[carbking]

Just as different power valves were used, Pontiac (I didn't check Buick, Cad, Chev, Olds or other makes using Rochester) used FIVE DIFFERENT of the power valve actuating valves on the tripower center carbs, and there are two different overall lengths.

Jon.

[Willshire]

At cruise the power valve should be closed due to the high vacuum. Perhaps the spring tension is too much for the vac. if you have 20in/hg at cruise i can't see the piston overpowering that. Power valve only opens on low vacuum. The amount of vacuum required to close it is dependent on the tension of the spring that the vac has to overcome

[Tom Vaught]

Originally Posted by Teej

Car is my daily driver, so I got to test it this morning. No change. I was hoping the PV wasn't seated on the washer correctly or something. Still runs very rich at cruise (~10) and will be great at idle (14.5 @ ~750rpm) One thing I have noticed is that when I stop, the idle sits a little high, about 1000 -1100 rpm and the AFR is lean (17) until I 'blip' the throttle and get it to fall back to 750-800, then its back to ~14.

May try the spring/string thing this afternoon.

I had an Olds Tri-Power customer in Florida one time who had a "hanging idle" and the issue was the distributor weight springs were too soft to return the mechanical advance properly to the idle position.

Tom V.

[Teej]

Latest:

I took the top off last night and tied a piece of string through the piston spring. Not as easy as it sounds. I think I had about 1/3 of the coils, and that gave it a pretty fair gap for the spring so I'm pretty sure it wasn't pressing the PV. And...No change. My test drive didn't allow me up to full cruise speed but I was still at 45-50 and running probably close to 2000 rpm. (Light for the tach is out, so I couldn't see it). But I was still running rich. 11 or so.

So I took it home, pulled the top again and this time swapped in a whole new carb top from that other center carb I have. (I know your are cringing Jon, but I've got to try something..) Got that all back together and guess what? No change. OK, that's not quite true, it did change slightly and now it was running about 11.3 on the drive into work. Still idles great at 14.5 and about 800 rpm. Drives decent. WOT was tough to get, but I'd guess it's still rich at 10.5. Hard to say if the accelerator shot was still playing a role though, I only had a short distance.

I didn't actually ever swap out the PV, so maybe that is my next try.

To your other thought Tom.. I can look at the distributor, but I recently put new springs on it. I guess it could still be bindng slightly somewhere though. I have the timing at about 12 initial (manual says 8) and a vacuum/mechanical advance that brings it upward of about 38 total. Not sure the exact rpm but i can check.

[carbking]

Two other possibilities come to mind:

(1) The pump discharge check valve may not be seating, causing a syphoning effect through the accelerator pump circuit.

(2) The A/F ratio meter not registering correctly??? Have you had anyone follow you at cruise? I would think that with a A/F ratio of 10 on cruise that the vehicle would resemble a mosquito fogger.

Jon.

[Teej]

I guess the meter is a possibility, but it would have to be "off" only in that band. Everything else seems to match up. Take it out and it will read 20.9 for free air. Step on the gas and it immediately richens up with the accelerator pump. Coast in gear and it goes way lean. My idle set screws change the reading with consistency.

I've wondered about why I'm not getting more smoke than I am... I have no idea.

As for the pump discharge check valve. That's the ball bearing under the accelerator pump right? Oh, I hope it's not that. Mainly because that was my first thought and I took the top off, looked at it, saw it was there and thought, "naw, what could be there?" And didn't take it out or clean under it. But apparently that will be my next step.

[carbking]

The discharge valve would be the ball under the "T" guide and spring under the venturi cluster.

The ball under the pump is the inlet check valve.

Jon.

[Teej]

It was raining yesterday and I didn't have time to take mine apart, so I pulled out the 'other' carb to look at the discharge valve to make sure I knew what I'd be looking for/at on mine. I pulled the T and saw the spring and SS ball. But if that is part of my issue of running rich, I was trying to think of my options.

1) Debris under the ball preventing it from sealing-- I'd think that would most likely be washed out with all the fuel flow, or have to be pretty big. Obviously the solution would be to clean it.
2) Damaged/pitted/rusted ball -- replace that.
3) Spring tension -- Not sure how to test or how sensitive this is. I could stretch it out a little I guess. It seems like a pretty weak spring overall and would think that the accelerator pump would easily overcome a slightly stretched spring.
4) Rough/damaged/worn valve seat. -- This seemed most likely. But I wasn't sure how to fix/polish it if that's the case. (Or if I could see it well enough) I'm looking for some polishing tips I could use but am open to ideas.

Could I test this like I did with the power piston? Take it out of the circuit maybe? Put a piece of something over the discharge hole and remove the acc pump and see if it runs rich?

