Ok, I have been pulling my hair out with this thing. I can't figure for the life of me why I can't run better times. The best to date I have gotten is a 12.85 @ 107 (I have trapped 108 a few times). Maybe I am expecting too much, if I am please let me know. The truck is a 5.3 that weighs 4800 with me in it. I have everything in my sig, and the heads have been slightly milled as was suggested by TSP when I bought them (I told them I was runing a Maggie). I also hand finished the ports to get every little bit out of it(I didn't nick a seat or anything, I have ported numerous heads). I have had a problem with my wideband getting hot during a run. It has gotten hot to the point where it shuts off and flashes a code. My speed is fairly good, but my time is low. This I assumed was telling me that I was leaving OK, but running out of power on top(maybe I'm wrong). I had been thinking about it, and assumed my converters were clogged or melted. I punched out the cheapie high flow converters I had in hopes it would make a difference. It didn't feel like it helped much at all. I will take it to the track to make sure wed or Fri. I decided to do a quick compression check. I didn't do the back cylinders as I was running out of time today and they were a pain to get at. All cylinders were 125. That seemed low to me on a milled head 5.3 with 66k on it. What else can I check? I am running at about 11 AFR with 18 degrees of timing. I have also tried up to 11.4 AFR and up to 26 degrees with really no improvement to my times. Does anyone have any suggestions or am I just asking for too much?

 

Your ET so highly dependant on your 60ft. Your time sounds about right with a 4.8 with a blower and heads....the 80e isnt helping any. How much boost do you have with that pulley?

 

I am hitting 10 PSI. I have been debating getting a 2.6 pulley.

 

Your mph is decent at 107. What is your 60 ft? What's your axle ratio & tire diameter? Are you using slicks?

If I read correctly, your compression test shows 125 psi across the board. That's really really low. As an example, my 150,000 mile 5.3 (tested today while changing plugs) is 185-190 psi. My engine is 100% untouched(read: stock) except for the cam, pushrods, valve springs, and rocker arms. Those parts are all Crane, and all have 50,000 miles on them.

AFR needs to be leaner. At least push it to 11.5-11.7 or so. Timing depends on your fuel. On 90 octane, somewhere between 16-18 degrees is about all you'll get away with most likely. If you're using better gas, or spraying meth(NOT WW fluid....) then you may be able to go to 20, or low 20's. But you'd better be monitering EVERYTHING and adjust everything only a little bit at a time. Detonation is your enemy, and may be lurking right around the corner.

Drive fast & take chances. If you are always going to take the "safe" route on your setup, you will not max out your setup, and may not get the results you think you are looking for. A "maxed out" setup is exactly that. It is maxed out, it's on the ragged edge. It's 10 pounds of **** in a 5 pound bag..... haha!

I'll check back on this thread for your answers to my first paragraph. But if your compression is really only 125 psi across the board, your "foundation" of your build has problems.

 

Whats your 60' and 1/8 mile specs?

Thats a good MPH.

I was running a 12.8 @ 108 before i swapped my cam for a blower spec one.

My new cam gave me lots more bottom end to get this pig moving better.

Sounds like you are lacking on the first part of the track hence your low ET compared to your MPH.

Went to the track last week and ran a 12.3 at 110.80 full weight spinning 4x4 outta hole!

Im noy done yet, but just wanted to share with ya, dont get discouraged, you'll get there!

That comp. test does sound off , Take Rogers advice and let us know.

 

I'm with the others on this one, I'd like to know your 60' as well. Your mph seems right, so I don't think it's pulling timing on the big end.

 

I am running stock suspension, 3.73's, 275/55/20's. I set them at 27 PSI. The weird part with my 60' times is I usually run 1.91. I don't leave the line too hard, and I can pretty much lay into it when my truck leaves the line. Last week for some odd reason it ran a 1.69 60. I have no idea how I did it, and have only made 4 passes since then, but can't seem to replicate it. Same time and speed though. It was a 12.8 @ 107.

I thought the compression was low. After work today I am going to put some air to the cylinder and see if it is leaking anywhere. I got the cam from TSP when I bought the heads. They said it would work fine, and now I am wondering if I should have double checked my PTV clearance. Last year I broke a rocker arm. It was an obvious bad casting, and there have not been problems since. The one part that had me scratching my head is I had a bent pushrod. It wasn't the broken rocker, that one was straight. The next cylinder had a bent pushrod. The rest were straight. I am going to do a better compression check after work today. I never pulled the fuel relay, or unplugged the coils. I just kept bumping the starter until it turned over a few times. I just didn't have time to do it properly yesterday, but I thought it would be fairly accurate.

 

I recently did a compression test on my truck. Gauge was only showing 55psi. It hadn't been used in a while so I had to spray some WD-40 in the line. & checked it with my air compressor to make sure gauge match the compressor gauge.

 

I will try that. This is an old gauge too. It is an old KD tool that my father has had for years. I am wondering if my low comp might be due to the larger overlap in my cam. They were very consistant however, and I am going to do a proper check today, so I assume the #'s will be higher. The truck does make pretty good mid range torque though.

Tim, and my fastest 1/8 was 8.06 that was when i pulled the good 60' time.

 

My cam has a lot Of overlap. My numbers were still in the high 180's & some low 190's with the lowest one being 170 something.