Engine bogs when floored

[one finger john]

Also along the lines of carbs, if you have a Weiand tunnel ram bottom look into coloradohotrodparts.com and their street tunnel ram ideas. Tunnel rams were never designed to be run on the street. Race only. Colorado Hot Rod Parts re-thinks plenum volume of the traditional tunnel-ram tops.
If you are married to the tri-power set up look into finding a normal low rise manifold from the usual suspects (Edelbrock, Weiand, Offenhauser, etc.) that will use your carbs and most of the linkage.
Give your present carb top provider a call to see if they can help.

John

 

[fletcherson]

From dead stop or cruising at 50 mph and I floor it, the engine bogs down like it going to die. I checked timing, looked for vacuum leaks ( found none) removed air filters and check to see if the pump and jets are working. So far have not located the cause of the bogging. Any ideas?

I want to express how much I like your setup. It's nice, clean, I especially appreciate the clean, neat fuel lines. No big bulky an stuff. I normally make my own fuel and vacuum lines out of steel line when I finish my builds. I don't chrome them, but if there was a inexpensive and convenient company that provided such service, I might. I also like the tri power setup. They work really well once you get them set, at least on a low rise, dual plane manifold. That's my experience with them. The difference between a tri power and six pack or three duce setup is on a tri power, the secondary carbs are simply dump carbs, no idle circuit. The others use three carbs the same with idle circuits and you have to synchronize them, like a multi carb bike. They each have their pros and cons... like everything else in life. Hope you get the bugs worked out soon!

 

[rubicon]

The two outer carbs just dump, no idle circuit in them. I will disconnect them from the linkage and see what happens when I put the pedal to the floor. I also have springs to change the advance on the MSD distributer if need be.

 

[one finger john]

Rubicon, at what point does the primary carb start to open the secondary carbs?
I believe that there is a ball on the primary linkage that determines when the secondarys will be opened. If you can, see if you can adjust that ball so that the secondarys are opened later in relationship to the primary carb.

To keep the present tri-power set up you may have to educate your right foot to simply not mash the throttle but to calibrate the amount of throttle opening you have.

If the ball is set at 50% primary opening for the secondarys to engage, then set the ball at 75% primary opening for the secondarys to engage to see if that improves drivability.

Look at the present set up as a Holly double pumper with the obvious mechanical secondarys. Thats all this really is. Educate your right foot or bring the secondarys in later. Or maybe both.

Essentially you have mechanical secondarys, the two end carbs, instead of vacuum secondarys that you can mash & go. Vacuum secondarys utilize negative vacuum to determine when the secondarys start to open.

John

 

[one finger john]

3rd edit. Vacuum secondarys utilize a spring to open said secondarys while I believe that engine vacuum determines when the secondarys will start to open. Vacuum drops, spring pushes secondarys open.

John

 

[409T]

I would say (and this is just a guess) it is the carb set up.
Get an Edelbrock manifold from a swap meet along with a 600 or 750 carb (AFB or Holly), take off the tri-power (no, don't sent it to me, seriously) and get the car straightened out, running wise.

I think carb setup too. Getting a swap meet manifold and carb setup as OFJ suggested is a good idea. I have spent LOTS of time with multiple two barrel setups, my 409 now has 6, and the accelerator pump squirt or rather lack of same is always a problem and always causes what you are experiencing. I really believe that those three 200 cfm carbs have enough poop to run the engine, but not enough pump delivery to overcome the rush of air when you put your foot in it. Just my 2 cents.

 

[one finger john]

And one finaltime Rubicon, could you give the board a detailed listing of parts, engine size, heads, compression, cam specs, converter and type, trans (OD ?)rear end gear, etc. B Really detailed.

John

P.S. Does it every recover from the hesitation or does it stay flat ?

 

[rubicon]

And one finaltime Rubicon, could you give the board a detailed listing of parts, engine size, heads, compression, cam specs, converter and type, trans (OD ?)rear end gear, etc. B Really detailed.

John

P.S. Does it every recover from the hesitation or does it stay flat ?

That will take some time. Right now I do not have all the info you are asking for. The engine is a 383 stroker with 422HP. Edelbrock E-Street heads, Tunnel Ram with triple 2bbl set up. Rochester 2G outside and 2GC center. Eagle crankshaft 3.750 stroke, Comp Cams roller cam shaft but I don't have the specs on the Cam. High performance pistons, either Speed-Pro or Keith Black. I don't have a gage to check compression but I'll get one. I'm suppose to use at least 91 octane. I'm running 93 with Ethanol. Today I disconnected the linkage to the two outer carbs. From a dead stop the engine still bogs down. When I accelerate slow then jump on it, it goes. Actually seems to go faster with just the middle carb. Could the advance be the problem? I can change the advance by changing springs in the distributor.

