1964 Riviera Dual Quad tuning?

[Guest Ricko064]

Hello All,

I just installed a factory 2x4 setup on my 64. I rebuilt the AFB's myself. The car runs well, but idles way too high, no matter what I do I cannot get the idle down. The following are some observations I have noted. I am a body person, not a mechanic, so I know little in this area.

When I hold the choke closed on the rear carb, there is NO effect on the engine. When I screw the air/idle (Large brass looking screw) in, no effect. The two smaller screws do have some effect on the carb. Started with them out 2 1/2 per shop manual.

Put my hand over front carb, car idles down to a real nice level, car sits and idles fine, till I remove my hand from covering the front carb.

What is wrong?! Some say timing, some say vacuum leak. Why does the rear carb have almost no effect?

Sorry in advance for my ignorance! Rick

[RivNut]

Does it do it with the linkage from the firewall to the carb disconnected? Also check the fast idle screw that sets the idle with the choke closed. Undo the linkage, then back off all of the external screws except the idle circuit screws. See what you get then.

[Guest Ricko064]

Will try all this. Someone also mentioned that the plates (?) in the front carb may be being held open. Though not sure that would cause rear carb to have no effect with choking and such?

Does it do it with the linkage from the firewall to the carb disconnected? Also check the fast idle screw that sets the idle with the choke closed. Undo the linkage, then back off all of the external screws except the idle circuit screws. See what you get then.

[RivNut]

You should be able to manually mess with the throttle linkage and tell if the butterflies are being held open. If you think that's the case, loosen all of the hold down bolts, and move the carb arould slightly while you open the butterfiles to WOT. When they're in a no-bind place, tighten the carbs down. Are you sure that when you rebult them they went back together correctly? You don't have a needle that's not closing in a jet somewhere do you? All sorts of things can go wrong, even putting a linkage rod on upside down could give you problems.

[Guest Ricko064]

Well, I am no expert for sure, but have rebuild AFB's before. All I really did was disassemble, check float adjustment per the manual, the clean and reassemble with parts from the kit. I just don't understand why that rear carb has no real effect on the motor. Usually when you close a choke, it flood the motor, kills it. This has zero effect. I will check the butterflys on the front carb/linkage. Sucker is idling way to high, until I restrict the air coming into the front carb, again, the rear has no effect at all.

[mt65riv]

I did have a problem with a linkage being put back on upside down that would not let the secondary plates seat.

Also check for vacuum leaks. If the carb blades are closed air is getting in somewhere. Check to see that the carbs are bolted down tight (with gaskets ) and anything that screws into the manifold is sealed and going where it's supposed to. Also check the manifold to head bolts. You can spray starting fluid around these areas and see if it goes even higher, if ti does, there's the leak.

Good luck.

Mike

[1965rivgs]

Closing the choke on the rear carb has no effect because the engine is breathing thru the front carb...that is why it idles down when you restrict the air flow thru it.

Did you take out the screws which secure the butterflies to the throttle shaft? If so, the butterflies may not be properly seated in the bore of the carb and are allowing air into the engine. Pull the front carb and check the butterflies. I`m confident something is not allowing them to fully seat in their bores.

If no problem with the carb you have a large vacuum leak which is bypassing the carbs...but I would focus on the front carb.

Why would this be a timing issue if you rebuilt the carbs??

Good luck,

Tom Mooney

[RivNut]

If nothing else, you could remove the front carb, block off the intake, and run a single line to the rear carb. Get it running, then, as Tom says, make sure the butterflies on front carb is closing all the way, then reinstall the front carb and see where you are. Might be a lot of work, but you can see if it eliminates the problem.

[1965rivgs]

He has already eliminated the problem by placing his hand over the front carb and cutting off any air flow. He has essentially done exactly what removing the carb and blocking off the manifold would accomplish.

Tom Mooney

[Guest Ricko064]

Thanks all for the ideas of things to check. I will be getting back to this in a few days. The timing thing...just something someone mentioned. Of course used new intake gaskets, but can re-check tightness of those bolts. I assume I can check the butterflies by looking down into the carb, and tell if/how well they are seating?

Will also check vacuum connections, ie: PCV, Brake booster. I have the rear vacuum port plugged which runs to a/c system until I get car running right, then will deal with those hoses needing to be replaced.

Will report with findings...

He has already eliminated the problem by placing his hand over the front carb and cutting off any air flow. He has essentially done exactly what removing the carb and blocking off the manifold would accomplish.

