[mikediaz]

intereseting approach Love the simplicity.

I don't have any of those metal plates lying around or a machine to cut some but that does seem like the easiest way to go.

However, it could be nice to have the whole setup installed so that the adjustments would reflect any minor nuances in the system (minute vacuum leak at the front/rear carb throttles)

It is certainly a good place to start. Have any extra plates lying around?

mike

[mikediaz]

Well instaed of a plate i could just use some gasket paper and a spare parts throttle body bolted on to hold it down on the front and rear.

[mikediaz]

which reminds me i had a dream overnight that I was testing my carburetor's accel. pump. Some french guy was helping me..?? It was werid but the accelerator pump did function properly.. then I played with it more and it kept on wokring but did so in a weird way. I got sprayed in the face with the gas squirting out of the venturi. Then the french dude got pissed because I was spraying gas all over the room... I think i'll take a few days off of working on these

mike
-but back to topic, i don't want this thread getting littered with thoughts on a dream i had -

p.s. here are some interpretations of seeing these things in a dream all from dreammoods.com:

Carburetor
To see the carburetor in your dream, represents emotional, spiritual and physical balance.

Gas
To smell or see gas in your dream, indicates that your need to be reenergized.

Room
To see a dark, eerie or confining room, denotes that that you feel trapped or repressed in a situation.

It adds up to little but oh well. will post as updates come along on the carbs.

[Jack Gifford]

As soon as you're through dreaming (and analyzing)-

Yeah, my remote idle adjusters are a pair. You obviously don't "need" them- a million people have adjusted Tri-Power idle mixture without them. I was just trying to eliminate all the little things that have irritated me on prior engines.

The photo by Carl of the two plates brings up a good point about tuning Tri-Powers, especially one that's had as much recent work as yours. The purpose of the plates is to totally rule out any problems (vacuum leaks, fuel seepage, etc.) of the end carbs, while you tune the center carb- which should include road-testing, to assure that all its systems behave okay (power valve, main metering, accelerator pump, choke). Once you're totally happy with tuning of your "2 bbl engine", then install the end carbs and tune the whole deal- after chasing down those nasty vacuum leaks in the end carbs!

If your experience is as limited as you say, you'd be wise to do a little "book larn'n" on carburetors. Once past some of the theory, a Pontiac shop manual would be a good investment- it will explain that an idle mixture screw is a fuel screw, so screwing it in leans the mixture (to the cylinders fed by that barrel of the carb). The manual will give a starting-point (probably about 1 1/2 turns out from lightly seated) and the procedure for setting the idle mixture.

Get some rest!!

[mikediaz]

Thanks for the update and tips. Ah yes I do see how the screws work to lean and enrichen the mix by providing more gas. I had assumed blindely that it provided a vacuum source to some part of the well where fuel would be routed.. blah (not important what i had assumed there as it was wrong).
I see now from what literature i got that it sucks fuel out of the well (under the venturi) and pulls fuel down. It works in conjunction by the tiny slit just above each screw that does more of the same thing the screws do.

I agree on the literature review thing. I have a service manual for my car (which does discuss the rebuilding and tuning of the tripower setup) along with a rochester service manual covering 2G and 2GC carbs. No doubt the more reading I do on the topic the better it will all turn out. I do believe I got a lot of the theory down but (as you can tell from my last assumption) am nooooo expert!

Anyways thanks again for the tips. I do believe I will tune the center carb alone first.


Question - the literature i've read usually mention that the center carb's throttle blades should have a small hole in each of them. I see it in one of the pictures in my manual too.. Both my original set of blades on the center carb as well as the replacement set I got off the parts carb have no such holes in em.
What gives?

[Carl A]

All of mine had them,these ones show diff sizes???? the large one is 1/8", the smaller one, a 1/16 " drill bit is to small, the other 66 carb I have is a perfect 3/32"

[mikediaz]

Carl A - thanks a lot for posting those pics and for roughly measuring the hole sizes!
p.s. Carl - shouldn't your screw heads be on the carb's side of the throttle shaft? I know it hardly matters because if they get loose it won't really matter what side... they'll make it into the engine either way but was just noting that.

