Stevo81

My trusty mechanic tells me my secondaries are opening too fast and flooding because the control rod is bent or wrong...It is from Ecklers, built by Tomco but they are in denial. He thinks I should buy a rebuilt from Recarbco $$$...any ideas? Thanks.

Dalannex

Which control rod????? It can't be the one on the passenger side of the carb because that doesn't do anything but hold the secondaries shut. There is a control rod that opens the lower set of butterfly's for the secondaries, that allows air to pull open the secondaries and allow more fuel in, but the rate of opening speed of the secondary top set of butterfly's and metering rods can be adjusted. There is a little hole facing horizontal next to where the top butterfly mounting shaft runs into the end of the top of the carb on the passenger side of the car, which has a little straight screw head in it. There is also a little screw, probably torx sticking straight up into the bottom of the top just underneath this hole. The bottom one facing up is like a lock screw that you need to loosen to adjust the horizontal one. Loosen the locking screw then the horizontal screw in the little hole can be turned to tighten or loosen the spring pressure that holds the secondaries shut. Once you get it where you want it tighten the lock screw again. You may want to disconnect the little rod that runs to the vacuum canister on the passenger side to prevent that from causing any resistance, then loosen the tension until the secondaries just drop open, then retighten until they flip shut, and my guess is you would want to go just a smidge tighter than that, then see what it does. If it still floods out when you romp on it due to secondaries opening too quick tighten them up a little bit more. See what that does for you then we'll talk again. :thumbs: :yesnod:


-Justin

Dalannex

Oh yeah, why is it he can't take this rod that is bent off and straighten it?????

-Justin

Gator81

Great reply, Justin!

It's not clear to me yet exactly what Stevo81's problem is with the carb. Maybe I'm just being dense (OK, I know I'm dense, but maybe even more so than usual! :lol: ) but, if the secondaries (I'm assuming he means the throttle plates, a.k.a., butterflies, not the metering rods) are opening sooner than they should, wouldn't that cause a lean-out condition, rather than flooding? I mean, if those throttle plates and the air valves above them are open when there's inadequate vacuum under them, we get a lot of air all at once but not a commensurate amount of fuel, right? It takes vacuum to get fuel past the rods. Am I missing something?

Either way, I think you're on the trail of his problem - the progression of primary-only operation to all-four operation is probably the most challenging aspect of setting up a Q-jet, at least to me. I think I would adjust the secondary air valve opening threshold so that it would only open when vacuum is extremely high, and then back it down in small increments until I was getting the air valve open at just the right point, where the primaries have maxed out their flow rate but the engine is still accelerating strongly under load. I don't know how to do that on a Q-jet that was not originally built for this particular engine, except to adjust it to where the secondaries won't open, then back it down in increments to where it opens at the right time. A Q-jet from some rebuilder somewhere isn't likely to be set up right, right out of the box.

Just a few thoughts, probably not even $.02... :rolleyes:

VegasJen

i'm confused also.
first off, it's ecklers we're talking about, not j.c. whitney. i thought they had some pretty high standards and a better-than-usual knowledge about these, and all other corvettes.
second, like justin and gator already said, if the secondary butterflies were opening too soon wouldn't that result in a lean condition? the only way i can think the secondaries would be flooding would be if the wrong secondary needles were installed. if that is the case, it couldn't be easier to change. the problem would just be finding the appropriate replacements.
just to check, there is a scew holding the lever that retains the secondary needles between the two butterflies. if you remove that, the lever will lift out complete with the two secondary needles attatched. there should be a code stamped into the needles. on mine it is 'CH', i would think yours should be the same, unless they actually had different ones for different regions.

PRESSURERAT

The only thing high at Ecklers is their prices!!! It sound to me like you need to find a good carburetor man...something harder to find these days. If you are not familiar with a q-jet, let some who is work on it!! I don't mean to sound rude, but it is easy to mess up the base settings and with a lack of experience find them again!! Spend the money for a 'new' one such as the Edelbrock version or have one built by a reputible company who does not mass produce them, such as tomco. My two cents.