Tom Mooney

[Ted "Wildcat65" Nagel]

Have you tried disconnecting the secondary carb linkage? My 65 will occasionally idle fast when the second carb does not close fully. The secondary carb depends on the accelerator pump spring to close- i've heard some people install a second spring to help close he secondaries. OK, let us know how this is going!

Ted

[Guest Ricko064]

Okay, thanks for all the ideas, finally had a bit of time to mess with this mess over the weekend. Disconnected and adjusted the linkage, although the front carb was not being held open by either the linkage, or the gaskets and such...butterflies were closed. I went around and tightened what intake bolts I could get to and also, re-tightened the 8 carb bolts. Car idles down somewhat more, still does not idle correctly, but is better. Noticed that it sets there running, and all of a sudden, it speeds up, then slows down, on its own, sometimes rapidly, but then calms down, just still not low enough. I sprayed carb cleaner around intake bolts, that did not speed engine up. I know that the front carb has a slight vacuum leak where the PCV and brake booster T comes out at the rear, so I will fix that. Someone also mentioned the check valve for the brake booster may be faulty? Are those standard type for all cars? Could this be THE culprit?

Over all, it runs better, but just not right, when in gear it shakes, possibly because the idle is still too high.

Plus now I have a pesky antifreeze leak I can't find. Installed all new hoses, water pump, and I have a leak somewhere near the radiator hose on drivers side, everything is tight as can be.

Also, can I somehow post a pic on here of my setup?

[RivNut]

Double click the "Reply to Thread" button to get to an advanced reply screen. Once there, scroll down until you find the "Manage Attachments" button. Click on that and see if you can't go from there. I'm not a techie by any means and I was able to figure it out. I'm pulling images from my computer, not directly from a camera. I don't know if you can do that or not. I'm sure that someone else will chime in and straighten us both out.

Ed

[carbking]

You have pretty well determined the issue is with the front carburetor, but a little more testing won't hurt.

Remove the front carburetor and block this portion of the intake AND the fuel line. You can easily make a block-off plate to block the intake, and a plug to block the fuel line.

Start the engine, warm the engine, and then adjust the idle. Check for vacuum leaks. Get a good idle. You could even take the car for a spin and see how it drives. The idle mixture control screws should be approximately 1 turn from bottomed (1 1/4 if running E-10). The suggested beginning adjustment for the air screw is 1 1/2 turns from bottomed. Start with these figures and then adjust. The mixture control screws will control the volume of a predetermined mixture of air and fuel. The air screw controls idle speed and is basically a metered vacuum leak.

Once you have the car running well on the rear carb, turn your attention to the front carb. While it is off, check the position of the throttle plates. The 2-??? numbers should be on the bottom of the installed plates, and the numbers should be in the hemispheres closest to the center of the carburetor. Check the linkage from front to rear to make certain the secondary plates are closed. Work the throttles to make sure none of the plates are sticking partially open. Check that the flange gasket covers all of the vacuum ports exposed to the throttle area in the throttle bores.

Once you are sure of the above points, reinstall the front carburetor, but do NOT hook up the throttle linkage. Does the idle quality change? If so, something is going on with the front carb, and you may need help at this point. If the idle quality does not change, reinstall the throttle linkage to the front carburetor. Does the idle quality change? If so, the linkage needs adjustment.

Tuning is just a word for eliminating possible problems until the actual problem can be isolated.

Jon.

Edited May 6, 2013 by carbking (see edit history)

[cobravii]

Here's something I ran into with mine.... If you put the intake gaskets on upside down you will get huge vacuum leaks between the intake and the heads. Vacuum leaks will cause a high idle.

[1965rivgs]

Barring any vacuum leaks from a faulty brake booster (squeeze off the rubber vacuum line with a needle nose pliers and check for change) or incorrect installation of intake gaskets, carb gasket, etc...an inconsistent idle speed is often indicative of worn throttle shafts/throttle body. While the car is running try to wiggle the throttle shafts back and forth and listen for a change in engine RPM. If the idle speed varies the engine is sucking air past the worn throttle shafts. Note that it is generally the rear or primary carb which suffers from worn shafts but who knows what the front carb has been thru? Could have had frozen shafts and someone buggered them up to get them freed up....

There is no idle speed screw on the dual 4 primary carb (unless someone has added one) so it is often a problem to get the engine to settle down to the same idle speed consistently, especially when there is significant wear on the throttle shafts. Good luck,

Tom Mooney

[Guest Ricko064]

Well once again, thanks everyone for more ideas. It will be a week before I get back to the car as I will be out of town.

