So Friday night I coaxed my iron-head, 9:1, carb/cam/headers/mild converter 1971 Charger R/T to it's best ET (13.44) since I got it running again in 2019.

I have what I think is a fuel starvation problem. Back in the day (around 2006), it ran a 13.42. When it ran the 13.42, the 660/330 ET ratio was 1.53 and the 1320/660 ET ratio was 1.55.

On the 13.44 run on Friday, the ratios were 1.55 and 1.57. Based on the 330 foot ET on Friday, if the ratios had been 1.53 and 1.55 instead of 1.55 and 1.57, it would have run a 13.14 ET instead of a 13.44, that's a big difference.

One difference is that in the old days, it had single plane intake and an 850 cfm carb, now it has a dual plane and 750. It 60-foots much better (it went 1.89 leaving from idle on Friday), but it doesn't feel like it pulls hard after 330 feet. Some of it might be the intake/carb combo, but a part of me thinks there is more going on. On a couple of runs lately, it the car has just all of sudden layed over near the end of the track, like it's not getting enough fuel at high rpm/mph (relatively speaking). Once it came back before the finish line, once it didn't.

The sending unit is about 20 years old, I am getting a new one, I am wondering if the sock isn't flowing well. The fuel pump is new. I can't believe the carb jetting is off too much.

Anyway, so I am not chasing my tail too much, I am curious about what other people's ET ratios are, especially if it's a high 12-sec or low13-sec car.

I'd really like to get into the 12s without putting my aluminum heads on yet.

Thanks.

Greg

!.575-1.585 is pretty close for most cars. this will get you pretty close.
http://www.wallaceracing.com/etcalc.php
Doug

I bet it's not running as hard at the big end with a 750 on it.

On my little motor the ratio is off because it just doesn't pull in high gear like a big motor.

To see if you have a fuel starvation issue, just put a 'T' in the fuel line by the carb, and run a hose outside the engine compartment so that you could monitor a fuel pressure gauge during the run. I have made a good number of passes with a fuel gauge and hose under my driver's side wiper when chasing this kind of problem.

And the 1.89 60' seems a bit 'lazy' to me. Street cars should be able to get into the 1.60s. If you can get the 60' there, that would go along way to your goal IMHO.

Thanks guys.

DVW- According to that calculator, my runs are pretty much spot on, so that's good I guess. On the other, I know for a fact it has "given up" in the middle of a run at least a couple of times, so there is some mystery to be solved somewhere.

DaveRS23- I may try the fuel pressure gauge on the windshield trick at some point. I agree on the 60-foot times, but I made a decision not to beat on it too hard with burnouts and on-the-converter launches until I am convinced it's running as well as it can for a 1.90's 60-foot time. I think it will do 1.70's eventually, 1.60's seems pretty optimistic but what do I know (answer: almost nothing)?

Greg

I learned a long time ago that the E.T. is in the 60'. Doesn't seem to hit the MPH as much, but has a big impact on the E.T. Especially in the 1/8.

More details on the car ? MPH?

9:1 iron head 440, 750 cfm carb, dual plane intake, mild cam, headers, looser converter (I thought it was a 2,500 rpm stall, then I found a note saying it's 3,500, I guess I need to test it and find out for sure), 3.91's with 28-inch tall drag radials, weighs just about exactly 4,000 lbs with me and a half-tank of gas (normally I run 90 octane ethanol-free, but I ran 93 with ethanol on Friday). Here are the three best runs from Friday:

1.96 5.57 8.63 80.04 13.53 99.56
1.91 5.52 8.59 80.06 13.49 99.43
Bumped timing from 18/34 to 20/36
1.89 5.49 8.54 80.16 13.44 99.91

See anything in there that's interesting?

BTW, here it is minus the drag radials and it now has the door stripes. It's ruff but it's real:

As Dave has already mentioned above , the first thing I would do is install a fuel pressure gauge where it can be viewed while going down the track. According to the Wallace calculator linked to above , your incrementals all seem to fall pretty much in line. It may be that your power level is just a little lower than you had hoped. If the engine is essentially a 440 magnum with headers , it may not be too far off the mark. Are you running a full exhaust system ? I had a low comp 440 in a 71 RR back in the 80s . 2 inch exhaust with glasspacks: 93 mph. uncorked : 102 mph. Couldn't believe it.

It looks to me like the 330 is suffering. I would bet shifting 1/2 earlier with this combo would help.
Doug

Switching from no alcohol gas to gas with it will lean you out.

On my pump gas junk it was worth 3 jet sizes richer for E-10.

f0rget the ratios, focus on the incremental times on the time slips and tune for improvement in all segments on it
Total timing, spark plug heat range and jetting as well as shift RPM are all tunable

Thanks for all of the help everyone, there is a lot for me to think about and hopeful build on, I really appreciate it.

To answer a few of the other questions, it has a full 2.5-inch exhaust.

It picked up from 13.6's to 13.4-.5 when I dropped the shift point from about 5,250 to 5,000.

As suggested, I will play with jetting and timing and so forth (including making sure it's getting enough fuel), and I may try my 850 cfm carb again. Once I think it's running as hard as it can from 60-feet out to the end, I will look into launching a little harder and trying to drop the 60-foot times into the 1.7's.

I try and fly the classic Mopar colors the best that I can, a lot times I have the only traditional muscle car in the street tire class in a sea of modern Mopar stuff, Mustangs, Camaros, BMWs, whatevers. They're fast but they're boring.

Greg

Keep up the fight and carry our colors proudly