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Topic Review (Newest First)
05-14-2010 03:07 PM
ap72
Quote:
Originally Posted by F-BIRD'88
I suggest after tuning with the wide band you remove it and install a common narrow band 3-4 wire heated type sensor and simple AFR gauge and use it as a general AFR monitor. (much like a temp or oil pressure idiot light. It will show up any afr changes as you drive. Save the wide band and its expensive/delicate 02 sensor for actual tuning.

The fact that the narrow band type is not exactly 100% accurate at rich ratios/WOT is not critial once the car is correctly tuned. It will faithfully show you if the AFR tuning becomes difference eg weather condition change, vacuum leak failing fuel system, blocked jet, blown power valve etc etc. It will also show ignition faults etc.
As a rule they are much more bullet proof.

great advice! I run one in every car I currently have. I cut the harness off of a 4 wire O2 sensor from a junkyard and use to to make a connector to the gauge inside the car. if I ever need to sap the O2 sensor its one wrench and unplug the plug- so easy a caveman could do it. Even without a wideban it can help to dial you in.
05-13-2010 09:13 AM
iambigperm It has the full "Pipes" 3 inch dual exhaust w/x-pipe. I think my wideband sensor is on its way out from all the lead so I just ordered an Innovate LM-2 wideband and it will be here tomorrow. Then I'll know for sure if its running lean. I used to leave the wideband in as a permanent gauge, but the sensors die too fast from the lead. I'm just going to use this new one for tuning and then take it out. The cool thing is the LM-2 is a full datalogger as well... As far as the secondary spring I honestly don't remember which one I finally settled on.
05-13-2010 02:35 AM
RustoRod What are you using for mufflers ? What spring do you have in the secondary of the carb ? You say that you have 4 psi of fuel pressure the whole way through and the A/F ratio is 13:1 but how do the plugs look ? It sounds like you could be running out of fuel.
05-12-2010 08:16 PM
iambigperm Thanks! I try to keep it clean... As far as the ground goes I even have a ground strap from the distributor to the body. My brand new MSD Pro-Billet HEI smoked the module a few weeks back and I'm thinking they don't ground too well through a distributor with a poly-carbon gear, o-rings on the housing, a thick gasket and a painted hold-down.
05-11-2010 11:30 PM
iambigperm That gives me a lot of stuff to try out. Is there any down side to running less than spec on valve lash?
05-10-2010 02:40 PM
ap72 If its all done that early than you have a problem somewhere. Look at your cam specs... Look at your dyno chart... they should have a certain relation...

That big of a solid roller cam should have no problem pulling to 6500 RPM.
05-10-2010 02:10 PM
iambigperm I don't think I would be shifting into overdrive in the 1/4 mile if I could make power to 7k. I am shifting early because its all done at 5700-5800 rpm.
05-10-2010 06:35 AM
ericnova72 If you are shifting into OD in the quarter you are definately overgeared, it reads that way from you first post??

I don'y think the carb is terribly too small, not enough to kill that much power, but it does sound lean compared to how most of the 750 VS carbs I've used on similar engines for several people, larger 4 sizes all the way around is close to where I would expect to end up after tuning.

I would have thought the wideband would show some kind of variance during a run, no 3310 is that linear a fuel curve, maybe your O2 sensor is too polluted??

The carb is too small but I don't think just that is killing 1 full second, but maybe it is 2-3 tenths each wrapped up in several small bits you'll find by tuning?? I would definately try a bigger carb if you could borrow one, it could point you in the right direction real quick if it makes a good difference.

So, maybe 2 tenths carb size, 2 tenths timing(seems a little high total, try 34-36) 3 tenths jetting, 1 tenth launch technique(finding the sweet spot at the line w/engine), 1+ tenth finding perfect shift points(try lower rpm shift to second to work the torque, higher rpm shift to third to use upper rpm HP) .