[Matt Meaney]

ok, first off you have some great people helping already. I am in no way an expert in any way. that being said, is there any chance you are running lean? a lean condition could result in a incomplete burn or even a misfire, which would result in raw gas being dumped into the exhaust and the sensor reading rich. maybe, possibly, what do you think?

[tom s]

Just for snicks with the change in dist,are you running a full 12 V to the coil or do you still have the ballast resistor or resistor wire?I asked because I chased a rich condition for a couple years that just ended up not enough voltage to the coil.Was night and day when we figured it out and ran the full 12V.Tom

[Teej]

Matt -- Could I be running lean and incomplete burn??? I don't know. I pulled all the plugs wondering if I was missing something. Running that rich I expected the plugs to be very dark, if not all but wet. But they were a light brown or tan color, which is what I've always thought was what I was shooting for. (feel free to correct me, anyone...) Most important to me was that they were all pretty much identical. So I don't think I'm getting a bad miss cause it would have to be all of them. Plus I'm using an LM1 meter with an exhaust clamp at the tail pipe. Not optimal I know compared to a bung at the bend, but it also allows me to swap between cylinder banks and it's pretty consistent. Maybe I'll also try adjusting the timing and see if that has any effect. I also wondered about other things that might affect it, but can't come up with anything. I would think an exhaust leak could read lean and be tough to track, but I can't see why/how I could get a false rich reading. And if it's truly 10.9 afr why isn't it smoking out the back?. Nothing.

Tom- Its still actually the stock distributor. The points are triggering an MSD 6AL box for the spark and the coil is new. I have not tested to see that I'm getting a full 12 V at the coil, but I will try that tomorrow. At this point I'll try anything.

[tom s]

Im not sure if you need 12 with a 6AL,might be worth a look.All I know is I hated my car so much I wanted to sell it.Finally took it to a hotrod guy and he figured it out.He is my go too guy when ever I get stumped on simple little things.Cant see the forest for the trees.Tom

[Dick Boneske]

Teej,
You do need 12 volts with the MSD box. I called and asked.

If you want to experiment, I can send you a different center carb, no charge. You've spent A LOT of time trying to dial this setup in. I noticed when you stopped at Surfside Suites, the idle was very rich--eyes watering. You've done all the things anyone would. Maybe it's time for a different center carb.

Remember, when it's at idle, there is no difference between Tripower and a single 2 bbl. car. Especially true when you checked to see that the end carbs don't leak air at idle.

Let me know what you want to do. This should not be that difficult.

[tom s]

Dick,that is how my 63 tripower cat was before I put 12 V to the coil.I was at a car show at Disneyland and cars behind me were complaining about the exhaust.I hope he finds he does not have full 12 V as it will be a easy fix.Tom

[Tom Vaught]

I have seen that mistake many times with people adding the MSD box and then just hooking up the wires. 12 Volt supply helps a ton vs low voltange as far as combustion goes. Idle under minimal load would be fine.

Tom V.

[tom s]

Tom,your right,idle was fine except for the HEAVY fuel odor.Car was very lazy.Tom

[Tom Vaught]

In his case Tom, based on other posts, he is reading 14.7 a/f or stoich at idle, right where he needs to be (if you can believe his meter).

Tom V.

[Teej]

OK, so I checked the voltage at the coil... Well, sorta. Not sure what I actually measured because things kinda snowballed. Car wouldn't start, no spark, etc. I ended up swapping in an MSD distributor (new) that I had been storing for my 66 project. Also new plug wires and when it still wouldn't start, I tracked it down to no voltage at the coil during cranking. Fixed that. Not perfect, but I get 10.5 V during cranking and full 13.7 volts during run.

And drove it again. Same issue. Meter reads ~11 at cruise So I don't think it's spark/ignition/miss related.

Dick, Thanks for the offer, I might take you up on that if we run out of ideas.

Tom.. I've wondered about the meter, but like I said, it seems to respond appropriately for all the scenarios. Really rich when the accel pump is pushed. Really lean on coast. And the calibration comes back as 20.9 as it should. And to be fair, when I saw Dick here in FL, I was still running all three carbs and not using the AFR. So it could have been really rich. I had been trying to tweak it by the seat of my pants, so to speak. (RPM, best vacuum, driving feel, etc.)

[Teej]

OK, against all testing methods, I changed two things. First was to swap the carb body. Still the same lid and base and venturi cluster. The second thing was the venturi cluster gasket. I used a new one that had a slightly different hole pattern. I should have taken a picture of both.

Anyway, new test drive was pretty short but the cruise was a little higher. 12.8 Will know more tomorrow on the drive to work.

oops, make that three things. Went back to the #62 Jets.

[Teej]

Drive to work was inconclusive. I don't think my accelerator pump is working. Not sure if I forgot a pin or what, but there is no spray that I can see. Plus there is a stumble as I take off that shouldn't be there.

May try to fix that at lunch.