1974 F Distributor Vacumm Advance/Retard?

[Rocky_LC]

It is refreshing to read a theread where:

1. The poster already has a plan
2. The problem and symptoms are clearly documented
3. The poster has a FSM and has read it.
4. The poster listens to suggestions and lets everyone know the response.

Very informative thread. THanks to everyone. I wish my troubleshoots went as well.

Rocky

 

[mikeob1]

Good News and Bad News I Guess

I sprayed two bottles of carb cleaner all around the manifold tonight. I got no response from the engine.

I did detect a vacuum leak around the carburetor. In the attached picture, I got a boost when spraying around the area in the red box. The leak seemed to be in the seam between the cast iron base and the middle portion of the carb.

Unfortunately, I ran out of carb cleaner before being able to pin point.

I'll test again tomorrow and see if I can isolate. At least, presently, it seems the manifold gasket repair job was successful.

 

[mikeob1]

case closed with the idle

Thanks to all who have helped me solve this issue.

I tightened carb bolts and have no vacuum leak.

So: There were two issues occurring.

1. I had a leaking manifold gasket close to the firewall.

2. The carb throttle plate is adjusted three different ways.

1. Fast Idle setting
2. Slow Idle setting
3. A screw that can only be adjusted with carb off. It limits how far closed the primary throttle plate can go.


I pulled carb this morning and noticed the throttle plate couldn't actually cover the "higher" idle fuel port because this screw was cranked in too far. I adjust screw #3 out so the throttle plate, in fully closed position without fast or slow idle screw setting weren't touching.

I backed screw #3 out. Since I had carb off, I pulled accelerator pump arm off and removed idle-cut solenoid. I sprayed carb cleaner in solenoid hole and watched it weep out both idle fuel ports located at the bottom of the flange. And I also saw it come out the air bleed in the top of the horn. This was the most convincing test to prove the idle fuel circuit in the carb was capable of supplying fuel to the intake.

Just for fun...i touched my idle solenoid to the batter and watched it retract.

I also pulled the idle mixture screw all the way out. With the carb off, you can see light all the way through the hole. I kept the spring off the idle mixture screw and sprayed it with some silicon lube so I could adjust it easily just to avoid chewing up the pretty brass head while adjusting.

I put carb back on...hooked up. I new now that the throttle plate was closed and the only place fuel could come from was the fuel hole in the bottom of the primary. I backed out the idle mixture a buch...like 3 turns.


I started it up and let it run for awhile choked...engine not warm, ya know.

I pushed choke off and verified the slow idle screw was contacting the plate.

Low and behold...the truck idles low. Problem solved. I drove it around a bunch and it was sooooo nice to be able to roll up to a stop sign, or step on the brakes and not have the engine die!

Now...for anyone who followed this thread...you're not going to believe this.

Most of my intitial test cruising was under 30 mph.

I took it to a faster road and ran her at like 45-50 for awhile.

All's good...cruising along...and i hear this sound that seems like a tire rupture, or the sound your air compressor makes when you let the air out. Pshhhhhhhhh!!!!

The thing is still running fine. I go to Sonic and get some fries. I start it and drive 1 mile back home. I pop the hood and find coolant on head. I had the valve vent plugged for testing and the plug is off.

I think I have a blown head gasket. I did compression test and found #3 and #4 to be 124 and 125 psi.

At least I know how to make the rig idle right. Now I guess I get to pull the head off.

 

[Pin_Head]

I wouldn't presume it is a blown head gasket w/o further testing.

 

[mikeob1]

Yes I agree, can't jump to conclusions.

Here is what I do have:

1. The sound that occurred during the test drive.

2. Coolent on the driver's side of the head.

3. Lower Compression numbers than a test a few weeks back.

4. Idle Intake vacuum dropped from 17 - 13 at idle from before test drive to after test drive.

I thought the sound could have been the charcoal canister.

Then when I saw the coolant I thought it was the radiator cap. There was no indication of a radiator leak on first inspection. If the cap blew I would have seen steam coming from the engine. And I would have expected to find coolant around the engine and a shiney clean spot on the inside of the hood above the cap.

More information: I was test driving with the air cleaner off. As such I had a soft rubber cap over the valve cover vent which is now gone. Another possibility is some sort of pressure build up in the valve cover. I could understand oil, but I wouldn't think water should find its way to under the valve cover cap.

I was going to stop by the store and buy a leak-down tester and run a leak down test.

I'll post what I find.

 

[rsbcruiser]

So today I got up before the sun and started in the garage while it was a balmy 90. I pulled my distrib off my 74. Gave it a good looking at and ready my trusty FSM. The points looked good, except they were gapped at .009 inch. I changed that to .016 inch based on FSM. I also checked the condensor and it was in spec at .022 micro-farads. Cap and rotor were fine and I added some new ignition wires from Napa. Nice wires, except the coil line was too short, so I used my old one.

I put in six new plugs (NGK-BPR5ES-11) gapped to .028 inch.

I put the dizzy back in and fired up the F engine and set the timing so the BB is dead on the pointer at 7* with the vacuum line DISCONNECTED FROM THE DIZZY. My tach was reading about 900-1000 RPM. I tightened down the clamp and double checked the timing. Same deal...7* pefect.

Now...I connect the vacuum line and check the advance. Low and behold, we are at TDC. 0*. The other end of the vacuum line is connected to the port on the intake manifold.

Which brings me to my question... What purpose does this vacuum retard serve?

Dude, unless you are trying to restore to original, first chance you get ditch that barking dog. It is probbly worn out anyways. Hit spector for one of there toyota dizzies and a petronox poinless sys. Never look back! Downey probably has the best dizzy with 40deg of advance. Gotta drill a new wire hole and punch out the pins to install the petro correctly, not a plug and play but worth it. Did you know that you have a special F engine? It has 9 to 1 comp and all other features of th 2f besides larger bore. Truly unique, the only year they did this.

 

[mikeob1]

I Got a Cylinder Leakage Tester

I read the instructions and am going to do the leak down test on Saturday morning. Does anyone have tips for getting each cylinder to TDC?

 

[mikeob1]

Also...here is video of my vacuum test

Here are two video clips of my vacuum test. Truck idling no choke.

http://www.youtube.com/watch?v=k6eLebirqsw

http://www.youtube.com/watch?v=NQEj2AmNyhs

I can spray the top of the intake behind the carb and after a second the guage will rise to 16. I'm not sure if this is really a vacuum leak, or if the carb is sucking in some of the fumes of the carb cleaner.

 

[mikeob1]

No leak down test - waiting for crank

I didn't get to do the leak down test this weekend. I did drive my cruiser around and it seemed to work fine.


Still idles down low, which is great...but it is a little rough (as you can see from my vacuum guage).


I'll post when I get a crank to rotate the crank shaft. I want to be able to place each piston at TDC, so the "rock against 4 th gear" trick wont work.

Talk to you soon.

 

[Pin_Head]

You can easily turn the engine with a ratchet on the alternator shaft bolt. If the belt slips, just press down on the belt to increase tension.

 

[Coolerman]

You can easily turn the engine with a ratchet on the alternator shaft bolt. If the belt slips, just press down on the belt to increase tension.

Especially if you remove all the spark plugs...