[Blue1967GTO]

Remember that Holley jet sizes are not the same as Rochester jet sizes.

I have (Rochester) 65's in my center carb and 74's in the end carbs. I haven't finished tuning for WOT yet, but it looks like these are probably the sizes that will work best. Jet size doesn't affect your idle anyway.

My power piston spring is the stock tripower spring, Mike Wasson said that works fine as long as you have at least 11" of vacuum at idle. Seems to work fine on my setup, I don't have any enrichment from the power valve at idle and I barely get 11" of vacuum at 850 rpm.

There are no holes in my center carb throttle blades and extremely small ones in my end carb throttle blades. Like so small you can barely see light through the holes.

My floats are set like this on Mike Wasson's recommendation:

End Carbs:
Set float - 23/32"
Set drop - 1 24/32"

Center Carb:
Set float - 21/32"
Set drop - 1 24/32"

I also have about 7 psi of fuel pressure. Replaced the old needle and seat fuel inlets with Mike Wasson's one-piece disc-style inlets. Those are so much better than separate needle and seat it's not funny. Rich, I'm sure Mike used those when he rebuilt you carbs.

The cause of off-idle stumble is usually either having your throttle blades adjusted into the transfer slots at curb idle (probably because your idle tubes are too small) and/or not having your accelerator pump linkage set properly.

[Tom Vaught]

Originally Posted by gtorich

Don"t know if that had anything to do with came next or what, but after shutting the car off, i had fuel dripping out of the venturi cluster pretty good..............

Have a good day boys

Rich

Until you get the float level correct on the carb so that it doesn't drip (fuel level is too high) you will never solve the tuning issues.

Tom Vaught

[Cliff R]

"Until you get the float level correct on the carb so that it doesn't drip (fuel level is too high) you will never solve the tuning issues."

+1

I would also vacuum and pressure test the needle/seat assembly, especially if you find that the float level is within acceptable limits. Unless the float arm is bent to one side and the float dragging on something, or bent up so high it hits the gasket before seating the needle, you should have control of the fuel in the fuel bowl.

I tested those self contained needle/seat assemblies for the Q-jet. I had a newcomer to the Q-jet business send me some samples, claiming they would take 11-12 psi without flooding issues, and flowed more than a stock type seat. His experience was limited to small block Chevy engines in circle track applications.

I street tested one in my 1977 Pontiac Q-jet on top of my old 455 at 514hp running pushing the Ventura to 11.50's. I got a bloody nose that day when my nose bounced off the steering wheel at the top of first gear when the fuel bowl went dry!

I pissed around with fuel pressure, and made a few more tests. At the same 7 psi I ran with a factory type .135" seat, the "improved" seat would not allow enough fuel into the bowl to keep the carb full on a hard run in low gear with reasonable traction.

Never before or since had the first hint of a fuel delivery issue with the old style N/S assembly, even with my new engine making quite a bit more power....FWIW......Cliff

[Blue1967GTO]

Does a Q-jet have one fuel bowl? I'm not too familiar with them but it seems that since there is one fuel line there is one needle/seat assembly.

Obviously a tripower has 3 fuel lines and 3 bowls so if a Q-jet has only one it seems each 2 bbl N/S in the tripower setup would need to flow only about 1/3 as much fuel as in a comparable Q-jet? So who cares if the one-piece N/S can't keep up in a Q-jet if it can in a tripower? Apples and oranges and not helpful in this context at all.

Let's keep Q-jets out of this discussion because that's not what Rich has and that's not what we are talking about. It seems to me that the only things a Q-jet and 2GC have in common is that they are both carburetors. Cliff I appreciate your knowledge and willingness to share it so please don't take this the wrong way I mean no disrespect I just don't want Rich to get confused.

I think Rich is chasing a problem that is not even related to the carbs (and in the process is actually creating some carb problems), I would bet $20 that the shaking problem is entirely a result of crappy motor mounts. My engine is very similar to Rich's and when it was first installed it shook an incredible amount. Replaced the motor mounts without changing anything else and now it hardly shakes at all.

[gtorich]

Originally Posted by Blue1967GTO

Does a Q-jet have one fuel bowl? I'm not too familiar with them but it seems that since there is one fuel line there is one needle/seat assembly.

Obviously a tripower has 3 fuel lines and 3 bowls so if a Q-jet has only one it seems each 2 bbl N/S in the tripower setup would need to flow only about 1/3 as much fuel as in a comparable Q-jet? So who cares if the one-piece N/S can't keep up in a Q-jet if it can in a tripower? Apples and oranges and not helpful in this context at all.