Is that a tri-power's center carb Carl or just a standalone 2bbl?


Anyone else out there got holes in their throttle blades that they know of? If you can measure them great if not, just saying that you do or do not would be a great help!


I'm trying to think how much of a difference those holes could make in the system. It would seem like they could make a big difference for idleing.

I can think of two things on this topic-
1 - the holes on the blades are equivalent to having the throttle blades open a smidge at Idle which is inturn equivalent to letting the idle needles out enough

or

#2- the holes are NOT equivalent to the needles because the needles allow a much more richer mixture in than what the holes would provide (since that comes from the venturi outlets rather than the well at the bottom of the venturi area which is where the idle needles get their mix from.. )
Are your needles screwed in rather-well? I don't know if it thats an easily-answerable question but if they were then it could help support theory #2.



Anyone got any ideas? I'll call the carbking tomorrow (he's closed by now). I'll post what i find out. Thanks all!

[Carl A]

Holes allow more air at idle,the carbs are from tri-powers I have had for years.

[mikediaz]

interesting.
well thanks for the info / pics. appreciate it.

I'll give carbking a call tomorrow and see his take on the situation as well.

I think at worst worst I could try and run the center carb without holes in the throttle blades and see if the idle is clearly off.

At that point ( and after exhaustively .... testing all other issues on the center carb) I could try to drill a hole in the blades and see if that helps...
An even crazier idea I just thought of is to at this point instead of going right to drilling, to remove one screw off of each throttle blade before going to drilling. The screw hole should approximate the conditions of the drilled hole.
I certainly wouldn't run the car like that for much more than a few minutes of idling to test the hole as a fix. If it fixed the rough idle I would drill the appropriate hole and replace the screw.

But again I'll do some more investigating and asking around to see what the word is on the holes in these things.

mike

[Carl A]

I just took the middle carb off another 65 tri (Virgin set-up)I have same holes as pic #1, the bigger holes is a 64 set, Now this is just me but you have gone to all the trouble to get your carbs right, I would drill the holes

[Carl A]

On another note what have you done to your car
motor, tranny, rear-end or is it all stock.

[mikediaz]

Well I bought the car last summer and have not done anything to it's engine beyond the basic tune up maintenance stuff. The seller didn't indicate any non-stock setups and it sure does feel nice and stock.
I figured this would play in my favor and make it easier to setup the tripower to run on it since it's always easier to make something stock run stock.

I totally agree with the getting it done right part and drilling the holes. My little plan just tried to avoid drilling the holes in the event they aren't needed and if they were needed to be sure of it before drilling. However, since you've got the virgin setups showing holes, and I see the various manuals showing holes in the blades as well as diagrams indicating flow through the holes on the blades I believe holes are the way to go. I'll keep doing some minor research on it as there is no hurry right now.

Carl - you mentioned the 1/16" drill bit was too small to fit into the first pic's holes (which were the same size as your virgin setup?) Do you mean the holes are a little bit smaller than 1/16" or that the 1/16" drill bit was too small to fit snugly into the hole (thus the hole is a bit biger than 1/16")? Trying to figure out what woudl be best size to drill mine

Thanks a million for your pics and willingness to pull up those carbs and check! Hope I didn't cost you any gaskets!
mike

[Carl A]

The hole is bigger than 1/16" but smaller than 3/32"The reason I ask about your car is I have some papers on what primary and secondary jet sizes you need richer or leaner, depending on if you have bored your engine, if you have changed cam if you have headers even what elevation you live at.

[mikediaz]

ah excellent info. Well nope i'm all stock so I should be good on that part but thank you again. Cant thank you enough for all the help!
i'm REALLY glad I asked about this question and thank you dearly for responding. Without you, I'd now be saying "well i guess i don't need holes."

I assume the best size for holes would be 5/64"

The exact location of the hole is probably not too important besides getting it mostly centered and leaving a little over an 1/8" between the bottom of hole and throttle shaft. Look about right?

[Jack Gifford]

Early Tri-Powers (I think up through '61 389's) had no holes in the throttle blades. I'm not familiar with later ones, but I remember someone talking about Pontiac adding the holes as engine displacement went up- to 400? to 421? to 428? to 455?

