428 first fire up
Cargo Master
Joined: Dec 2008
Posts: 3,213
Likes: 321
From: SW PA
disconnect the vacuum advance hose and put a cap on the carb side port
eliminate this system to start
set initial timing (at idle rpm) to 12-15 deg BTDC.
double check the timing marks adn pointer is correct wtih a piston stop if you have any doubt
start truck...if it doesn't idle relatively smooth and hold a vacuum showing 1-2" of bounce (with a decent gauge) then next step is to look further for vacuum leaks.
I suggest to disconnect all vacuum sources and confirm teh engine proper is good...then reconnect 1 vacuum line at a time.
If the carb is new i doubt it's your issue.
eliminate this system to start
set initial timing (at idle rpm) to 12-15 deg BTDC.
double check the timing marks adn pointer is correct wtih a piston stop if you have any doubt
start truck...if it doesn't idle relatively smooth and hold a vacuum showing 1-2" of bounce (with a decent gauge) then next step is to look further for vacuum leaks.
I suggest to disconnect all vacuum sources and confirm teh engine proper is good...then reconnect 1 vacuum line at a time.
If the carb is new i doubt it's your issue.
Thread Starter
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Senior User
Joined: Sep 2019
Posts: 252
Likes: 14
disconnect the vacuum advance hose and put a cap on the carb side port
eliminate this system to start
set initial timing (at idle rpm) to 12-15 deg BTDC.
double check the timing marks adn pointer is correct wtih a piston stop if you have any doubt
start truck...if it doesn't idle relatively smooth and hold a vacuum showing 1-2" of bounce (with a decent gauge) then next step is to look further for vacuum leaks.
I suggest to disconnect all vacuum sources and confirm teh engine proper is good...then reconnect 1 vacuum line at a time.
If the carb is new i doubt it's your issue.
eliminate this system to start
set initial timing (at idle rpm) to 12-15 deg BTDC.
double check the timing marks adn pointer is correct wtih a piston stop if you have any doubt
start truck...if it doesn't idle relatively smooth and hold a vacuum showing 1-2" of bounce (with a decent gauge) then next step is to look further for vacuum leaks.
I suggest to disconnect all vacuum sources and confirm teh engine proper is good...then reconnect 1 vacuum line at a time.
If the carb is new i doubt it's your issue.
1 line goes to booster
1 to dizzy
1 to pcv
1 to dash
tranny vac not hooked up yet
can I cap them all without side effects for checking process
Lead Driver
Joined: Oct 2018
Posts: 7,862
Likes: 2,359
Your initial timing setting means absolutely nothing unless your distributor curve is spot on. assuming it's fine is a big assumption since they seldom are. find your peak mechanical advance setting and if your distributor is even close the initial will take care of itself. .
Mountain Pass
Joined: Feb 2020
Posts: 118
Likes: 2
Yes you can plug all of them. Likely a good idea. I would not suspect a new carb just yet unless the settings are way off, could be. Do what the prior poster up from you stated. Then report back.
Timing is base, plus advance. Advance comes from RPM(weights and spring rate) and vacuum adds to this. One reason you pull vacuum advance out of the equation to start. Base timing at idle should be as stated 10-15 btdc, you can do more if the motor wants it but you are not to that point yet. Know that a change here impacts TOTAL timing by the same amount. BASE+ MECH. ADVANCE=TOTAL. Total timing, no vacuum, is what you need to watch out for. Depending on the setup it could be 35(modern heads) or if all factory more like 42 total(Iron heads). More to it than just this but the info is out there on the web on how to find it. Learn it because it is an important thing on older motors like this.
Good luck.
Timing is base, plus advance. Advance comes from RPM(weights and spring rate) and vacuum adds to this. One reason you pull vacuum advance out of the equation to start. Base timing at idle should be as stated 10-15 btdc, you can do more if the motor wants it but you are not to that point yet. Know that a change here impacts TOTAL timing by the same amount. BASE+ MECH. ADVANCE=TOTAL. Total timing, no vacuum, is what you need to watch out for. Depending on the setup it could be 35(modern heads) or if all factory more like 42 total(Iron heads). More to it than just this but the info is out there on the web on how to find it. Learn it because it is an important thing on older motors like this.
Good luck.
Thread Starter
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Senior User
Joined: Sep 2019
Posts: 252
Likes: 14
yes but not 100% it’s correct. Screwed all 4 corners in then backed out 1 1/4 turns. Ended up putting them all in 1/8 of a turn from 1 1/4. The 2 back ones were almost screwed all the way in when I started
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Senior User
Joined: Jul 2020
Posts: 175
Likes: 0
From: Land of Lunatis
Is your PCV system connected ?
The oil filler cap on the driver side valve cover looks solid, and should have a built in filter, or, a pipe connected the the air filter casing.
If you're at sea level, your vacuum reading should be +/- 18'' connected to ported, or +/- 20'' if connected to full manifold, both with vacuum advance plugged.
Also, that reading will be at +/- 800rpm, not any higher.
The oil filler cap on the driver side valve cover looks solid, and should have a built in filter, or, a pipe connected the the air filter casing.
If you're at sea level, your vacuum reading should be +/- 18'' connected to ported, or +/- 20'' if connected to full manifold, both with vacuum advance plugged.
Also, that reading will be at +/- 800rpm, not any higher.
Thread Starter
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Senior User
Joined: Sep 2019
Posts: 252
Likes: 14
I have some stuff disconnected in those pics because I’m working on disconnecting vacuum lines off. I switched to that silver cap and have not run engine with that cap. The first one has an elbow on top for going to air cleaner. I didn’t know if it would make a difference between the caps
Thread Starter
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Senior User
Joined: Sep 2019
Posts: 252
Likes: 14
I will try this as well. Hope to fire it up this evening again
Senior User
Joined: Jul 2020
Posts: 175
Likes: 0
From: Land of Lunatis
As long as you have a fresh air intake on one side, and the correct pcv valve connected to intake vacuum (back of carb maybe) on the other, your pcv system can be ignored for now.
Swap to manifold vacuum for now, and if nothing else, you'll have observed the difference it makes.
Swap to manifold vacuum for now, and if nothing else, you'll have observed the difference it makes.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
You should have no vaccum on the ported vacuum for the dist at idle. If you do idle settings and or secondary throttle plates need to be adjusted. That is the whole point of the ported vac or the dist.
Remove the vac line from the Dist when adjusting the idle mix or any other idle settings.