Regarding worn shafts and such, and again maybe this is a dumb question, but what are the options at that point? The large screw for the idle/air has little to no effect still on the car. Also, I do beleive I installed the metal intake gaskets properly as the "Bumps" were upwards toward the intake, basically installed the new ones as the old ones were installed. Didn't seem to notice a idle change wile spraying carb cleaner near the bolts on the intake.

I assume (Dumb idea?) the timing would not be playing a large role in this at this point?

I think it is getting better, matter of fact I know it is, as I think a major part was the carbs not being as tight to the intake as they should have been...I always hate to over tighten things.

Barring any vacuum leaks from a faulty brake booster (squeeze off the rubber vacuum line with a needle nose pliers and check for change) or incorrect installation of intake gaskets, carb gasket, etc...an inconsistent idle speed is often indicative of worn throttle shafts/throttle body. While the car is running try to wiggle the throttle shafts back and forth and listen for a change in engine RPM. If the idle speed varies the engine is sucking air past the worn throttle shafts. Note that it is generally the rear or primary carb which suffers from worn shafts but who knows what the front carb has been thru? Could have had frozen shafts and someone buggered them up to get them freed up....

There is no idle speed screw on the dual 4 primary carb (unless someone has added one) so it is often a problem to get the engine to settle down to the same idle speed consistently, especially when there is significant wear on the throttle shafts. Good luck,

Tom Mooney

[RivNut]

Well once again, thanks everyone for more ideas. I do beleive I installed the metal intake gaskets properly as the "Bumps" were upwards toward the intake, basically installed the new ones as the old ones were installed.

The rear carb mount has a hot air passage molded into it; it's horse shoe shaped. There are two gaskets that go on the rear carb. The stainless gasket does not have the passage in it but the fiber gasket does. Make sure you're using both gaskets. The fiber gaskets sits on the manifold and allows hot air to pass against the base of the carb. Because the the AFB carb is aluminum and the hot air is exhaust gas, the stainless gasket goes against the base of the carb. This combination allows the heated air to contact the stainless gasket which in turn transfers the heat to the base of the carb. All you need to do is make sure that the fiber gasket lying on the manifold has the cut-out for the hot air passage lined up with the hot air passage in the manifold. The stainless heat shield should be lined up so that the hole sizes correspond to the hole sizes in the manifold. The front carb does not have the hot air passage so it only needs a single fiber gasket.

Now for the mystery. I've never seen a metal gasket with "bumps" in it. Every heat shield I've ever seen has been perfectly flat. I have no idea what you have or where you came up with it. Perhaps the bumps are allowing that leak you've been fighting. The carb must be sealed to the manifold!

Edited May 7, 2013 by RivNut (see edit history)

[Guest Ricko064]

Sorry, maybe I said it wrong...the intake metal gaskets are the ones with the raised bumps for lack of better words, not the carb gaskets.

I am using gaskets and metal shims I got from Russ out at Nailheads in California. I sometimes wonder if I am ever going to get this right!

The rear carb mount has a hot air passage molded into it; it's horse shoe shaped. There are two gaskets that go on the rear carb. The stainless gasket does not have the passage in it but the fiber gasket does. Make sure you're using both gaskets. The fiber gaskets sits on the manifold and allows hot air to pass against the base of the carb. Because the the AFB carb is aluminum and the hot air is exhaust gas, the stainless gasket goes against the base of the carb. This combination allows the heated air to contact the stainless gasket which in turn transfers the heat to the base of the carb. All you need to do is make sure that the fiber gasket lying on the manifold has the cut-out for the hot air passage lined up with the hot air passage in the manifold. The stainless heat shield should be lined up so that the hole sizes correspond to the hole sizes in the manifold. The front carb does not have the hot air passage so it only needs a single fiber gasket.

Now for the mystery. I've never seen a metal gasket with "bumps" in it. Every heat shield I've ever seen has been perfectly flat. I have no idea what you have or where you came up with it. Perhaps the bumps are allowing that leak you've been fighting. The carb must be sealed to the manifold!

[RivNut]

Sorry, maybe I said it wrong...the intake metal gaskets are the ones with the raised bumps for lack of better words, not the carb gaskets.

I am using gaskets and metal shims I got from Russ out at Nailheads in California. I sometimes wonder if I am ever going to get this right!

