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Tri power rochester end carbs once and for all

Discussion in 'The Hokey Ass Message Board' started by 58_Ford, Mar 24, 2010.

  1. powdercoater46
    Joined: Oct 27, 2009
    Posts: 246

    powdercoater46
    Member

    Here's my 2 cents worth of experience. I found a problem on my friend's anglia tripower. Would not idle below 1200 rpm. With it running at high idle, with the air cleaners off, I placed my hand over the top of the rear carb and felt vacuum. At the same time, the engine speeded up. Removed my hand from that carb and went to the front and the same thing happened. The throttle plates on front and rear carbs had been messed with and were not seating properly as another member mentioned. If I would cover both front and rear carbs, the engine would idle down like it should due to the vacuum leaks being covered. The solution? We sent both carbs to a shop in Peoria Illinois where the experienced guy sealed the throttle plates and that was the fix. Anyone want his phone? PM me if u want it.
     
  2. 58_Ford
    Joined: Feb 23, 2010
    Posts: 118

    58_Ford
    Member
    from Phoenix

    gonna try that tonight. that article pretty much answered my questions. But I thought of something - My distributer is running off the back carb vaccum. Is this wrong since there shouldnt be any? if I put my finger over it it is a heavy pull
     
  3. tommy
    Joined: Mar 3, 2001
    Posts: 14,758

    tommy
    Member Emeritus

    That is the correct port but it is NOT a "PORTED" vacuum source as so many people believe. Yes the port goes into the carb above the throttle plates but the port turns straight down through the body on through the carb base into an area below the butterflies. It is manifold vacuum. That is where GM connected their vacuum advance on their cars. Just because the port comes out the side above the butterflies, it doesn't mean that it is ported vacuum.

    [​IMG]

    That port on the side ends up in the "mountain shaped" hole between the 2 lower bolt holes in this picture....below the butterflies....manifold vacuum. That is why they tell you to disconnect the vac. adv. and PLUG the connection when setting the initial timing. If you don't plug the hose or tube the engine won't start because of the massive vac. leak. Once the initial timing is set, reconnect the hose/tube and the timing light will jump up off of the timing tab.

    That port on the rear carb is manifold vacuum also so it won't make any difference which carb you connect the advance to. If you don't use that port, it has to be plugged for the engine to start.
     
    Last edited: Mar 25, 2010
  4. gasserjohn
    Joined: Nov 9, 2008
    Posts: 1,219

    gasserjohn
    Member

    I was a mechanic when this stuff was new
    there has been lots of threads on multi carb problems
    every one mentions having no vacuum leaks on non primary carbs
    the original secondary carbs had liquid sealer ...you fitted the butterflys & then applied this sealer ...let dry &then ''broke'' the seal when dry
    been along time but think sealer was a factory/dealer item......
    have run a tri power 312 ford &8 carbs on a lincoln 430 log manifold non progressive linkage esky roller cam >>>this engine idled fine had no BOG-FLAT SPOT ....all carbs mechanically synced.......had these when i was >>>16-18yrs old<<< ..........if you cannot fix it yourself find someone that can ...
    quit giving up &badmouthing muiti-carb setups...........Littlemans 6carb small block with nitrous is a great example !!!
     
  5. dickster27
    Joined: Feb 28, 2004
    Posts: 3,127

    dickster27
    Member
    from Texas

    Thanks John, I couldn't have said it better.
     
  6. powdercoater46
    Joined: Oct 27, 2009
    Posts: 246

    powdercoater46
    Member

    Vacuum advance is only for economy. I recommend connecting it to the center carb above throttle plate as in the photo shown earlier by Tommy. BTW; if the throttle plates are all the way closed on the rear carb and you have lots of vacuum there for your vacuum advance, could that mean a leaky throttle plates? think so.
     
  7. 58_Ford
    Joined: Feb 23, 2010
    Posts: 118

    58_Ford
    Member
    from Phoenix


    Thanks tommy. That is a pic I found off the web.It is an Impala. Only one I could find showing the port. Im running that GM carb on my Ford. Do I still use that port? Thanks again
     
  8. 58_Ford
    Joined: Feb 23, 2010
    Posts: 118

    58_Ford
    Member
    from Phoenix

    But according to tommy that goes to mani Vacuum, so ithe vac would be coming from below the throttle plates. I think:confused:
     
  9. BuiltFerComfort
    Joined: Jan 24, 2007
    Posts: 1,620

    BuiltFerComfort
    Member

    One more little thing to mention - if you almost always drive at part throttle, the end carbs may have months at a time not used - with nothing flowing through them, and thus gunk up. Thus some people run idle circuits on all 3 carbs to keep them flowing.

