Hi, I have a new 305 from Jasper with a different cam from stock (all they said that it was a better cam LOL). The car seems to run fine at 6 advanced which is stock (I believe) how much can I advance it, plus I am always, and will always run 91 octane in the car. I just don't want to advance it too much and than have detonation.

Thanks.

 

Changing the advance can only be done properly in the prom. By getting a custom burned chip.

 

ok, changing the base timing?

 

The base timing is set in the prom. Technically if you change the base timing via the distributor. The prom will still think its set at 6 degress of advance if you changed it to some other setting. I would ask this question in the DIY prom board.

 

Unplug the tan wire behind the AC compressor. Loosen up the bolt holding the distributor down. Connect your timing light to your #1 wire. Start the car, point the timing light at the tab. Turn the distributor to where you want your timing at. Then tighten down the distributor, turn off the car. Restart the car and check it again to make sure. Then turn it off, plug the tan wire back in, and your all set.

 

Oh, I know how to change the timing, done it plenty of times before. However, I want to know how much should I advance it just to give it a little kick, but without detonation.

I guess, what are you guys running?? Whats the advance that you are running?


I understand the prom thing, but advancing the base timing a bit never hurt anybody.

 

The prom controls your spark advance. By setting your base timing to any other setting than 6 degrees is not going to change your overall spark advance. Your base timing is basically set for starting purposes. When cranking the engine. The timing you set is what it will crank at. Once the enigine fires and reaches over 300 RPM the prom takes over. So you could set your timing at 8 or even at 10, but its not going to add more timing.

 

I had my base timing set at 15 degrees.

I had a snap-on scanner on it for knock counts. That was the best timing the motor liked.
I had used a mixture of avaition gas and 91 octane.

I could notice a difference at the track from 10 degrees to 15.

I would only recommend doing this if you have a scanner!
Otherwise you are just guessing!

 

My car loves 12* base timing and 93 octane.
It's noticeably slower with it set at it's stock 6* and running 87 octane...

 

But, it may actually make you go slower, as you now may be causing the KS to pull timing out, as you try to advance your base. Changing the tables in the eprom is the way to do it properly.

 

Well, not quite... You are correct to suggest changing the spark advance in the tune, but if you advance the base timing, the overall timing map will be offset by the difference you adjust. If you are supposed to have 6 degrees base timing, and, for example, 30 degrees at full load, 2500rpm, and you adjust your base timing to 10 degrees, you will end up with 34 degrees at that same point when the computer commands 30 degrees.. The proper thing to do would be to set the base timing to whatever it is set to in the PROM, and then adjust the spark tables to affect the spark advance.. So, yes it will affect the timing if you advance the base timing, it will offset the entire timing table. The best way to do it is to adjust the table in the PROM for the rpm/load ranges you really want to increase (WOT)... Hopefully that wasn't too long..

 

I can't believe you guys can run that much base timing (10-15 degrees) and NOT be triggering the KS. I run mine at 8*. If I go more it starts like sh-t when its warm.
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How does your O2 sensor like avgas??

 

All motors are different.
When at the track, the ecm would pull 2 degrees of timing out of the hole and then add it in later on when needed.

I have ran a mixture of av gas and premo at the track about 4 times and been fine.

Remember, do not try to advance the timing to the degree that I did unless you have a scanner or on a wide band.

 

I can't believe your 02 or cat liked having leaded avgas run through it. Hopefully on the short term it didn't cause any harm.

 

My mixture was 1 gallon of av gas to 3 gallons of 91 octane(mixture was about 93-94 octane)

No problems yet.....

 

Just curious.....wouldn't it just be cheaper to buy sunoco 94?

 

This is true. But, your elevation in Manitoba results in "thinner air" which has a similar effect as an EGR - which allows you to run higher timing.

Take your car down to sea level and you'll find you are detonating like crazy or your KS is pulling out more timing than you've added.

Brutalform is correct, it's the KS you need to control to obtain the max timing possible without having detonation occur. Advancing your dissy can often result in more timing being pulled out (retard) than you added, and this can result in slowing you down.

Lastly, I wouldn't add any leaded gas to my engine. However, I am not entirely sure that avgas is leaded in Canada either - it may be unleaded. But you should check.

Your biggest risk is if you get caught running avgas in a car. Avgas is illegal to run on vehicles that operate on the highway in most provinces. This is because avgas is not intended for the highway and thus there is usually little or no Motor Fuel Tax on avgas.

 

The closest to buy racing fuel would be 3.5 hours away. 113 octane is all I know of in Canada. Sunoco is USA only.

The av gas here is low lead in Canada.
I have a friend that runs a '64 Dodge Polara with a 440 with 12 or 13 to 1 compression and that is ALL he runs in his car is 100LL av gas!! But maybe he has done something different to his engine....

 

sunoco is definetly not USA only.. we have sunoco 94 here in windsor... its what i use