Redog

I have a 1968 350 Rocket motor in the car and the timing is currently at 34*, I read that the correct timing is 36*.

I don't have a speedo in the car right now, so I've been using the tach as my speedo, and it seems to be 500 rpm or so off.

With my rear end ratio, tranny ratio, and tire size, I should be going 55 at just under 2500 RPM's, but 55 miles per hour is more like 3000 now. It's like this for all the speeds, including at the track. I cross the finish line 500 RPM's higher than I did before.

I just don't like the motor revving that high, I'm at 3500 RPM crusining at 70 just to keep up with traffic, used to be just under 3000

EDIT: I know the caluactions are right, I pass a radar "your speed" sign everyday, and it's always dead on with every car I own, and was right with the old ign set-up

Oldsguy

You timing would affect the idle rpm a little but I don't think it would affect the operating rpm that much as you describe it. Have there been any other changes made between your previous observations to now? You mentioned HEI, I suppose that means you have put an HEI distributor in your car recently?

Olds64

I agree with Oldsguy. Timing isn't going to affect your cruising RPM that much. Rear end gears, transmission, and tire size will affect your cruising RPM.

Redog

There's been no other changes. With points it ran 500 RPM slower than it does with HEI.

rear end gears where changed 2 years ago with the 307

88 coupe

350 = Rocket. The phrase is redundant.

Correct total advance, as shown in the FSM, would not (for a variety of reasons) necessarily be best for your individual engine and/or your driving conditions. You can use dyno results or timeslips, or (if you had a speedometer) fuel mileage records, to find the optimum number for your own application.

Short answer: Your azz dyno won't see much difference between the two.

Nothing to do with your ignition advance.

Norm