QuestionQUESTION: Sorry but this is gonna be kinda long. All original car (came off the assembly line in June of 66). Factory put 1967 327(275hp) in car. This makes 66 GM Manuals useless. To make it even more confusing, this car was from California (had A.I.R. setup). All A.I.R. equipment was removed awhile ago. I am trying to set the timing but the 66 manual is wrong for my car. The 67 manual states 8BTDC. The 66 manual gives a few more choices: 4 different Distributor Numbers (#1111152=8BTDC, #1111116=ATDC, #1111153=6BTDC, #1111117=4ATDC).
Basically as you can see, I have a few choices to pick from. I've had this car set at 2ATDC (this is because I have the #1111116 distributor even thought the rest of the drivetrain is 1967) for awhile now and it runs ok but a bit sluggish and very low vacuum. I just rebuilt the carb and tuned it up so I'm trying to get it to run good. Any insight would be greatly appreciated.
ANSWER: I don't know of any situation or factory combo that would require AFter top dead center timing on any small block Chevy. No wonder you are getting sluggish response!
Typically, for a mild cam which your 275 horse version has, you would want about 10 degreet BTDC with the vac. advance disconnected and plugged. If you get pinging on todays lower octane fuel, then maybe go with 8 degrees BTDC. Fiddle with it till you get good idle, power and no pinging.
Don
---------- FOLLOW-UP ----------
QUESTION: Thanks for the quick response!
I set the timing to 10 degrees BTDC. Runs better. Still kind of unimpressed with responsiveness. Not that I want to make a habit of doing it but I can't even get this car to light up the tires from a dead stop.
One thing that is bugging me is that the best I can get on my vacuum gauge is about 15psi. I get very little adjustment out of my mixture screws. Basically, I'm setting them to acheive the most vacuum. (they end up being about a turn out each). My idle is set at about 750rpm park (600 to 650 in neutral). If I step on the brake and acheive WOT as soon as I left off the accelerator, the car wants to stall.
What do you think?
Thanks, Rick
AnswerA lot of things will determine if a car can spin the tires.
First, how healthy is the engine? You have had tuning problems so this could be suspect.
Second, what rear gear ratio do you have? I most likely is something higher than 3-1, a tall highway gear (low numerically) can kill starting power.
Third, what stall speed is your torque converter? Try applying the brake, and giving the car only a little gas, lifting from the brake and then flooring. What you describe might be getting the converter to stall speed before you lift the brake.
Finally, 15 inches (not psi) of vacuum is not all that bad, many hi-po cams will have less.
Have you checked for vacuum leaks around the carb? You say you re-built it, but did you get in all the correct gaskets? Quite often, if you pick the wrong gasket say between the base and the body, you can open up a passage that will lower or kill vacuume. Or could the throttle shaft be leaking a lot? Are all the ports that aren't being used plugged?
Did the car perk up any at all going from ATDC to BTDC timing? Are you 100% sure you set it right? Did you check that the vacuume advance on the distributor and that the weight advance all work correctly? Is the dwell set right? and also, how are the plugs?
Done a compression check to see if the rings are healthy and there is good compression?
If you haven't checked it out completely, do this before anything else. You have to know where you are before you can begin to improve things.
I hope some of this helps. I don't know your level of ability, so I don't mean to imply you haven't done all these things, but without knowing, I am just using the shotgun approach! :)
Don