    This is opposite of what lots of people said above, I know (seal off end carbs at idle). And I don't really disagree with them. A hotrodder will spend some time each drive at more than 70% throttle, right? :D

    The one time I saw someone doing this setup (I was a kid and didn't really understand what was going on at the time), the center carb was set to low idle, and the ends sealed with some sort of goop as stated above. Then he filed a little goop out of the way on the center of the throttle bore on the end carbs so it would leak a LITTLE air, and opened the idle needle just a tiny bit on the end carbs, speeding up the idle.

    Then by turning down the idle on the center carb, the idle was set correctly and a tiny bit of air and gas flowed through the end carbs, keeping everything from clogging.

    Seemed like a pain but it seemed to work for him.
     
  10. gasserjohn
    Joined: Nov 9, 2008
    Posts: 1,219

    gasserjohn
    Member

    also remember that not all carbs are able to be rebuilt
    sometimes corrosion/gas varnish buildup/ wear or collapse of a passage can render it unsavable........i was 'lucky' to be there backintheday when this stuff was new............
     
  11. 58_Ford
    Joined: Feb 23, 2010
    Posts: 118

    58_Ford
    Member
    from Phoenix

    Thats what I like most about H.A.M.B . There are quite a few that are from "back in the Day" and enjoy helping us NewBs carry on tradition. Ill be able to pass this knowledge to my kid. Of course Ill act like I knew it all along, "Been doin this since I was your age son" ;-D
     
  12. tommy
    Joined: Mar 3, 2001
    Posts: 14,758

    tommy
    Member Emeritus

    [​IMG]

    There was more than one type of vacuum connection on these carbs, a hose nipple and threaded port for hard line are two that I know of. Both of these are connected to manifold vacuum for the GM vacuum advance and should work great with a post 56 Ford V.A. dist.

    I read where people recommend "ported vacuum" for vac. adv. but I can find no such port on a Rochester 2bbl. Maybe someone can show me where it comes out in the venturi? I'm still learning.:D
     
  13. 58_Ford
    Joined: Feb 23, 2010
    Posts: 118

    58_Ford
    Member
    from Phoenix

    Tommy I have my vacuum advance connected to that nipple on the right carb of your pic
     
  14. chop32
    Joined: Oct 13, 2002
    Posts: 1,077

    chop32
    Member

    This one gets to me every time!
    This has always been my logic for using ported vacuum at the distributor, feel free to correct me if Im off track.

    Lets say you have a motor with 6 degrees initial timing. You also have 18 degrees centrifugal advance and 12 degrees vacuum advance available.

    Ported vacuum is low or non existant at idle and higher the faster the engine turns (more air flowing thru the venturies). At idle, this would give you only the 6 degrees initial timing that you have pre set in the motor by distributor location. As the motor starts to spin, the centrifugal advance and vacuum advance come into play. Your initial 6, the centrifugal 18 (lets say all in by 2500 rpm) and the vacuum that will top out at 12 degrees with the right amount of airflow thru the carb, giving you incrementally more advance the faster you go. This gives you a total of 36 degrees advance at full throttle. (right where you want it).

    Now, the same motor using manifold vacuum at the distributor. Manifold vacuum is highest at idle and deceleration, and pretty much non existant at wide open throttle.
    At idle you would have the same initial 6 degrees of timing and your vacuum advance of 12 degrees for a total of 18 degrees. As you bring the rpm's up your centrifugal starts to come in and at 2500 rpm (part throttle) you have full 18 degrees centrifugal advance, your initial 6 degrees advance and your 12 degrees of vacuum advance (asuming that your part throttle vacuum reading is equal to what it was at idle) for a total of 36 degrees.
    So far so good...now put your foot to the floor...your vacuum signal drops to nothing at wide open throttle (unless you have too small a carb(s), then you will get a bit of vacuum at WOT) and now your total timing is only 24 degrees...not the best thing for optimum performance, Id say. Then you back off the throttle and your vacuum advance comes back in under deceleration. Why would you need more advance while you arent even on the throttle??
     
  15. KoolKat-57
    Joined: Feb 22, 2010
    Posts: 2,965

    KoolKat-57
    Member
    from Dublin, OH

    Try this web site also, parts and info..... www.pontiactripower.com
    Lots of good info!
    I have tri power on my '57 and they work GREAT!
     
  16. 58_Ford
    Joined: Feb 23, 2010
    Posts: 118

    58_Ford
    Member
    from Phoenix

    Chop, Like Tommy said there doesnt seem to be ported vaccum on these. i have a tiny nipple at the very top right under the choke but it seems to go straight through to the throat.

