305 Slow Uphill, Dizzy Weights?

[maxtwms]

Hey guys, I'm sure you seen my posts on rebuilding this thing but may not recognize all my issues. I've replaced, adjusted almost everything g under the hood but I'm still missing something. ANY RESPECTABLE CHEVY POWER from my 305. It sounds great and drives great on a flat road but any time someone decides to slow down in front of me on an incline I have to wave in the rearview while I let one of the 3 gears catch me up to a decent speed.

Is this just part of having a 305 and 3.08 gears? Do I need to try and find the famed ignitionman weight set for my dizzy?

I'm timed at 12deg and have 18" vacuum. Haven't checked total vacuum or mech afvance yet. Any ideas? Do I actually just need to change heads, weights, gears, engine, etc? What gives?

Sent from my SM-G965U using Tapatalk

 

[bucket]

I DD'd my '84 C10 in stock form for a couple years. 305/350/2.56's. It had decent acceleration from about 15-45 mph, but besides that it was pretty gutless.

 

[1987 GMC Jimmy]

So you have no ESC stuff, and you’re just using run of the mill HEI? Mine won’t do that kind of timing unless I unplug the torque converter, which is a no-no. I’ve got a real bad torque converter clutch, and I think that’s screwing me up big time. I have the same issue as you right now. If I advance the timing to like 7* and run premium, I don’t, but I retarded timing to save on gas. It’s not horrible, but there are times where I’m waving in the rear view like you say.

 

[Rusty Nail]

Transmission slipping / fluid level / detent cable

Fan clutch failure / locked up full time

Exhaust restriction / catalytic convertor plugged


Wrong / bad spark plug gap

 

[chengny]

Hey guys, I'm sure you seen my posts on rebuilding this thing but may not recognize all my issues. I've replaced, adjusted almost everything g under the hood but I'm still missing something. ANY RESPECTABLE CHEVY POWER from my 305. It sounds great and drives great on a flat road but any time someone decides to slow down in front of me on an incline I have to wave in the rearview while I let one of the 3 gears catch me up to a decent speed.

Is this just part of having a 305 and 3.08 gears? Do I need to try and find the famed ignitionman weight set for my dizzy?

I'm timed at 12deg and have 18" vacuum. Haven't checked total vacuum or mech afvance yet. Any ideas? Do I actually just need to change heads, weights, gears, engine, etc? What gives?

Sent from my SM-G965U using Tapatalk

If I am diagnosing a SBC - one that idles smoothly and runs great under minimal loads - but will not pick up any appreciable loads (like going up an incline) and yet continues to run smoothly, as opposed to backfiring, bucking etc. The first thing I would do is the 3 basic checks of the fuel system supply to the carburetor:

Fuel Pump Flow Test:

1. Connect hose from carburetor fuel feed line to a suitable unbreakable container and crank engine.
2. Fuel pump should supply 1/2 pint or more in 15 seconds.
3. If flow is below minimum, check for fuel restriction. If there is no restriction, check pump pressure and/or vacuum.

Fuel Pump Pressure Test:

1. Disconnect the fuel line at the carburetor.
2. Install a low pressure gauge onto the line.
3. Start the engine.
4. Fuel pump pressure should be 4 to 6.5 psi.
5. If pressure is less, check for restrictions in fuel tank sender filter, lines or hoses.
6. Reconnect the fuel line.

Fuel Pump Vacuum Test:

1. Disconnect inlet hose at fuel pump and connect a vacuum gauge.
2. Crank or run engine until maximum vacuum is reached. If the vacuum reading is less than (15" Hg.), replace the fuel pump. If more than (15"Hg.), go to step 3.
3. Check fuel lines and hoses for splits, leaks or kinks by disconnecting each section of line and connecting a vacuum gauge. Crank or run engine until vacuum reaches it's peak. Vacuum should be at least 15" Hg. If less, repair or replace the malfunctioning line or hose.
4. If the fuel lines and pump check OK, remove tank unit, replace strainer and clean the tank.

