[wrea3_98]

Hi guys. I know this subject has come up many times but hopefully I only need a few minor tips. Its a 65 421 Catalina with a tri-power. Newly built engine, bone stock (068 cam, OE points distributor, factory compression, etc.) Bought the carbs/intake completely restored. Not sure who actually restored them bet they look fantastic. Anyway, just got cam broken in and I have been tuning the carb. Timing is set at 34 degrees and dwell is at 30. I have it firing right up immediatley cold or hot, and it idles cold at 1600rpm and warm at 700-800rpm. I used a vacuum gauge while adjusting the mixture and the best vacuum reading is at about 18 inches with a steady needle. The idle quality is decent (not perfect) and I'm sure it still need a little tweeking. I have the front and rear carbs off and the intake blocked as well. The issue I have is mainly just coming off idle. The 7-800rpm idle is almost acceptable but at about 1100rpm it runs fairly rough thru about 1400rpm and then above that its smooth and sounds great. Even reving it off idle, there is no hesitation or bogging. Just runs rough from 1100-1400rpms +/- as I slowly creep the rpms up. Does it sound like more air/fuel tweeking needed, timing, vacuum leak? No matter what I do (advancing the timing, playing with the AF mix, etc it always does the same thing at the same RPM. I havent found any vacuum leaks. Just wondering what you might think about it. I just hope its not in the carb itself. I have not measured the idle bleeds yet. I hear alot about opening them up to around .038. Thanks in advance.

[geeteeohguy]

Sounds like too much vacuum advance/spark advance. Try disconnecting the vacuum hose from the distributor and do it again. I hope 34 degrees is your total timing and not your initial, which should be about 6 degrees. Also, why on earth are your outer carbs removed? I've run tripower set ups for decades and never heard of such a thing. No reason to block off the outer carbs unless you're handing the keys to a valet parking attendant.....

[Dick Boneske]

Since you bought the Tripower from an unknown engine, it's likely that the center carb is from a 389, not a 421. The key differences are the idle tubes at .034" on the 421 vs. .032" on the 389, the idle air bleeds, which are .038" on a 421, .037" on a 389, and the idle channel restrictions at .049" on the 421 vs. .043" on the 389. I would check the venturi cluster and open them up accordingly if necessary. If you need, I can send a cluster to you already set for the larger engine--in trade for the one you have now. If you have a set of the small number drills, however, it's easy to do yourself.

I believe the above will correct your problem. If it doesn't, I would drill the center carb throttle plates like the factory did on the 421's. I can give you the size and location of the holes if you need, although I think these holes were there to provide enough air for proper idle speed on the larger engines without adjusting the idle stop so far in that the throttle plates are too far open to allow proper function of the idle circuit.

I've still not heard anyone come up with a reason why some of the end carb throttle plates had .030" holes in them and some did not. They were there for a reason, but, on this board, I've not seen an explanation.

Also, are the end carb throttle plates sealed with DAG 213---or are the throttle plates fit very well tightly? If not, whatever idle you get will be worsened when the end carbs are bolted on. In either case, you'll probably have to reset the idle mixture screws and idle speed.

Please let us know how you do.

[wrea3_98]

Yes, its 34 degrees total timing. Vac hose is already plugged to distributor. All of the tri-power guys will tell you remove the F&R carbs for initial tuning. This completely rules out any vacuum leaks or from the other 2 carbs and rules out any fuel from squeezing past the other two carbs and leaking in, both which can affect your tuning. It's also almost impossible to adjust the A/F mixture on a '65 with the front carb installed.

Originally Posted by geeteeohguy

Sounds like too much vacuum advance/spark advance. Try disconnecting the vacuum hose from the distributor and do it again. I hope 34 degrees is your total timing and not your initial, which should be about 6 degrees. Also, why on earth are your outer carbs removed? I've run tripower set ups for decades and never heard of such a thing. No reason to block off the outer carbs unless you're handing the keys to a valet parking attendant.....

[wrea3_98]

Thanks Dick. I will check all the sizes of the idle air bleeds, tubes and restrictors in the morning. I appreciate the offer for the trade out. I may hit you up on that since I have no micro bits. I haven't looked at the throttle plates yet for fitment. Thanks for all the valuable info and I will stay in touch on my progress. Take Care!

