35 mph WOT power loss

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DentalDart

DentalDart

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I've never noticed this before. Today while driving 35-40mph when I press the gas to WOT my car has a power loss. It loses power and rpms drop down before the engine catches then starts to go....

If you need specs. 30 over 340, XE268H cam, air gap, headers, exhaust.

Here is a quick video I was able to grab

 
We call that edelbog... (mostly kidding)
You're running an Edelbrock carb, right?

I'd check that the accelerator pump is working correctly and then maybe try increasing the pump shot to see if it helps the hesitation. It's also possible the step up springs or whatever controls the secondaries on your carb is reacting too slow.

If it's not an Edelbrock carb, ignore everything I just said! LOL
 
Phreakish said:
We call that edelbog... (mostly kidding)
You're running an Edelbrock carb, right?

I'd check that the accelerator pump is working correctly and then maybe try increasing the pump shot to see if it helps the hesitation. It's also possible the step up springs or whatever controls the secondaries on your carb is reacting too slow.

If it's not an Edelbrock carb, ignore everything I just said! LOL
Click to expand...

Yes I run the avs2 carb. Idk what an accelerator pump is or how to increase pump shot lol. I will do some reading on it though and figure it out.
 
DentalDart said:
Yes I run the avs2 carb. Idk what an accelerator pump is or how to increase pump shot lol. I will do some reading on it though and figure it out.
Click to expand...

When you hit the gas, there's an extra pump in the carb which will squirt fuel into the carb as the throttle is opened. It's what caused your vapors when moving the throttle when it would die after extended idling.

@RustyRatRod is right too, the trans should probably be downshifting at that speed when you mash it. That goes back to your kickdown adjustment...

Edelbrock carbs are notorious for being tough to tune the WOT bog out of, but many don't have an issue. Float level, pump shot, fuel pressure can all have an effect. But don't change more than one thing at a time and start with the accel pump since it won't affect everything else like the rest of the adjustments will.

Also, I'm sure better carb tuners than me will chime in - listen to them, I gave up on my avs and went to EFI because I'm a quitter LOL.
 
Looking at your tach. It looks like the RPM drastically drops off, almost like an electrical problem? Then comes back up. Not sure if that's what you are referring to.
 
Phreakish said:
When you hit the gas, there's an extra pump in the carb which will squirt fuel into the carb as the throttle is opened. It's what caused your vapors when moving the throttle when it would die after extended idling.

@RustyRatRod is right too, the trans should probably be downshifting at that speed when you mash it. That goes back to your kickdown adjustment...

Edelbrock carbs are notorious for being tough to tune the WOT bog out of, but many don't have an issue. Float level, pump shot, fuel pressure can all have an effect. But don't change more than one thing at a time and start with the accel pump since it won't affect everything else like the rest of the adjustments will.

Also, I'm sure better carb tuners than me will chime in - listen to them, I gave up on my avs and went to EFI because I'm a quitter LOL.
Click to expand...

Yea I just watched a video on where the acc pump is, what it does and how to check it...

Wouldn't the trans only downshift if the engine starts turning a lot faster? Right now when I go wot the car just bogs.
 
Dana67Dart said:
Looking at your tach. It looks like the RPM drastically drops off, almost like an electrical problem? Then comes back up. Not sure if that's what you are referring to.
Click to expand...

Whoa! Let's not bring up those bad juju gremlins in here....:poke: lol

Could it be a sharp electrical draw that causes the engine to bog before getting power. To me it feels like it runs out of gas before catching itself and starting to go again...
 
DentalDart said:
Yea I just watched a video on where the acc pump is, what it does and how to check it...

Wouldn't the trans only downshift if the engine starts turning a lot faster? Right now when I go wot the car just bogs.
Click to expand...

No. It has very little to do with engine RPM and much more with how far the throttle cable is pulled.
 
DentalDart said:
Whoa! Let's not bring up those bad juju gremlins in here....:poke: lol

Could it be a sharp electrical draw that causes the engine to bog before getting power. To me it feels like it runs out of gas before catching itself and starting to go again...
Click to expand...

Opening the secondaries in high gear with no kickdown at that low an RPM will cause the RPM drop.
 
RustyRatRod said:
No. It has very little to do with engine RPM and much more with how far the throttle cable is pulled.
Click to expand...