I know you recently went through your (Holley?) carburetor. Was that procedure done as an attempt to solve this issue? Or did the lack of power condition develop after the carburetor rebuild?

In several case during my time working on automotive engines (and I know this doesn't apply to your situation) I found that operation exactly as you describe was simply due to fuel flow restriction. All my carb experience is with Rochester Q-jets and most - if not all - of the time the inlet filter was the problem. If those tests prove the fuel supply system is good, I would agree with Rusty's last suggestion - to check for an exhaust restriction.

• Check for an exhaust system restriction:

1. With engine at normal operating temperature, connect a vacuum gauge to any convenient vacuum port on intake manifold.
2. Run engine at 1000 RPM and record vacuum reading.
3. Increase RPM slowly to 2500 RPM. Note vacuum reading at steady 2500 RPM.
4. If vacuum at steady 2500 RPM is more than 3" lower than at 1000 RPM, exhaust system should be inspected for restrictions, see Restricted Exhaust System Check.

 

[maxtwms]

Transmission slipping / fluid level / detent cable

Fan clutch failure / locked up full time

Exhaust restriction / catalytic convertor plugged


Wrong / bad spark plug gap

Not too versed in transmissions so I can't say one way or another. Mine's manual so Im not sure if I have the detent cable. I honestly don't know.
Just replaced the fan clutch. All is well.
Ive been wary of the EFE plate causing restriction. I do feel like I get pushback from exhaust. Going today to get the old glass packs taken off and have quieter turbo mufflers installed so Ill have him check to see if the valve is open and plug any leaks, if not remove and replace with tubing altogether.
Just replaced the spark plugs/wires/rotor as well.

 

[maxtwms]

If I am diagnosing a SBC - one that idles smoothly and runs great under minimal loads - but will not pick up any appreciable loads (like going up an incline) and yet continues to run smoothly, as opposed to backfiring, bucking etc. The first thing I would do is the 3 basic checks of the fuel system supply to the carburetor:

Fuel Pump Flow Test:

1. Connect hose from carburetor fuel feed line to a suitable unbreakable container and crank engine.
2. Fuel pump should supply 1/2 pint or more in 15 seconds.
3. If flow is below minimum, check for fuel restriction. If there is no restriction, check pump pressure and/or vacuum.

Fuel Pump Pressure Test:

1. Disconnect the fuel line at the carburetor.
2. Install a low pressure gauge onto the line.
3. Start the engine.
4. Fuel pump pressure should be 4 to 6.5 psi.
5. If pressure is less, check for restrictions in fuel tank sender filter, lines or hoses.
6. Reconnect the fuel line.

Fuel Pump Vacuum Test:

1. Disconnect inlet hose at fuel pump and connect a vacuum gauge.
2. Crank or run engine until maximum vacuum is reached. If the vacuum reading is less than (15" Hg.), replace the fuel pump. If more than (15"Hg.), go to step 3.
3. Check fuel lines and hoses for splits, leaks or kinks by disconnecting each section of line and connecting a vacuum gauge. Crank or run engine until vacuum reaches it's peak. Vacuum should be at least 15" Hg. If less, repair or replace the malfunctioning line or hose.
4. If the fuel lines and pump check OK, remove tank unit, replace strainer and clean the tank.

I know you recently went through your (Holley?) carburetor. Was that procedure done as an attempt to solve this issue? Or did the lack of power condition develop after the carburetor rebuild?

Several times in my time working on automotive engines (and I know this doesn't apply to your situation) I found that operation exactly as you describe was simply due to fuel flow restriction. All my carb experience is with Rochester Q-jets and most - if not all - of the time the inlet filter was the problem. If those tests prove the fuel supply system is good, I would agree with Rusty's last suggestion - to check for an exhaust restriction.

