1. what tells the distributor on a carb car when to fire, it isn't just juiced the entire time is it?
2. how do you hook up vacuum advance and other vacuum stuff when you have a two carb manifold?
thanks guys..
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1987 Formula 350, headman hedders, Accel supercoil, cap, rotor.
MAF screens removed. 160 degree stat and manual fan switch.
Best ET: 14.745@91.317mph-Stock
Best ET: 14.418@95.51 mph-Modded
Ridiculed Founder of the Traction Impaired Crew
another question,
what are vacuum/mechanical secondaries?
do I need a vacuum secondary carb to use a vacuum advance distributor and a mechanical advance carb to use a mechanical advance distributor?
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1987 Formula 350, headman hedders, Accel supercoil, cap, rotor.
MAF screens removed. 160 degree stat and manual fan switch.
Best ET: 14.745@91.317mph-Stock
Best ET: 14.418@95.51 mph-Modded
Ridiculed Founder of the Traction Impaired Crew
A carb doesn't fire. Too primitiave for that . Basically the most boost it gets is from fuel pressure which is basically nil by the time it comes out of the carb. The fuel/air is pulled in by vaccum, unlike a FI, it's "wet-manifold" which means the vaccum is made to pull in the fuel and the air together as opposed to just air.
You can hook them up anyway you want to, a good idea is to try and even them out a bit however most cars running two carbs only run the vaccum advance (if equipped) and the power brakes. You can also run the PVC valve from it and the heater (if you don't want to tap a runner).
No, two seperate things. A mechanical secondary carb is most commonly referred to as a double pumper, this is usually used for high power applications with large cams (can't provide the vaccum for the secondaries) and more often suggest from autos than manuals. The vaccum secondary carb opens it's secondaries depending on vaccum from the engine, there is a various assortment of springs (holley) in order to accomplish near-perfect timing of the secondaries.
A mechanical advance distributor means it uses no vaccum advance to determine the timing. It only uses centrifugal weights in the distributor. Most people run vaccum advance because you can run a more aggressive timing curve because vaccum is one of the best indicators of load. An engine under load can't take as much timing and engines under load have less vaccum. Vaccum advance distributors are mechanical advance distributors with some extra advance provided by the vaccum canister. The vaccum line for the distributor should always be hooked into a "ported" vaccum port, it will give you no vaccum at curb idle.
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1984 WS6 Trans Am Hartop
Former L69 Car under restoration
1984 WS6 Trans Am T-top car
4-bolt main 350, headers, Holley 650, T-5 and 3.23's.
Daily driver and restoration
Sorry, I misread the fist question. On non-CC HEI it is controlled by little triangle like things (can't recall the real name). When they pass eachother they send voltage to the ignition module which sends it to the coil which then sends it to the rotor and out through the plugs. The vaccum advance canister moves these "triangles" to advance timing and the weights move the rotor to advance the timing.
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1984 WS6 Trans Am Hartop
Former L69 Car under restoration
1984 WS6 Trans Am T-top car
4-bolt main 350, headers, Holley 650, T-5 and 3.23's.
Daily driver and restoration
[This message has been edited by 84FTA (edited October 24, 2000).]
Second, You want vacuum secondaries for auto trans, not mechanical, for the vacuum reasons you stated. Older autos (PG, TH350, TH400) need vacuum to operate, unlike the TH700-R4. Manual trannies like mechanical secondaries.
A mechanical secondary carb is most commonly referred to as a double pumper
Isn't a double pumper a mechanical secondary carb with a second accelerator pump for the secondaries, distinct from a regular mech. sec. carb with a single pump?
Yeah, I'm sorry. I mistated both those things. It's been a long day . Yes, that should of read most mech. secondary carbs are double pumpers. The other should of read they are more often suggested for manuals instead of autos. However, in street applications running mechanical secondaries/double pumpers even on a manual transmission aren't required. Gas mileage will suffer horribly because of the double pumper's power valve channel restrictors.
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1984 WS6 Trans Am Hartop
Former L69 Car under restoration
1984 WS6 Trans Am T-top car
4-bolt main 350, headers, Holley 650, T-5 and 3.23's.
Daily driver and restoration
[This message has been edited by 84FTA (edited October 24, 2000).]
. Basically the most boost it gets is from fuel pressure which is basically nil by the time it comes out of the carb. The fuel/air is pulled in by vaccum, unlike a FI, it's "wet-manifold" which means the vaccum is made to pull in the fuel and the air together as opposed to just air.
