L-89 TUNING TIPS. . . HELP

[justin_18_ky]

1969 camaro its a 396/375 horse l-89 aluminum head. . . i`ve got 12 degrees initial timing, and 36 total timing. . i`m toying with the idea of going to 16 initial, and 38 total. . we`re running AV. fuel 116 octane so 40 degrees of total wouldn`t be that bad . but it just doesn`t feel like its pulling as hard as it should be after about 5000 rpm. the valves are set at .025/.025. . . i was thinking about .023/.023 which would give me some more uppper rpm power, but anyways. . the carb is the original 780, but has 72 jets in the primary and 80`s in the secondary. i`m using the yellow spring for the secondaries, and a quicker cam for the accelerator pump with a 3.5 power valve. any suggestions to give the power i need to pull past 5 grand hard?? please don`t tell me that big blocks make most power under that rpm range. . because this is a factory solid lifter, .520 lift cam. . .the power band is suppose to be 3200-6200. . also the dwell is 30 degrees, and the gap for the points are .019, and the plugs are .032 for a little more upper rpm power, instead of the factory .035. . . please keep the suggestions stock, which means no headers, roller rockers, bigger carbs, or aftermarket ignition products, as well as no port work. .

[Chevy454]

I think you may find that your engine will like a little more total timing. We have had the best luck with our big blocks at around 39, and I think I remember hearing COPOpete say that his L-72s are right around 39 as well. I would like to hear what everyone else is running, though. The timing needs to be in as fast as possible, like around 2,500 rpms. That seems to be where most big block owners like it.

A quick question for you: are you running true aviation fuel, or just high octane racing fuel? If you ARE running the AV fuel, be careful...lots of ethanol in that stuff, and it's very hard on anything rubber (carb internals for example).

How do your plugs look after running the car? If you are planning on racing it, then you need to install fresh plugs, run a hard pass, then kill the engine as soon as possible, and check 'em. That will give you your best reading. Your power valve sounds a little low, but everything else sounds close. Not sure what the factory valve lash is for aluminum heads, though...for iron, I think it's 24/28. Any "L-89 gurus" here with the lash specs?

Pete (or anyone else!): jump in here and help us out!

[justin_18_ky]

well, its true AV fuel. . . a local motorsports place sales it. but it i'm using a 70/30 mix. . . 70-av/30-93 octane. . so i'm looking at 108-110 octane. i haven't checked the plugs since i put them in, but they only have 15 miles or so on them. what do you reccommend for the gap settings?? its the stock coil, so i can't go too big. the powervalve was a 6.5 and after having the carb rebuilt by a 'so-called' professional, he said that it was too big. i only agreed with him. but i thought that a 6.5 would be fine, considering the vacuum is about 10 hg.

so you think that the 16 degrees initial would be fine? and 39 total would be best? what if i dial up 40 and there's no detonation? the proper valve settings are .024/.026 for the aluminum heads. i'd like to go a little tighter for the upper rpm power, i'm running .025/025. . . so i'm thinking about .023/023. . .

[JoeC]

What gear and what trans do you have? You may be able to run the lightest springs in the carb and dist. Somtimes the only way to find out is trail and error. Did you degree the cam?

[Chevy454]

Ok, Justin...I seemed to have lost my notebook with all of our setups in it (I am still looking, though!), but I did find a couple of sheets with some notes on them.

For plugs, I run the regular gap, and regular old AC-43 plugs...nothing fancy. You need to install new plugs, and check them after a run, as racing and driving are 2 different things. Thats the ONLY way to get a true reading. As for gap & dwell, we run all stock settings, and it seems to run well with them.

As for jetting, this will also depend on your plug readings. We are running the power valves, and our jetting is at 78/86, but every set up is different. Your 6.5 power valve sounds closer than the 3.5, but I can't remember what mine is. We are running the yellow secondary spring (the longer one) as well.

As for timing, you want as much as you can get, and still be able to start it good, and not get any detonation. We have found 39 degrees works well on our cars, but once again, every setup is alittle different. Pete told me he usually runs around 40 degrees total, and 20(?) initial.

Valve lash is another variable that is kind of dependant on the overall combo. We are currently running 24/28, and it seems to work well, but I have been known to change it up a bit.

The above may not help you out much, but LIke JoeC said, a lot is trial and error as some engines like it one way, while others like it another. But, it sounds like you are already in the ballpark, so just keep fine tuning it.

I also noticed you said you were heading to Michigan for the PSMCDR. Have you ran the car before at the track? What tires are you running? What day are you planning on getting you Michigan? Pete, JJ, and I are all competing in "Certified Stock", so we should all be there a day or two early. We are all easy to find!

You need to read the May 2001 Muscle Car Review about Pete's dyno test on his L-72, and then check out this thread http://www.yenko.net/ubb/Forum1/HTML/000307.html

[Edited by Chevy454 (06-20-2001 at 11:45 PM).]

[justin_18_ky]

the gear is a 3.73, with an m-21 trans

it'll be running on the stock bias-ply, they hook up pretty good actually. . . but i dunno about the class, but the most stock possible, this is totally unaltered, and doesn't use bent rules. just a stock car ready to run, hoping for about 14.00-14.10 at 102-103. .maybe with a little better traction it'll be running 13.90's at 103 or so. . .

[Chevy454]

The "Certified Stock" tech is something new they added this year, to try and quiet a few rumblings about some cars. It involves a thorough inspection of the car, and an engine tear down, and then the engine components are checked. All cars, certified stock or not, all run against each other and are matched up by ETs. So, there really aren't different "classes" so to speak, just some cars are going through a tear down.

Which tires are you running...Firestone or Goodyear? Also, what tire pressure?

[justin_18_ky]

the tires are firestone wide oval . . . i think they work best on the street with higher pressure. . . the more the better until about 40 psi or so. . . . these are really old age bias ply tires too, not new tech. they still sway and find grooves just as original. hehe

the positraction unit works like a dream, it hooks up really good, leaves perfectly equal black marks like a locker or spooler would. . .

[Chevy454]

If your tires are very old, a change to a "newer" bias-ply repro tire would probably help you. After the tires experience so many heat cycles, the rubber in them goes to crap. Pete can attest to this as his '70 COPO Nova has NOS Polyglass tires on it, and he said they were pretty much useless when compared to the "newer" repro Polyglass.

On our Camaro, we are running around 44 psi in the rear, and about 46 psi in the front. The key is to make sure your black marks are even all the way across, which means your tires aren't cupping or overinflated. Pumping the fronts up is supposed to decrease rolling resistance.

It's not just the "old" Polyglass tires that are a little wild on the road. Our repros do the same thing...I guess it's just the nature of the beast!

[Steven J]

If your car doesn't pull well past 5000, and the carburetor and distributor are set up and tuned correctly, you may want to check to see if you have enough fuel pressure, or you might be in need of new valve springs.

[Chevy454]

I have also heard that if you wire your coil backwards the top end will go away. Of course that's just what I heard... http://www.yenko.net/ubb/smilies/images/icons/wink.gif