Wanted! Tuning Expert

[smoothfootn]

OK guys, I've got her running, now it's time to get her running well. 91 Conbrio. I've got the point gap @ .018, timing @ 10 deg. How do I tune to get a smooth idle? I was shooting for 800 rpm, is this too slow, fast? Both idle needles are 2 turns out. Can one of you experts give me some tuning advice? Also, engine doesn't want to start w/o a few pumps from accelerator, is this b/c the idle is set too slow, mixture too lean, or what?
Thanks!
b

[cadunkle]

Check your timing advance. Increase RPM and watch the timing as you do so. Should be a fairly smooth curve to full timing in around 2500-3000 RPM. Total timing should be around 32*-38*, depending on heads/cam/etc. will dictate where it performs best. 10* initial is pretty safe but if it'll take more initial without detonating or being hard to start (kicking back, slow crank) you can get a little more low RPM performance and a better hole shot. I'm talking like 12*-14* max, since it is a boat and under heavy load all the time. Just be sure you don't have detonation as it'll crack pistons and ring lands. Also make sure you're not getting crazy with total timing, 38* is a lot, 40 or more is just plain too much. If you're not experienced with tuning and listening for detonation, don't push your luck and a curve starting at 10* running up to mid 30's will be fine.

To adjust your idle use the throttle stop screw to set idle opening/RPM. I'd shoot for 650-700 RPM, or if it doesn't like that low just go as low as it'll idle and still be smooth when you put it in gear. Good starting point for the idle mixture screws is 1.5-2 turns out. Screw them in at 1/4 turn increments until you notice idle get a little rough, then go 1/4 turn richer. Then set the other side the same. Now go back to the first one you set and go 1/4 turn richer and slowly screw it in until the idle changes (rough) and then go 1/4 turn richer. Do the same with the other side.

Now check your idle RPM? Is it still where you want it? If yes, great. If no, adjust the throttle stop screw until it's back where you want it, then check your mixture screws again by going 1/4 turn richer, then lean until it stumbles, then 1/4 turn richer.

After this, check your timing again and make sure it hasn't changed. If not, you're done. If it did, set your timing back where you want it, adjust your idle speed back to where you want it, and recheck idle mixture.

[michael hunter]

Has the carb ever been rebuilt? Holleys are famous for power valve failure.

[smoothfootn]

Yes, I rebuilt it a month ago.

[cadunkle]

Note I was just looking through my owners manual and it states 600 RPM idle in gear. So shoot for that, or if it won't do that, just as close as you can get it and still be smooth.

[jet]

Yes...GET RID OF THE POINTS..$140!!! And it will run like a EFI!

[Chuck Yager]

Smoothfootn, It may be too late by the time you see this, but I have purchased the electronic conversion kit to get rid of the points on mine. I'm kinda hoping to get my carb buttoned back up and re-mounted then get to the conversion. If you want to get a look at the parts, shoot me a text or call and I can tell you how to get here. May be something to consider since our lake is about 3 1/2 foot from spilling over the dam right now anyways so we can't put the boats in the water for a little while anyways! LOL!

[cadunkle]

Electronic pickup ignition is definitely a worthwhile upgrade and one of the best bang for the buck for any engine running a points distributor. If you're considering any of the conversion kits I would advise against Pertronix. I had one fail in my car and Pertronix would not honor the warranty. They offered to replace the module at cost (nearly $90 they say). So I was out $130 for a piece that lasted under a year. I replaced mine with an Accel unit and never looked back. I've used several Accel points conversions in my own vehicles and engines I've built for people adn never had a failure, so can't comment on their warranty or customer service... But they are more reliable in my experience.

Just my experience. But either way you go, electronic trigger is a good investment, especially since it's pretty much impossible to find a quality set of point anymore. All I've found is cheap junk that pits fast and has weak springs.

[smoothfootn]

Thanks guys. I had a guy give me a Mallory 47 series last week and I plan on putting it in, but it needs some cleaning. I was just hoping to get things tuned up b/c I'm anxious to get out there. But as mentioned above, we are in Eastern, OK and had record rains here over the weekend. Tenkiller lake is about 30 feet above normal, so I won't be skiing too soon. I'll let you know how the ignition swap goes and will likely repost with some questions!!
Thanks!
b

[Chuck Yager]

Hope the Mallory works out!