 

[rubicon]

Remember, I'm new to this hobby. I need to tap into the knowledge that is on this site. So be easy on me if I don't have all the info or the questions seem vague. Also my Y, A & C keys are not working like they should. You may see no Y or C and multiple A. Plus my spelling sucks. LOL

 

[Spanky]

Listen, Rube . . . none of us knows it all. Some are surely more savvy than others, but the point is, we all want to help you solve your problem, BECAUSE WE'VE BEEN THERE!!! No apologies necessary!

Could the advance be the problem? I can change the advance by changing springs in the distributor.

I think you may be on to something there; without vacuum advance, the abrupt transition to WOT is gonna cause your symptoms. I'd play around with the advance curve and see what helps. Try changing just one of the springs and see what happens.

 

[one finger john]

Ruby, do not touch the advance. If it is o.k. on the initial (16*) and it has 32* total for now it's o.k..
At what rpm is the mechanical advance fully employed? The vacuum advance really is to improve gas mileage. For now leave it unhooked with the vacuum port plugged. We will deal with it later.
Still a problem are the engine specs and converter. Please answer my question, what are they ?

John

 

[one finger john]

I apologize, I didn't go farther up to see your initial post for today. Still need heads, cam specs, converter, trans type, rear end gears, and rear tire size.

John

p.s. If this is your first T and with that engine, running properly, it should scare the pee out you. No s..t.

 

[2old2fast]

The "bog" is caused by a lack of atomized fuel , when the throttle blades open quickley , the fuel/air that was in suspension in the plenum & port runners falls out of suspension into puddles, the accelerator pump is supposed to cover that "hole" in the mixture , if that hole is not covered , you get the bog.....your timing is a bit slow [IMO] at 32 , 36 "all-in" by 2200-2500 rpm would/could be better , again , call the guy who set up the induction system , he should have had your motor specs to build it for you , you don't sell many systems at that price w/o them working well "out of the box" please read through the lines ,I 've no idea what caused that & I'm not retyping

 

[409T]

The "bog" is caused by a lack of atomized fuel , when the throttle blades open quickley , the fuel/air that was in suspension in the plenum & port runners falls out of suspension into puddles

YES

 

[one finger john]

Oh great ToOldTOOFast, now we have to read between the lines.

John

 

[Spanky]

Today I disconnected the linkage to the two outer carbs. From a dead stop the engine still bogs down. When I accelerate slow then jump on it, it goes. Actually seems to go faster with just the middle carb.

If a 2 bbl on a 383 bogs off the line, I say accelerator pump first, then timing. JMHO . . . (And, YES, whoever set up the carbs initially should know how to fix it! Linkage . . . ?)

 

[one finger john]

I think there are other "mistakes" in play here.

"..... and more will be revealed"

John

 

[rubicon]

Ruby, do not touch the advance. If it is o.k. on the initial (16*) and it has 32* total for now it's o.k..
At what rpm is the mechanical advance fully employed? The vacuum advance really is to improve gas mileage. For now leave it unhooked with the vacuum port plugged. We will deal with it later.
Still a problem are the engine specs and converter. Please answer my question, what are they ?

John

3000 rpm TH350 trans. 3.48 gears 31" tires

 

[rubicon]

Ruby, do not touch the advance. If it is o.k. on the initial (16*) and it has 32* total for now it's o.k..
At what rpm is the mechanical advance fully employed? The vacuum advance really is to improve gas mileage. For now leave it unhooked with the vacuum port plugged. We will deal with it later.
Still a problem are the engine specs and converter. Please answer my question, what are they ?

John

Here is what I have on the Cam. Hope its what you are looking for. See picture.

 

[one finger john]

Rubicon, this might seem odd, but does the kick-down on the trans work ? You know, passing gear ?
Also, from a stop, is the trans in 1st gear. On deceleration, does it kick down into 1st gear when it comes to a full stop?
3.70, 3.90, 4.11 gears might work better.
First things first. Call hotrodcarbs.com and find out wtf is happening. Find out what cam specs will work with you carb set up or get a low rise three carb manifold and send the tunnel ram back. Too much plenum volume. Or a swap meet four barrel, dual plane manifold with either a Holly or Edelbrock 750 cfm carb.

Or agree to pay me $1500.00 per week plus room and board plus business class air line tickets (round trip) to fly out to where you are and I will guarantee to get it to run properly.

John