A year ago I replaced my tired ignition & distributor with a MSD setup which I have been very happy with.  However, I have not yet had the time to really fine tune it.  Since this setup gives me the ability to control initial timing, total timing, and the rate of advance I am particularily interested in finding the best timing setup.  I am interested in any tips anyone may have for setting timing on a high performance engine that doesn't fit specs in a book.

The engine's a 350/350 that's been rebuilt to be a LT-1, complete with solid valves, LT-1 intake, and a slightly larger cam.  Detonation is an issue and I run approx 96 octane by mixing in 110 oct. race gas to help control it.

Recently there has been discussion ("I hate Timing Lights") of setting timing using vacumn at idle which seems to be a sound method for obtaining an optimal setting.  Does anyone have any tips for finding the best total timing on an engine that is detonation sensitive?  And for finding the best spring combination for the rate of advance?

Thanks for the input!!

Rick.

This is what I used to set my timing by and it has made a big difference in the performance of my vette. I thought I was in the ball park before. After setting the timing up by Lars' paper, it made the car accelerate quicker. Give it a shot and see how it works for you.

How To Set Timing White Paper By Lars Grimsrud

This should open a window to Corvette FAQ and then open a window that is a Word Document. If not I guess I can copy and paste it here so we can see it. Let me know if the redirect works.
Eddie 7038448.2237384259

The link does work, thanks for the material!!

Does anyone have any thoughts on using vacumn to set curb timing as mentioned in "I hate timining lights"??

ricknhis6938448.7321527778

It worked Great for me, course I had my advance already set up by a dyno shop. It did give my car an extra kick in the pants. It wont hurt to give it a shot. Just back off the gas and readjust if you hear the pinging or can of marbles rattle. Thats too much advance if thats the case. Sounds as if though you got really high compression. Do you know what your running?

There was another thread recently where Ken and Matt and I all had issues with some of the assertions and recommendations made in Lars' article.

so ill describe my method.. 

Ive always used the system to set idle timing that i outlined in the "I hate timing lights" thread.  This gets the engine to its "hungriest state" and gives the best off idle response.

with an adjustable distributor like the msd..  I usually use trial and error to find the right state for the engine.. no two engines will be exactly the same.. there is NO correct setting that works best for every engine.

for example. i usually use the smallest limit bushing and the second weakest spring set to start..  generally these are too liberal but we need to see how it behaves.. 

I then fire it up and take it for a spin..  I have a highway on ramp a few miles from me that is very steep.. ill cruise on to it and then floor it while going up hill.  if you get detonation almost immediately then your ramp rate is too high and you need stronger springs.  if it continues to detonate once you gets your rpms up then you need to use a larger limit bushing.

with my 427.. the timing works best with the second limit bushing and third spring set.. since im still in the middle of my frame off.. i havent been able to retune for the air-gap intake..  the cooler intake air will allow slightly more aggressive timing.

 

Ben, I did a search, but could not find the thread that contained your problems with Lars' recommended method of setting timing and advance.  Can you point me toward it?

Tumarr-

It's 11:1 compression with a cam (& solid lifters) that has higher lift and longer duration than the stock LT-1 cam (which is already huge for the street).  Its stock compression for both the 350/350 in '69 and the LT-1 for '70.  Its a lot of fun but I wouldn't have built the motor this way.

cthulhu-

I think one of my biggest problems is that its hard to hear the detonation over the flow through mufflers.  Based on how its set right now (36 degrees fully advanced, I think, its still in storage) I don't think I would advance it any further.  I did hear some slight detonation above 3000 rpm although I suspect the vacumn secondaries may not be opening at the correct rate.  I'm trying to decide if I should re-jet also.

I've also heard of using a stop watch to set the advance by timing it from say, 2,000 rpm to 3,500 rpm.  This of course only works in a manual trans car with the clutch out.  Any thoughts on this idea?

The stop watch method is a bit tough to do.  This is just due to the accuracy factor of trying to operate the watch while driving and hitting it dead on.

But it is a measure of performance in that rpm range, and if accurate, could be used.  I would also try it going to higher rpm as well.  Perhaps a few increments of 500 rpm.

I figured it would work out if I took someone with to operate the watch and I'd try it a couple of times and take an average to try to elimate human error as much as I could.  I'm thinking that this may work out well for timing the vacumn operated secondaries on the holley as well.

Yes it will, but only do one at a time.  Other wise you won't know which did what.