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Post by Scoutpilot on Jan 18, 2015 12:25:06 GMT -5
Have you looked at the accelerator pump?
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athawk11
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Post by athawk11 on Jan 19, 2015 13:42:45 GMT -5
Yes Sir, I did. In fact, I replaced it on Sunday when I took the whole thing apart again. (I didn't replace it on the initial rebuild because of issues you had mentioned with new ones.)
I also thought I found a smoking gun. The air intake jet appeared to be clogged up. I cleaned it along with the rest of the jets and passages...still no idle. When I say no idle, I literally mean...It will not hold an idle no matter how far I drive in the idle set screw. Even if I get my testing tools, I'm not entirely sure how I'll be able to use them...unless I close the choke to keep it running. But wouldn't this give me false readings?
Tim
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Post by Scoutpilot on Jan 19, 2015 19:43:54 GMT -5
Having to idle with the choke closed is indicative of a vacuum leak. It could be a bad shaft with worn bores. have you mic'ed them? Nominal is .3125"ID/OD. Wobbly shaft is a vacuum leak. It could be a crack in the throttle itself. It could be an improperly seated rivet/plug. It could be a blocked Pump Jet vent. It could be a blocked barely vent.
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athawk11
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Post by athawk11 on Jan 19, 2015 22:03:27 GMT -5
I didn't remove the rivets because I don't know how to reseat them properly. Can you point out the pump jet vent? And the barely vent? Again, it may be a bad throttle shaft, but it would have had to go bad just sitting idle. (No pun intended)  Tim |
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Post by Scoutpilot on Jan 20, 2015 6:14:59 GMT -5
My apologies. I meant to write "barrel" vent. Removing the Air Horn and looking in the area of the Low Speed Jet passage you will see two holes in the barrel at the top. These are vents and need to be clear. Their size is calibrated and must not be altered. However, you can use a VERY FINE SOFT WIRE to probe and clean. Flush the passage with spray carb cleaner, then clean, dry compressed air. Below is a pic of the Pump Jet vent.
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athawk11
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Post by athawk11 on Jan 25, 2015 16:33:40 GMT -5
Scout,
Okay, I ran some tests on the motor, but I used the Carter that will actually hold an idle.
RPMs at idle: 750. (It sounds the best here)
Dwell: 0... No needle movement at 1,200 RPM
Vacuum: A steady 16 at idle. Elevation...5,400'. Throttle hard...drops to 5. Let off...climbs to 21 then settles back at a steady 16.
What do you think?
I'm beginning to think the Carter that lost its ability to idle is the carb I just "cleaned up". I may have confused it with the carb I have on it right now. I bought a couple new kits from Ron Fitzpatrick and will do a complete rebuild on my bad Carter. Hopefully this will get me back up and running.
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Post by Scoutpilot on Jan 25, 2015 19:25:08 GMT -5
750 may sound good, but 650-700 is best. I wouldn't let a carb out of my shop at 16. 15 is bare minimum. This is a no-choke idle? What is your mixture set at? Dwell has to indicate something. Can't be zero with the engine running unless there's a bad connection and then your Tach would be wrong. I'm still leaning toward a vacuum leak. I've got one in the shop right now. The client sent with the carb and kit what he claims is a NOS throttle shaft. It mic's out at .310". I've tried to use it in newly-installed un-reamed bushings. Other than a 42º Dwell, I'm getting nearly identical numbers as you. I'm going to cut a new .3125" shaft for it tomorrow.
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athawk11
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Post by athawk11 on Jan 25, 2015 22:57:18 GMT -5
Hmm, based on one of your links, I figured 16 was a pretty good reading at my altitude. It suggested a 1 point drop for every 1,000 feet rise in elevation would still be acceptable.
This reading is with 0 choke. This particular carb is working quite well.
The mixture is set at 2 full turns out.
I boughtf the same dwell/tach meter you have. It's hooked to a ground...black cable...and to the negative side of the coil...green cable. I revved the engine to 1200 RPM, held it there, then moved the switch to Dwell. The needle moves to center and barely wiggles. Am I doing something wrong?
Tim
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Post by Scoutpilot on Jan 26, 2015 4:55:49 GMT -5
The Actron Dwell/Tach is primarily for 12V, 6 and 8 cylinder engines, but. Doubling the 8 cylinder scale gives you the four cylinder readings. I check dwell at idle. Minor difference in set up, I connect ground (black) to the negative battery post and the hot lead to the post on the distributor. That shouldn't make a difference though. You are correct that one should expect a drop in vacuum readings as altitude rises, but I think yours could be better. Two turns out for the mixture is pretty much standard for an old throttle at or near sea level. Since you don't, and I'm assuming this, have a 75-548 High Altitude, One-Step Leaner Metering Rod installed, but instead the standard 75-547, the only option you have is to lean the mixture slightly with the Idle Mixture Screw. In about a month I should be clearing out the schedule and will be experimenting with plating some metering rods to bring them to the size of a 548. I intend to make a few and will be accepting high altitude volunteers to try them.
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Post by Scoutpilot on Jan 26, 2015 8:25:29 GMT -5
Tim. I searched my Metering Rods stock. I have found a 75-548 that mic's out at the requisite .o485". Do you want it?
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athawk11
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Post by athawk11 on Jan 26, 2015 12:53:30 GMT -5
Heck ya I want it. You hooked me up with one a year or so ago. I used it in the green Willys. This one would be for Rachel's Willys. (my Wife) I would also like to be added to your test team when you try the plating.
I remember seeing your conversation about plating the rods. Was it Lew Lagwig that tried this?
I'll try checking my dwell again tonight. I'll do it at idle. What should I see on the meter?
Let me know How much to send you for the rod. I'll shoot you a Paypal.
Thanks again for everything.
Tim
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Post by Scoutpilot on Jan 26, 2015 14:10:03 GMT -5
I figured you for a hard sell. Ouch! Stop twisting my arm. OK. More common rods are for sale on eBay for $10.00 each. The is a rare part so .... $15.00 to your door. PayPal at pacholskifamily@hotmail.com
I think I still have your address.
OK. Look this photo over and I think you'll get the idea. Both Dwell and RPM scales are set up with the top scale being 8 cylinder and the bottom is for 6 cylinders.
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athawk11
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Post by athawk11 on Jan 26, 2015 19:36:13 GMT -5
Scoutpilot,
Paypal sent.
Here is a video of my tests. After extensive reading, I would conservatively put my vacuum reading somewhere around 18 if we were testing it in North Carolina.
My vacuum was at a little better than 16, but I retarded the timing a little to see if this improved performance. I am probably about 3.5° before top dead center with the current meter readings shown in the video. I had read somewhere that retarding the timing at my altitude might improve performance.
None of this helps me with the Carter that won't idle, because it's not the carburetor installed right now. I still figured this would be good fodder for you and others that visit the OJC web site.
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Post by Scoutpilot on Jan 26, 2015 20:26:12 GMT -5
Where is the vacuum gauge hooked up? Manifold or carb? Your video does show a smooth idling engine. If you're happy with it, run it. But I would double check the points setting. It's probably at .022-.023"
The "no idle adjustment possible with the idle mixture screw" tells me, you've got a vacuum leak in the other one.
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athawk11
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Post by athawk11 on Jan 26, 2015 21:45:51 GMT -5
Thank you for the feedback. I will check the points. I'm also going to switch to copper core spark plug cables, and work on the idle and idle mixture a bit more.
While rebuilding the other Carter, I'll double check the throttle shaft for spec.
Thank you again for everything.
Edit...the vacuum gauge is connected to the manifold.
Tim
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