Timing on vintage 302 Z/28 A/S
Moderator: Team
Re: Timing on vintage 302 Z/28 A/S
I would like to know why faster burning race fuel burns even faster with slower burning pump gas...
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire
Re: Timing on vintage 302 Z/28 A/S
Flame propagation for hydrocarbon fuels can vary with fuel types (mostly in the number of carbon atoms in the mix. More carbon atoms=faster flame travel) but gasolines, generally in the C6H12 range, have the same travel rate at stoic. The primary variable affecting flame propagation with gasoline fuels what side of stoic the mixture is on. Leaner means a slower burn, rich is faster.
Re: Timing on vintage 302 Z/28 A/S
Yes, and race fuel manufacturers claim many of grades of fuel have a faster burn for more complete combustion at high rpms and less time for detonation to occur..I have to assume they mean a faster burn than pump gas...GerryP wrote: ↑Wed Aug 15, 2018 5:56 pm Flame propagation for hydrocarbon fuels can vary with fuel types (mostly in the number of carbon atoms in the mix. More carbon atoms=faster flame travel) but gasolines, generally in the C6H12 range, have the same travel rate at stoic. The primary variable affecting flame propagation with gasoline fuels what side of stoic the mixture is on. Leaner means a slower burn, rich is faster.
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire
Re: Timing on vintage 302 Z/28 A/S
Many of the additives that are blended in race gas because of their high resistance to detonation, also burn slower than gasoline does. Can be too much of a good thing. Adding a bit of good pump gas helps. Also tends to help drivability and reduce fouling missfire which also can result in net better engine power output overall.
With a 110 octane and just 11.5:1 CR you have room to blend a bit.
With a 110 octane and just 11.5:1 CR you have room to blend a bit.
Re: Timing on vintage 302 Z/28 A/S
Right now you have a 22degree mechanical advance curve. with 18deg initial base timing.
Recurve the distributor for a shorter 10deg advance curve by restricting the mech adv travel to 10 degrees. Now you will enjoy much better idle quality and better throttle response overall and may now not need to give it so much total advance 34-36 ish , YET enjoy much better overall performance.
24- idle 34 WOT
26 idle 36 WOT
Adjust to suit while watching the plugs and the real performance.
Don't get carried away with total max timing and do not confuse with a drag car.
Recurve the distributor for a shorter 10deg advance curve by restricting the mech adv travel to 10 degrees. Now you will enjoy much better idle quality and better throttle response overall and may now not need to give it so much total advance 34-36 ish , YET enjoy much better overall performance.
24- idle 34 WOT
26 idle 36 WOT
Adjust to suit while watching the plugs and the real performance.
Don't get carried away with total max timing and do not confuse with a drag car.
Re: Timing on vintage 302 Z/28 A/S
Not true, a false assumption and we have discussed it previously...Higher octane race fuels burn faster, detonation needs time to develop, a faster burn by itself tends to lessen detonation...And TEL doesn't slow the main burn, it inhibits spontaneous combustion of the end gases...F-BIRD'88 wrote: ↑Wed Aug 15, 2018 7:21 pm Many of the additives that are blended in race gas because of their high resistance to detonation, also burn slower than gasoline does. Can be too much of a good thing. Adding a bit of good pump gas helps. Also tends to help drivability and reduce fouling missfire which also can result in net better engine power output overall.
With a 110 octane and just 11.5:1 CR you have room to blend a bit.
Here's some info from Sunoco race fuel
https://www.sunocoracefuels.com/tech-ar ... ond-octane
Here's something from VP... read down to "Burning Speed"
https://vpracingfuels.com/about-us/faq/
And this is a good read on the causes of detonation...
http://www.contactmagazine.com/Issue54/ ... asics.html
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire
Re: Timing on vintage 302 Z/28 A/S
WIld Bills Octane Supreme, 6 pack is cheap goes a long way and really seems to work. I can run a few more deg timing, car is happy.
Post up pics of this camaro project..all time fav ride.
Uncle bought a 68z brand new when I was an itch
Re: Timing on vintage 302 Z/28 A/S
Consistently using 110 Oct Sonoco Leaded on the Street can lead to really heavy flaking deposits in your Combustion Chambers and Intake Ports. I just spent the day cleaning it out of my heads. I’m probably going to die soon.
73 Omega, 468 BBO, 4.185 ICON Pistons,RR/Wenzler Heads with HS 1.7 rockers and PAC 1220X Springs,J&S 5-main Halo with Billet Caps, .590I .580E 242I 256E HR Cam, 1000hp Carb,2" x 3 1/2" headers,Coan 2900rpm Conv.,TH400,3.73 12 bolt,11.32/118
Re: Timing on vintage 302 Z/28 A/S
I got right away from using leaded gasoline years ago.
This is one good reason. I do not use nor recommend any of the lil cans of octane booster. If you want to increase the octane of pump gas blend it with high (110) octane Unleaded race gasoline. This is cost effective and actually works. You got a lot of money wrapped up in your racing motor. What you stick in the tank matters.
This is one good reason. I do not use nor recommend any of the lil cans of octane booster. If you want to increase the octane of pump gas blend it with high (110) octane Unleaded race gasoline. This is cost effective and actually works. You got a lot of money wrapped up in your racing motor. What you stick in the tank matters.
Re: Timing on vintage 302 Z/28 A/S
You do not have the required permissions to view the files attached to this post.
-
- Pro
- Posts: 397
- Joined: Tue Dec 29, 2015 8:09 pm
- Location: TN
Re: Timing on vintage 302 Z/28 A/S
All you know when blending 110 octane race fuel and 91 octane pump gas is you have now diluted a perfectly fine race fuel to something else of unknown quality. You'd be better off putting the 110 directly in the tank and not worrying what concoction you've mixed. Especially on a ride like that.
- Dave Koehler
- Vendor
- Posts: 7206
- Joined: Mon Oct 04, 2004 11:19 pm
- Location: Urbana, IL USA
- Contact:
Re: Timing on vintage 302 Z/28 A/S
Geez, is that the way you bought it or was some restoration in order?
Dave Koehler - Koehler Injection
Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software
http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software
http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
Re: Timing on vintage 302 Z/28 A/S
It runs great, and really represents what was running during that era.
You do not have the required permissions to view the files attached to this post.
Re: Timing on vintage 302 Z/28 A/S
That's a nice piece of Kit you have there!
Would it be possible to get onto a dyno? that way distributor curving ,final timing and fuel will be set at what the engine is asking for .
Cheers.
Would it be possible to get onto a dyno? that way distributor curving ,final timing and fuel will be set at what the engine is asking for .
Cheers.