My 318 dyno results
Thanks! Replies in quote. :)
I have read other guys needing to open up the idle feed restrictor to get them to run properly, that's why I was planning on trying the same since I also see kinda lean cruise AFR (16:1).
Is there a problem? Don't get too wrapped up in the numbers. An engine can cruise lean, how lean depends on the load and the engine. Use the number as reference, so when you hit limits you know what they are.
Tests for problems
One test for IFR (and IAB) recommended by Mike Urich is to very slowly open the throttle from idle. If there it any miss or hesitation, its too lean. That requires a sensitive ear and some experience. I prefer same concept but driving. Very slowly increase the throttle from a stop to note if there are any dead spots or hesitations. Slow opening minimizes contribution and effect from the acceleration pump.
IFR changes can be sensitive, and when those restrictions are in the high position, they are less predictible. If you do anything here, start by placing them in the submerged position.
Last but not least. As you increase the throttle from light cruising to part power, the AFR should get leaner and power should increase. Approaching full thottle it should then get richer (power valve opening) and continue to increase in power.
-> If you are doing this from local roads, 30-50 mph, the carb will be transitioning from idle circuit to main circuit to main circuit with power valve opening.
-> If you do this from high speed roads, 65 mph, even at cruise, the carb will be mostly on the main circuit.
In between, it is too hard for me to guess as it will vary from combination to combination.
Changes to the idle air bleeds are a fine tune. In theory effect the top of the off-idle more than the idle. I find they effect both idle and off idle. A thin wires in them (run down to the aircleaner gasket so they don't move) is a handy way to experiment with restricting them slightly.)
IIRC, I'm at 1000RPM in park and get about 150RPM drop into gear. I have planned to try set it up in normal mode later on when everything else is setup right.
I was in a similar situation with my previous 340, using Comp Cams 280 HE cam.
Now with a slightly more radical cam, I can get it to idle in gear around 750 rpm. 800-850 in Neutral. Gets better as the engine gets warmer. (no choke right now)
As I learned , the correct timing makes a big diference.
Oh man, I have been too hung up seing other people with tight LSAs (longer duration though) even running locked out timing. I will try to lower initial timing! Would RPM drop be the correct indication to look for? Adjust initial for the least RPM drop into gear?
Yes that's a good way-
AFR on idle is hard to read, due to the valve overlap. :(
Yes, and its hard to know how accurate it is because the WBO2 interprets the Oxygen as AFR based on assumptions about how combustion occured. We can move timing around or other variables and sometimes it looks like AFR changed, but its not true. We know if the engine speed & load stayed the same, then with a carb - the AFR supplied stayed the same.
