Technical Tri-power Rochester 2G running rich

Hey guys
Just put a new fuel system in my car brand new all the way back. Starts up great runs great smooth idle but it is running rich. Air fuel mixture should be from closed 2.5-3 turns. They are set factory and are matched carbs. I am wondering if I need to adjust just the middle carb because the front and back don’t kick till much past idle.

 

I think an accurate tri power setup only has idle mixture needles on center carb.
End carbs have the ****erflies sealed closed at idle, thus no need for an idle circuit.

 

You need smaller Jets in the center carb. I tried several sizes getting mine correct.

 

Were the carbs set up for a tri power, or all they all the same stock jets, etc. to use individually? It’s going to make a difference. Not to say one of the above isn’t right. My only experience is 94’s on yblocks, and the end carbs would be different jets, and sometimes blocked power valves on the end carbs.

 

Are you idling on all 3? Progressive or straight linkage? Which brand of intake?

 

Only the center has mixture screws, 1 3/4 to 2 turns out is usually about right.
Just for your information, Pontiacs had #62 or #63 jets in the center and #68 in the outers on the '65 389 engines.
Factory set to what, are all three the same carb number, or are they original Tri-power carburetors? How do you know it's running rich? smell or by gauge?
Original outer carbs have heavy throttle blades that shut 100%, no mixture screws, and no air flow when not fully opened. The center is primary carb up to 60-70% throttle with linkage as shown just above this post.
If all three have mixture screws, its testing time, and without a gauge in the exhaust, its going to be a lot of back and forth of adjustments. Your air velocity through each carb is going to be fairly low if all three are idling, so standard settings are not going to work as they should.

 

Is it running rich all the time or only at idle? If it is all the time you may have a jet or float problem. If it is only at idle, I would look down each carb throat and see if there is any fuel dripping from the venturis.

 

Fule pressure??

 

Is it rich or does it just stink? Could be excessive hydrocarbons and not necessarily rich. Is it progressive linkage? Outer carbs are secondaries?

 

What are the factory setting for a sbc with tri-power?

 

There are none!

NO sbc with factory tripower.

 

thought so thanks

 

I had a 350 SBC with an Edelbrock manifold and a set of 348 carbs. I set everything to the 58 348 tri-power with the stock hydraulic cam Powerglide engine/trans car and it worked great!

 

There almost was.....
The gm L-70 option that got canceled before it went into production....

 

Get yourself a vacuum gauge and re-adjust the idle mixture screws....

 

Tell me you are not trying to run them on straight linkage-all at once! End carbs on correct setup has no idle screws-dumps only.

 

It would be easier to attempt an answer had the OP supplied additional information.

Information that would be helpful:

(A) Engine displacement
(B) Engine state of tune (cam, headers, etc.)
(C) Carburetor information - OP states matching new carbs. Looks like Eastwood paint to me.
(C-1) What are the carb identification numbers
(C-2) What fuel valve orifices are installed
(C-3) Are the carbs genuine Rochester or Chinese imitations
(C-4) What size jets are in each carb
(C-5) Do all three carbs have idle screws. If so, are all three being used. ONLY effect low RPM mixture.
(C-6) Are power valves in all three, or just the center. What size are the power valves.
(D) OP states idle mixture from 2 1/2~3 turns. This is true on Rochester 2-barrels made AFTER 1967 only (the ones with the long smog emissions taper). Earlier Rochesters should be from 3/4 turn to a maximum of 1 1/2 turns.
(E) Fuel pressure (this correlates with C-2 above). Cannot read the pressure gauge in the picture.
(F) Is linkage solid or progressive, cannot be certain from picture. If progressive, roughly what primary angle do the secondary carbs start to engage.
(G) Engine vacuum. Too low vacuum could have power valve(s) constantly engaged.
(H) Firing voltages at the plugs, yes I see the MSD coil, but not as important as firing voltages
(I) Was the system bought as a system, or pieced together. If a system, have you contacted the selling vendor.

Answer the above, and unless C-3 is Chinese imitations, this group should be able to help you isolate and adjust the issue.

Jon

 

I have progressive linkage real Rochester 2g carbs manual choke. They are set so that it runs on the middle and doesn’t kick in the other carbs until it gets to a certain gas pedal. They are actual tri-power carbs running a little over 4lbs of pressure. I basically went with 65 GTO setup. My stock fuel pump was putting out 6-7lbs which is way too much I out a low flow fuel pump on it and it puts out about 4lbs to 4.5lbs by what the gauge is saying.
Having a vacuum leak type noise coming from it. But I can’t find an air leak on it anywhere. Seems to be the center carb is making the noise. I tried all of the vacuum ports and it showed nothing. This doesn’t make it miss or run like **** find fine just a little rough. Might just at startup. I don’t drive it often. I just did a bunch of upgrades.
including a video walk around hearing it start from sitting cold and idling.

 

Factory progressive linkage was slotted, both to determine the angle (you mentioned foot-feed position) when the secondary carbs begin to open, AND the secondary linkage on the front carb to prevent either the front or rear carb always being cracked open because of the rate of expansion of the linkage rod. Cannot tell from your picture but most A/M progressive linkages simply ignore this issue, and the linkage is fixed to both front and rear carbs, creating a minor problem.

