Best Way to set the idle mix on a 4160

[patrickt]

Originally Posted by steve meltzer

i actually thought of that, but dismissed it as a "Zebra". probably on my list. 30-40% chance of rain tomorrow, so may have to drive the p/u to work, if not i'll drive the car and check it out. thanx. s

If you've never used one before, it's kind of a "screw-spike within a screw-plug." There's also an easy way to find TDC without having to turn your engine backwards. Just pull the #1 plug, put a long stick in the hole so that you can observe the rise and fall of the piston, and turn the crankshaft via the crank bolt until the stick comes all the way up, and then starts to go back down. Put the TDC finder in the hole and screw the spike down gently until it comes in contact with the piston head. Mark the timing pointer's location on the balancer. Then rotate your crank again one full turn until it comes back up again and is stopped by the TDC finder. Mark the timing pointer's location on the balancer. TDC should be at the mid-point between your two marks. If it's not, then either you screwed up this process or the balancer has spun. Uhhhhh, just to be on the safe side, take your ignition key and hide it in your sock drawer with a sign on it that says "Did you remember to remove the TDC finder?" Trying to fire up your car with the TDC finder still screwed in your spark plug hole is a great way to start a really bad day.

[steve meltzer]

thanx Patrick. i believe i have piston stop device from a few years back. ?? this weekend or ?? thanx. (I hate work...it's the curse of the middle class). s

[patrickt]

Originally Posted by steve meltzer

thanx Patrick. i believe i have piston stop device from a few years back. ?? this weekend or ?? thanx. (I hate work...it's the curse of the middle class). s

Just have one shipped to you Prime from Amazon. That'll give you an excuse for not doing it tonight. Make sure the threads are right though for whatever head you have on that Vette. This one looks just like the one I have.

[steve meltzer]

OK, i have a green one will that do in a pinch? <G> s

[patrickt]

Originally Posted by steve meltzer

OK, i have a green one will that do in a pinch? <G> s

Never miss an opportunity to buy another tool. Here was the thread on when I spun my balancer, ridiculously long, as usual. What was funny is that I was staring right at the balancer, with the timing light on it and watching the marks dance everywhere you could possibly imagine, and it took a good minute or more before my brain could register the fact that it had come completely apart. Crankshaft Dampner Separated -- Arghh!

[steve meltzer]

most impressive! I doubt that's my problem, as I have nice steady marks on the balancer with a timing light...we all love tools, and last winter I bought an Innova timing light. gawd I love that light. nice. s

[davids2toys]

Originally Posted by patrickt

I would feel better if we could confirm our measuring marks. Eight or nine years ago, I spun my harmonic balancer inside the ring. Right after I did it, I was hearing a funny "clang," like a bell ringing, and when I put my timing light on the marks they were absolutely crazy. For a moment, I was absolutely dumbfounded, because what I was seeing was impossible. Then I took a step back and figured it out. I think you should use a TDC finder, a piston stop, in your spark plug hole, and just double check that your timing marks are indeed accurate.

A few years ago when i first bought the car I thought I had that problem, not blown apart like yours, but I thought it might be slipping because initial timing was reading very high, but it ran good. I thought it could be a false high reading do to a slipping outer ring. I did all you said to do and reset my timing to what was recommended but forget the exact setting. At that point I did not know the problem so I tightened the hold down bolt at the distributor, then I marked all the way across the back of the dampener on one side. This would include both steel rings and the rubber in between. Now whenever I am working on something, I check out the stripe to see if anything is slipping. The stripe is still 100% in tact indicating that my dampener has never moved and was not the problem

[steve meltzer]

OK, the saga continues...drove the car yesterday....ran great, no hiccups, no stalling and no scaring the feces out of me. I didn't have time to recheck the timing, tho' I suspect it's fine. will recheck this weekend, and, if unchanged, will punt on the piston stop, at least for the moment.

Here's something weird that's been going on for several months and could be related, but not sure....when the car has been sitting overnight (tho' the ambient temp in my garage is in the 90s) the throttle arm is very hard to move initially. Meaning, when you step on the gas pedal, your foot meets immediate resistance, then, with sig. more pressure, it gives way, and the pedal and entire throttle mechanism move well the rest of the time. Disconnecting the linkage from the carb's throttle, or main shaft, arm proves it's in the carb, NOT the linkage to the pedal.

So, when cold, something's binding in/on the carb that "unsticks" once warm. Even driving the car to work, parking and heading home after an 8 hour day does NOT yield this weirdness. Other than the same gremlins deployed by me ex, any thoughts? Related to the off idle stumble? Probably hard to tell without the carb in your hands. Next, i was going to put the carb on the bench and check it out, and or, loosen the hold down nuts and see about that. thanx. s

[patrickt]

Originally Posted by steve meltzer

Here's something weird that's been going on for several months and could be related, but not sure....

