thinking about playing with my timeing

[Guest]

I have a bone stock 78 gs550, I was wondering if anyone has advanced their timing above 17 degrees.
what I am looking for is better throttle response, but I don't want to make it hard to start.
if you've tried already this what was your experience.

[Steve]

Getting your jetting right will probably do more for throttle response than advancing your timing.

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[tkent02]

A long time ago, when my 550 was fairly new (less than 100,000 miles) I did a little experimentaion with ignition timing. No dyno runs, just seat of the pants stuff. Played with both advanced and retarded timing. Came to the conclusion that Suzuki had it set in just about the right place.

Never played with the cam timing on the 550..... yet.

[posplayr]

My only experience was with an small block 327 Chevy. Interestingly the stock ignition timing is identical to a gs. 4 deg initial/28 deg total. From a old hot rod msg mod write up the suggested increasing the initial advance to about 11 deg, but limit the mechanical advance so that total advance stays about the same. After I did that the acceleration was dramatically more lively. I did this in about 1977, so excuse me if I forget some of the details.

[koolaid_kid]

posplayr has it correct. Your timing consists of both the initial timing and full advance of your mechanical advance. When I played with this for cars, it was for increasing power, not throttle response. Having said that, you could advance it until you hear ignition rattle, then back off. Using premium fuel could also give you a bit more room to play, at the cost of paying more for fuel.
Unfortunately, you have VM carbs, so throttle response will be limited to the fuel/air mixture, which was an issue with the VM carbs. Which is why everyone abandoned VMs in favor of the CV carbs.

[barnfresh 78gs]

good points all! I haven't laid a finger on the carbs yet, might go that route before I try to re-invent the wheel... and the timing I was thinking of changing the initial timing. the throttle response on mine seems slow on and slow to back down... but steve makes a great point about the carbs (jetting)... it's a 35 year old vehicle with no fuel filter, and all I've done is chemical cleaning to the internals... and it hasn't always been mine....

[koolaid_kid]

If you have not rebuilt the carbs yet then you need to do that first. You will find the guide on BassCliff's web site. Note the parts that you will need, which does not include an aftermarket rebuild kit. Mainly new o-rings and gaskets. Good luck.
And the only timing you can change is the initial timing, unless you want to shave the weights on the timing advance unit (highly NOT recommended).

[Steve]

Having said that, you could advance it until you hear ignition rattle, then back off. Using premium fuel could also give you a bit more room to play, at the cost of paying more for fuel.

Did you really get more power with the "premium" fuel? I mean real, dyno-proven power?

Yes, you could advance the timing more, but actually, it would be required to advance the timing more because "premium" fuel (really, it's just higher-octane) burns slower, so it needs to be lit sooner to achieve BMEP at the proper time.

Higher-octane fuel actually has fewer BTUs per gallon, so simply changing fuel and advancing the timing would not add any power. If anything, it would take some away. Where anyone got extra power, it would be because of increased compression. Increasing compression would increase the heat, which would light the "regular" fuel mixture, requiring a switch to "premium" fuel, which required advancing the timing.

Sure, there were also cases where the factory timing was set up for emissions rather than power, but that just involved setting it correctly, not legally.

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[koolaid_kid]

Didn't say he could get more power, just that he could advance the timing more.