Calibration question

[Ron Gusack]

Many years ago I decided to convert a 750 Dominator to a 1050. I bought some BLP blocks, banjos, etc. It always read lean on my logger but seemed to run fine. In 2015 I decided to do some jet testing and here are my results. This is all 1/8 mile and a 433 BBC. If mph went up more than a little, I made another jet change.
93 jet 105.80 mph
95 jet 107.47
96 jet 108.49
97 jet 109.02
I'm tired of jet changes at this point so I put the 9375 on with 91 jets and went 110.76
I'd like to put the 2 circuit back on to see if it's more consistent but a 97 jet seems enormous and people tell me I've got something screwed up. Here are the numbers.
IJ .037
IAB .076
MAB .025
TSJ .058
E1 .022
E2 Blank
E3 Blank
E4 .025
E5 Blank
Kill .026
It's got .106 holes in each throttle plate and (2) .027 bypass jets in the top.
See anything obvious?

[jmarkaudio]

Did the angle channels get opened up to at least .160 on the metering blocks?

[Ron Gusack]

They measure .155. I can open them up some if you think that's the issue. I need to find more consistency to help cover weak driving skills. The car will pick up or slow down .02 in 60 and sometimes I absolutely can't find a reason. In April I picked up .026 in 60 but the 60-330 splits were only .001 different. I tend to leave the line with water temps pretty cold, 130-135. On this run I was at 154 cause he burned me a little. Could I pickup almost .03 in 60 because I was 20°warmer, I don't know but it sounds plausible I guess. I'm about ready to go back to E85 and I'm still scared of alky.

By the way, Justin Lamb feels that smaller than the quickest/fastest carb for combo x is often more consistent.

Thanks for any thoughts!!

[68 HEMI GTS]

Your combo struck me as oddly familiar.

I have a old style 750 I converted to a 1050. Mine wants a ton of fuel as well compared to other dominators I’ve built with the same blp parts. Even set up like this it’s low 13’s at WOT on my 512. I figured it had to do with the old style carb being short and the booster single being possibly weaker??.. had me scratching my head a little. I had to go with the old style carb to get it under the hood. Runs like a bear, just thought the tune up seems funky on paper. Especially since I’ve built and tested atleast 5 or 6 other dominators on this car and none of them wanted to be set up this rich. Usually 82/92 with a .076 PVCR will put it in the mid 12’s at WOT. Usually only need a .037 squirter on the back as well.

MAB .028
IAB .063
TSJ .063
IFR .040
PVCR .086
Blp block IFR low .028,plug,plug,.028,plug
Blp 16 hole annulars
82/96
Squirters .035/.047
Angle channel .161
Steak tubes reamed to .162
BLP throttle shafts.

[Ron Gusack]

Not that it really matters, but I was running a 427 BBC then with 13.4 compression. At the end of that season I bored it and lowered the CR to 12:1. I looked at my average AFR numbers from 60' to the 1/8.
95 MJ average was 16.72
97 MJ average was 15.94
I would think the engine would be popping with numbers this lean but it ran fine with slight signs of detonation. I sent the entire system to Racepak to have the AFR calibration checked and they said it's all good. They suggested that I might have a leak in the header somewhere, but I couldn't find anything. Bracket racers claim leaner is more consistent but I've never heard any quoted numbers. The 9375 does well but will throw a major curve at me for no apparent reason. I'm thinking of just going back to E85 after I get some unskirted banjos.

[RFSPHPbb]

if those numbers were right you'd be sitting on mounds of burnt pistons. it;s getting air into the exhaust somehow. do you have bungs on both headers?

[Ron Gusack]

Not on both headers but in multiple tubes on one. I've tried both bungs. There were some early signs of detonation but nothing major. It's only at those numbers for a tad over 6 seconds. The bungs are tigged in and I couldn't find any signs of leakage but I don't remember how I checked. The flange was flat and straight. I think I tried vacuum and then pressure but it wasn't easy to seal. I'll make a plate to bolt on to the collector flange with a nipple in the middle to put a vacuum hose on and retest. I'll have to close all the exhaust valves. It's been years since I tried the last time.

[Ron Gusack]

Here's an update on this old post. I made a plate with a nipple on it to test the seal on the header pipes with the O2 sensors. I put some air pressure in and used soapy water to look for leaks. I found none. I cut the threaded end of the plugs off to read the afr because I trust that more than the O2. I do not kill the engine at the end of a run and pull a plug before driving back to the pits, but I see no signs of it being super lean.

I still experience an occasional loss of ET for no apparent reason. It's a killer for a bracket/index car to lose a couple numbers in a race these days so if you have suggestions, please share. I trust the driveshaft sensor and see no loss of traction. I don't use a weather station but take a screen shot after every run from airdensityonline which is only a few miles from the track.