Jimmy P

iTrader: (177)

Who is doing the dyno tuning for you?

mattster03

iTrader: (22)

As you mentioned, it's a little hard to make out the numbers... but it appears your HP curve is peaking at 6,000 rpm. what are the full specs on your cam? I need to know LSA and if there's any advance ground in. Take a look at other 402 H/C results and note where they are peaking... usually closer to 6,500 rpm or higher.

Forced_Induction

Corvette Center in CT are tuning it.

http://texas-speed.com/shop/item.asp?itemid=846

That's my cam. I'm using 1.7:1 rockers though which brings lift down to .614

slvrbackls1

iTrader: (2)

I still think your using the wrong pushrods if your head is decked. My 408 put down those exact same numbers at first then i switched to the shorter and correct pushrods and hp went to 480 through catback and then to 500 with cutouts open.

Forced_Induction

That's what I've been thinking. That's gonna be the next thing ill look into.

redtan

iTrader: (5)

Was this on the same cam or a different one?

Forced_Induction

Smaller cam, sorry forgot to mention that.

Slowhawk

iTrader: (12)

Was the motor broken in and seated right?I've seen gas washed rings lose 30hp.

What is the inlet design? I've tuned a few RX7's with LS motors and seen some restrictive intake and exhaust bends that kill power.

Forced_Induction

I had the motor tuned after assembly for break-in, rev limit was set to 4k and then I put 1k street miles on it.

Intake is an Airaid C6 Corvette LS2 CAI with 4" piping with a huge filter in front of my radiator

Forced_Induction

Here's the graph:

jimbob

iTrader: (4)

STD corrected also. So, 445 or so SAE. That's way low. For a refernce a cam I specked with way less duration for 402 with 10.8 comp and 5.3 stage II's from TSP. Did 460 unlocked (big Yank) and 9 inch. Full weight the car ran 10.9 it's first time out in 2500 DA (summer). So yeah, you should be 500 easy with those heads and cam...

The non ported 78mm Fast, peaked at 6300 rpm. And only down 15 rwhp at 7200rpm.

Patrick G

iTrader: (14)

Looks like it's down 1 cylinder (especially since the dyno numbers are STD). A healthy engine should make close to its cubic inch displacement in torque at 3000 rpm. This 402 only makes about 370 lb ft of torque at 3000 where it should make closer to 400-410 rwtq.

Slowhawk

iTrader: (12)

Really? For break in here we start the car on the basic tune and hit our load dyno ASAP.Car is under a pretty good load right away then WOT pulls to atleast 6000rpm. Cooled down then doing WOT pulls/tuning. Always get a good ring seal this way.

Either way,they are correct. The corrected #'s we ussually go by are 10-15hp less. I suppose the tune could be off but I'd probly guess not firing 1 cylinder. Hard to say not seeing the car.

SSPerformance

iTrader: (76)

Its way down on power have them do a leak down test and see were u stand

Sprayed1998

iTrader: (10)

Pull valvecovers

odarabla

iTrader: (1)

This is so not true!! I had the Harland sharps on my H/C/I stock bottom end LS1 and use to spin it to 7200rpm at the track all the time (rev limiter was set at 7400rpm) and never had any valve float issues. My car made 447rwhp and 403torque through a stall auto and a strange 12bolt and ran a best of 10.90@123mph. They maybe heavy on the tip but if properly set up they shouldn't cause any valve float..
After my LS2 402ci is finished I plan on using them again on the new motor..

Funny how some people hate them and others praise them..

Patrick G

iTrader: (14)

Were you running Trick Flow heads with their standard dual valve springs? If not, then you can't compare results. The TFS heads have heavy valves. The HS rockers are heavy at the tip. The TFS springs are marginal for this combo. Swapping to stock or Yella Terra rockers normally cures the valve control issues.

nocooler

iTrader: (5)

Pull the spiral flow off - they are fine for duals but become restrictive on single setups.

odarabla

iTrader: (1)

No I upgraded the valve springs per Futrals request and yes I have the TFS 215cnc heads. But this is another reason I said you shouldn't have an issues when properly setup. I am ditching the TFS valves for bigger lighter weight valves for the new build. At the time I didn't know people were having issues with the HS rockers because of the weight and just went with what Allan Futral wanted me to use.

03EBZ06

Just a few ideas:

23 deg spark looks fine, but that cam I question. Those heads eat up airflow at low lift and work well w/aggressive ramps, LSL, XER. Do you have the 0.2 numbers on that cam?

cranking compression check and leakdown. My similiar equiped and IDIOT built 402 (0.0010+ clearanced piston/wall) was 215psi. It was checked w/both a 236/240-112+0 and a 247/255-113+2. Both came out about the same. I would expect yours to be higher. The 112 Had 20rwtq over the other. The 113 got it on top,.

What is the eng vacuum at WOT. If you are at or near sea level, you should not be seeing 100kpa at WOT. If you do, your engine's airflow is stalled. At 6-7000ft, expect around 85kpa. W/cams about I was around 97kpa @ sea level.

smoke the intake check for leaks.

check the valve springs visually. that kind of power loss is usually something significant.

engine tolerances: piston/wall in particular. That cam has 3 degrees ground in advance. If you advanced the crank gear from 0, you are going to be way off. Make sure the crank gear is at 0 or retarded IMHO.

hope this helps.