So here's the story I dyno'd my car today(mod list below)Was pulling some good numbers until 5600rpm when the car dropped power dramatically!!I told the guy to run it out to 6000rpm from 6k to 5600 (only 400 rpm!)the car dropped 90rwhp!! How is this possible?Valve float?By the way the car made 345rwhp with a hotcam only!!Now it has custom grind comp with stg 1 stock ported heads.Today It only made 350rwhp My A/F was 11.8 -12.2 the 1st run 2nd run was 12.0-13.4 wierd difference.Pulled 4 deg knock retard the 1st run,2nd run pulled 12 deg.Injector duty cycle was 100%.I know it needs injectors but They wouldnt have made the car die like that it never leaned out that bad!!And it needs a tune.But still not a reason to lose 90rwhp in 400rpm.One concern i do have is for some reason I have RR that wont seat on the spring directly it kinda angles towards the side,Very little but still it does.Any thoughts would be a great deal of help,Thanx!

Mods:Its a 96 LT1 T/A 6Spd
224/238 Comp Cams Custom Grind
Stock Ported Heads stg 1
Comp Cams 987's with about 20k miles
Comp Cams 1.6 NSA Pro mags
Full Bolt-ons
Delteq
Stock injectors
Walbro 255 hi pressure

 

Post the dyno graph. What guideplates/pushrods do you have in there.

Also, the rocker does sweep across the tip of the valve during motion, so long as it isnt overly opposed to either side (at least 90% of the tip should always be on the valve) then your okay. Bent pushrods or bad guideplates can cause it to be too far over.

 

Sorry about that I have comp hardened push rods and comp guideplates unfortunatley I dont have a scanner at my house so I cant post the dyno n e time soon ,maybe towards the end of the week.

 

Comp guideplates are not correct for the LT1 engine. They will cause the pushrod to rub against the side of the guideplate.

The only ones that I know work are the GM guideplates, or adjustable ones. Shoebox has a comparison showing the GM guideplates to the comp guideplates. The comp guideplates do not center the rocker tip over the valve stem.

I'm not sure this is causing most of your problem, but it could contribute to the knock retard if it's causing excess noise that your knock sensor is picking up.

Dan

 

I was lost 30-40rwhp above 5700 and it turned out to be a bad coil for me...

 

Thanx for the replies guys,ill take the ideas into consideration.I think I may know what is causing it, I have about 40k miles on the 987's,probably to many miles for a performance spring,the heads were on my buddies car b4 mine and they had to withstand about 460rwhp on the kit so yeah I think they may be giving up high in the powerband.If those arent it then Its prolly the RR's sliding off the spring at high rpm's.I dont know how to post the dyno graph I have it burned on a CD if it anyone can help me to do that,it be appreciated,Thanx!

 

If it's not the fuel then it is probably the spark.