4bbl to tri power
- Thread starter eddies59
- Start date
If you're looking for a stock intake 4 bbl, I don't have need for the one off my '59 348 250 hp motor.
I'm sure there are a few cast iron 4 bbl paper weights floating around this site which will fit your needs.
Sir, my next project for my 1958 Impala coupe will be another 348 as well. I'm looking to purchase another 4bbl intake manifold that is not cracked. Recently I bought one off eBay that revealed a crack below the carburetor (after I had it dipped and blasted). I don't fault the seller as he couldn't see it beneath all the gunk. If you have a price, let me know. 6232612735
Not that I'm against selling you mine for a fair price, you may want to take Cecil up on his offer if for no other reason than the postage will probably double the cost. Nearly 40 pounds of cast iron is expensive to ship.
The main concern I can come up (with my limited experience) would be whether or not the tri-power came off a vehicle with an automatic transmission or not. And even this concern is quite workable. If I'm not mistaken, the manifold for an automatic has a nipple for vacuum while the manual may have a screw in place of the block off. Other than that, I think you're in good shape.
ragtp66
Well Known Member
I assume your talking about a 59+ tripower. I am not as schooled on the 59 stuff but 58 tripower is of course 58 only the fuel inlets on the carbs are all pointing toward the radiator on 59&+ they point to passenger side, the 58 also has a vacuum control on the drivers side. If you have factory power brakes there is a tripower only check valve assembly. In 58 the only auto trans was Turboglide with tripower and used one of the carb studs which is hollow for the vacuum modulator. A few other quirks that I am forgetting. Try to make sure the carbs you get have good straight base plates as they are usually warped from over tightening and cause nearly impossible to find vacuum leaks. You will be constantly tinkering with the tripower where the 4bl is a more hasselfree option.
ragtp66
Well Known Member
I assume your talking about a 59+ tripower. I am not as schooled on the 59 stuff but 58 tripower is of course 58 only the fuel inlets on the carbs are all pointing toward the radiator on 59&+ they point to passenger side, the 58 also has a vacuum control on the drivers side. If you have factory power brakes there is a tripower only check valve assembly. In 58 the only auto trans was Turboglide with tripower and used one of the carb studs which is hollow for the vacuum modulator. A few other quirks that I am forgetting. Try to make sure the carbs you get have good straight base plates as they are usually warped from over tightening and cause nearly impossible to find vacuum leaks. You will be constantly tinkering with the tripower where the 4bl is a more hasselfree option.
You will "NOT" be constantly tinkering with the trip's once they are set up they will be trouble free. I've owned enough of them, running a tripower now.
Lt.FrankDrebin
Well Known Member
The original 3x2 setup does NOT require constant tinkering. All it is is a 2bbl carb with two extra 2bbls that kick-in when needed. The most important thing in a 3x2 setup is to have the secondary carb throttle valves sealed as air-tight as you can get them. I see that there is a totally rebuilt front carb on FeeBay now for a good price, and the throttle blades appear to not allow any light through, which suggests an air-tight seal.
chuckl
Well Known Member
You don't need to be constantly fiddling with a 3 X 2 setup. Set it up correctlyI have a 59 tri-power set up (progressive linkage) on my rebuilt 1961 348. when I bought the set up, it had new shafts (with seals) and new plates installed. I went through problems of high idle, flooding, stalling, etc. When I tore down the carbs, all the gaskets had shrunk and was leaking air/fuel from all areas. The bases were warped from over-tightening.
I had the bases "decked" and then added a 1/2" phenolic blocks under the carbs. I inspected the shafts and plates and found they were leaking air, big time. I tried to reseat the plates to shut the air out of 1 and 3 carbs--no change. I removed all the plates and fitted each plates to the best-fit throat. I then smoothed the throats with 1000 grit sand paper. If you just loosens the plates and close the throttle, the plates will not necessarily center and shut off the air. The plates also need to be rotated a bit, as well as slid up against the throat with a bit of pressure on the shaft, at the same time.
With a quality kit(s) installed and the linkage adjusted correctly, my engine will idle at 400 RPMs before it stumbles. Even with a mild cam and 10:1 pistons it will idle smoothly at 650. The engine is very strong and gives me no problems. Mileage is very good.
Use quality overhaul kits, center and rotate the plates, set up the progressive linkage so that at idle they are closed completely (shine a light in the throat), use mild but not excessive spring pressure on 1 and 3. You will not need any more that 4 1/2 to 5 lbs of fuel pressure. Much more than that, the pressure will override the needle and seat and cause the carbs to flood. I run 4 1/2 lbs, but the engine will not starve for fuel at 3 lbs at WOT. Also, adjust the float drop about 1/16" higher than called for. This helps prevent the needle from trying to **** sideways and stick partially open. Some cheap kits have shorter needles that do not seat correctly.
