TECH: Tri-Power How-to *Now with lousy pics!*

First of all, I'll have to apologize for quality of these pics. When I built this set-up, I only had camera of my cell-phone to use.
I built this set-up last winter for most active Finnish Hamb-guy, attitudor.
But here we go;

We are starting with three sets of gaskets, power valve plugs and other small stuff.


Eelco progressive linkage and five Rochester 2GC carbs. Believe me, it will take a while before you've managed to collect 'em this much. And yeah, brand new Offy intake! (Edelbrocks are something you'll see at every corner and sidewalk...)



This is my carburetor-disassembly-center. Or something... I built this low-tech carb-stand out of plywood and some bolts.

When you disassemble carburetors, be careful with those venturi assemblies.

One passage has spring and ball, clean that passage, eventhough new spring would've not come with gasket set. That ball will be there stuck for sure!


Here they are cleaned. First with fuel, then dipped for a while in citric acid, and finally brass wire brushed. (Free tip; reserve time for that episode..

About citric acid; ten minutes is enough, if you leave them there for overnight or something, you've lost one good carb-top. Ask me why I know...

First we'll put on jets, power valve plugs on secondary carbs and venturi assembly. Primary carburetor still has power valve. Notice that all venturis must be same size in all carbs. Cut also small rod (on upper half of carb) that used to push power valve.

Secondary carbs are only for dumping fuel, that is all what secondaries need to do. That is why idle circuits on secondary carbs are eliminated (except on this set-up in question...), they don’t have choke, and no throttle stop screw either.


Now we'll assemble it!
Float must be adjusted. Height/drop of float differs in all engines and center/end carbs. This small measurement-tool usually comes with gasket-set.



Measuring float drop.


Hint: First attach pump plunger with retainer to lever, after that, attach it to another lever. It's easier that way.


Two carburetors bundled up, one more to go. Then we'll start working with throttle bodies. Notice small boxes again...


Fuel inlet assembly has two gaskets, it is important to remember put them both on, especially on secondary carburetors.


More cleaning... For every part.
Throttle bodies were cleaned in fuel (right),
dipped in citric acid again (center),
and finally painted. (quess which?)



Longer shafts on throttle bodies are attached with small screw. Also, screws of butterflies are there with thread-lock. Make sure you'll put those butterflies there on right way, because they'll fit also on "wrong" way. (You'll understand what I mean when you assemble these.)
Looking against light is also good to check this thing!

Because 2jet-carbs were in production for a long time, gasket-set usually includes few different gaskets.



Idle vent valves got new rubber gaskets. They are "simple-tech"; bend tang to make sure that valve opens and will close also. Easy is always fast... and usually affects more than you'd believe.
But hey, here is pic of phase we've been waitin' for!


Studs attached.


Progressive linkage was used.


Brass fuel fitting go on last.


Her it is on it's final destination, picture linked without permission...



So, there it was.
I know that I'll get some opinions posted below this, about another way how this thing would be easier, better, more ideal, or such. That is ok, I also might learn something.
My biggest idea with this post is to -like Ryan says- to help community.

Cheers!
-Otto-

 

Great post, I do have several questions . You do not show plugging the idle screw holes in the secondary carbs, how did you do it? Do you get a good seal on the secondaries with the stock butterflies? What jet size do you run? Thanks

 

Tri-power carbs main problem is vacuum. The secondary carbs have to be totally sealed or they wont run rite,

1. Idles screws have to be plugged first off. Screwing them in just wont cut it, as well as all extra hole that are not needed, etc

2. Second the butterflys have to be completely sealed off , if you see light it aint gonna run rite.

I tried this two different times and it just will not run rite, you are better off paying the extra $$ and getting the correct carbs/ bases or buying new bases to start with that are for tri-powers. Where the butterflys run up and down in the cylinders they get ovalled and will never seat with the proper new degreed butterflys. They look great but I would bet a couple couple paychecks it just wont run rite. This has been covered numerously

 

I thought someone would ask this.
Yes, on secondary carburetors you should get butterflies totally sealed. Few different styles of stock-butterflies exist, some of them will give you more tight sealing than others. When disassembling many 2GC's you'll notice it.

