4180C rebuild observations and questions

[Saturn V]

Today I finally started the rebuild of the 4180C 80163 service replacement carb that came on my car when I bought it 3 years ago. The engine is hard to start cold and runs very rich (10.8:1 AFR) at full throttle. I have a separate thread with pre-teardown AFR measurements and questions here. I plan to continue that thread with post-rebuild tuning observations and questions. This thread will be devoted specifically to the rebuild. I've got lots of pics to post later, but already have an important question.

The throttle baseplate appears to be warped. The best measuring tool that I have is a steel framer's square, but it is new. When I measure the bottom surface of the baseplate (the part that faces the intake) from corner to corner, it appears to be pretty flat, with maybe only a few thousandths gap on one corner. When I measure across the other two corners, if I place the square flat against one corner, I can measure .020-.025" air gap at the other corner.

The new base gasket is about 1/8" thick, so is 020" too much warpage, or within tolerance? What else should I measure/check? There are probably places in town who could mill the baseplate, but likely not today on a holiday weekend. I'm tempted to put it back together and run it. Comments?

[Saturn V]

Just found this thread where FoxChassis said that he used a block sander and file to straighten his warped base plate. I might try that.

http://vb.foureyedpride.com/showthre...ock-84-GT-carb

[mustangxtreme]

I've used a thick sheet of glass with wet/dry sand paper and some light lubricant like WD-40/PB Blaster. Sand in a circular motion and rotate the part every now and again to even out the material removal.

[Saturn V]

I've used a thick sheet of glass with wet/dry sand paper and some light lubricant like WD-40/PB Blaster. Sand in a circular motion and rotate the part every now and again to even out the material removal.

That sounds like it would work. I ended up digging out my old auto body long sanding block. I went through 6 strips of 180 grit paper and this worked well, though it was tedious. Thanks for the tip, FoxChassis.

Got the carb running ok, though with some stories and pics to share. But later ... need to spend time with my family now.


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[Saturn V]

OK, I finally finished some fine tuning on the carb today and have time to document the rebuild. I used the Holley 3-1346 rebuild kit.

I was tempted to go ahead and increase the primary jet size and install the 4150 secondary metering block conversion kit, but I ended up keeping it basically stock, since I wanted a back-to-back comparison to how it ran before the rebuild. Besides, the engine is completely stock, except for the Performer 302 intake. I figured if the #62 primary jets and stock secondary metering plate are OK for a 210 HP 85 engine, they should be OK for a 175 HP 84 engine, even with more alcohol in the fuel today. At least I’ll try the stock config before modifying further. Here's how it is today:

Primary jets – #62 (622, close limit) I think 83-84 got #61 jets and 85 got #62’s. This is a service replacement carb that was installed on 84-85, and maybe 83’s?)

Secondary metering plate – 34R-10465-B (stock for 85, I believe)

Secondary spring – Plain (one step stiffer than stock purple), after some tuning

Stock .028 accelerator pump squirter – I had a .031 ready to install, but it required a cone-shaped screw that I didn’t have, so I re-installed the original.

As of today, the car still runs really rich (10.5 AFR) at full throttle and idles rich (12-13), too. I didn’t find anything unusual inside the carb during the rebuild, so I don’t know why it’s running so rich. AFR at cruise (40 MPH) is 14-15, so I think the primary jets are OK? I’ll post more comments in the separate tuning thread.

http://vb.foureyedpride.com/showthre...180-AFR-tuning

[Saturn V]

I used an old aluminum cake pan to catch the fuel from the float bowls.

[Saturn V]

The primary bowl was relatively clean inside, just a little sediment in the lower corners.

[Saturn V]

I don’t know what that red-colored piece of crud is on the power valve. I saw some of that on the old spare carb that I tore down to experiment with removing the emulsion tubes. The crud almost looks like it’s something from the gasoline that has settled out and formed around the power valve spindle?

[Saturn V]

I tried to carefully pry the front metering block with a small jeweller’s screwdriver. I still managed to knick the outside of the metering block and a little bit on the main carb mating surface, but not enough to interfere with the gasket surface. See the upper left corner of the second pic below. Maybe there’s a better way. Whatever you do, be careful not to scratch the gasket surfaces.

[Saturn V]

There have been a couple of posts recently about the little clip that holds the choke rod to the choke plate. I believe it is called the choke rod retainer. Here you can see the black plastic clip. Mine was loose, so I replaced it with the new one that came in the Holley rebuild kit.

[Saturn V]

I don’t know why clutch-head screws are used on the metering plate. I just used a narrow flat blade to remove/install them. The screws were pretty loose on mine … barely finger tight.

As-found secondary metering plate. 34R-10465-B. I believe this is the same as factory for 85, not sure about 84.

[Saturn V]

Here’s the bottom side of the throttle body. There are some rough machine marks visible. Are these typical, or has someone likely tried to flatten the surface?



As mentioned above, the bottle of the throttle body wasn’t as flat as it should be. I measured about .025” gap in a few spots, mainly in the middle and at the mounting holes. So I sanded it with an auto body sander and 180 grit paper for about 45 minutes. I finally got it flat to within about .005” in a few spots (as best as I could measure, no guarantees).



I sanded in different directions to try and get the surface more evenly flat.

[Saturn V]

OK, so I tapped the emulsion tubes (4-40) to remove them (see other thread where I did that on a junk carb for practice).

http://vb.foureyedpride.com/showthre...oval-with-pics

However, on my good carb, these just didn’t want to come out with the shoulder. I tried wiggling all different ways, but the shoulders wouldn’t budge. Not wanting to damage the tubes, I abandoned the removal and carefully tapped them back in. The carb seemed relatively clean overall, so I rationalized giving up on these. So now I had brass shavings in the emulsion tubes and couldn’t remove them to ensure all debris was removed.