[mikediaz]

might have even been earlier. I have a rochester service manual dated 1958 and it shows and mentions the holes. However it is mentioned under the "Idle air by pass system" which it claims is only on "some model 2GC carburetors." These carburetors (at least in '58) had the big idle air adjustment screw (big flat head screw with a spring on it like the idle air speed/mix screws but much bigger and on the opposite side of the carb). Wouldn't surprise me if they fixed the system up by '65 to remove that big air adjuster screw and have just the small holes on the blades.

[Jack Gifford]

My '61 SD Tri-Power (alum.) which I bought in '61 has no holes in the throttle blades. The '57 I once had didn't have them either.
Probably not a big deal either way. A 500 cfm Holley 2-bbl that I put on a Ford 289 had the holes. I couldn't idle it as slow as I wanted, so I closed the holes by "riveting" solder into the holes.

[mikediaz]

Well I got a chanced to talk to Jon today at the Carburetor Shop. I don't like to post quotes or anything because I'd hate for people to disagree with him when it wasn't him saying it on this board but with that being said I'll go ahead and explain his general consensus.

He said he further explained the holes in the throttle blades subject in the thermoquad thread (i believe it's in the Street section). He said the holes were added as Pontiac started using larger cams on the engines. He didn't give me an exact date or anything but he recommended I try it without drilling holes first. If the idle is off then I can try the holes. I was planning on doing this since it saved the life of my blades should I not need the holes but good to have a confirmation from Jon.

Thanks to all for the input and hole sizes discussed here. i've noted them in case I have to use them!

A few other questions I had for Jon which I have asked (or wanted to ask) on this thread previously:
As far as the composition replacement float on the center carb-
He says the center carb uses a smaller float than the end carbs and that in his opinion, the composition floats aren't as good because of the possible degredation caused by some fuel additives.


Another long-lost question answered:
My venturi cluster on each end carb has a small brass shield/plate held down by the venturi's center screw. Where should the center screw's fiber washer go?

Answer - That was a diffuser for squirting.
Screw set against gasket gasket against plate and plate against the venturi cluster.

Worth noting- the center carb's venturi's screws are smaller than the other outer ones. Subsequently they use a smaller fiber washer on their venturi center screw as well.

----------
Hope this clears up some questions. Of course, I'll post (way down the line) whether my idle was so off it required drilling [after trying with non-drilled blades].
======
I figure this is worth noting as well:
In the Street section I was talking with a guy about his 68 firebird's tripower and he had mentioned DAG sealant for the bores.
Jon advised me that the DAG sealant is a carcinogen as well as a dimentia-causing agent. Very nasty stuff and recommended I stayed away from it. He says it was used way back when these cars were made mainly to counter-act shoddy production line work, and that I shouldn't have to use the sealant to get the bores to shut nicely. I'll post similarly over in that thread.
I had no intention of using it but wanted to note that.

Making progress every day!
Thanks all,
mike

p.s. please post any questions / comments! I wonder how many views this thread will have when its all said and done?

[mikediaz]

Yes yes the headline is true! Upon removing the front carb's throttle shaft from its base it seems to have torsioned itself somewhat out of shape.

Good news is its blades did come out just fine minutes before that so I'll just need a new shaft. The blades are swimming in berryman right now. Ah well what's the fun in these projects if you can't spend a few bucks

I think I'll order from Ames (but i'll check out PY too as I hear they have excellent products too...)

Mike

[mikediaz]

Well it was such a nice day and it was the weekend (so no homework) so I figured I'd get to work on the carbs again.

The third carb came out pretty nice. As mentioned in my last post I did damage the throttle shaft getting it out so please note that *******the throttle body shown in the following pics is a spare parts one I used just so I could sit it atop somthing for the pics*********

That being said, the throttle body is the only part left on the third carb to do.

Once I get the new throttle shaft and get it in it will be time to get to work (and order) the missing linkage piece (slide bar) and choke to manifold lines and fuel lines... and air cleaners.... and.. nevermind just enjoy the show!