• Check for an exhaust system restriction:

1. With engine at normal operating temperature, connect a vacuum gauge to any convenient vacuum port on intake manifold.
2. Run engine at 1000 RPM and record vacuum reading.
3. Increase RPM slowly to 2500 RPM. Note vacuum reading at steady 2500 RPM.
4. If vacuum at steady 2500 RPM is more than 3" lower than at 1000 RPM, exhaust system should be inspected for restrictions, see Restricted Exhaust System Check.

Thanks Chengny! This is a lot of good info. I rebuilt the carb just so I could root out any issues that could be there. It was pretty gunky and my mixture screws didnt seem to do anything. As far as I remember, the filter seemed fine but it was just a visual inspection. Like I said earlier Im replacing the exhaust today and having the EFE checked.

The fuel line checks seem like a lot of work but def worth it if I get enough torque uphill. I really appreciate you laying out the procedure like that. Ill check back in later this afternoon.

 

[maxtwms]

So you have no ESC stuff, and you’re just using run of the mill HEI? Mine won’t do that kind of timing unless I unplug the torque converter, which is a no-no. I’ve got a real bad torque converter clutch, and I think that’s screwing me up big time. I have the same issue as you right now. If I advance the timing to like 7* and run premium, I don’t, but I retarded timing to save on gas. It’s not horrible, but there are times where I’m waving in the rear view like you say.

Yea, all the emission stuff was off when I got the truck and has an HEI. Ive tried to retard further to something like 8-10 but Id get dieseling really bad. Although, that was before I adjusted all the valve lash which led me to find a valve or two cranked far enough down, I'm positive they were never seating. This leads me to believe the dieseling was possibly due to running a bit rich and extra air being allowed in a chamber or two. I been running 92-93 octane to mitigate this and I haven't had an issue.

I agree that it makes no sense to diesel while retarding but that's what would happen. I don't get any pinging going up hills or anything, just maxing out 1st gear and then slug through 2nd most of the time.

 

[Rusty Nail]

Man. trans has no detent cable. Disregard. I'm not familiar with your truck, my bad.
Re: the EFE plate.
I have taken it out, removed the plate , and re-installed the "valve", before.

Good luck!

 

[shiftpro]

They should never have dropped a puny 305 into full size 4x4s.

 

[maxtwms]

Just got a call back from the exhaust shop and said they couldn't work on it because my gas tank was covered in fuel. I drove it to advance to grab a sending unit gasket set and looked under the truck and noticed it was sloshing out, prob lost a cup there in the parking lot. This makes me think its the gasket around the sending unit and not a hose. I suppose it could be a hole in the top of the tank but that seems unlikely since the truck is in pretty decent shape everywhere else (body-wise). Would a bad gasket cause this much to slosh out? That could also be the reason for a few other problems Ive been having...

 

[Rusty Nail]

/thread

 

[maxtwms]

Fixed the tank and got exhaust. Belt's continued to be a problem until I got the right widths and tension.

I turned my timing down from what should have been 12 before my balancer install but was 20 somehow. Must have vibrated out... Now I'm at 10 and it's much more responsive. May try to get to 8 tomorrow if it acts right during the day. Just tracking changes..

Sent from my SM-G965U using Tapatalk

 

[shiftpro]

Fixed the tank and got exhaust. Belt's continued to be a problem until I got the right widths and tension.

I turned my timing down from what should have been 12 before my balancer install but was 20 somehow. Must have vibrated out... Now I'm at 10 and it's much more responsive. May try to get to 8 tomorrow if it acts right during the day. Just tracking changes..

Sent from my SM-G965U using Tapatalk

Was it the gasket causing the massive leak??

 

[maxtwms]

Was it the gasket causing the massive leak??

Had to be. It was pretty dry rotted cracking all the way around. That's the only thing that could cause the sloshing spits. I replaced the hoses for good measure too so it could have contributed. Though not nearly as much.

Sent from my SM-G965U using Tapatalk