So I just sprayed carb cleaner through the other end of the passage for a few seconds until I was satisfied that all shavings were gone (I hope). I felt a little defeated in not removing the emulsion tubes to clean them out, but sometimes you have to fight the more important battles. I just sprayed a bunch of carb clean through the passages. I only bought one large can of carb clean and used that up and part of another can that I already had throughout the rebuild. So have at least two full cans ready.

[Saturn V]

In gathering all supplies, I went to the grocery store and spent about $5 on disposable aluminum pans. I used a large, square one for the carb base.



Then I carefully crumpled the pan around the carb, to minimize the amount of volume of the Berryman Chem-Dip carb cleaner required to submerge the carb body.



I used a small, rectangular pan for the primary metering block and secondary metering plate. The fit was almost perfect. I placed both of these in a plastic oil drain pan, in case the aluminum pans (particularly the one that I crumpled) developed a leak (it didn’t).

I let these soak for a couple of hours. More time might have been better, but the carb looked to be relatively clean and I wanted to get it back together the same day.

After the soak, I sprayed all passages liberally with carb cleaner and followed up withcompressed air blowing, more carb cleaner, then final blowing.

[Saturn V]

I filled another small, rectangular pan with water and submerged the floats to check for air bubbles, but they looked OK.



I used some other pans to hold parts after I cleaned them.

[Saturn V]

The old accelerator pump transfer tube o-rings looked to be pretty worn out (flattened on the edges).



I parts in the rebuild kit aren’t individually labeled, but I picked the o-rings that looked closest to the correct size.

[Saturn V]

As suggested by JACook, I dipped the power valve gasket in fuel before installing the power valve. The little gasket bubbled for about 30 seconds.
I thought I took a pic of the new power valve to look-up the numbers, but I guess I didn’t get a good pic. The markings were different from the previous power valve, but it still appears to be the two-stage type. I think I recall seeing C 5? I need to look that up later.

[Saturn V]

For the fuel bowl transfer tube, I installed the new o-rings on the outside and the old o-rings on the inside. This way the new o-rings will provide the first seal inside the float bowls. I also applied a very light coating of Vaseline to the o-rings, per what I’ve read. I think that helps the ensure that the O-rings don't bind and get damaged during installation.

[Saturn V]

The accelerator pump cam was pink, with the screw in the #1 slot. I re-installed it the same way.

[Saturn V]

The vacuum secondary check ball was missing … I assume the previous rebuilder didn’t install it. I’ve read that the check ball will slightly delay the secondary opening, but that the check ball helps ensure that the secondaries open and close more smoothly.

Speaking of check balls, I remember that the accelerator pump nozzles had a check ball underneath, but I've also read that some carbs instead have a little metal piece that looks like a plumb bob (with a cone-shaped tip). I didn't tap on the ball, as suggested, just re-installed the original (since I dropped and lost one of the balls that came in the rebuild kit).



The as-found spring was purple.

[Saturn V]

I bought one of the Quick Fuel adjustable vacuum secondary actuators, but the little gasket was missing and the hex (.050”) of the tiny Allen screw used to hold the set screw in place stripped on me, so I didn’t use this one. I think I’ll take it back and try and get a refund at the local speed shop.



I always like backup plans, so I installed the Holley quick-change spring kit that I had also bought. I did install the check ball that came in the carb rebuild kit. I also put the purple spring back in for initial tuning.

[Saturn V]

After re-installing the carb and starting the engine, I had a hard time getting the primary float level adjusted. Somehow, the adjusting nut got a crimp in it and wasn’t letting the needle screw through, so the level was set way too low. I re-used one of the old nuts and all was OK.

[Saturn V]

With the purple spring in place, the secondary throttle hangs up a little and won’t close all of the way. I fiddled with it and got it closed more. I couldn’t find anything binding.

I later tried the first yellow spring (lighter than purple), but it seemed that I could still feel a bog. Then I went to the plain spring (stiffer than purple) and it seems that the bog is smoothed out more.



Oh, yeah … the sorry old instructions that came in the kit have been photocopied so many times they are almost unreadable. The part about adjusting the secondary throttle screw says adjust until the screw hits the tab and then “3 … 4 turn”. Huh?? Is that ¾ more turn, or 3 or 4 turns? I downloaded the original copy at the Holley website and it said 3 or 4 turns. But that is totally wrong and resulted in a very high idle at about 3500 RPM. I experimented and in the end ½ turn seems to be OK for my engine.

[Saturn V]

During removal to adjust the secondary throttle screw, I noticed that the black throttle base gasket that came in the Holley rebuild kit is getting wet with fuel and separating. I replaced it with a good Motorcraft part and scraped the residue from the carb base (it all came off cleanly with one swipe of a razor blade).

[Saturn V]

I experimented with different screws to try and replace the stupid secondary throttle screw, since it’s almost impossible to adjust with the carb on the car. But in the end, I left it in. Any other screw will be too loose and there’s not really room for a locknut or anything else to secure the screw and keep it from vibrating loose. It’s hard to see, but it appears that the screw has been spread open a little where the flat is cut. You can tell that the screw gets harder to turn once the flat is inside the carb base. You need to use a small flat blade to adjust … about 1/8” or 3/16” wide. I have a small screw ratchet that I was going to use to try and adjust this screw with the carb on the engine, but the last time I put the carb back on, I installed it with ½ turn past contact and that results in 800 RPM idle speed when warm, so I got lucky.