Let's keep Q-jets out of this discussion because that's not what Rich has and that's not what we are talking about. It seems to me that the only things a Q-jet and 2GC have in common is that they are both carburetors. Cliff I appreciate your knowledge and willingness to share it so please don't take this the wrong way I mean no disrespect I just don't want Rich to get confused.

I think Rich is chasing a problem that is not even related to the carbs (and in the process is actually creating some carb problems), I would bet $20 that the shaking problem is entirely a result of crappy motor mounts. My engine is very similar to Rich's and when it was first installed it shook an incredible amount. Replaced the motor mounts without changing anything else and now it hardly shakes at all.

Im starting to think the motor mounts certainly is helping any............i know i bought the high end korean ones. LOL

Just an update for those following............today i ended up opening the idle tubes to 0.039, turns the mixture screws out 1 turn, ran fairly well, engine still shaking some.

When warm i had the idle at about 800-875, just guessing there because the tack is bouncing around some. Vacuum was about 12-13. Took the mixture screws out 1 1/2 turn, not much difference from 1 turn out.

So far as of right now, im at 0.39 on the idle tubes, 0.076 on the mixture screws, and 0.125 openining on the throttle blades..............these were already in, i didn"t mess with them.

I think i got the leaking on the carb setteled, i had a piece of plumers paste in the check ball .............very small piece.

I was under the impression you could use the paste on the brass fittings, just not the teflon tape. The only reason i put it on that big brass bolt going into the carb was i was leaking gas out that thing big time. I cleaned it up pretty good.

I haven"t tried it yet...............but i have an extra venturi cluster, i was thinking of going 0.45-0.50 on the tubes just to see how it ran.................i don"t really want to go further on mine now.

Anything else you guys would do different...............let me know.

Thanks

Rich

[Cliff R]

"Let's keep Q-jets out of this discussion because that's not what Rich has and that's not what we are talking about. It seems to me that the only things a Q-jet and 2GC have in common is that they are both carburetors. Cliff I appreciate your knowledge and willingness to share it so please don't take this the wrong way I mean no disrespect I just don't want Rich to get confused"

Nothing I mentioned was meant to confuse anyone, and no comparison need to be made between a Q-jet and 2GC carburetor in this thread. What is important here, is that "pound for pound", "apple for apple", the self contained deal is NOT as good as the stock type fuel inlet seat.

Not trying to confuse anyone with anything here, just pointing out that direct testing showed that those little deals are somewhat restrictive compared to the stock type seats. Three fuel bowls, or one, the fuel pump has to have the capacity to fill them, and the Tri Power set-ups use small lines and split them at junction block(s), often at right angles thru small fittings. Anyhow, in my experience with this hobby, any sort of restriction at that point in the carburetor is NOT a good thing.

I never meant that any comparison between the two carburetor designs be made here. We do have a potential flooding condition present. Just looking at how those self contained N/S assemblies are made, they would NOT clear themselves very well in direct comparison to the stock type. The "disk" or valve doesn't have nearly as much room around it, and the ones I tested offered very little movement of that valve away from the opening of the orifice in the full flow position.

In a nutshell, they were highly recomended to me, I tried them, didn't like the results, and was simply passing on the information.....FWIW.....Cliff

[Tom Vaught]

Typically a foreign particle (like the plumber's paste) can cause the flooding. Remove the foreign particle and the issue goes away.

I WOULD NOT open up the other cluster to .045-.050, "just for grins" as that would be destroying a perfectly good cluster.

If you still have the shaking issue after a .038" IFR and a .125" hole in each primary blade and you have sealed up the end carb openings so that there is no leakage there then it comes down to:

1) What are the camshaft specs?

2) What is the initial timing?

3) Ported, manifold, or no vacuum advance?

4) As was mentioned the motor mounts BUT that is low on the list.

Tom Vaught

[Cliff R]

"Typically a foreign particle (like the plumber's paste) can cause the flooding. Remove the foreign particle and the issue goes away."

+1

Difficult if not near impossible to tune the center carb unless you have the fuel level under control.

A good way to clean a needle/seat assembly is to shut off the fuel to the carb while the engine is running. This causes the float to drop and the needle to move away from the opening of the fuel inlet seat.

Right before the engine dies out, turn the fuel back on, and allow the incoming fuel flow/pressure to "flush" the needle/seat assembly. I've used this procedure countless times with good success when we test carburetors here. 9 times out of 10 this saves pulling the carb and manually cleaning out anything lodged in the needle/seat assembly. We can then complete the testing, then take the carb apart, blow out any debris, etc.

