distributor solenoid purpose?

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66plyValiant

66plyValiant

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don't mind my stupid question but what purpose does the wire to the vacuum advance serve? I'm new to bigblocks and don't know. will a normal small block distributor fit?

its a 400 B engine being removed from a '77 tradesman 300 to go in a '77 adventurer long wheel base stepside
 
first off no... a slant has its own dizzy, a small block has its own dizzy, B engine have there own, and then RB and hemi share a dizzy...

as for a wire to the vac can im at a loss... as its run by VACUUM not electricity lol... are you sure its not the lead for the internals, which a single lead would be points...
 
805moparkid said:
first off no... a slant has its own dizzy, a small block has its own dizzy, B engine have there own, and then RB and hemi share a dizzy...

as for a wire to the vac can im at a loss... as its run by VACUUM not electricity lol... are you sure its not the lead for the internals, which a single lead would be points...
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no its most definatly electronic ignition, I'm very familure with small blocks and slants but this is the first big block I have had the chance to do much to, I knew slant distributors only fit slants but wasen't sure fitment from small to big block, it looks identical

wire definatly goes directly to the advance canister, but the van isn't lean burn or have any emissions stuff on it. It also has the normal vacuum line to the advance as well as the wire, I have seen points distributors this way but never electronic ones

rock auto lists it as "W SOLENOID OPERATED VACUUM ADVANCE UNIT"
 
66plyValiant said:
no its most definatly electronic ignition, I'm very familure with small blocks and slants but this is the first big block I have had the chance to do much to, I knew slant distributors only fit slants but wasen't sure fitment from small to big block, it looks identical

wire definatly goes directly to the advance canister, but the van isn't lean burn or have any emissions stuff on it. It also has the normal vacuum line to the advance as well as the wire, I have seen points distributors this way but never electronic ones

rock auto lists it as "W SOLENOID OPERATED VACUUM ADVANCE UNIT"
Click to expand...

well it has to be an emissions thing... it must open or close the adv canister even if the vacuum isn't there... get more timing in under certain conditions...
 
here is what I found on another forum

" on some 400 CI's there is a separate Advance Solenoid that is part of the vacuum advance. The solenoid only get power during start to help with starting"

this makes sense because the wire went to the relay wire on the starter solenoid (small wire for starter)
 
The solenoid built into the vacuum advance permits a retarded timing setting at idle to attain correct idle speed with a relatively wide throttle opening for cleaner exhaust at idle. Power to the solenoid goes through a closed-throttle switch on the carburetor so as soon as the throttle is moved off idle, the timing jumps back up to normal. If you eliminate the solenoid, you might be able to attain a passable idle speed and mixture, but not a good one.

Read more here (start at bottom of page and then move on to the next page).
 
slantsixdan said:
The solenoid built into the vacuum advance permits a retarded timing setting at idle to attain correct idle speed with a relatively wide throttle opening for cleaner exhaust at idle. Power to the solenoid goes through a closed-throttle switch on the carburetor so as soon as the throttle is moved off idle, the timing jumps back up to normal. If you eliminate the solenoid, you might be able to attain a passable idle speed and mixture, but not a good one.

Read more here (start at bottom of page and then move on to the next page).
Click to expand...


dan, I have read through that article but one thing that confuses me is that the wire runs directly from the starter relay wire to the advance canister on the distributor.

It looks factory with the heat resistant coating that mopar used. there appears to be no spot on the carburator or any spare wires for a throttle stop switch

I'm only concerned because the engine ran very very well in the van and I would like it to run the same in the truck
 
66plyValiant said:
dan, I have read through that article but one thing that confuses me is that the wire runs directly from the starter relay wire to the advance canister on the distributor.
Click to expand...

Fer serious? That's weird. In that case, the only purpose it could serve is to alter the timing in one direction or the other (advance it or retard it) during engine cranking to improve ease of starting with whatever basic ignition timing setting was used.
 
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