Many that have done a TPI swap into a carb G-body need to address the wiring connections going through that connector. Hopefully post #5 will be helpful in identifying the wires... https://www.thirdgen.org/forums/tpi/691253-91-tpi-305-older.html#post5657472
Off idle BOG at WOT
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Might want to remove that filter by the tank. Carb/mechanical fuel pump set ups should only have filters between the pump & carb. That other filter might be adding an to the bogging by creating extra resistance in the fuel flow & not allowing the proper volume of fuel the pump is ment to push.
Will do. Willing to try anything at this point. To my disappointment, the bog is back, and it going away was just a coincidence.
Now wondering if the culprit is something else. Seem to recall that at one point you mentioned the stall speed on the converter being around 2200, and that you are running 20 inch wheels and a 3.73 rear end ring/pinion combi. By any chance do you happen to know what the gear ratios are in your t-mission?
Nick
Nick
Gonna suggest that you decommission that plug completely. Just reviewed your specs post and did not see what version of transmission you are running but with having a lock up as you say, the best possibilities are either a 200R4 or a 700R4. I did a t-mission swap a couple of years ago and the 700R4 that I chose to use had the electric lockup. How it worked in my particular instance was that that the way the lockup was powered/wired by the factory, it was active in all four gears. Using the brake disconnected it temporarily but as the vehicle accelerated, it would reset and go active again. The physical switch that controlled all this was actually located on the brake pedal and was the same switch that actuated the brakes. in my case, depressing the brake pedal both brought the brake lights on, and temporarily broke the connection to the lock up circuit. If your transmission had the lockup feature to begin with, then it is possible that the lockup did not take its power from the CCC/ECM but got it directly via a switch such as the one I just described. Only way to know for certain is to take a flashlight and take a look at the brake pedal up by where it is attached to its bracket to see if you can identify how many contacts the brake light switch has. Should you see just two then the power is only to the brake lights; if you see four, one pair near the pivot shaft of the pedal and the other pair near the other end of the switch, then that second pair is power to the switch from a 12V source, and power from the switch to the lockup plug in down on the t-mission case.
Nick
10 hours and one good night's sleep later, just and purely as a suggestion, I am going to propose that you swap out those 20 inch wheel/tire's and replace them with some 16's, just to see what difference the shorter tire will make to you initial acceleration.
What I am thinking is that the 20's are too tall a tire for your level of engine build. Not going to get too far into the physics and mechanics of circular rotation and motion but the bigger the tire/wheel, generally speaking, the greater the amount of inertia or resistance to movement that has to be overcome. For a car, torque is the force, applied to the wheel, that overcomes its tendency, aka inertia, to want to stay at rest.
Your choice of motor, a 350, even if built up from stock, has more of a reputation for horsepower, or speed if you will, than for torque, or low end acceleration. It's strong point is its ability to build rpm quickly. It was it's bigger brothers, the 396/427 that were the torque monsters of their era, along with the big block BOP's, and their counterparts across the aisle in Ford and Dodge country.
So, when you whack the throttle pedal, your motor does its best to initiate motion BUT, it has to overcome the weight of the vehicle, the parasitic horsepower loss throughout the drivetrain, plus the combination of rear end gear x Tire height/circumference and, it just might be proving too much workload for the engine. It, the engine, is telling you this by displaying lousy acceleration and bogging when you go to WOT.
Even at cruising speed, when you try to suddenly accelerate, the amount of inertia or resistance to change in speed is still high enough that the vehicle does not respond as quickly as you would wish it to.
You have the acceleration of a 10 T Dump truck (which uses a double transmission combination to overcome inertia and weight) when you want the acceleration of a Ferrari.
With the 16's mounted and secured, even a lap or two around the hood or a short blast up the highway ought to give you a feel for whether the vehicle is responding more enthusiastically to input from the go pedal.
Nick
What I am thinking is that the 20's are too tall a tire for your level of engine build. Not going to get too far into the physics and mechanics of circular rotation and motion but the bigger the tire/wheel, generally speaking, the greater the amount of inertia or resistance to movement that has to be overcome. For a car, torque is the force, applied to the wheel, that overcomes its tendency, aka inertia, to want to stay at rest.
Your choice of motor, a 350, even if built up from stock, has more of a reputation for horsepower, or speed if you will, than for torque, or low end acceleration. It's strong point is its ability to build rpm quickly. It was it's bigger brothers, the 396/427 that were the torque monsters of their era, along with the big block BOP's, and their counterparts across the aisle in Ford and Dodge country.