    [​IMG]
     
    Last edited: Mar 25, 2010
  17. gasserjohn
    Joined: Nov 9, 2008
    Posts: 1,219

    gasserjohn
    Member

    my post got me thinking about the sealing dope i mentioned
    before i starting searching i read the link about another oldster who is doing the restoring of tri-powers
    he says ''special gm sealer used''was called '''DAG213'''....
    that's it!!! i remember it now!!!!!!!!to easy ...Always thought of this stuff when doing 4barrels w/o 2ndary idle circuits
    he makes a good point >these old carbs need to be restored by someone like him ....READ HIS SITE
     
  18. 58_Ford
    Joined: Feb 23, 2010
    Posts: 118

    58_Ford
    Member
    from Phoenix

    Then how is one supposed to learn to do it themselves? :p
     
  19. tommy
    Joined: Mar 3, 2001
    Posts: 14,758

    tommy
    Member Emeritus

    I don't know a bunch of theory. I won't ever try to BS you. I did cut my teeth on GM cars in the sixties. I want it to run like they did back then. Every GM car that I ever messed with in that era required that you disconnect the vac adv and plug the line to it when you set the initial timing with a light because it does have high vacuum at idle. I figure the GM engineers know more than I do.

    I never heard the term ported vacuum until I got on the net around 10 years ago. I couldn't figure out what you guys were talking about. I knew that there was always a high vacuum at the advance at idle when tuning up a 50s-60s GM car.

    I have since learned about the Ford 48-56 system. I don't understand it. I just know that it exists and that it can be a problem with multiple carbs. I'm not interested in learning about it.

    I want the fuel economy that comes with a vac adv system. I did learn here that with full vac advance at idle the engine will run cooler. I occasionally get stuck in traffic. I'm not a racer. I build for the street.

    This article by a GM engineer is what I go by. Manifold vacuum for vac adv.

    When I built the carbs for the above system I stuck the nozzle of a can of gum cutter into the vac adv port on the carb to see here it went inside. It goes down through the body of the carb into the base plate and comes out under the butterflies....manifold vacuum. That's how GM does it and it's good enough for me. Unless you drill your own ports in the side of the carb, you can't run "ported vacuum" on a 60s era Rochester carb.
     
    Last edited: Mar 25, 2010
  20. chop32
    Joined: Oct 13, 2002
    Posts: 1,077

    chop32
    Member

    I had a tiny nipple like that once, turned out to be a mole...Sorry, couldnt resist!

    Some GM vacuum ports can be deceiving. Im not saying that Tommy (or the carb) is wrong, I guess I left out the part wondering why GM did not have a provision for ported vacuum on these carbs? Id like to say that they learned this method later, but Ive found '97's with a (factory?) ported vacuum connection.
    We are all learning as we go, Im just hoping that someone can tell us what the reasoning behind this was? Did all earlier motors run manifold vacuum to the distributor?

    I just read Tommys post (I type way too slow). My intent was not to put you on the defensive and I wasnt questioning you. Sorry if it came accross that way.
     
    Last edited: Mar 25, 2010
  21. badlefihand
    Joined: Apr 20, 2007
    Posts: 318

    badlefihand
    Member

    Sounds to me like you better start over.You dont need matching end carbs or tri-power carbs to start altho a matched set would be nice( about $150- $300 apiece for org that need overhaul.) Buy the end bases from Vintage speed $150 or check ebay he lists sometimes.,no idle curcut,no idle screws ,no vacume,no sticky stuff to set butterflys with.End carb butterflys are thicker than reg 2g carbs, no leak, machined and lapped in to fit.no problems. No vacume to end carbs plug all vacume ports on end carbs (all), remove choke plates and plug holes.Leave power valve in or plug, either way. Check metering jets for size, Pontiac uses 68s + on end carbs, 62s on center. chevy 307 ,327 use 52s + on all 3, You may have to experiment on metering jets. All vacume off carbs comes off center. Why vacume off end carbs ,when they open at 70 percent there is very little. Center carb is a regular 2GC with jets you chose. Keep fuel pressure at no more than 5#s some times you need a small hole in end carb butterflys. You need pumps on all 3 carbs. put a decent kit in all carbs, clean well and pay paticular attention to float level.the kit will have instructions. That is what I have done,no use playing modifying bases ,lots of head aches there. My 2 cents. Looks like your thread got hijacked by ported vacume, dont believe I ever head of that on a 55 year old 2GC carb.
     

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    Last edited: Mar 25, 2010
  22. all of that leaves out one thing-- LOAD

    take the engine you described and put it in a 3/4 ton pickup with a camper on the back. Try to pull a steep hill. The thing is HEAVY, so you throttle down to pull the hill, but guess what? it starts to rattle. Fuel injection automatically backs out of the timing, us "old school" guys have to do it manually, OR, as you described, when the throttle is down, the vacuum goes down, the vac advance backs out, pulls some timing out, and up the hill you go, without detonating your engine.