Back to those self-contained fuel inlet seat assemblies. Due to the way they are constructed, and function, they would be much more difficult to "flush" out using this procedure as the disk/valve doesn't move very far from the opening when the float drops, and it has more material around it blocking possible escape paths for the debris......Cliff

[Blue1967GTO]

Rich - clean up your stuff, put it back together, and come see my setup.

[carbking]

Got to echo Cliff's comments about the one piece fuel valves. And they are made for a lot of carburetors other than Q-Jets and 2-G's.

We bought out a carburetor shop that used them (we wanted a lot of the other stuff they had). I personally placed 7,000 of these valves in scrap brass, and had them melted down.

As Cliff mentioned, they simply do not have the flow available that the conventional fuel valves have; plus we replace a lot of them for customers that drive only occasionally and have them stick.

I did an article on various fuel valves a few years ago. Thought it was on my website, but it isn't. Will try to find it and get it on the website.

Jon.

[Tom Vaught]

X3 on the "Floating Valves" and the flow losses.

Tom Vaught

[carbking]

Found the article:

http://www.thecarburetorshop.com/Fuel_valves.htm

In the category of useless trivia:

One of the points in the article concerns bowl fuel level and seat orifice size. To date, the largest seat orifice I remember seing was used on the Schebler Duplex carburetor original on the Duesenberg Model J. The seat is a whopping 0.250 inch. Thats right, a full quarter inch hole feeding that carburetor. I suspect some of the aircraft units are larger, but we don't do aircraft carbs.

Jon.

[old66tiger]

Rich,

Back to basics here. We need to know what your engine wants and the only way to deduce this is to do a simple test. At idle, take you hand and slightly place it over the opening of the carb...Does the engine speed up or slow down? Also, do you have full control of the idle circuit with the screws? Can you kill the motor by turning the screws all of the way in? If not, you are still functioning on the transition circuit. It simply will not run worth a crap when running too far onto the transition circuit. Also, your idle ports maybe too small yet. I think i had my tri-power idle ports set at almost 0.090" Going larger is OK as long as you are smaller than the OD of the needle. You will still have control over the mixture going into the base of the carb. Get Doug Roe's book. He tells you what to drill these ports to based on the size of the needles.

Also, pull the plugs and take a look at them. You may have a fouled plug (or two or more) by now and that will make it run like garbage and it will point the finger at something else. All too much, running problems are blamed on something else when fixated on trying to solve a specific problem.

ALSO...Do not go bigger on the clusters. While you can fix them and re-drill them, not advised at this time.

Bob

[gtorich]

Originally Posted by Tom Vaught

Typically a foreign particle (like the plumber's paste) can cause the flooding. Remove the foreign particle and the issue goes away.

I WOULD NOT open up the other cluster to .045-.050, "just for grins" as that would be destroying a perfectly good cluster.

If you still have the shaking issue after a .038" IFR and a .125" hole in each primary blade and you have sealed up the end carb openings so that there is no leakage there then it comes down to:

1) What are the camshaft specs?

2) What is the initial timing?

3) Ported, manifold, or no vacuum advance?

4) As was mentioned the motor mounts BUT that is low on the list.

Tom Vaught

Tom the cam is a roller SD "old faithful" believe its a 236/245

Intial is 12 before tdc, with 18 from the msd

no vacuum advance on the msd.......i get those two mixed up, my hose hooks up to the carb, i take it thats ported.

Got the motor running pretty good tonite, think im gonna leave it there.........idle about 825-900 range, bounces around on the tack so hard to really tell where im at, also the vacuum is around 11-12............then 12-13, that isn"t excately real steady .

Just wanted to say a big thanks for all you guys helping me out, its been a very frustrating summer so far with this car.

Rich

[old66tiger]

Tom brings up a good point. Ported or manifold advance? On a stock 2bbl, it will always be manifold as the 66 2GC never had provisions for ported. Do you have the vac advance connected? My engine ran poorly without the vac advance connected with the TP.

[gtorich]

Originally Posted by old66tiger

Rich,

Back to basics here. We need to know what your engine wants and the only way to deduce this is to do a simple test. At idle, take you hand and slightly place it over the opening of the carb...Does the engine speed up or slow down? Also, do you have full control of the idle circuit with the screws? Can you kill the motor by turning the screws all of the way in? If not, you are still functioning on the transition circuit. It simply will not run worth a crap when running too far onto the transition circuit. Also, your idle ports maybe too small yet. I think i had my tri-power idle ports set at almost 0.090" Going larger is OK as long as you are smaller than the OD of the needle. You will still have control over the mixture going into the base of the carb. Get Doug Roe's book. He tells you what to drill these ports to based on the size of the needles.

