LT-4 383 Rebuild "LOTS of Pictures" by BlackHarleyMan

By diyauto
( 2 )

4 minute(s) of a 70 minute read

9-6-2008


Base tune has been installed, and Ed got four pulls in before the transformer across the street exploded and took out all of the power to the shop. Here's my baby after Ed installed the base tune and offers me a a ride around the block.

Click the image to open in full size.

She's not through the woods yet because it was discovered during dyno pulls 1-3 that she hesitates at ~5000 rpm as if she hits a rev-limiter. Between pulls number 2 and 3 we monitored the fuel pressure and discovered that my original fuel pressure was set at 50psi on the rail. Ed adjusted fuel pressure down to 46psi and during pull number 3 discovered that 1. Motor started hesitating again at 5000 rpm and 2. fuel pressure dropped during the pull from 46psi down to 30psi. This indicated that the stock fuel pump was not able to keep up with the demand of the motor. I brought the Racetronix's 255gph pump with me so Ed swapped out the fuel pumps and conducted pull number 4. Pull number 4 reviled that the fuel pressure was stable throughout the pull, with no loss of or drop of pressure at the rail. And that the motor responding like it hit a rev limiter moved from 5000 rpm up to 5800 rpm. Ed believes that they may a wire or connection problem in the ignition system. All of my components are new. The MSD Opti, MSD Wires, MSD Coil and even the ignition module. Due to the storm and loss of power with my car sitting on the dyno, we had no choice but to call it a day. Ed will continue to tune my car as well as Will's during the upcoming week and I should be all done by next weekend. The base pull indicated a torque value of ~322 rwtq, and fourth pull indicated 407 rwtq. The problem with this pulls is that he has yet to go above 5800rpm and the curves keep climbing. I failed to record the last two dyno pulls but here pull number 2, and with each pull the slope stayed the same, but moved up ~30 to 40 rwtq with each pull. I do know that Ed has a LONG way to go, because my air/fuel ratio is all over the map and he was busy trying to figure out my apparent miss at 5K before going any future with the accurate tune. Here's dyno pull number 2, you'll notice that the pull breaks up just around the 5K range and never goes above it.

Click the image to open in full size.

I guess I'm VERY excited about the END result and have been pleased that the motor is running so strong. According to Will and Ed both, there is ALOT left in this motor and as soon as he sorts it all out, she should be VERY strong. Ed also believes that the LT's don't make big numbers on his machine as compared to the LS based motors. He also stated that Rob (BlueWasp) has about the strongest LT-X based motors that have ever been on his dyno and his number was ~440rwhp. Either way, I'm looking for a VERY strong running motor that streetable and capable of smoking that C6 Z06 in my club!.......LOL

I'll update the status as I get it, and thanks again for checking it out. I also haven't noticed any cooling problems or any other issues other than a very small seep of oil from the AFR's and the stock composite covers. I am going to have to work this issue out further at a later date in order to have a 100% leak-free solution. Just know that the AFR's are going to require work to seal with stock valve covers!



Comments