Olds mobile distributor questions
Thread Starter
Registered User
Joined: Jan 2020
Posts: 2,896
From: Sarasota Florida
Olds mobile distributor questions
Oldsmobile distributors, are small blocks and big blocks distributors interchangable? Does these hei conversions like pertronix and such eliminate the need for advance springs etc and vacuum advance?
Barely Registered
Joined: Feb 2014
Posts: 2,629
From: Gillespie County, Republic of Texas
Andy, Olds V-8 distributors are physically interchangeable among second-generation engines (1964 and after, ex 1964 Gen I).
HEI is a term for a specific type of distributor used by OIdsmobile. It does not use points, so Pertronix does not apply.
Pertronix are only used for points replacement within points distributors. When using these, you must continue to maintain the weight and vacuum advance mechanisms originally installed.
There are other points replacements that incorporate centrifugal and vacuum advance, accessible and adjustable by a smart-phone app. These are relatively expensive.
Gary
HEI is a term for a specific type of distributor used by OIdsmobile. It does not use points, so Pertronix does not apply.
Pertronix are only used for points replacement within points distributors. When using these, you must continue to maintain the weight and vacuum advance mechanisms originally installed.
There are other points replacements that incorporate centrifugal and vacuum advance, accessible and adjustable by a smart-phone app. These are relatively expensive.
Gary
Last edited by VC455; Mar 6, 2022 at 02:53 PM.
CH3NO2 LEARN IT BURN IT
Joined: Jul 2010
Posts: 5,635
From: Land of Taxes
Oldsmobile distributors, are small blocks and big blocks distributors interchangeable yes dimensionally, no in calibration? Do these hei conversions like pertronix and such eliminate the need for advance springs etc and vacuum advance No you still need to tailor it to your application or have someone set it up to the application?
If you want to do it right get a DUI HEI for older school approach. This means you will need to tailor the vacuum & centrifugal events.
New school is the programmable HEIs that allow electronic settings of the vacuum and mechanical settings<<<<CATS AZZ that's the direction Id go.
Thread Starter
Registered User
Joined: Jan 2020
Posts: 2,896
From: Sarasota Florida
If you want to do it right get a DUI HEI for older school approach. This means you will need to tailor the vacuum & centrifugal events.
New school is the programmable HEIs that allow electronic settings of the vacuum and mechanical settings<<<<CATS AZZ that's the direction Id go.
New school is the programmable HEIs that allow electronic settings of the vacuum and mechanical settings<<<<CATS AZZ that's the direction Id go.
I have set the air fuel several times-to highest vacuum, 15 inches, timing checked several times, its at 10 degrees BTDC, total at 32 all in by 2500. Now when setting the dwell it stays solid at 28, until I rev the motor, dwell starts heading down to 25 at around 2500-3000 rpm. So before I pull the carb off again I-figured I would try a different distributor.. I have no experience changing metering rods and fine tuning a carb..so in pursuit of trying not to chase my tail anymore this was my plan…any advice?
Phantom Phixer
Joined: Dec 2011
Posts: 5,530
From: Apopka, FL
. am still having a lean issue at idle and a lean surge at cruise.. Plugs are showing electrodes almost white, porcelain light brown. I ran a compression test to rule out internal issues with compression, all good.. So I figured I would put the pertronix unit in the 400 distributor, install it in the W30 and see if that cleans it up.
Check all hoses and connections to the PCV , power brakes , heater , or anything else run by vacuum.
Check the carb gaskets and intake manifold gaskets by spraying them with carb cleaner while the engine is running .
If there is a leak the engine will speed up a little.
A pertronix will make no difference in performance or power from a points system.
Thread Starter
Registered User
Joined: Jan 2020
Posts: 2,896
From: Sarasota Florida
It sounds to me like you may have a vacuum leak.
Check all hoses and connections to the PCV , power brakes , heater , or anything else run by vacuum.
Check the carb gaskets and intake manifold gaskets by spraying them with carb cleaner while the engine is running .
If there is a leak the engine will speed up a little.
A pertronix will make no difference in performance or power from a points system.
Check all hoses and connections to the PCV , power brakes , heater , or anything else run by vacuum.
