Technical Cadillac 390 power loss when in gear

Wouldn't think your timing curve could make a great deal of difference. .gonna reread entire thread

 

You’re a glutton for punishment

 

For your additional viewing pleasure:

A vacuum reading at idle:

 

Do you have a tachometer on the beast?

 

For testing, yes

 

Points distributor ?

 

Hei came out in 72 or 74 I think

 

Pertronix Ignitor II

 

Okay. Seeing you don't have points, you need something to pull the timing back at idle. So just put one of the lightest springs you got on it and try it. See if it responds better. If it doesn't, then your problem is probably not timing related.

 

The thing is. .at least with the Judge, driving with the tach. .your sense of "correct gearing" is pretty easy to evaluate by the seat of my pants. ..driving with the tach would confirm if the trans is stuck in a higher gear. .wild ass guessing. ..

 

Wouldn’t a stiffer spring pull the timing back at idle as it would be holding the weights from moving outward as easily?

 

Drove it with the tach after dropping the exhaust and adding the spring, but the tranny is acting stranger than before, but it was getting late so I couldn’t diagnose it completely tonight.

 

So can you feel the three shifts?

 

Currently feel 2 didn’t seem to want to get up into 4th, I believe. Was a short test drive due to the lack of exhaust and time of day.

I can test again in the morning

 

Tomorrow ....

 

Hard to tell from a video sometimes, but it sounds like it's wound out pretty good. Set the idle RPM to 450-550 or so, nice and slow and then see what you got.

 

That’s at 580 rpm. I think it is just the echo off the hood and garage door making it sound higher :shrug:

 

Going to start from ground zero, I think. Plan is as follows:
1) leave exhaust disconnected
2) disconnect all vacuum driven items and plug manifold and carb vac ports
3) compression check
4) verify TDC markings with piston stop and ensure valves are full seated when @ TDC
5) check plug wires for correct firing order
6) set timing w/o vacuum advance connected for max manifold vacuum -1” and record degree value of initial timing
7) test vacuum advance with hand pump.
8) attach vacuum advance to ported vacuum port
9) tune carb air/fuel using vacuum gauge and tach and set idle speed
10) check voltage at coil
11) spark quality test
12) check for vacuum leaks
13) test drive...if it is still an issue:
A) reattach exhaust
B) drive to transmission shop

Thoughts?

 

Let's just confirm that your transmission hasn't flaked out on ya... unusually low RPM going through the gears and seemingly no pep smells like you're just operating way below your torque and horsepower curves but that's just me. See you this afternoon!

 

Do you have a dial micrometer with a magnetic base laying around there anywhere? Sometimes it's hard to tell just by looking if one or more cam lobes is not giving you the lift you should have.

 

Probably a good idea...it’s acting a bit flakier since I went through the valves and changed the fluid. And I have already done all the above anyway it would just be repeating things to go through the motions.

Still have a huge atf stain to clean off my driveway...

 

I have a dial meter but not a mag base.

 

I'll bring mine then Plus should I bring my power washer?

 

That would be spectacular...

 

Somehow I'd blame the Pertronix. I don't trust them. At least on a GM with points some you can adjust the dwell while it's running. Maybe the 62's dizzy cap doesn't have the metal window to open up to get to the points.

 

I would too but the problem existed prior to the pertronix installation. And it uses the existing cap/rotor. And I have swapped them as well.

 

Ah OK. So that might rule that part out. Have you tried swapping coils? Another thing you might need to check is spark plug gap if you haven't done so.
Another thing to consider is the torque converter, it could be slipping. Have you tried power braking it?

 

I came late to the party, but it sounds like an exhaust restriction of some kind. Had it happen before and it sounds like the same symptoms. I might have missed it, did this just start? Was it fine then it wasn't all the sudden?

 

Just got the car a couple months back it’s always been like this... I currently have the exhaust pipes disconnected at the flanges. No marked improvement other than sweet sweet sound of an engine with no exhaust