MSD Atomic EFI

[dhamp]

Ya know, one of the big things with that carb over time, was those rear butterflies sticking after everything warmed up.. Another thing, that engine may do better with the 800cfm Q Jet, if you dont go efi.

Maybe that's why my old man had 'em tied open. I just assumed that they weren't operating and did my rudimentary testing.... I drove it hard to get a butt-dyno reference, then untied the secondaries, then drove it again. I couldn't tell any difference. Was it a safe assumption that they're opening? If they're not opening under full throttle, would it bog or something indicate they weren't opening? If I rev it for a certain amount of time, should they open? Or does the engine have to be loaded (actually pulling the weight of the car) to get enough vac to open 'em?

 

[Jims86]

Maybe that's why my old man had 'em tied open. I just assumed that they weren't operating and did my rudimentary testing.... I drove it hard to get a butt-dyno reference, then untied the secondaries, then drove it again. I couldn't tell any difference. Was it a safe assumption that they're opening? If they're not opening under full throttle, would it bog or something indicate they weren't opening? If I rev it for a certain amount of time, should they open? Or does the engine have to be loaded (actually pulling the weight of the car) to get enough vac to open 'em?

Q jet right? secondaries are mechanical. they did have a Vacuum break for the top secondary butterflies.

 

[dhamp]

Q jet right? secondaries are mechanical. they did have a Vacuum break for the top secondary butterflies.

So if I grab the throttle linkage and pull it to full throttle, they should open up? I'm "pretty sure" it's a q-jet. I remember my pops talking about having a Rochester and when I bought a new throttle cable i got the one for rochesters and it fit/worked. I thought I had a pic of the carb, but I can't find it.

 

[Jims86]

So if I grab the throttle linkage and pull it to full throttle, they should open up? I'm "pretty sure" it's a q-jet. I remember my pops talking about having a Rochester and when I bought a new throttle cable i got the one for rochesters and it fit/worked. I thought I had a pic of the carb, but I can't find it.

Yup, full throttle, and the secondaries open. the top secondary valves open by the air passing them...that way, the secondary metering rods operate on the damds of the air entering the engine. Kinda like a mechanical Mass Airflow System.

 

[dhamp]

Thanks for the info. Next time I have the car with me I'll get pick to verify and test out the mechanical operation to see if it's working.