well the saga of trying to get the 383 to run good continues. this is the 2nd time ive taken it to the track, I THOUGHT it was running alot better... guess I was wrong. I disconnected the MAP sensor which seemed to make a world of difference and I disconnected the drivers side O2 sensor since theres a major leak in the drivers side header causing that whole bank to run extremely rich. now its fine without the O2 sensor unplugged. yeah I know its probably a bad thing to run without sensors plugged in and im asking for punishment. the car also pulls 8 degrees of knock retard at WOT. I shoulda went with a carbuerator
I made a total of 11 runs, I screwed up some runs so I wont even put them in here. (all bests of each part are in bold)
Run 1
R/T .321
60' 2.040
330' 5.671
1/8 8.643
MPH 82.54
1000' 11.217
1/4 13.390
MPH 103.94

Run 2
R/T .333
60' 1.946
330' 5.515
1/8 8.471
MPH 82.89
1000' 11.038
1/4 13.201
MPH 104.57

Run 3
R/T .389
60' 1.916
330' 5.522
1/8 8.497
MPH 84.30
1000' 11.080
1/4 13.26
MPH 103.55

Run 5
R/T .300
60' 1.841
330' 5.510
1/8 8.531
MPH 81.32
1000' 11.191
1/4 13.441
MPH 100.46

Run 7
R/T .257
60' 1.847
330' 5.467
1/8 8.465
MPH 81.70
1000' 11.072
1/4 13.278
MPH 102.31

Run 9
R/T .103
60' 1.856
330' 5.514
1/8 8.559
MPH 80.52
1000' 11.210
1/4 13.454

Run 10
R/T .254
60' 1.785
330' 5.438
1/8 8.489
MPH 80.25
1000' 11.150
1/4 13.406
MPH 99.75

Run 11
R/T .184
60' 1.839
330' 5.489
1/8 8.559
MPH 79.97
1000' 11.231
1/4 13.491
MPH 99.91


so there you have it. I really wanted a 12.99999 or better but didnt quite make it. The car comes out of the hole super strong. I was thrilled when I pulled a 1.7x 60' time. then the car falls flat on its face. it has no pull on the top end at all. its freakin odd. I seriously need to find my cars top end. I dont know where I can gain 15 mph. theres no reason the car shouldnt trap between 115-120. I dug up my old bolton best time... IM ONLY RUNNING SLIGHTLY FASTER NOW THAN WHEN I HAD JUST BOLTONS!!!

Run BEST BOLT-ON RUN
R/T .439
60' 2.100
330' 5.857
1/8 8.960
MPH 79.15
1000' 11.623
1/4 13.842
MPH 101.94

what is going on here!? I tested fuel pressure up to 6200 rpm and it was at 43 psi. my knock retard as said before just sits at 8 degrees. I cant have my MAP sensor plugged in due to my low vacuum (6 inches at idle) and it going crazy. my O2 sensor needs to remain unplugged or it dumps dangerous amounts of fuel into the drivers side.
what can I do to gain those 15 mph? I just dont think that getting rid of the knock retard, fixing some exhaust leaks, and a dyno tune will get me 15 mph. I think im gonna be sick


on a happier note, I only lost once throughout the whole night to an LS1 camaro that was pulling 1.7ish 60' times, trapping 110-111 and running bottom 12s. we were neck and neck to the 60 foot mark then he kinda left me in the dust.

 

Something is seriously wrong. You should have more than 6inches of vaccum at idle. If you are running an LE3 cam i'm pretty sure Bret designs them to be streetable. I'd say you need to find out why the vaccum is so low and fix that. You really just need to go through and fix all of your obvious problems. You need to get rid of the Knock retard because thats killing you too.

 

we CAN NOT find a vacuum leak. we even loosened the intake valves, covered the tb holes and blew air into the intake. it held pressure very well slowly bleeding out the tb. I have been going through and fixing/testing stuff out for a month now. some of the things I have to wait and dont have a choice when they get done. I have no idea what is wrong!

 

That cam in a 383 should be at least 14inHG. My guess is the cam was installed wrong or the TC is off a tooth or maybe as simple as you have too much preload on the lifters.


Also, never unplug the MAP sensor!

 

Why would you disconnect the MAP sensor? That's like poking both the PCM's eyes out????????? It needs MAP for ignition timing, and a few other items. No wonder it has no power. If you were getting a code for high MAP, that's because of the fact you have no vacuum at idle, not because the MAP sensor is faulty. It still would have functioned at WOT.

You need to solve the vacuum problem. I wouldn't keep pushing it down the track hoping it suddenly finds more power..... something is seriously screwed up and you need to find out what it is.

 

my cam has a pretty long duration and alot of overlap, I seriously doubt it would see 14 inches at idle. my idle is a little on the low side at roughly 950-1000. bret said this cam was intended to be more of a race cam than a street cam.
we checked the cam several times, its installed properly. the timing chain is NOT off a tooth. we checked and re-adjusted the valves three times. they all have the proper amount of preload for a comp R lifter. mechanically there shouldnt be anything wrong. I'll plug the MAP sensor back in and fix the knock retard.
my worry before I got the engine together was that I wouldn't have all the supporting mods that lloyd suggested. well now I have everything except LT headers (I have macs & a high flow cat) and an electric water pump which I dont want. Im not sure how much these would be holding me back.

 

I'd still think you should have more than 6in of vaccum. I'd find out what most people have with the LE3 cam. I could be wrong but like i said i'd still think this cam was made to be streetable, and it should be even more so in a 383.

 

What does Bret say about all this? He would know how the cam should perform. I can't believe that 6" of vacuum at idle is what its supposed to be. I have always disliked trying to diagnose anything over the internet, but you know that you really have to have the basics covered before you can make any progress. Fix the header leak and plug back in that O2 sensor. Hook up the MAP, too. What kind of tune do you have and who did it? Seems like once you get the basics worked out you should get to a dyno or a good tuner with a lap top and see whats going on in there.

I would not flog it a the track anymore until I knew what was going on.

--Alan

 

Hell a 260ish on a 112 cam has 10" so yours should have more.
My advise is to get the "R" out and put in stock lifters they will do your job nicely and check the intake gasket while ya have it off.