ill start with what i have, its a 355, ross racing -6cc forged pistons, eagle rods, ported heads, comp xe230/236, comp 1.6 pro mags, crane 10308 springs good to .600 lift, hardened pushrods, msd coil, taylor wires, ngk tr55's, pcm4less tuning to start with, and ive been playing with it with lt1_edit...

now, right after i built my motor, i took it to the dyno, and it made only 313 rwhp at 5300rpm, and before it got to 5400, it dropped over 90rwhp. computer was pulling 5 degrees of timing starting at 5300. A/F was pretty close, no lower than 11.5, and no higher than like 13.5...At the dyno, i programed out up to 7 degrees of timing...started at 35 total at 5000rpm, and i went as low as 28, and knock sensor was still picking up knock...so im pretty sure its false knock...So i replaced the opti, with a dynaspark...problem still there. i programed out the knock sensor, helped, but still losing power. then i was told it was my lifters, so i just put in a set of comp r's, and its still losing power, every time, through that rpm range. the power loss isnt as bad anymore with the comp r's, but its still there...i dont know what else to do, both o2's are high 800 MV's, still pulling timing, and even when i program it out, it still loses power...im about to part out this car and put it back to stock, its driving my nuts

 

Lack of fuel is unlikely, given that it was so rich and it is probably not rich enough to make the power drop that much. Ignition is unliklely, but I would still change the plugs and wires before doing anything else. That leaves a mechanical problem such as valve timing being (cam ground or installed wrong), bad valve spring(s), valves maladjusted. I'd think about those things. I also wonder why it's so rich. Are there any intake restrictions? What is the MAP at WOT? Though I doubt fuel, what is the FP at WOT? Bad injector(s)?

Just some things to get you started.

Rich

 

Still has stock 48mm TB, thats the only intake restriction, map at WOT was a little over 90, highest i saw was 95, i dont know fuel pressure, its set at 43.5 and my injectors are running in the 75% duty cycle range at WOT, they are 28#/hr injectors. Would valves maladjusted really cause this type of power loss? ive adjusted them and readjusted them many times, all different ways, and i still see the power loss. One of them started taping today, which sucks because the comp r's went in last friday...i hope one of them didnt go bad. my nuts are locking, and i run a stud girdle, so there is no way one cam out of adjustment

 

Make sure your air filter isn't collapsing.

 

When you get a motor that "noses over" at a certain RPM it's usually either outrunning the fuel supply, has an electrical (ignition) gremlin or is floating the valves.

It sounds like you've done some work work on ruling out the first 2, but the valve springs concern me. I looked up those springs on Crane's website but they don't give any real information about them. Seat pressure, open pressure, installed height, etc.

I DID notice, however, that they are supplied with their own retainers and a variety of shims. Which would lead me to beleive that they require some setup to achieve correct installed height and probably only work with the retainers that Crane supplies. I you just drop them in the stock pockets and/or play mix-n-match with the retainers you're probably going to have a problem. Not sure who setup your heads VERY easy to make a mistake when setting up valve springs, especially if the shop is not familiar with your particular setup or choice of parts.

I won't even mention the number of times I've had less-than-reputable shops throw stock valve springs back in the heads with a 1/16" shim under them and said they were aftermarket high performance "matched" valve springs. There's a reason I own a valve spring tester, height mic and set up all my own valvetrains.

 

the springs are good to .600lift, and have 150lbs on seat (150 or 140, i cant remember, the cam calls for 130 though) the heads were set up by a very reputable shop that only does cylinder head work, they used crane retainers and all the stuff from crane, i know they used it because i brought it all to them, and inspected them once they were assembled, and its all the stuff i brought them. I just re-lashed the valves, and took another datamaster scan...still showin 5 degrees of retard right at 5300 rpm...if you want, i can send u the datamaster file, you can check it out and tell me what you think, im at a complete loss here

 

talk to Fastbird on here, he may be able to help you with trouble shooting the comp r's

 

I would tend to go with springs also. I ran a set of those springs with 1.5 rockers and a 218/224 CXE cam and at 6,000 power nose dived so hard I thought the motor was hurt! CXE cams are hard on springs and you need a good set to live with a CXE cam.

BTW I would not push any higher then 12.5 on a dyno. I have found they run a hair leaner when you get them on the street then on the dyno.

Good luck man you have some good info in this thread!

 

okay, its gets weirder, the other day i was out driving, and no power loss, anywhere...it pulled like a bat out of hell all the way to 6800 ....last night, was missing again at 5300 ...i dont get it ...the only thing that changed was the weather...it was pretty cold out when it wasnt missing anymore like 40 degrees

 

and also, if its springs causing this power loss, why would it show full retard no matter where i have the timing set? would something make noise cause of incorrect springs?

 

fill it up with a tank of high octane gas (100+) and see if the problem still persists in the non-cold weather

 

its deffinatly false knock, ive taken total advance all the way to 28 degress and i still see 5 degrees of retard

 

If you got a strong 6800 pull out of it then it's not the springs. If the valvetrain is not working right it will nose-dive every single time at the same RPM without exception. Ditto a mechanical engine problem like rings, valves, etc. If you're SURE you have good fuel pressure at WOT in the upper RPMs at all times without exception then you are down to one thing and one thing only: something electronic.

Given that your engine is fuel injected and EVERYTHING is electronic you need someone WAY smarter than I am to help you diagnose it.

 

I had a similar issue with my supercharged car and it was the air filter collapsing. Just something to look at.

 

check your MAF, maybe borrow one from someone see if that makes a difference. i just had the same issue