See post #13 in this thread - good advice. http://forums.aaca.org/f177/new-65-riviera-owner-350346.html

[Guest Ricko064]

Yes, good point. I have been doing cars for 30 years, only body, very little mechanical. I am just outside Orlando, used to live in Chicago...there I could find anyone to fix anything. Not so here. Would like for someone to spend some time on it and get to the bottom of it. We'll see how this goes...

See post #13 in this thread - good advice. http://forums.aaca.org/f177/new-65-riviera-owner-350346.html

[RivNut]

I'm sure that there's someone out there who would enjoy and all expenses vacation to sunny Florida to help you with your car.

[1965rivgs]

The metal gasket under the carb to insulate it from contact with exhaust gasses in the crossover passage is not necessary on the dual quad manifold. The casting is not drilled between the groove immediately under the carb and the exhaust crossover passage in the manifold. It is therefore impossible for any exhaust gas to contact the base of the carb. A typical base gasket is all that is needed on the dual quad manifold.

Tom Mooney

[Guest Ricko064]

Good morning all,

Just about to get back into this as the summer is slightly cooling off here in Florida. Whats special about the booster check valve on this car? Everyplace I go, it lists the check valve from '67 on up, aren't they the same?

I am going to re-torque all carb & intake bolts, replace booster check valve and teflon tape and retighten any and all fittings into the intake. I am hoping this is not a situation of the throttle plate shafts being worn and causing the leaks as I wouldn't know what to do at that point. Still can't post pics, says size is too big and I don't know how to change that. If anyone thinks that a pic would help I can e mail them.

Thanks!

[Guest Ricko064]

Hi All,

Just wanted to ask perhaps a dumb question, was suggested by someone. Still can't seem to get my idle down, granted my knowledge on this mechanical side is limited. It was asked if I adjusted the timing. Being as this was a single carb car, did I adjust from the basic 2 BTDC, to 12 BTDC per the shop manual. My reply was no! They said if I don't get the timing closer, then the idle won't come down and I won't be able to adjust the rear carb properly. So, question is, is this correct? Can the timing be causing this idel issue and lack of adjustablility on the rear? Don't have much hair left to pull out!

[arnulfo de l.a.]

A worn distributor will definately cause idle issues such as the one you describe with the idle suddenly going up then suddenly settleing down.worn distributor counterweight springs can cause this.Have someone who specializes in rebuilding distributors look at it.you would have to pull it out.before you do pull it out check the condition of your timing chain. do this by rotating the crankshaft(by hand) and watching the rotor to see if starts to rotate at the same time you start to turn the crankshaft.if the rotor does not start to turn at the same time that you start to turn the crank, you have a loose timing chain.a loose timing chain would also prevent the car from ever idleing smoothly because you will not be able to get the timing right.Hopefully no one ever linebored the crankshaft bores.If they did you are stuck with the loose timing chain problem.

suerte,

arnulfo

[Guest Ricko064]

Well, the up and down thing seems to have gone away, at least I am not seeing this. At any rate, what I am wondering is if the timing is off as I mentioned...single carb versus dual carb timing setting, would that cause the car to idle high and not allow any tuning with the rear carb? I hate to mess with the timing if this could not be a possibility. Someone mentioned that if the timing is off with regards to the single, versus double carb setting, that would cause the high idle.

A worn distributor will definately cause idle issues such as the one you describe with the idle suddenly going up then suddenly settleing down.worn distributor counterweight springs can cause this.Have someone who specializes in rebuilding distributors look at it.you would have to pull it out.before you do pull it out check the condition of your timing chain. do this by rotating the crankshaft(by hand) and watching the rotor to see if starts to rotate at the same time you start to turn the crankshaft.if the rotor does not start to turn at the same time that you start to turn the crank, you have a loose timing chain.a loose timing chain would also prevent the car from ever idleing smoothly because you will not be able to get the timing right.Hopefully no one ever linebored the crankshaft bores.If they did you are stuck with the loose timing chain problem.

suerte,

arnulfo

[RivNut]

What happens if you disconnect the throttle linkage from each carb, and from the firewall? The carbs would be setting on the manifold with no linkage involved. In this configuration, does the car idle? There's also a fast idle screw that is on the lower part of the linkage the tip of the screw sets against a stepped part of the linkage that is connected to the choke.. It's used to keep the rpm's higher when the choke is closed. As the choke opens the linkage moves and the step become smaller so the idle comes down. This is usually the only screw that has any bearing on how fast the engine idles. The idle circuit screws on the front of the carb are only active when the venturi are closed. Usually you screw them in until they seat then back them out 2-1/2 turns. When you've done that, you shouldn't need to adjust them again unless you have a stumble at idle around 800 rpms. My feeling is that some part of the linkage is hold the main throttle shafts on the rear carb open. Perhaps the linkage between the front and rear carb is adjusted to short; that would hold the rear carb open at more than a idle. If you can't get it to idle with the linkage from both carbs unhooked, take off the front carb, bolt on a block off plate and just work with the rear carb until it's running properly.