     
    Last edited: Mar 25, 2010
    Blues4U likes this.
  23. mach1oh
    Joined: Feb 15, 2010
    Posts: 27

    mach1oh
    Member
    from ohio

    The vacuum port for the advance on the carb is on the base plate , the long square piece coming out of the back of the base plate needs removed and replaced with a brass screw in nipple and it should be on the center carb only
     
  24. chop32
    Joined: Oct 13, 2002
    Posts: 1,077

    chop32
    Member

    Thats a very good point, I didnt take into consideration older, higher compression motors on the crap we have for gas now.
     
  25. Lobucrod
    Joined: Mar 22, 2006
    Posts: 4,120

    Lobucrod
    Alliance Vendor
    from Texas

    That nipple you are pointing to supplies filtered air to the choke heater circuit. There would have been a hose from this nipple that connected to a tube that sticks out of the top of the passenger side exhaust manifold. The tube through the manifold would then be connected to a copper tube that ran up and connected to the threaded connection on the choke. All this was to use exhaust heat to warm up the choke thermostat. All worked pretty good till the tube going through the exhaust manifold burned out and carbon swould foul the choke assembly.
     
  26. tommy
    Joined: Mar 3, 2001
    Posts: 14,758

    tommy
    Member Emeritus

    [​IMG]

    I did lap in the thicker butterflies for the end bases as it was recommended. I used the old Dupont chrome polish because it has lots of grit in it and it was on hand. The brass butterflies seated pretty quickly wearing the high spots away to get a good seal all the way around.

    [​IMG]

    I set them up in a vise with a return spring going down to the C clamp. This let me just push the butterflies open and let the spring snap the butterflies closed with a lot of force. The chrome polish acted like valve grinding compound wearing away the high spots on the brass butterflies seating them into the bores.

    [​IMG]

    This is what I ended up with, a wide seal all the way around the butterflies. The mixture screws were removed and 5 minute epoxy is pushed into the holes until it comes out the holes inside the throttle bore.

    This is all done for you by the guys that supply the replacement tri-power end carb bases. I'm just cheap and enjoy doing things myself if I feel that I can handle it.

    I bought the extended shafts at the same time for the progressive linkage and the wider slots for the thicker butterflies in the end carbs. The extended shaft for the center carb uses the stock thinner butterflies. If anyone wants to do it yourself, I recommend talking to Charlie at Vintage Speed. I'm pretty sure that he supplies the tri-power conversion kits for Speedway. There are a few carb builders on this site that may be able to supply the parts. I can only speak of my experience.
     
  27. 58_Ford
    Joined: Feb 23, 2010
    Posts: 118

    58_Ford
    Member
    from Phoenix

    I learned so much by this thread. Thank You all!!!
    I tossed and turned all night wanting to get up and pull the carbs. I called out sick today ;-D. gonna pull them now. I put my hands over the end carbs and it killed the engine,did feel vaccum. Gonna take pics and post them of before and after.Thanks again. When done I will explain everything I did and let you all know how she runs
     
  28. 58_Ford
    Joined: Feb 23, 2010
    Posts: 118

    58_Ford
    Member
    from Phoenix

    Just got the rebuild kit, All the float levels are for GMs , any suggestions for a ford 390?
     
  29. badlefihand
    Joined: Apr 20, 2007
    Posts: 318

    badlefihand
    Member

    I would Build them as GM, but go at least in 60s (a guess)for jet size Dont know ford jet size but you can find that out,or build to 389 or 400 pontiac ,that is as close as I can call. Float level has to be according to which carb but most 2Gs are very close on float level as far as I know.That baby must eat the fuel same way and you dont want to starve those end carbs when you open them,they suck the air.
     
  30. brian hurst
    Joined: Jul 5, 2009
    Posts: 2

    brian hurst
    Member
    from michigan

    Sounds like all three carbs are primary.the secondary carbs even with the idle mixture screws all the way in ,the hole in the throttle blade will still send vaccum signal to the venturi and pull gas just like if the floats are stuck.also bassically short circuiting the primary carbs idle funcion with 4 small vaccum leaks.i have seen guys solder these hole shut but the proper base is the way to go.rochester 2 jet also has a booster or power valve in the bottom of the float housing you'll need to remove them and plug them.i was able to get parts from pontiac tripower.com .the stumple in the low mid range tip in is the wrong accellator pump arm that attaches to the throttle shaft trying to pump to fast
     
    knotheads likes this.

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