Thread: 78 Trans Am getting some love

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If you're at 20°, either your vacuum advance is hook up while your checking or your idle speed is high and bringing in mechanical advance.

If your mechanic advance is all in at 2500 rpm that will be your TOTAL, and that's OK, BUT, check it at the higher rpm to be sure. Not unusual to see stock timing curves still advancing clear up to 4000 rpm. If that's the case, you'll leave a lot of horsepower on the table if you don't check it and fix it. You will only be at 4000 momentarily.

Something must be goofed up, 20 is at 750 RPM with the vacuum advance disconnected .I was asking questions earlier about full advance and initial timing because I was having this problem. I better take a closer look at some things. I will double check, but it seemed like I was all in at about 2200

Originally Posted by 53 Chevy5

Something must be goofed up, 20 is at 750 RPM with the vacuum advance disconnected .I was asking questions earlier about full advance and initial timing because I was having this problem. I better take a closer look at some things. I will double check, but it seemed like I was all in at about 2200

Sounds like your curve is starting too soon, put heavy springs in it and check it, if the base timing comes down that's the culprit (your idle speed will drop too). You'll have to start moving springs around to get it dialed in. Try a heavy spring with a light spring. It's OK to mix and match the springs to get what you need.

Double post

Originally Posted by 53 Chevy5

Double post

I'm not see your post other than the above???
Is there another problem?

I had kind of a freak out rant about the Trans Am engine last night but I deleted it this morning. I guess what's still going on with the car is it runs a lot better down the road but I cannot get that thing to idle good. It acts like it is cammed way more than it is. I am still struggling to get 10 in of vacuum and the exhaust fumes will absolutely kill you, it burns your eyes. The idle mixture screws do change the way the motor runs, but I cannot get the fumes down. I have the base timing set at 12°, vacuum it will go to 24. I actually put the vacuum on port vacuum now just to keep the timing back at idle to try to burn up some of the fumes. I can find zero vacuum leaks anywhere. It almost seems like the more it runs the worse it gets. I was thinking about pulling the valve covers off this week and the timing cover and checking the cam timing with a degree wheel to see if that is off.I am pretty much at my end for adjustable things on the outside of the engine.I said in my rant last night that I'm one cuss word away from throwing this POS in the garbage and dropping in an LS lol. In my defense I was quite high and exhaust fumes.

HOLD ON! Don't give up yet. And, lets take one step at a time. It's running rich, we just need to see why, the low vacuum is trying to tell us.
Is the vacuum steady, moving slowly up and down or jumping?
I know you said base timing is at 12°, but did you try the heavy advance springs to see if it's advancing too soon?
Have you checked fuel pressure?

The vacuum is jumpy, not steady. I double checked the springs and they are middle of the road springs and the weights don't move until about 2200. I can adjust the timing good at idle, it will retard or advance like it should.According to the timing light.It will go to about 30 with total which isn't quite enough but I am less concerned about that ight now vs the idle and fumes.I have not checked fuel pressure, One other thing is it will diesel after it is shut off, I assume it is because it is idleing to rich not because of too advanced timing. If I force feed it butane through a vacuum port it will run great.

If it runs good down the road, I’d say the camshaft timing is probably not the problem. If a Holly carb it idling too rich, check the power valve to see if it is blown, and make sure the float levels are set correctly.

Originally Posted by Driver50x

If it runs good down the road, I’d say the camshaft timing is probably not the problem. If a Holly carb it idling too rich, check the power valve to see if it is blown, and make sure the float levels are set correctly.

This is a different style Holly, it's called a "Street Demon" ( not to be confused with their old "Demon" carb) and it does not use power valves,. I had this same idle problem wit the Q jet so I'm almost ruling out the carb, hopefully it doesn't come back to the carb, or I'll swear off Holly forever.....again.

Ok. I just googled a street demon, it’s a totally different carburetor than I was picturing. Did you look down the carburetor throat, while it was idling, to see if any fuel was dripping out of the main fuel circuit?

Originally Posted by Driver50x

Ok. I just googled a street demon, it’s a totally different carburetor than I was picturing. Did you look down the carburetor throat, while it was idling, to see if any fuel was dripping out of the main fuel circuit?

No I did not, I will check that as well.

I did get to read your rant this morning.. I didn't respond as I needed time to mull some things over.

Obviously it's running way rich, and it's a new carb right? SO did you have to set fuel level during initial setup?
I am not familiar with the new Holley so all I can do is guess. But before installation did you check the new carb for loose fasteners? I've actually had that happen! They must have a fuel enrichment circuit in that carb and it more than likely uses vacuum to draw the gas into the engine,. Have you discussed any of the settings with Holley Tech support?

Glenn, Yes, when I get frustrated I start jumping around too much. I'll start checking some of these things out this week, one at a time.
I've had trouble keeping this car running good since I've owned it, people wonder why I never drive it lol.

Originally Posted by 53 Chevy5

I've had trouble keeping this car running good since I've owned it, people wonder why I never drive it lol.

Now we're getting to root. Is this a motor you rebuilt?