63mako

Thought I would post here too. My car is a 63 custom but I am usually on the C3 Tech and performance forum. The carbs are Large Base Rochester 2 bbls. Front and rear carbs are 1970 Chevy 350, 400 carburetors. They are front inlet, pre emission carbs. The center is a mid 70's Mercruiser Marine 350 Chevy carb. To be Coast Guard approved need side inlet and boats need electric choke. The front and rear base plates are 1966 Pontiac GTO Tripower cnc'ed aluminum reproduction base plates with lapped in brass throttle plate for an airtight seal when not in use. It also eliminates the idle circuit. The power valves were also eliminated in the front and rear carbs, not needed as they are just dumpers, they work exactly like a big secondary on a 4 bbl. The front and rear tops are 1966 Pontiac tripower reproduction tops. The Center carb base plate is 1970 base plate off one of the end carbs. The center throttle rod is a 66 GTO tripower throttle rod that was drilled and tapped. inserted a #10 stud and drilled and tapped a piece of the 1970 throttle rod and threaded it on to the end to extend it to accept the pass side linkage to activate the front and rear. The linkage is a modified tripower linkage for a small base setup. Had to shorten the center arm and grind the bottom of the choke housing for clearance The fuel lines are stainless steel, I bought a fuel block, Stainless line, fittings, and a 3/8 pipe bender. Had to move the fuel block forward to clear the manifold with the regulator and inlet so the center line looks a little funny but that is all I could do. The plate nitrous system is from the 60's. It was originally a custom 75 HP shot built by 10,000 RPM for a GTO but I drilled the spray bars to the correct size for a 150 HP shot and added NOS Cheater solenoids. It is jetted at the solenoids and the lines were modified to fit my Chevy. The rebuild kits were from pontiactripower.com. It took me about 5 months in my spare time to research, gather parts and assemble this. I got about $1300 in it and a ton of work. Hope it works as good as it looks. I did my homework so it should. 2 bbl carbs are rated differently than 4 bbl's. Adjusted CFM is about 816 CFM which should be about perfect for my 500 HP 383.

Jalopy31

Wow! Your workmanship is impressive, and you've built it on a reasonable budget as well. I hope it does indeed run as well as it looks.

I recently ran across the pontiactripower.com website after running into some issues with the tri-power on my street rod. They are a great resource that I wish I had run across earlier. Another good source for tri-power parts/information is Automotion Inc (www.hotrodcarbs.com). Larry has a good website as well.

Just curious - what type of needle and seat are you using in your carbs? Mine use the ball & seat type, and I have had occasional problems with the secondary carbs flooding when they apparently do not seat well. A friend that is into Pontiac restorations suggested that I change them back to stock needle and seats because they are more forgiving. I have not done that yet since the problems are becoming less frequent now. I'll usually get it out where I can open the secondaries every time I drive the car now to keep fresh fuel in them. I believe this has helped since I only get to drive the car a couple of times a week.

Again, I am very impressed with the setup you have built, and I hope all goes well when you get it running.

TB

63mako

Stock needle and seat, A fuel pressure regulator and guage set to 6 PSI will probably solve your problem.

macdarren

I have a question....where do you get the little Heim-Joints for the linkages? I have been casually looking around for some to spruce up my linkage setup but all I can find are really cheezy ones and nice but too big versions. Yours look to be a good size and definitely not the poor quality ones I have seen around.

Thanks
Darren

63mako

The linkage came from Vintage Speed. I had to modify it for my application but all the stuff I got from him was top quality.

Vogie

Great looking setup and craftmanship. Just curious about a couple of things.

In photo one, looking down the throat of the center carb, I don't see a spray bar. Am I missing something?

You said you drilled the spray bar(s). Does this mean that there are no N2O Jets to regulate the flow?

Even though used during WW2 (a bit differently), I didn't realize that Nitrous had been in use in autos that long.

63mako

The plates have a spray bar running from the front for the nitrous and the rear for the fuel at the center of each carb. They are stacked one above the other nitrous on top fuel under. The center of the nitrous block is open. The center web of the carb baseplate is obstructing your view of the bars. The front bar (nitrous) has 2 holes pointed down at a 45 degree angle centered in the opening. The fuel bar enters the back and also has 2 holes spraying sideways. The spray patterns intersect in the bore to atomize and mix the fuel and nitrous ( very similar in theory and function to nitrous port injection) you get a spray into each of the 6 throttle bores.

I had to enlarge the holes. This old system originally didn't have jets. The spray bar holes were sized to deliver the correct ratios of nitrous and fuel for a 75 HP shot. very crude. I opened the holes up enough to accept a max 150 HP shot on both sides and jetted the system at the solenoids. If the holes are too big jetting at the solenoids you have a pressure drop in the system at the furthest holes from the solenoids. If they are too small you can't get as much power.

Yes this system was one of the early drag racing setups from the mid 60's. It was custom built by 10,000 RPM in Southern California for a GTO Tripower drag car. They are still in business building racing components. Nitrous systems were few and far between then and were race only, very crude, basic systems. NOS Company has been around since the mid 70's and they really brought nitrous use into the mainstream with new designs that made nitrous use more dependable and less damaging. I have used this old plate setup but use modern components in the rest of the system to make it function like the newer versions. NOS Cheater solenoids, NOS Jets. Bottle heater to keep nitous pressure constant, a fuel pressure regulator to fine tune the nitrous/ fuel ratios, a wide open throttle switch so it only opens when all throttle plates are open and a MSD window switch to turn it on only after a set RPM (2800)and off at a set RPM (6300). My plan is to set my RPM Rev limiter on my MSD box at 6500. Then I can powershift at 6500 with no NOS (it kicks out at 6300) and when the RPM's drop after my shift and clutch engagement, it will kick back in reducing driveline shock. I have actually been working on this for almost 2 years but started assembly in March. Took a long time to put it all together but it should work well. This will all be dialed in on an engine dyno with A/F meters at each exhaust port (8 total) to make sure it is set up correctly