These are stock butterflies. This (and next) picture is from my another 3x2 project.


Original tri-power throttle bodies -and repro-ones also, of course- make really tight seal; butterflies on them are more thick and spring is pulling them closed. How I did it on this set-up (and my own also):
I first screwed idle screws in, so they were closed. On the backside of throttle body, there is very small pipe, it was also closed.
When whole set of carbs was bolted on intake, I just put there spring to close secondary throttle bodies.

There goes spring from lever of front carb to attaching stud of center carb. Because sec. carbs are linked on the other side, one spring is enough. You could also put it somewhere between firewall and carb to make clean set-up. Spring which you'll see between firewall and carbs is stock spring to return throttle pedal and to close center carb.


When it was time to tune this engine, center was tuned first of course. After it was ok, idle screws on sec. carbs were opened, but only just a little. If I remember right, I opened 'em about half turn each. This is the trick with stock throttlebodies and butterflies! And you're right, they'll pass some air... but only very little amount! It runs with idle valve screws closed on side carbs, but opening them just a little, makes engine run smoother because fuel flow is more even and equal.
I've been running this kind of set-up for four years now, and it runs really smoothly. It is not idling on high rpm eventhough you could presume that.

Jet size is something you'll always get long conversation about, especially with people that have not ever even built 3x2 system... But I'm using 55 on center and 50 on the sides.
Sec. carbs could also have smaller jets, but I have not found them.
Been thinking to collect small stack of jets, and take them to someone to solder them closed. Then buy some small drills and make smaller holes.

 

Very timely post for me as I'm getting ready for the change to Tri power for my 40! Thanks.

 

i did the same thing to my Trips but i blocked off the front & rear carbs(made them secondariers)I filled the power valve hole with lead(Got a punch & filled them with a fishin sinker & tap away!!)then removed the idle screws & did the same.I ran it with all 3 carbs as primaries & thought it was running good, As soon as i converted teh ends to secondaries the performance was unbelievable!!
AND my mileage increased by about 25%!!
Excellant post!! lotta great info, they came out real nice( Now i'll have to put mine in citric acid!!lol
JimV

 

This post will be greatly appreciated

when I go to rebuild my caddy tripower

WHERE DID YOU GET THE GASKET SET?

Thank you very much

 

Well said ! Tri powers are the best set up going when done right but they can be a nightmare when it is missmatched. You always know when one is wrong. The secondarys or useally blocked off or the have the adj. screws still in them. When you start the motor up if you put your hand over the top of the secondary carb and it sucks it wont work correctly. Great post !!!

 

did you get the kits from elco also? this tech is a lot of help for me. my set up does not run right. I know what to check and look for now.vacuum leaks in the secondarys.thanks

 

great post, thanks.

good lookin setup too.

 

Where the hell do you get citric acid??? Old orange juice??

 

Otto, good to see you yesterday, no problem with borrowing the pic. Thanks again for rebuilding my carbs. Good tech.

Citric acid was bought from an agri store, think they let pigs drink it...

--mika

 

HAHAAHHA! That's great!! I have a feed store a couple miles from me, I'll have to ask there.

Great post Card-Otto! I learn better with big color pictures!

 

Kudos to Carb-Otto. I don't know a shit about tripowers...

 

Thahks for the pics, I'm doing a 2 x 2 with Rochester carbs, you just saved me several stupid questions.

 

I have read some old posts about using the 2 outside carbs as primarys and the center carb as a dumper, the idea is that this minimizes the problems with vacume leaks. People have much luck with that?

 

Set of progressive linkage and extended throttle shafts were bought from www.eelco-usa.com
Gasket-sets, power valve plugs, fuel inlet fittings and other small stuff (on first pic) were bought from www.vintagespeed.com
Offenhauser intake is from www.speedwaymotors.com
Carburetors were bought from E-bay and swap-meets in U.S

Using two outside carbs as primaries would give equal fuel flow, but it would also give very much fuel to engine on low rpm. It affects that engine would be idling higher than you’d want it to. You’ll also miss the best part of progressive tri-power system; when you slam pedal to floor, she’ll roar like an angry attorney in a court! Feels like shifting smaller gear! That is reason why you’ll want two secondary carbs.

