warms up it runs pretty decent but I need to adjust the carb as when you floor it, I am experiencing a bit of lag sometimes feels like it's going to die. I drove it around the neighborhood and it feels pretty nice and smooth. I think some tweaking and it will be nice.