Lauper84

A 700rpm drop under load is insane. I’ve done everything I can think to do and everything everyone one here has suggested I do—except replacing the torque converter.

I think I’m done. ready to sell this thing. I really just wanted a nice 78-81 four speed anyway but figured this could keep me entertained for a while. Didn’t think it would be such a money pit.

dan5

You have proven that it is possible to to run at 1200 in park / 800 in gear and you know that to do better than that will likely require a torque converter change.
Something changed and you'll need to go back to fundamentals to track it down. The problem will be spark, fuel, or mechanical. Given the short time frame where something made a large shift, you need to back to fundamentals and understand why power at idle has dropped.

• Does the car have other driveability symptoms? Is power good, throttle response the same, and so forth.
• What is your fuel pressure and did your regulator shift setting?
• Is the timing the same? Initial and vacuum?
• Is the vacuum level in neutral the same?
• The carburetor is new and just installed. It is possible that a small piece of build related debris has found its way into an orifice.
• All the plug wires connected tight? Any audible misfire in the exhaust?

It's hard to make a long distance diagnosis without more information. I am sorry it is being difficult, but every mechanical malfunction has a root cause if you look hard enough. It certainly can be discouraging, I've been there.

GeneralDisorder

iTrader: (1)

Thanks! Things have changed a bit.... AFR heads and such, Had to swap valve covers because my request to drill the AFR heads for center-bolt was not realized. Simple mis-communication I suspect. No big deal.

Yes it's pretty much all business. LoL.

GD

dan5

To add to my earlier comments, if you go through the basics and they're good, I would check the carburetor. I have not worked with the Street Demon before, it is a different animal from a traditional Holley, so I pulled up the instruction manual. I expect you have this for reference.
Street Demon instructions

If it was mine, I would start by checking the air bleed orifices (they ought to be in the air horn below the choke plate) to be certain they are clear. You can even spray a little carb cleaner down them. If that doesn't work, next would be to remove the carb and check the jets and idle feed orifices. The instructions show how to remove the base plate and access the jets. I would check that the primary jets are clean and that the idle feeds are clear. Don't use wire to clean them. I think that the red circled areas are the idle feeds, but I only have the picture to judge. Normally in this type of carb, the idle pick-up feeds are at the bottom of the bowl like in the picture, feed to the top of the bowl, then down the body to the mixture screw passages. It only takes a speck of debris to block these and mess up your idle. Watch for anything floating in the gas from the float bowl.


On a separate note, if you can get it back to 1200 / 800, they do have a paragraph regarding long duration cams. Yours isn't that long, but combined with your torque converter, this might apply to your situation. You should check your manifold vacuum at 800 in gear. If you're close to the 8-10 inch range, the metering rods may be lifting and richening your idle in gear vs in park.