Gotcha.

I guess I go buy some more transmission fluid... pull the pan and then mess with the pressure adjustment.

Also mess with the carburetor
 
DentalDart said:
Gotcha.

I guess I go buy some more transmission fluid... pull the pan and then mess with the pressure adjustment.

Also mess with the carburetor
Click to expand...

Is the kickdown adjusted correctly? I would do that first, rather than pull the pan.
 
RustyRatRod said:
Is the kickdown adjusted correctly? I would do that first, rather than pull the pan.
Click to expand...

Yea im pretty sure it is, its actually been shifting really well the past couple days. I was having flare up issues on the 2-3rd shift, and right now its the best its ever been since rebuilding it.

My valve body does not have the governer ground because I couldn't do it, so there isn't the manual downshift at any speed, but the transmission should do it normally by itself. Ill check it out.
 
I seldom say this, but I feel I need to;
Get rid of that Metering-rod carb;
There is likely nothing wrong with it, but it is a terrible carb for a newbe to learn tuning on.
Get yourself a 650DP; set it and forget it. Yeah it will likely be rich; but it will fly. And it may not get decent fuel mileage. But it is an easy carb to learn, and has great throttle response.
Once you get the Holley tuned, then you can go back to the Eddy.
Btw if you buy a NEW 650, order a 10.5PV, and a tuning guide, along with it.
Nothing wrong with a used one tho, put up an ad on FABO and see what pops up.

As for the KickDown;
On 1970 and older V8 A904s the KD was set to to downshift with the pedal on the floor. It had very little to do with rpm or speed, so long as the governor pressure did not interfere.
On 71 and newer A904s, You could adjust the KD to downshift at part-throttle, so that you didn't always have to floor it all the way. This is IMO very desireable.

The governor, if you are still using it, needs to be matched to the rear gear, as it only has a limited amount of adjustability. So if your gears are different from the ones your trans is tuned for, then you may have to modify the flyweight or buy a kit from A&A or such. If you don't know anything about transmissions, then there is not much to be seen by dropping the pan. Adjustments, except for line-pressure and bands, are all done by swapping out parts.
 
DentalDart said:
Yea im pretty sure it is, its actually been shifting really well the past couple days. I was having flare up issues on the 2-3rd shift, and right now its the best its ever been since rebuilding it.

My valve body does not have the governer ground because I couldn't do it, so there isn't the manual downshift at any speed, but the transmission should do it normally by itself. Ill check it out.
Click to expand...


What year is the transmission? It should have the part throttle kickdown unless it's an early one.
 
AJ/FormS said:
I seldom say this, but I feel I need to;
Get rid of that Metering-rod carb;
There is likely nothing wrong with it, but it is a terrible carb for a newbe to learn tuning on.
Get yourself a 650DP; set it and forget it. Yeah it will likely be rich; but it will fly. And it may not get decent fuel mileage. But it is an easy carb to learn, and has great throttle response.
Once you get the Holley tuned, then you can go back to the Eddy.
Btw if you buy a NEW 650, order a 10.5PV, and a tuning guide, along with it.
Nothing wrong with a used one tho, put up an ad on FABO and see what pops up.

As for the KickDown;
On 1970 and older V8 A904s the KD was set to to downshift with the pedal on the floor. It had very little to do with rpm or speed, so long as the governor pressure did not interfere.
On 71 and newer A904s, You could adjust the KD to downshift at part-throttle, so that you didn't always have to floor it all the way. This is IMO very desireable.

The governor, if you are still using it, needs to be matched to the rear gear, as it only has a limited amount of adjustability. So if your gears are different from the ones your trans is tuned for, then you may have to modify the flyweight or buy a kit from A&A or such. If you don't know anything about transmissions, then there is not much to be seen by dropping the pan. Adjustments, except for line-pressure and bands, are all done by swapping out parts.
Click to expand...

Tony told me to get a double pumper a couple times as well. I bought the avs2 because I read they were the easier ones...

I have a newer vb with part throttle kick down... with a tf2 kit. It needs the pressure adjusted on the vb a bit though. I also don't know how to adjust it to have part throttle kick down... it has never done that for me...