Some people want to use all carbs as primaries. That is most difficult set-up to tune, because all carbs should be synchronized. It is possible of course, but needs equal jetting on all carbs (which here is not used). It also gives a lot fuel/air to engine, so Strombergs might be better for that because of their smaller cfm. As an example, small base Rochester 278cfm and Stromberg 81 135cfm, so you’ll get the point...

 

Great post...I'm about to do the same thing. I've got the carbs...still need the intake. Thanks!

 

For kits, hit your local Oreilly and grab a Walker 15289c, they're usually in stock. It's $12 and the best rebuild kit I've ever used. Fits perfect and they've improved a bunch of the components over an NOS kit I once used. Oh yeah, DO NOT use an NOS kit. In 50 years, the rubber has warn out. I picked all the pieces of my accelerator pump outta the well after I learned this lesson...

 

Thanks for all the awesome info SERIOUSLY

you didnt have to tell us anything

thanks

 

Great post Otto.

Mika, looking forward to riding along when you put that car through its paces soon!

 

Thanks for the post Carb-Otto. I will be re-working my triples this winter, and will reference this post.

 

Ok if you are using the Vintage Speed or Speedway kits should all the carbs be the same part number? I have about 8 carbs but only 2 are the same part numbers.
Thought on the carb part no?

 

thanks for posting this . I have early Edelbrock casting C355 intake . I have correct ( non adjusting bases ) . All 3 carb's , do not have idle vent valve's . Should the center one have one ? Will be running on 265 chevy , what should the jet's be ? It had 54's in the middle and 55's in the front and back ! But im sure they have been drilled out . This is a stock motor , what jet's would be good ? thanks in advance . PECK

 

Hot Rod Carb. has parts like throttle shafts, thicker butterflies(to prevent sticking on end carbs), jets, even complete bases for sec. carbs, at least that's where we found good parts and help a few years ago.

 

Sorry, can't find them now, must have changed hands.

 

Just as another way to prepare the end bases, I removed the mixture screws, and used Permatex liquid steel. I held the end of the tube against the screw openings, and squeezed until it was oozing from all openings. After it was dry I trimmed the excess material and sanded the front where the screws would be. I painted all three bases with cast blast and they look like factory tri-power bases. I've been running them for two years now and no problems at all.

 

Please explain the power valve plugs-- do you plug the center carb too---how come you don't need them, thanks great post.

 

TomCat1; No, power valve is not plugged in the center. On the sides they are, because secondary carbs are only for dumping fuel, that is all what secondaries need to do. That is why idle circuits on secondary carbs are eliminated (except on this set-up in question...), they don’t have choke, and no throttle stop screw either. My mistake, I did not write this on first post, so I fixed it to there.
And now when I wrote that there, I lost one picture, it seems to be only a link?
Some help, anyone? Ryan?

Unclee; Maybe you meant this one? www.hotrodcarbs.com

Peckerhead28; Those 55’s for secondary carbs are IMO big jets, maybe you can buy smaller ones from your local speed shop? Same jets fit also for Rochester Quadrajet, which might be good to tell for that kid behind the desk.

Noland; If you have ’58 Cadillac engine, 365 cid with 3x2, adjust float level to 23/32” and float drop to 1-29/32” on all carburetors
If you have ’59-’60 Cadillac 390cid engine, adjust float level to 15/16” and float drop 1-29/32” on center carburetor and on the ends you’ll want float level 23/32” and drop 1-29/32”
I checked these numbers on the chart.

 

I think the jet size matches letter size drill bits, solder the existing holes up and drill them out to desired size. You may want to have someone with a lathe make you a jig to center the hole and keep it square. Also do a search here to see results of my question qabout using Holly jets.