I am only mentioning the 2 bbl vs. 4 bbl throttle cable because it has been a problem with several of my friends (and myself), before. Having a throttle cable be pulled back from engine movement (under power) can be a dangerous thing – especially if you are in an area with a lot of traffic or pedestrians close by at the time.
I have run into a fence in a beat-up pickup, after a 4-bbl changeover. The cost to fix the fence cost more than damage to the pickup.
I’ll take your word you are fine – but please make sure the throttle cable has plenty of room in two areas:
- The cable attachment/adjustment area. The clamp should be on the cable metal end about mid-way (depending on adjustment needs). If the cable clamp is close to either end – it causes problems.
- Also, make sure the cable (black part) has wiggle room after adjustment. If the cable is taunt (between the clamp and firewall) when at rest, then when the engine tilts under acceleration (or power stall), the cable will pull itself rearwards in the clamp (which will hold the throttle open).
This picture is from a forum member here who installed a 4-bbl.
Two things that I see in this picture: One is the cable adjustment clamp (yellow arrow) is holding the black cable down – and not at the metal end (red circle). You can also see the metal part of cable, is not touched at all (orange line).
Second item is the cable has 0 (zero) wiggle room (pink line) between engine and firewall. In this case, when engine tilts to passenger side of engine compartment (under acceleration or power stall), the cable WILL pull on the cable clamp, pulling the cable rearwards (in other words, in a throttle held open position).
Another issue was a lack of kickdown linkage.
This member needs a longer cable (which I think he fixed).
Lastly, the cable in clamp should be parallel with valve cover – and not in an angle. The same thing for kickdown linkage. The Thermoquad engine throttle cable and kickdown linkage is, for the most part, on top of the valve cover (which I know Thermoquad is a bit wider than the AFB/AVS/Edelbrock carburetor design is.
Here is a picture I took from my '77 2-bbl:
You can't see it, but the throttle cable (between engine and firewall, can be moved about 1½" either way - so it has plenty of movement area.
Red lines are the metal cable adjustment area. Pink lines are the clamp width. Clamping the cable on the black plastic area is a very bad idea. Also, clamp is designed to hold not damage the metal end - but a person (or engine) can and will be able to pull the cable right out of adjustment - if a person tried.
Having cruise control makes pictures of this, a bit more difficult.
All I want is for you and others to be safe, out there. If everything is good, then great. I have worked on enough of these cars to see un-safe problems out there – and I just don’t want you to become another statistic.
BudW