Check the carb gaskets and intake manifold gaskets by spraying them with carb cleaner while the engine is running .
If there is a leak the engine will speed up a little.
A pertronix will make no difference in performance or power from a points system.
CH3NO2 LEARN IT BURN IT
Joined: Jul 2010
Posts: 5,635
From: Land of Taxes
Sounds like a lean fuel condition. The carb is not tailored to the engine, wrong adjustments, gasket set, or a potential vacuum leak....nothing to do with ignition.
Is this an OEM QJet?
What year W30?
What carb number do you have?
What sizes are the primary rods/jets, secondary rods, cam & hanger letters??
What does the primary power piston setup look like in this carb? Are all the parts there or not?
When you assembled the air horn did you pinch the primary rod hanger? Common mistake causing a very lean condition.
Need to do basic rebuild checks like throttle plate seal, butterfly valve seal & timing, Check base, bowl, and horn warp. Are the rods straight?
Once verified all is in spec assemble then concentrate on each circuit one at a time.
To get it right you need to know some specific details of your combo. Engine....cam profile, compression. Drive train, trans, converter & rear gears.
15Hg vacuum signal is OK but right on the line of having to make some idle circuit and transition mods.
Next step, the carb then gets a basic setup or ballpark tune to the above known specs, then super tuned from there.
Once you have verified everything above is in "spec" start playing around with the big levers first...IE Primary rods and jets. Then verify the AVS door clock spring is not too loose or too tight. Then look at Secondary rods hanger and cam.
If this is not an original W30 carb, consider making the power piston modification to make it adjustable... if the provisions are there.
The only way to make this less painful if you are not into playing around is to take the car with the carb installed to a dyno Or send it out for a Pro-rebuild..
Is this an OEM QJet?
What year W30?
What carb number do you have?
What sizes are the primary rods/jets, secondary rods, cam & hanger letters??
What does the primary power piston setup look like in this carb? Are all the parts there or not?
When you assembled the air horn did you pinch the primary rod hanger? Common mistake causing a very lean condition.
Need to do basic rebuild checks like throttle plate seal, butterfly valve seal & timing, Check base, bowl, and horn warp. Are the rods straight?
Once verified all is in spec assemble then concentrate on each circuit one at a time.
To get it right you need to know some specific details of your combo. Engine....cam profile, compression. Drive train, trans, converter & rear gears.
15Hg vacuum signal is OK but right on the line of having to make some idle circuit and transition mods.
Next step, the carb then gets a basic setup or ballpark tune to the above known specs, then super tuned from there.
Once you have verified everything above is in "spec" start playing around with the big levers first...IE Primary rods and jets. Then verify the AVS door clock spring is not too loose or too tight. Then look at Secondary rods hanger and cam.
If this is not an original W30 carb, consider making the power piston modification to make it adjustable... if the provisions are there.
The only way to make this less painful if you are not into playing around is to take the car with the carb installed to a dyno Or send it out for a Pro-rebuild..
Last edited by droldsmorland; Mar 6, 2022 at 08:07 PM.
'70 4-Speed W Machine
Joined: Feb 2020
Posts: 1,248
From: North GA
Andy the drop-off in dwell makes me think your problem could be with the distributor shaft, or other type distributor issues, i.e. worn bushing, worn cam, etc. Bad springs in the distributor could also be responsible for your loss of dwell angle. Do you know someone with a distributor machine that could test it for you?
You seem adamant there is no vacuum leak causing your problems. I assume you know your carburetor should not possess a power piston (’70 W30 4sp).
You seem adamant there is no vacuum leak causing your problems. I assume you know your carburetor should not possess a power piston (’70 W30 4sp).
Thread Starter
Registered User
Joined: Jan 2020
Posts: 2,896
From: Sarasota Florida
Andy the drop-off in dwell makes me think your problem could be with the distributor shaft, or other type distributor issues, i.e. worn bushing, worn cam, etc. Bad springs in the distributor could also be responsible for your loss of dwell angle. Do you know someone with a distributor machine that could test it for you?
