Thread: Bogs down when letting clutch out

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When I originally read the post my first thought was also the rear end ratio (possibly combined with tire height). I didn't post that response because after looking up the ratios for the Z cars, to me it looks like the gear set should be deep enough to easily get the car moving especially with the 1st gear ratios of the T56, provided it's the original rear end.

Here's a link to the site I used......by the way it would help to know what year the car is.

Transmission and Rear End Gear Ratios


If you don't find an issue with the brakes dragging (either front or rear), I would start looking at the engine.

If you brought the car into my shop with the complaint you have this would be what I would check.

I would first start by verifying it is a 350........a lot of 305s have been sold as 350s to the unsuspecting over the years. You can check this by looking up the block casting number located at the upper drivers' side rear of the block near the bellhousing area.

I would do a quick visual check of the intake, carburetor and exhaust looking to see if they are a good match for the street and not the drag strip and that the exhaust is not overly restrictive.

Next check would be to listen to the engine, basically to get an idea of how radical the cam is...... the more radical the cam the less bottom end torque you have to get the car moving. I would then check the carburetor for any obvious issues (vacuum leaks, sufficient accelerator pump shot, relatively well tuned, or that a computer controlled carb has not been installed on a non computer controlled engine). If the engine has an EGR installed I would also check to verify that it isn't stuck in the open position (and that it's NOT plumbed directly into a full time vacuum source).

I would then move on to the ignition and verify the condition of distributor cap, rotor, wires and plugs. When I have the distributor cap off I would verify the vacuum advance and mechanical advance are both functional. A stuck mechanical advance could easily be the problem. I would then check the timing and in addition to the static timing look for around 32-36 total degrees of advance at 2200 to 2500 RPM.

If nothing obvious has shown up to this point I would likely do a compression test looking for low cylinder pressure. Chances are you will have found the problem by now. If not the final check I would recommend would be to pull the timing cover and verify the cam has not been installed in a retarded position.

Well that's my 2 cents anyway.



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