So, when you whack the throttle pedal, your motor does its best to initiate motion BUT, it has to overcome the weight of the vehicle, the parasitic horsepower loss throughout the drivetrain, plus the combination of rear end gear x Tire height/circumference and, it just might be proving too much workload for the engine. It, the engine, is telling you this by displaying lousy acceleration and bogging when you go to WOT.
Even at cruising speed, when you try to suddenly accelerate, the amount of inertia or resistance to change in speed is still high enough that the vehicle does not respond as quickly as you would wish it to.
You have the acceleration of a 10 T Dump truck (which uses a double transmission combination to overcome inertia and weight) when you want the acceleration of a Ferrari.
With the 16's mounted and secured, even a lap or two around the hood or a short blast up the highway ought to give you a feel for whether the vehicle is responding more enthusiastically to input from the go pedal.
Nick
Transmission is a th350c (w/ lock up). It has been rebuilt, and strengthened/upgraded but original gearing. I'm assuming
- First gear: 2.52 to 1.
- Second gear: 1.52 to 1.
- Third gear: direct drive, i.e., 1.0 to 1.
- Reverse: 2.07 to 1.
I'll check the brake pedal. So far, I have confirmed that the connector in question (and pictured) is called an ALDL connector, and that pin F connected to pin A will activate lock up, which is what I have wired. What I need to figure yet is which side (black or white connector) goes to the trans because my spaces are on the black connector's side. I would like to have that brake button active maybe...but I am running my switch through a vacuum switch, so might not matter. Idk..
I agree that the smaller wheels should perform better. I'll put this on my list of things to try. Today, I'm fattening up the secondaries, installing a new accelerator pump, and removing 1 of 2 fuel filters...to see if I can find any changes.
For the sake of argument, I personally know of and have seen Monte's with 20 and 22 inch wheels run like monsters. I know of one guy in particular with a completely stock 350 and 20" rims...and does burnouts with no brake. 3.73 rear. Maybe 700r4, I can't recall but..
I guess my point is, I see and know people running larger rims and have better performance. Even have a friend that brake torque his 305 with 22" rims, which has me crying over here.
My biggest beef is that I can hear and feel the dead "stop". When I slam the pedal, it almost sounds like air...and the car just doesn't even try to go. Tells me it should be carb related but...again, going to try everything. Maybe I'll get a chance to change wheels today.
I was fiddling with the carb moments ago. The accelerator pump seemed to be working fine. But...my question is...is the runner gasket for the pump supposed to be so air tight? Seems to me it is giving not only a shot of fuel...but a small shot of air due to the tight seal. 🤔 Thinking out loud...
I did not specifically include the TH350 w/the third gear lockup because it works a little differently than the two that I mentioned. In the 350 variant, only third gear locks up and there are just two wires attached to the plug that fits into the socket located on the driver's side of the case. It still uses the double terminal switch that sits on the bracket above the brake pedal but there was no VOES (Vacuum over Electric Switch) as part of that circuit. My 700R4 does have that switch, however.
Unlike the 4 spds, the 350 does not depend on internal pressure in the case for a signal to shift. The 350, even the E version and its variants, all depend on vacuum. While there are ports on the carb that do offer full time vacuum, I personally found it better to use the vacuum port on the intake, located just ahead of the timer. In the stock iteration, there is a shaped length of tubing that is attached to the vacuum module located down and just ahead of the tailshaft housing on the passenger's side of the case by a short length of rubber hose. Up at the top at the vacuum port, another short nipple of tube makes that connection.
The stock vacuum module as it comes from the factory cannot be adjusted for shift timing. There are supposedly aftermarket versions that have that ability.
Nick
Unlike the 4 spds, the 350 does not depend on internal pressure in the case for a signal to shift. The 350, even the E version and its variants, all depend on vacuum. While there are ports on the carb that do offer full time vacuum, I personally found it better to use the vacuum port on the intake, located just ahead of the timer. In the stock iteration, there is a shaped length of tubing that is attached to the vacuum module located down and just ahead of the tailshaft housing on the passenger's side of the case by a short length of rubber hose. Up at the top at the vacuum port, another short nipple of tube makes that connection.
The stock vacuum module as it comes from the factory cannot be adjusted for shift timing. There are supposedly aftermarket versions that have that ability.
Nick
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