You seem adamant there is no vacuum leak causing your problems. I assume you know your carburetor should not possess a power piston (’70 W30 4sp).
You seem adamant there is no vacuum leak causing your problems. I assume you know your carburetor should not possess a power piston (’70 W30 4sp).
Thread Starter
Registered User
Joined: Jan 2020
Posts: 2,896
From: Sarasota Florida
Sounds like a lean fuel condition. The carb is not tailored to the engine, wrong adjustments, gasket set, or a potential vacuum leak....nothing to do with ignition.
Is this an OEM QJet?. -> 256 original quadrajet
What year W30?-> 1970
What carb number do you have?
What sizes are the primary rods/jets, secondary rods, cam & hanger letters??. —>I do not know this, I will pull carb in afew days and try to get this info.
What does the primary power piston setup look like in this carb? Are all the parts there or not? -> looks complete
When you assembled the air horn did you pinch the primary rod hanger? Common mistake causing a very lean condition.—> when I installed I just gently dropped the rods down into the jet , didnt force anything so feel confident on that. However from your post I will be looking at all areas.. I do have Cliffs book, along with the service manual
Need to do basic rebuild checks like throttle plate seal, butterfly valve seal & timing, Check base, bowl, and horn warp. Are the rods straight? —> they looked good when I had it apart, a company called National Carb stickers was on the carb as the 3rd owner had them rebuild it, I assume they added the power piston and bigger front jets.
Once verified all is in spec assemble then concentrate on each circuit one at a time.
To get it right you need to know some specific details of your combo. Engine....cam profile, compression. Drive train, trans, converter & rear gears.
15Hg vacuum signal is OK but right on the line of having to make some idle circuit and transition mods. I know this info, its a 4 speed , 3:42 geras, cam is not the w30 cam was changed years ago to a crane cam, 226/234 @ 50, 491/516 valve lift, hit-282-2-nc cam
Next step, the carb then gets a basic setup or ballpark tune to the above known specs, then super tuned from there.
Once you have verified everything above is in "spec" start playing around with the big levers first...IE Primary rods and jets. Then verify the AVS door clock spring is not too loose or too tight. Then look at Secondary rods hanger and cam.
If this is not an original W30 carb, consider making the power piston modification to make it adjustable... if the provisions are there.
The only way to make this less painful if you are not into playing around is to take the car with the carb installed to a dyno Or send it out for a Pro-rebuild..
Looks like a I have a good size learning curve to work on, I am decent with most mechanical but not internal quadrajet..will take my time and see if I can do this thing..thank you
https://www.amazon.com/Rebuild-Modify-Rochester-Quadrajet-Carburetors/dp/1932494189/ref=sr_1_3?’crid=1J29J707CAVTL&keywords=carburetor +books&qid=1646625568&sprefix=carburetor+books%2Ca ps%2C100&sr=8-3
https://www.amazon.com/Rochester-Car...s%2C100&sr=8-7
Is this an OEM QJet?. -> 256 original quadrajet
What year W30?-> 1970
What carb number do you have?
What sizes are the primary rods/jets, secondary rods, cam & hanger letters??. —>I do not know this, I will pull carb in afew days and try to get this info.
What does the primary power piston setup look like in this carb? Are all the parts there or not? -> looks complete
When you assembled the air horn did you pinch the primary rod hanger? Common mistake causing a very lean condition.—> when I installed I just gently dropped the rods down into the jet , didnt force anything so feel confident on that. However from your post I will be looking at all areas.. I do have Cliffs book, along with the service manual
Need to do basic rebuild checks like throttle plate seal, butterfly valve seal & timing, Check base, bowl, and horn warp. Are the rods straight? —> they looked good when I had it apart, a company called National Carb stickers was on the carb as the 3rd owner had them rebuild it, I assume they added the power piston and bigger front jets.
Once verified all is in spec assemble then concentrate on each circuit one at a time.
To get it right you need to know some specific details of your combo. Engine....cam profile, compression. Drive train, trans, converter & rear gears.
