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View Full Version : New best n/a!



White90GT
02-21-2005, 10:17 AM
Already put the info in another post, but thought I'd put it here since this is where it goes.
At the braggin rights national event this Saturday, I used the several hours of test and tune time to play with my n/a tune a little and try for a new best.
Previous best on this motor with the current converter (before I got it re-stalled) was an 11.41@115.29 mph with a 1.54 sixty foot. The converter was way loose stalling to around 5200 rpm and didn't give me a lot of top end speed (hence an 11.4x at only 115mph), so I had it tightened up to around 3800 (or I had hoped). It wound up feeling tighter than that and more like my old 3200 rpm converter felt. I had taken it to HMP with the re-stalled converter about a month ago and managed another 7.27@93.5mph with a 1.59 sixty foot which was right on with the 11.41 pass' 1/8 mile time.
Anyways, on to Saturday:
Got there and made a pass and was shocked with a measly 1.64 sixty foot and 11.6x@116.x mph pass. Tried raising the timing to 20* base + advance up to around 44 * with no luck, time just got worse with a weaker launch. I tried doing a few things with the timing including pulling the spout and running a flat 36* of timing still with no luck and down to a 1.70 sixty foot at this point. So Brian Warwas suggested adding fuel pressure. I looked and had leaned it out a bunch on a previous outing with only around 33 psi of pressure. I kicked it up to 40 psi and was rewarded with a 1.60 sixty foot and 11.45@117.x mph. I raised another 2 psi to 42 and was rewarded with a slightly spinning 1.59 sixty foot and 11.31@118.9mph pass! Hot lapped to back it up with an 11.35@118.2mph pass. Was running short on time and needed to get a couple nitrous passes in, so I strapped in the bottle and ran a 10.91@120mph hitting the rev limiter around the 1000 ft mark. Time to up the limiter a little. I am a little upset that the converter now feels so tight on the bottom for launching, but still seems loose up top causing me to be on the rev limiter at such a low mph. Any ideas why that is? Its a trans king 8" converter. Are 8" converters just not that efficient in the top gear? Sixty foots on the nitrous were in the 1.51-1.52 range all day hooking solid and all the 1/8 mile times were in the 6.9x@99 range. I was running 15* of base timing on the 75 shot with a mix of 93/104 gas.

Scotty
03-04-2005, 05:28 PM
Congrats on the new best!! Sounds like you're on the right track with your tune. I'd have to agree with your converter killing your mph. I'm running a 9-1/2" converter that flashes to around 5200, but my mph was in the 123 range. I'm not sure another 320 feet would yield another 3mph, but you're not loosing THAT much. What are you launching and shifting at? I'd like to see a little better 60-ft, but you're not too far off the mark. Mine averaged 1.490 with the old motor. I guess that actually is quite a bit, considering it's the 60ft........ Are you spinning?

As for timing.... man, I just can't see how anyone can run that good with any sort of advance. Mine is all in by around 1800 with a total of 34*. Basically, it's locked in except when you first start it or at idle. (which is the only reason it's NOT locked in... starting it..... initial is 18*).

I'm not trying to boast about my car or anything, but merely using it as a comparison because we were so close with my old motor.

So what ever became of the last motor you had that you puked? Is this one very different than the one you had? If so, what did you change?

Scotty

Guffinator
03-05-2005, 02:39 PM
Good job Carl!

White90GT
03-05-2005, 09:18 PM
I'm bringing the car up on the foot brake to around 3000 rpms or so. It wasn't spinning that day, even on the nitrous. On the 75 shot it was pulling 1.51 sixty foots and running 10.90 hitting the rev limiter around the 1000 foot or so. I may consider trading this converter off for a 9 inch, or just have my 10" PA converter re-stalled to about 4000. This 8" just seems too inefficient even though the mph and ET are right on for the motor pass, 11.31@118.9. I'm going to play with the tune more and get a few more goodies to see if I can get the 11.00 on motor.
This is a completely different shortblock since the old one was trashed, but its still a 347. Same brand crank and rods, but Ross dished pistons brought compression down from 11:1 to 9.9:1. I'm running a HOlley Systemax intake instead of the Victor 5.0 that I was running (considering switching back to see what it does). Same cam and other bolt on accessories, but I had a little more work and a 7 angle valve job put on the heads.