You and the car are getting better all the time. How's the power delivery.. coming up on the cam quicker and maybe more power as a result of lifter adjustments?
Don't know for sure. The car seemed to have better mid-range. Although my best 60 ft was on that run. First time the car broke into the 1.7 range. I muddled the issue by also changing the timing down to 37*.
Racing today. The Club runs are today and tonight. Hoping to go a few rounds to help with club points. I have the timing now set at 35*. We'll see if it affects the ET, or more specifically the 60ft times. I'm going to keep walking the timing down until the ET/mph drops off. I also talked to the guy who I bought the QFT 650 carb from. He gives written instructions to be sure to set the four-corner idle on the carb before running it. I told him I was pleased with the two tenths I picked up with the carb and the first thing out of his mouth was the question "Did you set the four-corner idle?". I told him that the carb ran fine out of the box and since I had the idle set at 1200 rpm it was off the idle circuit. He said set it anyway and expect it to run a tenth faster. So I did. We'll see if it helps. However, it's going to be high 90s during the afternoon practice runs, so it remains to be seen if I will see any improvements from the timing change and the carb idle adjustments. As always, the drag strip will tell the tale. Hopefully I can figure out what it's telling me. Jim
Dose the motor have pop up Pistons if so then you will need to run more timing but if it's got flat top 32 to 34 most times
It has flat top pistons. It made the most power on the engine dyno at 38-40*. I'm slowly working my way down on timing. I usually only get three to five runs on it each time I go out. A couple of practice runs and the number of rounds I can go. So far, I've only made the third round once. I've not been changing anything at the strip because I need consistent times before eliminations. Then back at the shop during the week I'll evaluate what it did and see where I think I need to go.
Ultimately.. you will always end up robbing peter to pay paul when it comes to ignition timing compromises. So you will hurt one part of the run(power band) in trade for making another section stronger and end up hitting the point of diminishing returns because one negative loss offsets another positive change too greatly to give a net loss overall. No way to add timing on the bottom of the rev range and pull it back out on the top with a conventional distributor advance setup. So, what works well for leaving at 3300 rpm off the converter.. just isn't the same requirement for a top end charge in high gear. Or any of the gear changes and torque multiplication variations in between. Just about any motor out there will always prefer more timing at lower rpm/under the engines torque peak. And pulling timing as you run through the last 50-100 feet will often allow the engine to pull a bit harder/further past peak power(overrev). Fatter power curve and won't nose over as quickly on the top end. Only way around that is with a programmable 6 or 7 box(I've run the programmable 7 box and it is AWESOME!). Or you could install a single or multi-step retard capable box or module to allow you to run the higher ignition lead that the engine needs to make more power under the torque peak and still end up with what it needs(less spark lead) to make more peak HP and run harder on the top end. As always.. speed costs.
Recap of last night's Firebird effort: D- I kept it shiny side up so it's not an F! It was the first hot day of racing so far. It was 91* for the first practice run and 93* at the beginning of elims. First run was a 12.56. I was expecting it to run slower with the temps, but a sluggish 1-2 shift (me, not the car) obviously hurt the ET. What I mean by sluggish is I didn't get it shifted until it bumped the rev limiter. Second run was 12.499, but was marred by a slow 2-3 shift. It's hard for an old fat man who's soaked in sweat by the time I get to the water box to concentrate. RTs were not good either, .14s for both run. After a two week layoff, I'm obviously behind the car again. And, as usual, we only got two runs before elims. Knowing the car should be a bit faster even with the hot temps I dialed 12.49 for the first run. Made a nice clean run, good launch, crisp shifts, .138 RT and ran 1 12.430. Broke out. The other car broke out, too, but only by .054 to my .060. Multiple double breakouts flummoxed almost everybody. The tower guy said that even though the air temp had gone up 2* to 93, the track surface temp had gone down 20* because the angle of the sun had decreased between 6:00 and 7:00 pm. Don't know if that was it or not, but double breakouts were rampant. Temp was back down to 75* by the time elims were over at 11:00. So, with the hot temps I don't know if the timing reduction and carb tuning helped or hurt the car. We race both days next weekend so I may get myself back to some consistency and get some stable weather to see if I can tune some hp into the car.
have you tried to raise the rev limiter rpm a bit after the lifter preload adjustments were made to see if you've successfully extended to peak power band?
I have not. I presumed that the more pre-load I have the earlier the valve float. Do I have that backwards? I have the rev limiter at 6100 now.
I would have the limiter set at 6500 minimum,that way you know you can get the most out of the mtr without hurting it.
Dan, why would I do that when I know it valve floats at 6200? At a minimum valve float hammers power. At a maximum it breaks valvesprings and bends pushrods.
