I can't drive 55 (1 Viewer)

What do you think the issue is?

  • Fuel Delivery

    Votes: 2 8.3%

  • Carburetor

    Votes: 11 45.8%

  • Vacuum Leak

    Votes: 1 4.2%

  • Transmission/Transfer Case

    Votes: 3 12.5%

  • Ignition Timing

    Votes: 2 8.3%

  • Clutch

    Votes: 0 0.0%

  • Other

    Votes: 5 20.8%
  • Total voters
    24
  • Poll closed .

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MatthewMcD said:
I just had another thought, I haven't rebuilt or even disassembled my distributor. I have only done static testing of the vacuum advance.
Is there a test that I can run to prove that the vacuum advance is working correctly? (Since this is related to the Rochester carb...)

If I remove the vacuum advance assembly, are there serviceable parts? (Photo in earlier posts.)
Click to expand...
You've got the hard line running from carb to dizzy so it's gonna be hard to send a vacuum to the dizzy advance diaphragm while the engine is running, right?
But you can test that the plate moves when you apply vacuum? That advance mechanism does come apart for easy cleaning, check to see if your weights swing freely and your springs are intact. A pertronix would probably help. I got a replacement diaphragm from @4Cruisers once...
 
As pighhead mentioned, the vacuum advance has an arm that extends into the distributor and attaches to the plate. When vacuum is present it rotates the plate to advance the timing. You can see if the vac advance is working by connecting and disconnecting the vacuum hose and using the liming light and watching the timing mark . Mechanical advance is the primary advance mechanism, vacuum advance helps in efficency by advancing timing in low load situations and it advances the timing beyond the mechanical advance and smooths out throttle input. You've already checked the mechanical advance by twisting the rotor and it snapping back. Once you get ahold of a timing with an adjustable timing strobe, you will be able to determine at what rpm the mechanical advance starts to advance and at what rpm it's all in.

There should be no difference between 2hi and 4hi. The shifter at the tcase cone operates the 2wd, 4wd shift collar internally. The shaft and arm on the top of the tcaset is the range shifter. Hi, lo, and neutral.
 
I know transfer case ratios changed over the years but with mine in Lo, 4th was the only usable gear on the road. I maybe got it over 25 once in Lo but the gear noise and jerkiness was so great that I don't see how anyone could drive around for very long without realizing there was a problem.

My guess would also be with the throttle linkage assembly but it's hard to say how they hooked it up with the Webber carb. I know my throttle linkage is very sloppy after 50 years but it will still go to WOT. I would also look at the choke assembly to make sure it's opening up all the way, and on that note check the air filter! I have also heard of cases where the carb to intake manifold gasket was wrong or expanded with age to choke off much of the incoming charge.

I drove for a while with the wrong/incorrectly set points and it can also make it feel like a dog over 30mph. When checking compression adjust your valves beforehand for the best results. Having everything by the book makes a big difference! Best of luck
 
1728308447921.png


I contacted the PO to be sure I wasn't chasing his ghost. He confirmed that when it was his DD he would do 60-65.

Spent yesterday afternoon cleaning the choke cable and getting the throttle cable and carb return springs sorted out.
I plan on warming it up and getting the compression numbers today.

Pighead said:
You've got the hard line running from carb to dizzy so it's gonna be hard to send a vacuum to the dizzy advance diaphragm while the engine is running, right?
But you can test that the plate moves when you apply vacuum?
Click to expand...
Yes there is a hard line (with a short section of rubber line in between) that runs from the carb to the vacuum advance. The plates move when I apply vacuum. It also moves and rebounds when I push the Octane Adjuster.

Edit: Used the wrong pic for the meme. :)
 
Last edited:
MatthewMcD said:
View attachment 3744011

I contacted the PO to be sure I wasn't chasing his ghost. He confirmed that when it was his DD he would do 60-65.

Spent yesterday afternoon cleaning the choke cable and getting the throttle cable and carb return springs sorted out.
I plan on warming it up and getting the compression numbers today.


Yes there is a hard line (with a short section of rubber line in between) that runs from the carb to the vacuum advance. The plates move when I apply vacuum. It also moves and rebounds when I push the Octane Adjuster.
Click to expand...
When you swing by, if you have an extra :30 minutes today, we can do your valve adjustment.
 
RevISK said:
When you swing by, if you have an extra :30 minutes today, we can do your valve adjustment.
Click to expand...
Valves NEEDED adjustment. So, with the help of @RevISK I earned my valve adjustment merit badge. The engine sounds AMAZING, and runs so much better, more perky and responsive to the throttle, but it still does not go faster.

Compression numbers this afternoon.
 
It seems you've done about all the test for the dizzy. As someone suggested you might want to check the point gap or dwell. It can effect timing. You will have to retime it after an adjustment. You can adjust points with a feeler gauge or dwell with a dwell meter. Make sure the shaft doesn't wobble. I would probably look more closely at the carb and vacuum leaks.
 
MatthewMcD said:
Valves NEEDED adjustment. So, with the help of @RevISK I earned my valve adjustment merit badge. The engine sounds AMAZING, and runs so much better, more perky and responsive to the throttle, but it still does not go faster.

Compression numbers this afternoon.
Click to expand...
It was a massive difference in how this truck ran after the valve adjustment. Astounding really.

Seeing Matt’s face light up when he started the truck after was priceless.
 
OK, I have to say, preparing myself for the compression test results was like "looking forward" to a cancer screening. :)
1150
2142
3130
4135
5135
6150

Since I had them out, here are the plugs:
20241007_190342675_iOS.jpg

Put it all back together and took her back out for a speed test, she sounds better, but still working too hard to get to 54 mph.

20241007_194849000_iOS.png
 
you can pull the skid, drain tcase, remove side inspection/pto cover, jack up rear, make sure its in 2wd, I spin driveshaft by hand to confirm on mine, then shift & spin, put trans in nuetral, spin tire with foot, chalk a tire if its open so dline spins and watch gears, look at collar when shifted to see if it is moving all the way, if you have hubs, leave them unlocked and engage 4wd, spin with foot & feel nose cone for bad bearing. Are brakes dragging ?, is e-brake dragging ?
 
MatthewMcD said:
OK, I have to say, preparing myself for the compression test results was like "looking forward" to a cancer screening. :)
1150
2142
3130
4135
5135
6150

Since I had them out, here are the plugs:
View attachment 3744436
Put it all back together and took her back out for a speed test, she sounds better, but still working too hard to get to 54 mph.

View attachment 3744437
Click to expand...
Wasn’t #3 the one that one of the oilers wasn’t so, excited?
 
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