Originally Posted by Dick Boneske

Since you bought the Tripower from an unknown engine, it's likely that the center carb is from a 389, not a 421. The key differences are the idle tubes at .034" on the 421 vs. .032" on the 389, the idle air bleeds, which are .038" on a 421, .037" on a 389, and the idle channel restrictions at .049" on the 421 vs. .043" on the 389. I would check the venturi cluster and open them up accordingly if necessary. If you need, I can send a cluster to you already set for the larger engine--in trade for the one you have now. If you have a set of the small number drills, however, it's easy to do yourself.

I believe the above will correct your problem. If it doesn't, I would drill the center carb throttle plates like the factory did on the 421's. I can give you the size and location of the holes if you need, although I think these holes were there to provide enough air for proper idle speed on the larger engines without adjusting the idle stop so far in that the throttle plates are too far open to allow proper function of the idle circuit.

I've still not heard anyone come up with a reason why some of the end carb throttle plates had .030" holes in them and some did not. They were there for a reason, but, on this board, I've not seen an explanation.

Also, are the end carb throttle plates sealed with DAG 213---or are the throttle plates fit very well tightly? If not, whatever idle you get will be worsened when the end carbs are bolted on. In either case, you'll probably have to reset the idle mixture screws and idle speed.

Please let us know how you do.

[wrea3_98]

The parts appear to be 389 parts as you decribed Dick. I am still tuning right now at hot idle. Im having some richness issues. When using a vacuum gauge off one of the PCV valve ports I can get 19 inches but the car is way too rich. I'm still trying to tweek it a bit to find a happy medium. The idle is at its smoothest but again, way too rich.

[facn8me]

Have you bolted the other carbs on yet? Even though they "seal" they can allow a lil air thru them and that may lean it out. By the way I use a 1/4 long wrench and can turn the mixture screw 1/4 turn at a time with the other carbs on.

[geeteeohguy]

Wrea, I've been running tripowers for about the past 35 years continually, and I've always had all three hooked up and operating. I guess you know something I don't. I apologize.

[geeteeohguy]

Also, please post what you find. You can verify a lean condition with a little carb cleaner or propane added to the center carb during the idle to cruise transition. If it smooths out, it's too lean, and it was not a timing induced misfire. If it stays the same, try pulling the vac advance hose. Again, I've never had issues with vacuum leaks running tripower units, and I've run a lot of them. Still running the one my '65 GTO was built with in '65, without issue. Good luck.

[wrea3_98]

@ facn8me

Yes the carbs are all on now. Definately not too lean. Way too rich actually. I removed the plugs, cleaned them, checked gaps and reinstalled them. They were pretty black and somewhat moist. F&R carbs are dry inside during idle. No leaking fuel anywhere inside the carbs. Fuel pump is regulated 3.5psi and I adusted the mixture with a vacuum gauge to get 19 inches of vacuum and the best idle quality I could get. Still not running very well under 1200rpm. Stumbles a bit at idle. If I lean it out, it runs worse and I still get gassy smoke out the exhaust. Defintely burning the eyes... The book says to warm it to operation temp and the choke is wide open. Turn the mix screws in until it stumbles and tries to die and then back them out until you get the best idle quality and vacuum. Not sure if its fouled plugs or not. I went thru a rear carb needle and seat sticking and gas was flowing into the intake and it flooded and wouldnt start. I removed the carb and fixed the issue. During this time the plugs were soaked all the time. I have been told to replace them for sure. I may try going up in heat range. I also noticed that it fired right up with the #3 plug wire removed (accident). I popped the wire back on and it didnt change a thing. Hopefully its the plugs.

[wrea3_98]

No need to appologize. Ive restored several cars but am still somewhat of a tripower newbie. I have run a couple sets in the past with little to no issues. I got the "center carb only" info on this forum from many other members as well as a couple high end tripower experts that we all speak of in here. I think it just eliminates any blame of the outer carbs when tuning, (fuel, vacuum leaks, etc).

Originally Posted by geeteeohguy

Wrea, I've been running tripowers for about the past 35 years continually, and I've always had all three hooked up and operating. I guess you know something I don't. I apologize.

[wrea3_98]

I had a lean condition early on and when I covered the center carb it raised the idle. I have set the mix with a vacuum gauge (19 inches at 850rpm). Now I am so rich its killing my eyes. I am replacing plugs and chasing the idle quality issues from a RICH standpoint. The plugs were caked with black, moist soot and the exhaust is smoking till my eyes tear up. Ive tried to back off the mixture a bit but it starts to stumble bad enough that I have to richen it back up. May go up a notch in heat range when I replace the plugs. After messing with it, I pulled #3 plug and it was black but dry. Others were more moist. I forgot to re-attach the plug wire and fired it. It started right up and idled somewhat normal. I saw the wire off and reattached it. Never changed the idle, rpm or operation at all. Hopefully its fouled plugs.

