When tuning for a higher than stock compression ratio ( 11.2:1) where should the base/advance timing be altered? What I mean is should the base timing be advanced and the spark tables be less agressive, or should the base be retarded and the tables be more agressive or should the base timing be left stock and just set the advance tables????? I'm just looking for a starting point here. If any of you could help it would be greatly appreciated!! Any general rules of thumb?

 

Higher compression and you'll want less base timing so you can get the thing started.. Then the rest of your timing should be based on lots of driving and logging..

Some guys like to keep it within a degree or two of knock.

-- Joe

 

8d is about the best mechanical, slash module initial timing there is. Much more then that and the motor won't want to crank hot, and much less and the motor windmills when cranking.

22-26 at idle, and cam decides what you'll need.
28-38 at cruise depending on if you want mileage or engine life.
24-42d at WOT depending on how often you want to get inside the engine. Lots of perforamcne can be had at 26-30d total timing.

 

I am running 11.8:1 compression with my setup.

In order to get the performance I wanted out of it, the indicated timing is up at ~40*, with race gas.

On the recent dyno pulls I made, the track experiements I did were verified again. If I pull 2* from the base timing the car will loose ~4-5 MPH, on the dyno after the guy told me there was no way I would loose that much, I retarded the timing back 2*. The very next pull was about 35-40HP less and ~40ft-lb. The technician on the dyno couldn't believe it. I then went 2* advanced from the original setpoint. The car gained back about 20Hp and an equal amount of TQ. But still wasn't back to the normal HP/TQ level.

Now with that being said, I question the accuracy of my timing tab, the balancer keyway location, and even the possibility that the balancer might have slipped on the inner hub at one time. We degreed the cam, but did not place the balancer on the crank to verify that 0* was actually 0*. I plan on when I get the car back from getting the moly roll bar installed this week, to use a piston stop to indicate TDCs and locate the zero mark.

The whole process is an exercise in futility since I have found the "sweet" spot for the max HP/TQ of the car. So I will not change it regardless of the findings. Its just a question I want answered as to what my max timing really is.

The point I'm trying to make is do not shoot for a given number. You have to find out what delivers the best results for what your after. I wouldn't care if my timing light was telling me I only have 5* of timing, as long as the performance was there.

I will say that not having a mixup as I have, will make figuring out that timing much much easier. But do not be afraid to go to the different ends of the spectrum for testing. Key your knock sensor enabled, and listen for ping.

I get the impression here that people are sooooo afraid to go outside the boundaries of 26*-32* that many people never find their correct timing. Good heads or not, play with the timing and you will be surprised at what you discover. I would start low and increase it 2* at a time. You will feel where the car picks up and drops off, then go back and move it in 1/2* incriments. This part might need a dyno, or track testing, using NOT et, but mph as an indicator.

Here is a link to my recent runs in Etown....you will like what compression does for you! You might want to try race gas for added insurance on the track. Especially with higher compression, sproting those hyper pistons.
https://www.thirdgen.org/techbb2/sho...hreadid=195325

 

So your back to pump gas?.
For some folks the bank roll is limited and they'll go alot further with less timing and never miss a couple degrees timing. BTW, that's the difference from racing to street use. Suggesting tuning to the absolute limits to someone asking basic guestions, is also slightly off key, IMO.

 

Your opinion grumpy is duly noted.

 

Thanks everyone