Does you car have it's original 12* distributor in it? Or has it been replaced with a single four barrel 2-1/2* unit. Is the cam original? Your cam could have been ground straight up, 4 degrees advance, 4 degrees retarded, or something else. Has someone put an offset key between the crank and the lower gear? When the cam was installed, were the gears perhaps a link off? There are so many variables, it's hard to know where to start. Sometimes it's easiest to tear it all apart and make sure that everything is installed correctly. If you do take it down to the cam gears, get a degree wheel and make sure that the cam is installed correctly. Everything needs to be calculated as a unit: cam, key, gears (perhaps the nylon is gone from the teeth and the slack in the timing chain isn't let you time it properly,) distributor, advance mechanism, etc. etc.

In your initial post, you said (and I quote) "I am a body person, not a mechanic, so I know little in this area." Perhaps it's time to trade some body work for some mechanical work.

[1965rivgs]

Hi All,

Just wanted to ask perhaps a dumb question, was suggested by someone. Still can't seem to get my idle down, granted my knowledge on this mechanical side is limited. It was asked if I adjusted the timing. Being as this was a single carb car, did I adjust from the basic 2 BTDC, to 12 BTDC per the shop manual. My reply was no! They said if I don't get the timing closer, then the idle won't come down and I won't be able to adjust the rear carb properly. So, question is, is this correct? Can the timing be causing this idel issue and lack of adjustablility on the rear? Don't have much hair left to pull out!

NO!!! ...assuming your observations are accurate. The dual quad static timing specs are in conjunction with a ported vacuum signal to the distributor vacuum advance can, unlike the standard setting which uses full time manifold vacuum. Therefore, on the dual quad setup, the engineers built the necessary idle advance into the static timing (aside from performance considerations..). If you did not change the vacuum source for the dist vacuum advance (or your distributor) from the original manifold vacuum source then your timing is unchanged. If you did change the vacuum source to the ported nipple on the rear carb then it is true that your timing has changed and is retarded relative to where it should be, but that would cause the idle speed to be reduced, not speed up. Besides, no matter where the timing is at, you should be able to reduce the idle speed by closing off air flow into the engine via the brass air bleed on the rear carb, assuming you have no vacuum leaks.

You stated at the beginning of this thread that the idle speed came into compliance when you covered the front carb. The engine should NOT be breathing at all thru the front carb at a curb idle speed. Your problem is in, or has to do with, the front carb.

Tom Mooney

Edited January 4, 2014 by 1965rivgs (see edit history)

[Guest Ricko064]

Thanks again for the replies, I will try to answer questions.

The distributor in this car is the original, that is the original that came with the car in the single carb setup. When reading the manual, it calls for 12 or so degrees for the dual carb setup, while the single setup calls for 2 degrees. Linkage last time was entriely disconnected from the carbs/car so there was no physical connection between each carb, and none to the car, still no idle down. Have retorqued intake, carbs, checked and rechecked all fittings, used teflon tape as well on threaded parts. Sprayed carb cleaner and scuh around intake to note for speedup/idle change and onserved none. Any adjustments on rear carb have zero effect on cars running behavior.

Don't know why, but I sort of think indeed the front carb has something to do with this as mentioned, but felt the timing is way off as well.

If a block off plate for the front carb is made, how is that made and out of what so there are no vacuum leaks over that relatively large area?

As also mentioned, I am on the west Orlando area if anyone knows of someone who is very good at these motors/carb setups?

[Guest Ricko064]

Ugh! Just checked the linkage, plates inside the carb and all look good. Plates closed and linkage disconnected. Now the car is apparently running so rich it wants to miss and is blowing black smoke. Tried screwing screw in on the primary and only slightly helped. Put my hand over the front carb and the car dies. Seems like there is more issue than one. If anyone knows of anyone in the Orlando area that knows these exceptionally well and would be willing to make some extra dollars, please let me know. It kills me to have this running so bad and I hate to go back to the single carb setup after all the money and work so far. Thanks for any help. Rick

Yankee064@yahoo.com