My other issue is when I hooked all the linkages to check proper operation. As I can see, the rear carb hangs open and I have to pull it back the throttle shaft back to zero by hand so it doesnt blow the engine. My pedal linkages are unhooked and it looks like it's in the acclerator pump rod attachment location. That plate is pretty loose where the rod hooks on. Needs re-punched into place to tighten it up. If I disconnect everything and work the center carb, its just fine. If I rev the center up and manually open the rear as I go, it springs back with no issue. If I hook up the linkage rev it up, the rear carb hangs open. All external linkages clear each other just fine. I had the top off the rear carb yesterday to fix a needle and seat issue and I did notice the accelerator pump linkage inside seemed a little sticky, almost binding a tad. I wonder if its hanging wide open inside. Its always something.....

Originally Posted by geeteeohguy

Also, please post what you find. You can verify a lean condition with a little carb cleaner or propane added to the center carb during the idle to cruise transition. If it smooths out, it's too lean, and it was not a timing induced misfire. If it stays the same, try pulling the vac advance hose. Again, I've never had issues with vacuum leaks running tripower units, and I've run a lot of them. Still running the one my '65 GTO was built with in '65, without issue. Good luck.

[facn8me]

Agreed. It's always something. I had a clogged accelertor pump circiut on my "new/rebuilt" carbs.

I would recomend new plugs. Then I would check the point's, then timing then hook up the advance. Starting 2 turns out on each mixture screw go back and forth turning each about the same. Give it a few seconds to stabilize adjusting idle screw as you go to hit target rpm. You technically want highest rpm not vacuum but it will be close. Then turn in a quarter turn to "lean" it out. Maybe you can tighten the spring on the end carb's a lil? Finding a bind with multiple linkages can be a pain

[flat-bill]

Have you verified that the power valve in the center carb is closed at idle. If the PV piston is stuck the idle will be very rich. Good Luck, Billk

[wrea3_98]

Today I re-timed the car and made sure the dwell was still at 30. On the carb, I started at 1.5 turns out and had to go out a bit till the idle was alot better. I did back them off about 1/4 turn and still have lots of teary eyes. The linkages all seem OK. Nothing rubs at all externally as I can see. The rear accel pump rod bracket is pretty loose whereit was peened on and may be doing something squirly to the rod, causing the pump to stick open. I thought I was done with geometry 20 years ago, lol. I just emailed Mike Wasson to see if he sells the newer style screw on pump bracket. He has fronts listed but no rears on the site.

Originally Posted by facn8me

Agreed. It's always something. I had a clogged accelertor pump circiut on my "new/rebuilt" carbs.

I would recomend new plugs. Then I would check the point's, then timing then hook up the advance. Starting 2 turns out on each mixture screw go back and forth turning each about the same. Give it a few seconds to stabilize adjusting idle screw as you go to hit target rpm. You technically want highest rpm not vacuum but it will be close. Then turn in a quarter turn to "lean" it out. Maybe you can tighten the spring on the end carb's a lil? Finding a bind with multiple linkages can be a pain

[Sirrotica]

Highest vacuum or highest rpm is not always the best setting for idle mixture, you want the engine as smooth as possible, meaning you want it steady as far as rocking on the mounts. If you can't get it smooth then there's probably another reason such as a vacuum leak you haven't found or a weak cylinder. BTW there is no magic setting of mixture screws to get the best idle, the 1 1/2- 3 variances you see printed in books or magazines are just ball park settings to start from. Each carb and engine needs it's own particular setting, one size does not fit all. Many times when someone bottoms the mixture screws out the over tighten them and make a flat area on the taper of the screw causing the screws to be unresponsive to adjustments, you might want to remove the screws and inspect them.

Are you sure the balancer hasn't slipped on the hub and the timing isn't where it should be? If the car has power brakes the diaphragm could have a leak, pinching off the brake booster hose with a pair of needle nose pliers while running will confirm this one way or the other. I used to have a Snap On balance tester that would kill one cylinder at a time and it would tell you how many RPMs each would drop letting you zero in on a weak cylinder. The same thing can be accomplished with a tach and pulling one wire at a time and observing the amount of RPM drop.

