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Octane is fun
https://slantsix.org/forum/viewtopic.php?t=46740		 Page 2 of 2
Author:  Doc [ Mon Oct 24, 2011 8:52 am ]
Post subject: 
Quote:
... I think that the fuel distribution for cylinders 1 & 6 is absolute junk as well, ...

Don't guess about "wet" intake manifold fuel distribution, do your "homework" and adjust accordingly.

With all my work with SL6 engines, it's usually cylinders 2 & 5 that run lean on factory intakes. (wet fuel tends to collect on the plenum walls, then moves down the runners, giving 1 & 6 an extra "shot" of fuel)

Install a clean set of plugs, then run & "read" them.
DD
Author:  Dart270 [ Mon Oct 24, 2011 10:56 am ]
Post subject: 
You may not have the timing you think you have, if, for example, the damper ring has slipped. 115 psi cranking is quite low and shouldn't ping at all on 87 octane and 30 deg, unless engine is really about to overheat.

In my experience, timing around 28 deg on a high comp performance NA engine makes max power.

Lou
Author:  Dan-o [ Mon Oct 24, 2011 3:40 pm ]
Post subject: 
Timing is good, its a freshly rebuild dampener and I marked it when I assembled the motor. When we were dyno tuning it, 26* was peak power and just as it was starting to ping.
Author:  Aggressive Ted [ Mon Oct 24, 2011 5:43 pm ]
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Dan-o,

What is your compression ratio? 10 to 1?
and what cam are you running?
Author:  Dan-o [ Mon Oct 24, 2011 9:37 pm ]
Post subject: 
I think I did the math at 9.7:1 static, and it is the Comp K64-240-4 Cam. I was in a rush to install it after the Erson springs and cam wiped out my rockers, so I just installed it dot to dot.
Author:  Dart270 [ Tue Oct 25, 2011 5:17 am ]
Post subject: 
Sounds like the cam is really far retarded to get that low cranking psi. That will make for low power, high heat, and possibly pinging.

Lou
Author:  Dan-o [ Tue Oct 25, 2011 6:49 am ]
Post subject: 
I had thought about that myself. But I don't want to pull the timing cover without the motor out. Last cam swap I did in the car things didn't go well for the oil pan gasket, so I'll want to re-do that one. If I get the gumption this winter after SEMA and everything maybe I'll give it a go.
Author:  Doc [ Tue Oct 25, 2011 8:55 am ]
Post subject: 
Pull the valve cover and take a look at the valve events, to get an idea on where the cam ended-up.

The most important event to find... when the intake valve closes.

Also check to see how well centered the overlap event is at TDC Exhaust.
Do all your check at the recommended lash setting(s).
DD
Author:  KBB_of_TMC [ Tue Oct 25, 2011 9:22 am ]
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In my '75 /6, I experimented with the EGR to control pinging at part throttle, and it worked quite well and had no effect I could measure on mileage. At WOT I didn't have a problem, and found that too much EGR really cut WOT power. I also found that turning the EGR 100% before turning the engine off prevented dieseling, so I built a box to control the EGR from the driver's seat w/ 3 settings; 0% EGR (for WOT), 100% EGR (for shutdown), and normal vacuum amplifier control (the rest of the time).
Author:  Eric W [ Tue Oct 25, 2011 4:49 pm ]
Post subject: 
A little transmission fluid also works, poured SLOWLY down the carburetor while reving the engine to around 1500-2000rpm. Be warned: Doing this WILL smoke out the neighborhood!
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