toyin

I just got this car 3/3 and on the drive home the check engine light came on When I got home I took to a local tuner and had him take a look at it. The codes were for knock sensors so we looked at the harness and the harness was cut so we fixed that and threw it on the dyno (dynojet)! The car only made 308HP at first than making some changes on the tune the best we made was 417HP 473TQ. The car ran strong all the way to 5K and then would fall on its face HARD. At this point I’m not sure what to think I know the previous owner made 501HP and 516TQ(mustang dyno) in Denver (I’m 2k feet lower than that). The only thing that comes to mind is maybe were missing something in the tune (I really don't think so) or maybe the valves are floating? Everything on the tune looks good until 5k. I have a copy of the graph if you guys wouldn't mind looking at it. Below is the list of mods that have been done to the car. The HP numbers were using water/meth but the previous own didn't have it installed yet when he made 500HP.

Any idea's or checks you guys could think of? Were kind of lost and could use some direction any and all help is very much appreciated
Mods are as follows:
Dragon Pro Street M1000 intercooled supercharger kit using the Whipple 3.3L supercharger
Dragon Pro Street DX1 cam
Ported GM 317 casting heads with Manley valves, dual springs & titanium retainers
CTS-VR lifters
Dragon Pro Street ported oil pump
Upgraded timing set
Ceramic coated American Racing Headers
B&M short throw shifter
160 deg thermostat

Thanks
Austin

toyin

Sorry guys i can't get the file to upload into a PDF or word form if someone would i could email it or text them the file

SPRAYED 01

iTrader: (22)

Check compression, spark plug wires,plugs, lifter preload,springs. I could go on for a while. You need to look at the very basics first could even be a damaged exhaust causing a restriction.

toyin

The cats weren't bad but while i had them off i cleared them out, the rest of the exhaust was in question so before welding it back up we ran did a dyno pull and that was the best numbers we got. Ill definitly look at the spark plug wires and plugs. The lifter preload and springs will have to wait till this weekend.

Keep the tips and checks coming guys it's very much appreciated!

itsslow98

iTrader: (18)

I bet the motor is hurt. I would definetly do a compression and leak down test. And if you beat on it on the way home that likely did it due to the huge drop in elevation.

toyin

One thing i can honestly say is i didnt beat on the car it never saw above 3 grand till it was on the dyno. Im not the type of person to by a car like this and beat on it till i know it's sounds. Im not in a the market for a new engine. There is no strange engine noises it just seems weird that the car performs fine, pulls hard and sounds healthy until 5k. Over the weekend im going to check the above mentioned items and pull the valve covers and spark plugs so i can borescope all eight banks and verify no scuffing or scoring on the cylinders.

GmanSS

iTrader: (3)

Honestly your probably looking at belt slip or valve float. Do a good inspection of the drive belt for dusting or glazing. My procharged camaro's power was falling off over 5K and my belt was glazed over. New belt tightened properly and it screamed till redline.

toyin

I did have a belt slipping issue pretty bad when i first go the car due to a worn out tenstioner. I can looked over the belt it's in good shape, i can look over the pulley's to see what they look like. I put on a new Katech manual tensioner that im alot happier with.

punishmentcycle

iTrader: (6)

Any updates?

Andy0x1

Appears to be an old issue, did you ever figure out what it was?

I installed CTS-VR lifters in an L67 engine, with COMP 105 # springs. Had horrible valve float at 5k. I changed to 130 # springs, and now it's good to ~6k Not sure why the CTS-VR lifters are so horrible for valve float, they only weigh like 4% more than the stock lifters which did close to 7k on the 105 #ers

I also have a cammed V which is how I came across this thread... looking to add some boost. Who sells the whipple kit for these cars?