Hmmmm, nothing like an elderly patient that continually presents with new and unusual symptoms. First thing I would do is give the areas surrounding your primary shaft and linkage a good spray with WD-40, work the linkage back and forth, and then give it another spray. Even on a well-behaving carb, you'd be surprised at how that improves the smoothness of it all. Then see if that has done any good or not.

[steve meltzer]

OK, let me try that before I remove the carb, which I was about to do. thanx. s

[steve meltzer]

Patrick, i drove the car pretty hard on Friday and Saturday, after shooting a bunch of carb cleaner, not WD40 (my usual, defiant self!), on that throttle shaft, and any other part of the carburetor that would hold still, but it made no difference. This AM I really had to put my foot on the pedal to move the throttle, then it "broke loose" and great thereafter. (BTW, the off idle performance is pretty good...and might be better with the new "red" pump cam, which should be here tomorrow. Timing remains nice and steady at 10° BTDC).

Would taking the carb off the car, and onto the bench help any?? I guess I can just live with it, but I like things to work the way they were intended. thanx s

[patrickt]

Originally Posted by steve meltzer

Would taking the carb off the car, and onto the bench help any?? I guess I can just live with it, but I like things to work the way they were intended. thanx s

I think you have to. And here's why, anything that can stick in the "closed" position can get a notion to stick in the "open" position. Short of "off-roading" in your Cobra, the scariest thing I can imagine is a stuck throttle at anything close to WOT conditions. Hopefully you have a rev limiter on your car, so you can throw in the clutch and listen to her bounce of the limiter until you can reach for the key, but it will still be a pretty significant safety hazard. Of course, if you don't have a rev limiter then you'll get the opportunity to chat with blykins about "so how hard is it going to be to fix this window in the side of my block?"

[MOTORHEAD]

re: sticking carb. Sounds like a throttle plate sticking against the bore .

[steve meltzer]

I was thinking that, but there are so many moving parts that i wasn't sure. If the carb isn't perfectly square on the intake it wouldn't take too much for something to bind and get cattywampus. thanx. s

[steve meltzer]

OK, took the carb off the car so I could get a better idea about what the heck is going on with this sticky throttle. I believe that the small, curved/bent rod that links the primary throttle mechanism to the secondary shaft (on the left side of the carb) was causing my problem. By bending and straightening that linkage rod mechanism, the primary now moves easily and freely. Have yet to drive the car, but it seems like a good start, as, on the bench, the accelerator arm moves perfectly.

Also, the carb leaks fuel from the passenger's side. Bowls and Accelerator pump appear to be dry and not the source of the leak. How do i proceed to the diagnosis?

thanx, and sorry it has taken so long to get back to this. s






thanx so much. steve
(I can post a picture if anyone is interested...just need to move to another computer)

[patrickt]

Alright, that's progress... I think.. That little rod on the driver side of the 4160 serves to close the secondaries, should they be open, when you lift your foot off the throttle. There should be no binding, tightness, or stiffness. Having a little "looseness" to it all is normal. To diagnose your fuel leak you should use ultraviolet dye and a black light. Do not be misled by fuel leaking out the throttle shafts because you squirted gas on to the primary butterfly valves while you were testing for binding over on the driver's side linkage. Make sure your bowls are filled up normally (just by running the engine and then shut it off). Put about an eye dropper full of uv fuel dye (available on Amazon) down each vent tube of the carb. That's one for the primary and one for the secondary. Then DO NOT TOUCH THE CARB and under no circumstances work the throttle to induce a squirt. Watch the carb for the next couple of days under the black light. Look around the bowl gaskets, metering block gasket, the little cork gasket around the idle mixture screws, and everywhere else. Then report back.

[steve meltzer]

Great! thanx Patrick. much appreciated.
Wonder if i can use cat piss for my UV dye...it shows up (everywhere at my place) with a black light! s

[patrickt]

Originally Posted by steve meltzer

Great! thanx Patrick. much appreciated.
Wonder if i can use cat piss for my UV dye...it shows up (everywhere at my place) with a black light! s

Only if you consider your engine bay to be equivalent to a litter box.

[patrickt]

Oh, and you'll need a little mechanic's angled mirror to see under the fuel bowls at the base of the carb. The way you do it is angle the mirror so you can see the gasket line at the base of the bowl and then shoot your black light so it bounces off the mirror and hits the underside. Of course, you should see no signs of fluorescence for at least three days or more. Do it in a totally black garage and you can't miss finding the leak.

[steve meltzer]

thanx so much, Patrick. got the angle mirror, but on my way to Petsmart for the cat litter! s