MagikDraggin

These are the present mods on my '96 LT1

ZZ409 Cam 227/517
1.5 stamped steel roller rockers w/HD springs
52mm Throttle body
Heads reworked w/2.0 Int valves & 1.56 Ex valves
TB, Intake, Exhaust, all gasket matched & polished
K&N filter
TB bypass
160 Tstat
TPIS 1 5/8 Ceramic coated LT headers
Mini-cats, H-pipe, Corsa mufflers, 2 1/2" piping
2600 B&M hole-shot Torque Converter
3.54 Thick Richmond gears (in factory D36 case)
Taylor Spiro Plug wires
Adj fuel pump regulator, set @ 42# at idle
LT4 knock module

I just got back from D&M Corvette shop just outside of Chicago (real nice place btw) getting the vette dynoed and the results are 315 rwhp and 305 rwtq with an A/F ratio of 13.2 below 4k and 12.8 up to 6k, ending up with 12.7 at 6200rpm. Computer reprogrammed by BV Performance, also of the Chicago area.

This is with new A/C platinum plugs, new fuel filter, new 02 sensors.

What do I need to do in order to reach 350 rwhp N/A and around 330 rwtq (no spray, just motor)?

mackeyred96

I have almost the same mods as you and Cartek gave me 360 rwhp and I run 11.5 at 120.

FoolCrzy

You could try 1.6 Roller Rockers, to start.

bogus

Or 1.7s.

Either way, ditch the stamped steel pieces... they are icky-poo.

mackeyred96

I'm using the comp pro mag 1.5.

Timmy!

But what cam are you using? Or is that top secret?

Timmy!

Was this on a Dynojet dyno? The HP seems very low for your setup.

MagikDraggin

Yup! I only go to shops with Dynojet setups. I thought it seemed kind of low myself.

This is the third Dyno I've had on the engine in the last 9 months ( at Doug Rippey Motorsports in Minneapolis), (at Dynotech Engineering in Ft Wayne Indiana) and (at D&M Corvette near Chicago) and believe it or not, the last run (after the A/F ratio was adjusted) is the best to date.

What really tics me off, is that the best the car runs at the strip is hi 12's lo 13's, mostly lo 13's.....and I keep reading about all these guys with their "stock" or "almost stock" LT1's running as good if not better!

Timmy!

First thing I would do then is throw a good set of Roller Rockers on there, Comp Cams Pro Mags 1.5 or 1.6's. If that doesn't boost your HP, then I would start pointing to your heads because with the bigger valves and porting you should definitely be making more HP than you are! I guess it could be that your heads can't flow enough for the ZZ409 cam too.

Can you post the picture of the dyno chart?

MagikDraggin

I appreciate that "icky" and "FoolCrzy", but more than one perf shop has told me that for HP to bucks ratio, the 1/6's aren't worth the effort and that for this cam, the 1.5's are a better match.

I originally had a set of aluminum "pro-type" rockers and snapped one of the roller tips off at 4500 rpm and damned near shelled out a piston in the process.

That's why I decided to go with the steel ones as replacements.

I was told the most "realistic" gain I could expect out of 1/6 rockers was 4-5 hp max.

MagikDraggin

Oh yeah great numbers and times....but look at your final drive gears and that 4400 stall converter. I'm sure that makes up for a lot of the difference in our track times......don't know about the HP though.

I want this beast to go like hell when I punch it, but I also like to be able to drive it over to Wally World once in a while too....(driveablilty issues with the wifey).

HammerDown

I wouldn't even worry about that. As far as I know there's only one person on this forum that has gotten into the 12s with a stock LT1.

DSSKing

What rear end gear do you have? My L98 was an absolute stone with a 3.07 gear. Changed to a 3.54 and it really woke up the car.... Could play a factor. If the engine produces 315 RWP, it should easily run 12's..... low 12's..... but if it can't launch properly, then there's your problem.....

Just my two cents.

Nathan Plemons

What are the complete specs on the cam?

Do you have flow numbers for your heads?

I picked up 14 horsepower when I went with 1.7's over 1.6's. Certainly not a bad horsepower / dollar gain.

MagikDraggin

What sort of heads would you recommend for the setup I have?

Here is the dyno printout from yesterday.

Nathan Plemons

Pure and simple you're running out of air. Rockers would help this some but ultimately you need some really good cylinder heads.

Call up my friend Brent @ Total Engine Airflow and tell him I sent you. Tell him that you're looking for a set of heads and some 1.6 or 1.7 rockers. He can hook you up with the whole package, CNC ported heads 7/16 studs and some kick *** springs and retainers. I guarantee it'll be over 350 rwhp.

Here's my dyno graph with stock heads, notice how the power starts to fall off at 4000 RPM's, look familiar like your graph above?



Here's my dy no graph with the TEA heads, power still drops off in the upper RPM, it's unavoidable. Just notice that it makes more peak torque, holds that peak longer, and then drops off more slowly.



Here's the exact same setup with 1.7 rockers, it's basically the exact same graph, just shifted upwards by 11 pounds of torque across the board.



There is no reason why you can't see these same gains. BTW, an electric water pump will free up 7-10 straight to the wheels as well.

MagikDraggin

I've following your progress with the different rockers. I am only relating what those guys told me.

Here is the printout on the cam specs. I no longer have the flow numbers. The heads are LT1's bored for LT4 valves w/ a 3 angle grind and the chambers were polished. Nothing else done that I know of.

MagikDraggin

And I'm willing to be that would be the Mojo Man? I heard him run at Bowling green a couple years back. Strong running LT1, that's for sure.

Timmy!

It really has to be your heads. Something's not right there because with that big of a cam you should be making some good numbers! Are you sure they gave you the heads that they said they did?

MagikDraggin

I appreciate ALL two cent's worth here. The rear gears are 3.54 Richmond HD (thick) gears. I originally had 2.59's in it. 30mpg was great, but also really dog-earred off the line.

Now I get 24 mph and it goes a lot quicker, but needless to say, I am not at all happy with the power figures.

As far as the launch, I get very little wheel spin at the track. It bites right after I punch it. On street tires no less. I feel this indicates some sort of problem as well, but I have no idea what it may be.

So far the general concensus is the heads are restricting the air flow. I'll look into that first.