This morning was unusually cool, compared to the heat wave we've been battling most of this summer. I took advantage of the 70 degree temps and headed to the garage. My plan? To try and hunt down the demon causing my engine miss. Having picked up yet another carb rebuild kit, as it was cheaper than piecing together the few parts I needed, swapping jets was first on the list.
I went two jet sizes smaller on both the primaries and secondaries. I fired up the engine to make sure it was leak free, then adjusted the idle down a bit, as the rpm's were getting out of hand. Next, I adjusted the idle mixture screws, as the engine still seemed a bit rich, judging by my burning eyes. Lastly, I gave the distributor a slight twist, advancing the timing an unknown amount from the 32 degrees I had it at. At that point, I took her for a spin around the neighborhood followed up by a short cruise on the freeway to downtown Detroit.
The engine miss was still there, though I could tell that overall, the tune was much better than before. As I pulled into the garage and shut off the engine, the engine wasn't ready to die just yet, and sputtered a bit. As I said, my timing advance was a shot in the dark, and it appeared to be a bit too much, and when combined with the idle that was still too high, it created a run-on situation.
Next up, I got out the timing light to nail down total advance in timing that wasn't guess work. The guessed total advance was 40 degrees, just a tad higher than what I was shooting for. I backed the timing down to 38 degrees, which comes in immediately due to how I have set up the MSD pro billet distributor. I then backed down the idle a bit more, and leaned all four idle mixture screw about an 1/8th turn more. This seemed to smooth things out and lower the idle in both drive and park to more acceptable idles. I also adjusted the electric fan thermostat so that the fans come on when the thermostat opens at about 195 degrees. This will prevent an un-needed pull on the alternator from 4 fans running when they weren't needed. I was off for another road test!
I think this tune-up pretty much nailed it! It feels like I found an extra 50 hp with this tune. The throttle response is unbelievable, off idle, as well as from a roll. The idle characteristics are much more well behaved, jumping between about 800-1,000 rpm's, and negating the need to two-foot it at stop lights. The backfires at idle were non-existant, and aside from one "cough" through the carb after I jumped on the throttle a few times, my issues seem solved. I think the carb cough may be attributed to the float levels, which may need to be raised just a hair.
As for the engine miss? Well, it still seems to be there, though it is nowhere near as rough as it was. The engine seems to be running smoother than it has ever ran before. As for the engine miss that is still present, I'm really beginning to feel at this point it may be the Accel spark plugs. Searching the net, I haven't found too many people who have had too many nice things to say about them, other than their shorty design allows the much needed clearance some of us need. I did read that AC Delco's rapid fire plugs are slightly shorter than stock plugs, and I think Bosch and NGK also may make shorty plugs worth giving a shot. In their defense, the fact that I've had some serious tuning issues may have attributed to fouling out a plug or two, and have lead to an early demise. Last time I bought new plugs I bought 135 degree Taylor wires, which allowed some additional clearance, and perhaps enough to allow me to go back to standard plugs. At the time, I wanted to try everything possible to gain as much clearance as possible.
Next up, I think I'll run down the valve lash one last time, and she'll be good to go for the 2011 Woodward Dream Cruise. So ready, that I may even cruise a bit this year, that's how confident I am with this tune. After a lot of headaches, burning eyes, or numerous attempts, this engine is finally getting to the streetable level I had envisioned with this build. Who said 700 hp can't be streetable? Toss on my 250 hp nitrous kit and I'm knocking on nearly 1,000 hp, probably 9 second car, which I'm growing comfortable with the thought of driving a couple hours away. Life is good.
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