The burning eyes from idling is lean or timing way off, or pre-ignition from a hot spot in a combustion chamber, something glowing such as carbon or a sharp edge. Filling a pop bottle with water and drizzling a small stream down the throat of the carb while running at about 1500-2000 RPM will remove carbon from the valves and piston tops and combustion chambers. Carbon can cause uneven compression, hot spots, hold a valve off it's seat. Running 16 ounces or so will many times smooth out an engine that you can't make idle correctly. Probably be some people scratching their heads on this one, I can tell you though it does work and I have smoothed the idle out and stopped pre-ignition on many many cars that no one else could make idle smooth. Done the way I've described it there are no problems, just don't drown the engine with water while doing it. You'll see the carbon come out the tailpipes behind the car.

You might also want to rev the engine and manually hold the choke fully closed while opening the throttle plates, opening the choke back up before it stalls and then rev it and repeat 2-3 times. If there is any small particles of dirt in the carb many times doing this will raise the vacuum in the circuits enough to dislodge it pull it through the circuit.

Some old time causes and cures for older cars that I learned during my years fixing them from the late 60s early 70s. Maybe one of these might apply to your case or not, the other things already suggested are just as valid, just some other things to check.

Good luck finding your problem............

[wrea3_98]

Thanks for the info. I've used the water trick (and the tranny fluid trick) for older engines in the past. My engine is new with cam just broken in, no carbon buildup, all cylinders have 160psi or better, timing and balancer are perfect, (even tried 2 balancers to compare marks), brake booster not hooked up. Capped off at carb. Spark plugs are black and wet. Definately not lean. Was lean originally. I covered the center carb and the RPMs took off. Not anymore as I re-timed it and richened the mix. I'm 2.5+ turns out now. I adjusted by ear, rpm, smoothness. I did have a vacuum gauge handy so I hooked it up and its well into the normal range of 17-22 inches with a very steady needle. No drips etc inside the carbs when running or when shut off. The floats are set perfect. Havent checked power valve yet. Fresh restored carbs but who knows. Plugs are being replaced tomorrow. They are mostly wet and black after 45 minutes of "on and off" running in 5-8 minute intervals, even after I cleaned them good yesterday. Too rich for sure. I dont think it was so bad until I installed the F&R carbs but Im not really sure of that.

[Sirrotica]

Before you change the plugs I'd try the closed choke and try to pull any dirt out, won't hurt the plugs at this point, better than running the new plugs rich.

Have you checked the float for gas inside if it's a brass float? It just takes a tiny crack or pin hole to let a little gas get inside and make it heavy enough to not shut the needle off completely.

Fuel pressure test?

Known good coil and wires, especially coil wire?

[wrea3_98]

I may try that first. Cant hurt. I mentioned earlier in one of my responses that #3 plug wire was off after I pulled the plug to inspect it. It was black but dry. The other few I checked were more caked with soot and a bit moist. I forgot to pop the #3 wire back on and fired it up. Fired right up and idled as it had been. I saw the wire laying there and popped it back on. It made no change at all. I am going to change the one plug and wire first and see if it runs any better. They were both new but the plugs have been royally soaked over the past 2 weeks due to other issues. I haven't checked compression in that cylinder since I did it a couple weeks ago. The car runs very well thru the 1500-4000 rpm range without a hitch or a stumble. The floats are brand new and are not filled with any fuel. I've checked twice. Carbs are newly restored. New coil, new wires, new points, new medium advance springs. Whole engine is 100% restored to stock specs. No more than an 1 1/2 hrs of run time on engine and that was 5-10 min at a time after cam breakin. The engine didnt seem to run rich for me until I reinstalled the F&R carbs so I am aiming towards that a little. They are bone dry while the car is running on the center carb, so who knows... I just have to pick one thing at a time. Cheap stuff first. I appreciate all the advice. Most guys dont take the time to really get into it.

Originally Posted by Sirrotica

Before you change the plugs I'd try the closed choke and try to pull any dirt out, won't hurt the plugs at this point, better than running the new plugs rich.

Have you checked the float for gas inside if it's a brass float? It just takes a tiny crack or pin hole to let a little gas get inside and make it heavy enough to not shut the needle off completely.

Fuel pressure test?

Known good coil and wires, especially coil wire?

[geeteeohguy]

Another thing: are you doing the carb adjustments and getting black plugs with the air filter on? I've had issues with restricted center-carb air filters in the past if they are the pleated paper ones.....they get loaded up with crud easily, and act like a choke. I switched to K&N filters in the early '80's and no more problems.