UKPaul

Hmmmm, flooding? OK, following on from Justins advice in setting up the spring tension, when you slacken off the Torx (or socket head in my case) lock screw make sure that you have a screwdriver holding the tension adjusting screw in place. When the lock screw is slackened off the adjusting screw will just ping out & you'll have no idea where it was set at. For an '81 he manual says that the adjusting screw should be set 7/8 turns in from the point where the secondaries just flop open when backing the screw off slowly ie. loosen the lock screw, then slowly back off the adjusting screw until the secondaries flop open, then turn in the screw 7/8 turn & tighten the lock screw. Don't turn the adjusting screw in much further than 1 turn otherwise it'll damage the small spring behind it.
If that cures the problem then back the screw off in very small increments to get the best "feel" when the secondaries open.
If the "bent rod" refers to the linkage on the bottom of the carb, then this can be accurately set (bent!) as described in the manual & Doug Roes book.
:cheers:

UKPaul

Warning! That screw is very short & is extremely easy to drop :(

Have any of you '81 guys ever changed the secondary needles to richer ones? Are they easy to obtain?
:cheers:

Gator81

Hey Paul! :cheers:

The stockers are CH, right? No, I don't know where to look for them, but being as I haven't been so fortunate as to increase the air flow capability of my engine so far as to need more fuel, I haven't needed to look! What a nice little problem you've managed to create for yourself! :lol:

If I recall correctly, Roe's book lists rods from leaner to richer, so you should be able to pick from the list which ones you need by letter code, then start looking for the 3 old codgers in the entire US of A that have been scavenging all the old Q-jet parts and hoarding them for that fateful post-apocalyptic day when the few people who actually know how to fix big dumb carburetors will rule the world. I'm sure, if you find one of those old geezers, he'll fix you right up (as long as you know you're looking for CJ's or CK's or whatever).

Here's one possible source:
http://www.nardek.com.au/Rochester/s...teringrods.htm

and another:
http://www.carbs.net/rodshang.asp

:seeya

81vette

Paul, I ordered my rods from Summit when I went to the dual exhaust way back when. They use to list them in their catalog.

Mark



[Modified by 81vette, 1:47 PM 10/7/2003]

UKPaul

Hi Gator :)
Yet again! :D
I guess I'll just get a selection of rods & see which ones give the best result. Of course, there's also various hangers to play with as well :rolleyes: I think the secondaries are running slightly lean as, since fitting Headers, the exhaust note sounds a bit flat under "enthusiastic driving techniques" & I'm sure it had a bit more "pull" last year. Old codgers? Geezers? Have you been watching re-runs of The Sweeney? If so, thanks for the links "coz there aint no rods on my manor, mate" ;)
Mark,
Were you running the stock E4ME when you changed the secondary rods? If so, what size did you fit to compensate for the duals? I really just need an idea for a starting point to get me in the right area. Thanks.
:cheers:

Dalannex

Actually if the secondaries are opening too soon it will cause a flooding problem becasue of this. I used to always set the secondaries on every q-jet to be just tight enough to barely hold them shut. And almost every time if I was driving down the road and stomp on it there would be a quick almost stall, then it would go, obvious signs of a sudden rich symptom. This happens because the lower butterfly's open and the air comes in, which pulls the top set of butterfly's open lifting the secondary jets at the same time. By having too little tension on the secondaries they open right up almost all of the way with little airflow required to do that. More spring tension will cause more air to be required to pull the secondaries from closed to full open, which causes both a slight delay in opening, and a slower opening rate. So now I set them to just enough to close, then go maybe an eighth of a turn more, then take the car out and at a nice highway cruising speed stomp it to the floor, if it chokes a little bit I need to go tighter, if not it seems to me that anything looser is too weak.


-Justin

Stevo81

Thanks, folks...again I have learned, between the forum and Roe book...Seems the secondary throttle opens and the vacuum pulls the sec air valves open, but too fast...so there are two methods of slowing it: a spring and a air dashpot...the experienced mechanic knows this and has checked both, so I am taking the carb off and to Recarbco, where they will test it...will post results