15Hg vacuum signal is OK but right on the line of having to make some idle circuit and transition mods. I know this info, its a 4 speed , 3:42 geras, cam is not the w30 cam was changed years ago to a crane cam, 226/234 @ 50, 491/516 valve lift, hit-282-2-nc cam
Next step, the carb then gets a basic setup or ballpark tune to the above known specs, then super tuned from there.
Once you have verified everything above is in "spec" start playing around with the big levers first...IE Primary rods and jets. Then verify the AVS door clock spring is not too loose or too tight. Then look at Secondary rods hanger and cam.
If this is not an original W30 carb, consider making the power piston modification to make it adjustable... if the provisions are there.
The only way to make this less painful if you are not into playing around is to take the car with the carb installed to a dyno Or send it out for a Pro-rebuild..
Looks like a I have a good size learning curve to work on, I am decent with most mechanical but not internal quadrajet..will take my time and see if I can do this thing..thank you
https://www.amazon.com/Rebuild-Modify-Rochester-Quadrajet-Carburetors/dp/1932494189/ref=sr_1_3?’crid=1J29J707CAVTL&keywords=carburetor +books&qid=1646625568&sprefix=carburetor+books%2Ca ps%2C100&sr=8-3
https://www.amazon.com/Rochester-Car...s%2C100&sr=8-7
Last edited by Andy; Mar 7, 2022 at 03:09 AM.
'70 4-Speed W Machine
Joined: Feb 2020
Posts: 1,248
From: North GA
My 7040256 carb had been tinkered with too when it arrived. The engine ran terrible. I broke open the carb and found a power piston, and wrong jets, just for starters. I boxed the carb and sent it to Ruggles who returned a beautifully calibrated device. While the carb was out I pulled the distributor cleaned, and lubricated it, then tested on a Sun.
From the Sun Distributor Manual: "A dwell variation in excess of 2 degrees indicates worn distributor shaft or bushings."
Hope this helps.
From the Sun Distributor Manual: "A dwell variation in excess of 2 degrees indicates worn distributor shaft or bushings."
Hope this helps.
Thread Starter
Registered User
Joined: Jan 2020
Posts: 2,896
From: Sarasota Florida
My 7040256 carb had been tinkered with too when it arrived. The engine ran terrible. I broke open the carb and found a power piston, and wrong jets, just for starters. I boxed the carb and sent it to Ruggles who returned a beautifully calibrated device. While the carb was out I pulled the distributor cleaned, and lubricated it, then tested on a Sun.
From the Sun Distributor Manual: "A dwell variation in excess of 2 degrees indicates worn distributor shaft or bushings."
thank you, I talked to Cliff, bought a kit from him, he no longer wants to build carbs. Sounds like I definitely need to get distributor out to someone for rebuild. I am goung to try DrDans thought process as best as I can, if that doesn’t do it I will seeif Cliff can recommend another builder..doubtful, he is pretty strong minded lol
Hope this helps.
From the Sun Distributor Manual: "A dwell variation in excess of 2 degrees indicates worn distributor shaft or bushings."
thank you, I talked to Cliff, bought a kit from him, he no longer wants to build carbs. Sounds like I definitely need to get distributor out to someone for rebuild. I am goung to try DrDans thought process as best as I can, if that doesn’t do it I will seeif Cliff can recommend another builder..doubtful, he is pretty strong minded lol
Hope this helps.
'70 4-Speed W Machine
Joined: Feb 2020
Posts: 1,248
From: North GA
I doubt you are creating enough vacuum to even pull the power piston into play; that open passageway needs plugging. There should be no primary rods in your carb either. I like being hands on too, but sometimes it pays to just write the check.
Sparky's Carburetor gets high reviews from folks here, and there are others that can do your carb right, Bob Stone comes to mind, aka Carb Dr. Lexington, PA.
If you want one stop shopping check out Everyday Performance (Ken comes highly rated from the Buick community) he is great for quadrajets, distributors, and parts per posts found online here.
Best of luck to you whether you do it yourself or get help....
Sparky's Carburetor gets high reviews from folks here, and there are others that can do your carb right, Bob Stone comes to mind, aka Carb Dr. Lexington, PA.
If you want one stop shopping check out Everyday Performance (Ken comes highly rated from the Buick community) he is great for quadrajets, distributors, and parts per posts found online here.