Also, pull the plugs and take a look at them. You may have a fouled plug (or two or more) by now and that will make it run like garbage and it will point the finger at something else. All too much, running problems are blamed on something else when fixated on trying to solve a specific problem.

ALSO...Do not go bigger on the clusters. While you can fix them and re-drill them, not advised at this time.

Bob

Bob, as of now i can kill the motor putting in the mixture screws........when i first started this stuff, when i put my hand over the center carb, it would pick up on the idle.........now when i do this, seems to slow down some and if i cover it compelty it dies out. I ended up putting on the end carbs tonite, and while running and putting my hands over the end carbs i feel nothing. Im gonna pick up some new plugs this week, they are a black sooty color, i guess you cant idle for a week or two without issues. LOL............so far im gonna keep everything the same for now..............about the only thing i can go bigger on is the mixture screws in the base. Im gonna run the car for a few weeks and see whats what.

i"ll keep in touch with ya.

Rich

[Tripower455]

Originally Posted by Blue1967GTO

Remember that Holley jet sizes are not the same as Rochester jet sizes.

Yeah, some of them are, some of them aren't. IIRC, the Rochester number is the orifice size. The Holley ones are kind of close.

My center (Holley 68) are .069". My ends are 65, which is .065". The bigger they get, the more difference it seems.

I have (Rochester) 65's in my center carb and 74's in the end carbs. I haven't finished tuning for WOT yet, but it looks like these are probably the sizes that will work best. Jet size doesn't affect your idle anyway.

What CID, heads, cam etc? Those weren't even close with my setup.

The cause of off-idle stumble is usually either having your throttle blades adjusted into the transfer slots at curb idle (probably because your idle tubes are too small) and/or not having your accelerator pump linkage set properly.

Mine were opened up to .038, I had the idle mixture perfect, and still had the dreaded stumble. I opened up the acc. pump squirters in my cluster and that completely solved this issue without having to be stinking rich otherwise.

[gtorich]

Originally Posted by old66tiger

Tom brings up a good point. Ported or manifold advance? On a stock 2bbl, it will always be manifold as the 66 2GC never had provisions for ported. Do you have the vac advance connected? My engine ran poorly without the vac advance connected with the TP.

Bob, i had that mixed up with the answer i gave to Tom V. I have manifold advance now, my msd dist has no cup for me for advance.

My center carb is not orginial, and where you can run a ported deal, i have a plug in there now.

So are you saying that i need to get a distributor with the vacuum advance already on it.

Rich

[Cliff R]

Now i had this set up on my old motor which was the same except 6X heads and a 60919 cam...........now the cam is a roller 235-246 OF from sd and the alum heads.

You do NOT need a vacuum advance to cure this problem. The engine should idle as well as, or even better with the new cam, as it has less overlap and shorter seat timing than the 60919 cam, and the compression should be quite a bit higher with the smaller chamber heads.

I've used both of those cams in 455's with KRE heads. In my old engine at 10.5 to 1 compression, the 60919 cam idled around 11-12" vacuum with noticable lope.

My new engine is slightly higher compression, but idles at 13.5" vacuum, very smooth with slight hint of a "lope", it uses the same 236/245/112 cam you are using.

I use 10 degrees initial timing and no additional timing from the vacuum advance at idle with both engines.

I suspect here that you may have a fundamental problem someplace, vacuum leak, lifter too tight, bad plug wire, spark plug(s), etc.

I've used the 236/245/112 cam in lower compression 455's with aluminum and iron heads, and it idles fine. It does start to get a bit "aggressive" down around 9.5 to 1, but vacuum is still around 11-12" and idle is steady......Cliff

[Hillard]

Originally Posted by gtorich

Bob, i had that mixed up with the answer i gave to Tom V. I have manifold advance now, my msd dist has no cup for me for advance.

My center carb is not orginial, and where you can run a ported deal, i have a plug in there now.

So are you saying that i need to get a distributor with the vacuum advance already on it.

Rich

Rich, you say the center carb is not original but is it a true tri-power center carb or just a standard 2 bbl? I don't know much about tuning the tri-powers but I can tell you that we worked on one here that had just a standard 2 bbl carb. We couldn't get it to run right at all. Tried 2 or 3 more, rebuilt them and all of them ran like crap. Finally we got a hold a real tri-power center carb and it ran like a dream. Something about having an idle compensator. Again, my knowledge of these carbs is very little but that was one experience we had here. FWIW