1959 cadillac fresh 390 with tripower vacuum leak

[dgworks845]

    I have a 59 caddy that ive been restoring for 10 years, ive added a tripower unit to this original 390 cid. and when I say I added it. I mean i've meticulously added the correct distributor, dash pot, rebuilt each carb. bead blasted the intake , checked for cracks...with all details right down to the new vacuum diaphram and tested the vac. switch.
     When I first start it cold it runs at the choked fast idle fine, then as it warms up she starts running rough and is clearly in trouble with vacuum because if I put my hand over the center carb it races up and runs smooth again. I've sprayed carb cleaner around trying to find where the leak is coming from but found nothing, ive replaced all vac lines including climate controls, had the booster rebuilt by professional company. This has me stumped.... at this time I cant even adjust the air mixture to the center carb or time it for that reason... Any ideas out there? Thanks for your time on this matter. signed, dwayne

[Jeff Wilk]

Do you have the aux vac tank on the firewall that mounts above the brake booster?  Have you tested that flow valve as well?

[Dan LeBlanc]

How about removing and blocking vacuum lines on the engine?  Then if it's running fine with all ports blocked, bring back the devices connected to the vacuum sources one by one. If the car starts to falter after reconnecting something you'll know where to look. There are too many variables at the moment and you could go off chasing in all sorts of directions without a systematic approach.

Have you hooked up a vacuum gauge yet?  If so what's that reading?  To set fuel mixture and idle speed you need a vacuum gauge also.

[76eldo]

Dan beat me to that answer.  By blocking all of the vac lines you will be able to check to see if it's the center carb or the manifold itself.  The hard line going to the distributor can probably stay connected.

The fact that you say it starts cold but the problem comes on when the engine warms up makes me suspect a manifold or gasket leak.  These sort of problems can be frustrating but with systematic troubleshooting you will get it.

Brian

[curly]

It could also be plugged idle passages in the main carb.  When the choke is on, or when choking by hand you are forcing fuel from the off idle and high speed passages of the carb.
Remove the idle mixture screws and blow air through the passages, also try opening them up 1/2 to 1 turn more, see if it helps.

T  Lewis

[dgworks845]

startling discovery, the center carb is not shooting a nice needle stream of fuel like the outter carbs are, (i had the engine not running when i did this) of corse. So all though its  acting like a vacuum leak, i'm mearly regulating the (too much) air flow to mix with starving fuel flow. I removed the top of the rebuilt center carb, played with the pump and didn't get it to squirt like the other ones. I remember buying this pump on line the cup is made of leather, I let it soak a day before installing it.
   I tried another pump and it works fantastic except the rod is too short. It's for a corvette carb.. so i just ordered a replacemnt from napa and gave them the original part # 700 0278...thanks for all the insite gang, i'll let you know tomorrow about 11am est..
    I just cant wait to move this car on its own power.. after ten years of jacking it up and down and pushing it back and forth

[76eldo]

That's pretty exciting. By the way, welcome to the message board.  I'd love to see some photos of the car.

Good luck,

Brian

[dplotkin]

I assume you know that the outer carbs are correct they have only high speed circuits, no idle or low speed. In a tri-carb setup you have to make sure the front & rear carb throttle plates are completely shut, otherwise you have a massive vacuum leak.

Dan

[dgworks845]

I assume you know that the outer carbs are correct they have only high speed circuits, no idle or low speed. In a tri-carb setup you have to make sure the front & rear carb throttle plates are completely shut, otherwise you have a massive vacuum leak.

Dan

thanks dan, yes they are completley shut, however the center one never is completedly shut.... I changed the accelerator pump and now is squirting the way it should. Now I don't have to dump gas down the carb to get it started... I also backed off the idle mixture screws a full turn and now it is running great (rich) but somewhat normal..
     i'm about to time it and  wanted to know more about the vacuum gauge while adjusting this center carb.... I have 32-42 lbs. of vacuum depending on the idle and that reading  was taken off the vac line supplying the vac canister for the outter carbs this line i also have split for the dashpot idle mechanism..... is this right? should I have T'd off this line that runs from the rear of the rear carb....You guys have been so helpful... thanks for all your input on the matter... I'll try to post some pics

[76eldo]

I'd pull a vacuum source right from the manifold. Your reading sounds very high. Should be about 21 for a healthy engine and should read steady.

An older mechanic with expertise on Caddy Tri Power told me that when. They are running correctly it will seem a bit rich.  I have a 1960 convertible with factory tri power and went through my whole setup when I bought the car. My vacuum diaphragm was split inside so the secondary carbs did not open. I got mine redone by Mike at Mastermind Inc and it works great.
Make sure your linkage is moving freely with no binding.

Brian

[curly]

Rule of thumb for manifold vacuum is 18-20 inches at sea level.   Take the reading directly off the intake manifold, power brake line is a good choice on that engine.

T Lewis

[dgworks845]

T at what rpm  do i take this vacuum check at? i can tel u that 32-42 was at 2400 rpms at least. It seems I can't lower my idle to a normal 450 just for timing i'm at 1000 at the lowest. and can not get it lower to do the rest of the fine tuning...my vacuum lead is off the front carb for the power brake unit, I took my test off the rear which suppors the tripower auxillary vacuum canister and splits it with the dash pot idle mech.,,,
   right  now my new accelorator pump went bad..... can someone tell me where they have gottern th

[imf222]

tripowers are great but impossible to
adjust

they really had good reason to throw m out
in those days

[76eldo]

Ron,

All you need to do is get the center carb, a common Rochester 2GC to run correctly.  The end carbs are pulled open on 3/4 throttle by the vacuum switch opening and allowing vacuum to pull in the diaphragm, thus moving the linkage.  The end carbs are simple with no choke or idle circuit.  As far as normal driving, the car runs on just the center carb, like any other car of the period with a 2 barrel carb.

The problems occur when you use an old kit that gets eaten up by the ethanol, or if the wrong person "rebuilds" the carb.

BR

[dgworks845]

im withyou brian where can i get a accerator pump for such a carb that is made of rubber and not leather. that is made for this large 2bbl. and comes fully assembled with its own springs>>>? that is my current problem as of now... napa one failed....my original circular spring that holds the cup tight to the outter venturi walls is too big.... so i left it out.....and now its not squirting the way it should again...

[Jeff Wilk]

Dwayne,  google Classic Rebuilt Carbuerators here in NJ.  Call and ask for Phil.  He does lots of work for our Cadillac region and has done several Cadillac tri-powers including mine and dozens more from that era. He can get the exact parts you need quickly.

Jeff

[76eldo]

I'm not sure where to get the individual part. Try the shop in the post above this one.

[Ralph Messina CLC 4937]

Dwayne,

Here’s the contact Jeff referenced above:

Custom Rebuilt Carburetors; 200 Wood Ave Ste A; Middlesex NJ08846; (732) 356-4333
Web: customrebuiltcarburetors.com

HTH,
Ralph

[dgworks845]

 :Dthanks for the info i;ll contact him tomorrow.... ive had it with this car for today.... this used to be fun for me. but it seems i have to do Everything and i mean Everything at least 2 times and sometime 5 times over......The best part is you buy these manufactured parts only to manufacture them in the way it was supposed to be in the first place... nothing is easy anymore....

[dgworks845]

I mean Ralph... gee how can I get my member # below my name with the CLC badge???LOL