Add them all up and you are where you want to be. I never really worry about the first few passes, they're just to get a baseline to work from, now you have to test to tune your combo. I don't think there as any "silver bullet" single part here.
05-10-2010 04:07 AM
a1supersport Yeah that 700r4/4000-stall, 4.56 struck me as kinda steep...even with the 27's. I'm guessing you've already shifted to 2nd way before the 60ft. mark. What kind of rpm are you pulling through the traps?
05-10-2010 12:09 AM
iambigperm That sounds like its worth a try. I'll see who's a good buddy this week. Do you think that my 700r4, 4000 stall, 27 inch tall tire and 4.56's are a bad combo?
05-09-2010 11:16 PM
66GMC CFM Calculator

383 ci 7500 RPM with 100% VE = 831 CFM
383 ci 7500 RPM with 92% VE = 764 CFM

That's what the figures say, but they do sound low to me.

I ran a 351C to 6000-6500 RPM and according to this the 600 CFM (1850 Holley) that I started out with should have done the job. Not so ... it seemed to run out of breath around 5500. I upgraded to a 750 CFM (3310 ) and that seemed to do the trick.

I'd suggest asking a buddy to borrow something a little bigger (850 CFM) and give that a trial pass.
05-09-2010 10:45 PM
iambigperm The carb is the only thing on the engine that isn't brand new. It was on my last motor than spun to 7500 no prob with a smaller cam. I'd rather have a double pumper, but this works for now I think...
05-09-2010 10:35 PM
a1supersport The thing that looked odd to me was the Holley 750 vac.sec (3310?)...
05-09-2010 10:17 PM
iambigperm
Please critique my setup! I may have mismatched some stuff...

I took my 84 Regal to the strip this weekend for the first time with my new combo and the results were a tad disappointing. Here was my best pass:

60' 1.843
330 5.241
1/8th 8.104
MPH 85.95
1000 10.568
ET 12.680
MPH 106.13

Air temp was about 70 degrees. Racing at night in Las Vegas....

I shifted 1-2 at 6200, 2-3 at 5700, 3-4 at 5700

Now here is my setup:
383 sbc
Forged flat top pistons w/2 valve reliefs
Eagle rods, stock crank (all balanced of course)
Engine Quest Heads. 200cc intake runners, 64 cc chambers
Crower Solid Roller 00426S grind
ADV Duration 288/290 Lift .570 .584
Duration @ .050 250/252
108 Lobe Center
.026/.028 Valve clearance
Cam was degreed
Comp 1.5 Stainless Rockers
Crower springs (matched to cam)
Cloyes aluminum timing cover with thrust bearing
Victor JR intake
Holley 750 Vacuum Secondary w/ choke horn removed. Jets 72/81, high flow power valve(4.5")
Holley Red fuel pump
MSD Pro Billet HEI distributor, MSD Wires, Accel shorty plugs
Hooker headers, small primaries, 3" collectors
3" dual exhaust w/x-pipe, no cats, mandrel bent
700R4 Trans, fully built, full manual valve body
JW Custom 4000 Stall 10" w/full size lockup plate.
4.56 Gears (Maybe too low but I changed to these because with the 3.73's I couldn't use overdrive unless I was really breaking the speed limit. My last motor had a large solid cam and it wouldn't cruise under 2000rpm)
Total timing is set to 39 degrees
27x11.50x15 Hoosiers
Car weighs 3390 lbs
Running race gas at the track

I have a fuel pressure gauge in the car and it reads at least 4 psi all the way to redline. I also have a wideband air/fuel meter and it reads 13.0 all the way up. Aside from the 1/2 shift, power really drops off at about 5800 rpm. With this setup I was really expecting to be shifting around 7k. There was no hesitation or missfire during the runs and I never lost traction. Someone suggested I might have too much gear and converter, but this thing drives great, even on the street. I was launching at about 2,000 rpm on the footbrake and it was flashing to 3400 or so. For a 4000 stall, this thing drives pretty tight. I did build this as a street car and would like to see it in the 11.50 range in the quarter mile. I don't think this should be a problem. Any ideas? One thought I've had is that maybe my wideband isn't reading correctly after all the lead I've ran through it. Any ideas anybody? Sorry for the long post, but I tried to be thorough.

Thanks!
Marcus

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