I would highly suggest disconnecting linkage from both secondary carbs to see if the idle changes. From there, I would suggest installing block-off plates under the secondary carbs, and tuning for idle and primary operation on the center carb alone.

There have been a LOT of pixels disturbed on the internet on fuel pressure for tri-power, when in fact, the fuel pressure debate is due to a failure of the "rebuilder" to use the correct fuel valve seat orifices in the secondary carbs; they should be 0.086 inch. Most (maybe all???) of the FLAPS kits contain at least 0.101. I ran 7 1/2 psi on my correctly rebuilt '64 GTO tri-power with NO issues.

Jon

 

I will try the above. I bough them from Charlie Price at Vintage speed

 

I currently have the same linkage on my carbs. Jon brings up a good point. On this linkage the secondary carb pivot balls that are installed on the ends of the throttle shaft must be properly adjusted. You must have a little front to rear slop in the linkage rod that runs between the two secondary carbs. You do this by loosening the locknut slightly on the front carb pivot to ensure the secondary throttle plates are fully closed. This insures both throttle plates close independently of each other and are not held slightly open by the linkage rod. You can see this adjustment on Charlie Price's youtube videos.

Watch how much you loosen the locknut though because too loose will cause the br*** barrel the primary rod slides through to bind up. This is one of the reasons I am looking to replace my linkage set up with something else. Good luck.

 

You mention that you have actual 1965 Pontiac tripower carbs.

Might be interesting to compare the casting numbers on your carbs to this list from my website:

https://www.thecarburetorshop.com/Tripowerspecs.htm

I think you will find that NONE of your castings have the casting numbers in the list. Pontiac NEVER ran tripower carbs that look like yours.

Jon

 

I set them up like GTO's were setup because it was easiest to find setup and adjustment videos and I didn't want to go by dodge or Chrysler because I am running a GM engine. After 1960 I am a Pontiac fan and I loved the 65 GTOs were setup which is why I wanted tri power but no they aren't gto carbs

 

Truth be told that is probably where I screwed up at is in the shaft adjustment because I was having problems getting it adjusted. My last tri-power never made that sound before.

 

Have you contacted Vintage Speed with your issue? It might be covered under warranty.

You should look up Vintage Speed on YouTube and watch his videos on Rochesters. He goes into great detail on the rebuild and setting up his linkage. He doesn't use a standard needle and seat like most rebuilders use.

I would verify the fuel pressure at 4.5 to 5. Loosen the 10-32 screws attaching the secondary linkage, tighten snug, back off 1/4 to 3/8 turn - this will allow the linkage to move free and not bind. Put a vacuum gauge on to full vacuum and verify how many inches as this will affect the power piston and power valve. If your vacuum is too low the power valve might be opening when it shouldn't and cause it to run rich. A float might have a leak and it's dropping causing it to run rich.

Lots of possibilities. Contact VS and see if under warranty and his advice. If can't or won't help post that and what diagnosis you've done and we will help the best we can.

 

I took off the secondary linkage on the p***enger side and the caulk link went away. High rpm but no vacuum leak so I know it is in that rod keeping one carb open I have sent an email to Charlie with a video. He hasn’t gotten back with me yet. I am using his video for setup. Only difference is I went to manual choke on his recommendation. Straight rod from center to front carb and doesn’t get in the way. I have tested all other settings and verified they are the same. When opening WOT they all hit/bottom out at the same time. The bar on the right is set at one o’clock(pointing at center carb fuel line. The stop slides are correct, front side 1.5” and check WOT. Back side slide is the width of my Allen key used for tightening it.
I went to school for Motorcycle repair to keep my Harley in line. While there, I used the triple gauge set up for bikes with 3 carbs. Easily done to fine tune. But to date, I have never but a vacuum gauge to test a car.I actually went and bought one from reading this thread. But I don’t know the numbers I am supposed to have to use it or what a proper reading is. I have been looking online and YouTube but not found that answer yet.

My center carb base has a port in the rear which is ported. I haven’t seen a manifold port on my Edelbrock C357 intake. I had to split off vacuum in the back. They are as follows: PVC, A/C vacuum from inside, and the transmission vacuum line. I am using a MSD pn 8360 distributor with no vacuum advance

Thanks Rob

 

Forgot the VS link I am using

 

‘I see you have the same setup as mine in carbs, progressive linkage ad Edelbrock c357

 

Rob, now you know the secondaries are stuck open. With the linkage off open the secondaries wide open and let them snap back. Are the closed? ***uming yes. When adjusting the heim joints ensure your 10-32 screw is perpendicular to the secondary arm and slides in the heim and arm like ****er. Adjust heim until it does. Then Tighten snug and back off 1/4 to 3/8 loose. For the rod from the primary to the front carb where it slides. Apply some grease like Super Lube to the rod and slider. This will ensure no binding.

The primary rear port will be full vacuum. Connect here with vacuum gauge. If stockish 14-18 inches and Hotter cam will be less. Generally 12 inches or higher no change to the power piston. Less then the spring should be weaker. Charlie removes four coils on his systems. Report back what you have. Personally I wouldn't run the pcv from the rear, but from the primary carb so the pcv vacuum leak is distributed to all cylinders rather than a few.

Yes, I build vintage induction systems. They are pretty and work very well. Brian