What do you mean still using the governor? Doesn't it have to be in the vb? Per the directions of the tf2 kit it needed machined, in my early 904 vb it was already correctly machined, the later 904 vb it is not machined and I didnt have the stuff to machine it myself and covid had everything shut down when Tony and I rebuilt the transmission...
 
DentalDart said:
Tony told me to get a double pumper a couple times as well. I bought the avs2 because I read they were the easier ones...

I have a newer vb with part throttle kick down... with a tf2 kit. It needs the pressure adjusted on the vb a bit though. I also don't know how to adjust it to have part throttle kick down... it has never done that for me...

What do you mean still using the governor? Doesn't it have to be in the vb? Per the directions of the tf2 kit it needed machined, in my early 904 vb it was already correctly machined, the later 904 vb it is not machined and I didnt have the stuff to machine it myself and covid had everything shut down when Tony and I rebuilt the transmission...
Click to expand...

I have a really nice Holley 600 DP if you are interested.
 
For the TF-II
A&A can send you pre-machined sleeves and weights to set the upshift rpm to whatever rpm you choose, and then you will have a small window of adjustment availability to fine-tune it.
Adjusting (fine-tuning) is done by the KD mechanism, it's all external.
The only adjusting you can do "on the VB" is to; line pressure, and the TF2 kit tells you where to set it. When you set the "line-pressure" to their specs with their parts, it is usually a one-time deal .

Automatics are pretty simple; Here's a quick overview;
The faster the engine spins, the more line-pressure is produced..
The faster you drive, the more governor pressure is produced.
The further your throttle is opened, the higher the line-pressure is commanded to be.
Line pressure is your main controller.
The governor comes along and fights the line pressure to command a shift.
If you have an argument with the governor, and want the rpm to be higher prior to the shift, your main way of doing that is tell the governor to back off, using "Throttle pressure", aka KD pressure, the mechanism connecting your carb to your KD lever.

The line pressure is increased by the throttle pressure to fight the governor pressure, into delaying the shift to a new higher roadspeed..
That's all there is to it.

The 600DP is more than adequate for your combo in the city. If Rusty offers it to you complete for a good price, I'd say jump on it.
 
Last edited:
DentalDart said:
Yea I just watched a video on where the acc pump is, what it does and how to check it...

Wouldn't the trans only downshift if the engine starts turning a lot faster? Right now when I go wot the car just bogs.
Click to expand...
The motion of the pedal commands downshift,then rpms climb. If you mash it to floor, it is supposed to downshift.
 
AJ/FormS said:
For the TF-II
A&A can send you pre-machined sleeves and weights to set the upshift rpm to whatever rpm you choose, and then you will have a small window of adjustment availability to fine-tune it.
Adjusting (fine-tuning) is done by the KD mechanism, it's all external.
The only adjusting you can do "on the VB" is to; line pressure, and the TF2 kit tells you where to set it. When you set the "line-pressure" to their specs with their parts, it is usually a one-time deal .

Automatics are pretty simple; Here's a quick overview;
The faster the engine spins, the more line-pressure is produced..
The faster you drive, the more governor pressure is produced.
The further your throttle is opened, the higher the line-pressure is commanded to be.
Line pressure is your main controller.
The governor comes along and fights the line pressure to command a shift.
If you have an argument with the governor, and want the rpm to be higher prior to the shift, your main way of doing that is tell the governor to back off, using "Throttle pressure", aka KD pressure, the mechanism connecting your carb to your KD lever.

The line pressure is increased by the throttle pressure to fight the governor pressure, into delaying the shift to a new higher roadspeed..
That's all there is to it.

The 600DP is more than adequate for your combo in the city. If Rusty offers it to you complete for a good price, I'd say jump on it.
Click to expand...

I set the vb throttle pressure plate to where it said to per their instructions. Ive always had a slight flare up on the 2nd -3rd shift. Ive adjusted the band and adjusted the kd and have never been able to get it to go away. Right now its the best its ever been... ill double check kd linkage though.

I dont have any bog when going WOT from a stop, only when cruising. If I ease into it there is no bog at all, only WOT.

Reason I think 750 is it will allow me to continue to upgrade the engine then not be back to having to small of a carb...
 
Just double checked the kd and adjusted it a little. It is 100% slack free at WOT now... now I just have to drive it and see what happens. I also want to check out my acc pump in the carb, make sure it is working as it should.

20201219_165309.jpg
 
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