Best of luck to you whether you do it yourself or get help....
Last edited by tnswt; Mar 7, 2022 at 12:18 PM.
Registered User
Joined: Sep 2017
Posts: 5,219
From: St. Paul Minnesota
. Ok, reason I asked is a bit long so I will keep to the point best as possible.. reason I ask the question is I happen to have a pertronix I never used and figured I would put it in a stock 400 olds distributor I have..the reason is to rule out a tuning issue I am having on my w30 455.. I have put in new points, condensor, put a Ruggles kit in the carb, new plugs and am still having a lean issue at idle and a lean surge at cruise.. Plugs are showing electrodes almost white, porcelain light brown. I ran a compression test to rule out internal issues with compression, all good.. So I figured I would put the pertronix unit in the 400 distributor, install it in the W30 and see if that cleans it up.
I have set the air fuel several times-to highest vacuum, 15 inches, timing checked several times, its at 10 degrees BTDC, total at 32 all in by 2500. Now when setting the dwell it stays solid at 28, until I rev the motor, dwell starts heading down to 25 at around 2500-3000 rpm. So before I pull the carb off again I-figured I would try a different distributor.. I have no experience changing metering rods and fine tuning a carb..so in pursuit of trying not to chase my tail anymore this was my plan…any advice?
I have set the air fuel several times-to highest vacuum, 15 inches, timing checked several times, its at 10 degrees BTDC, total at 32 all in by 2500. Now when setting the dwell it stays solid at 28, until I rev the motor, dwell starts heading down to 25 at around 2500-3000 rpm. So before I pull the carb off again I-figured I would try a different distributor.. I have no experience changing metering rods and fine tuning a carb..so in pursuit of trying not to chase my tail anymore this was my plan…any advice?
Andy the drop-off in dwell makes me think your problem could be with the distributor shaft, or other type distributor issues, i.e. worn bushing, worn cam, etc. Bad springs in the distributor could also be responsible for your loss of dwell angle. Do you know someone with a distributor machine that could test it for you?
You seem adamant there is no vacuum leak causing your problems. I assume you know your carburetor should not possess a power piston (’70 W30 4sp).
You seem adamant there is no vacuum leak causing your problems. I assume you know your carburetor should not possess a power piston (’70 W30 4sp).
My 7040256 carb had been tinkered with too when it arrived. The engine ran terrible. I broke open the carb and found a power piston, and wrong jets, just for starters. I boxed the carb and sent it to Ruggles who returned a beautifully calibrated device. While the carb was out I pulled the distributor cleaned, and lubricated it, then tested on a Sun.
From the Sun Distributor Manual: "A dwell variation in excess of 2 degrees indicates worn distributor shaft or bushings."
Hope this helps.
From the Sun Distributor Manual: "A dwell variation in excess of 2 degrees indicates worn distributor shaft or bushings."
Hope this helps.
CH3NO2 LEARN IT BURN IT
Joined: Jul 2010
Posts: 5,635
From: Land of Taxes
Sounds like you're performing some good logical troubleshooting steps. Makes things much easier. If Cliff did it call him and talk. He'll help you through it if you ask nice and listen.
Keep in mind there was a reason the power piston wasn't installed in the bigger power 70 carbs. Wouldnt activate the power piston properly (lean) on the BB cars, especially the 4 speeds. Rochester/Delco modified this assembly to get it fat enough to handle the BB monster.
You are very lean per the spark plug read. This means a leak or very little fuel is being introduced in the first two/three circuits of the carbs op sequence, idle/off idle/tip in.
Is the cam choppy?
How many turns out on each air/fuel mixture screw?
Keep in mind there was a reason the power piston wasn't installed in the bigger power 70 carbs. Wouldnt activate the power piston properly (lean) on the BB cars, especially the 4 speeds. Rochester/Delco modified this assembly to get it fat enough to handle the BB monster.
You are very lean per the spark plug read. This means a leak or very little fuel is being introduced in the first two/three circuits of the carbs op sequence, idle/off idle/tip in.
Is the cam choppy?
How many turns out on each air/fuel mixture screw?
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