I recently built the engine in our 2001 Vette. The car is primarily a show car so I didn't go real crazy with it. It made 386 at the wheels and has ran 12.22 @ 113 on drag radials with the stock 3.15 gears. Here's the build:

Stock crank
Eagle 6.125" H-beams
Probe forged flat tops (.010" positive deck)
Mahle moly rings gapped at .022" and .023"
King bearings
SLP oil pump
COMP XER 281 232-234 / .595"-.598" 112 LSA
COMP 850 lifters
COMP double roller
Cometic .041" head gaskets
Ported 241s (310-220 @ .600")
Racetronix 42# injectors
Stock LS6 intake
Lingenfelter ported stock throttle body
COMP 7.35" pushrods
Scorpion 1.7 roller rockers
Taylor 8MM wires
AC Delco rapidfire 12s
OBX longtubes with cats
A.I.R. delete
K&N air intake
OBX "axle back"
CPT "Pro Race" 4L60E
Protorque 3200 stall 9.5" converter
Stock 3.15 gears
Full weight C5 coupe

The car runs and drives great. I was just expecting atleast 400 RWHP and an 11 second timeslip.

 

Assuming there are no mechanical issues, tune would be the obvious place to start for me.

Who tuned it? If not you, have you consulted them? If 386 didn't satisfy you I assume you would have at least given a funny look at the guy running the dyno? Even if the tune is spot on for the motor, you have the electronic transmission to tune as well.

 

Dyno numbers don't really matter but the 113 trap speed does seem a tad low. I'd be curious about the tune as well

 

The car was tuned by Horsepower Addicts, which is a very reputable shop in our area.

Frank

 

Post a pic of the dyno graph and the track timeslip. Your MPH is an 11.9 ET but lets get some pics first

 

 

Car is dead hooking and shift points are at 6500.

Frank

 

My personal opinion is that you are losing a lot in your 60 foot.

 

I had a yank 3500 in my car and pulled a 1.76 on a street tire leaving at idle. Ran the same time as you in the 1/8th in a bolt on Trans Am @88 mph.

 

Also looks like the car really flattens out at around 5500.

 

Yeah. The 60 sucks. The 3.15 gears aren't doing us any favors. Looking to go to a set of 3.90s.

Frank

 

That will defiantly help. Is this a daily driven car? I'd almost say that if you don't mind hurting a little of the city drivability, grab a bigger stall.

 

The converter is a 3200 stall Protorque which has the same stall characteristics as an SS4000 Yank. I own a transmission shop so I've driven a huge amount of cars with different converters.

The car is a show car that my wife and I built together to have fun with. We've won 4 trophies with it this season, and it scored 98 out of 100 points in concourse judging at Carlisle. She comes from the show car background and I've always been into drag racing. We built the Vette to be a little of both. We're definitely not looking to be the fastest thing out there, but I'd like to get it into the 11's, before I spray it..

 

RPMs makes HP..so why flat between 5500-6500? I am sure your tuner is reputable..and because of that they should be able to answer this for you. If it were a stick car, I would wonder if the clutch was slipping. Maybe you could apply that in an automatic sense.

Throwing stuff at the wall:

Valve float? Running out of air(intake or TB)? Spark? Cam accidentally advanced bringing everything down a bit RPM-wise?

You pick up 75 HP between 4500-5500. I would expect you to make similar gains in the next 1000RPM. That would put you where you thought you would be. Torque drops off quickly at the end and for that reason with no other changes I'd like to see how the car performs with about a 5900-6000RPM shift point.

Still, I'd call the tuner and have them explain the dyno sheet to you. Something is funky past 5500.

 

Looks like it was dyno'd with the converter locked?

I'd ditch the roller rockers and put stock rockers back on there. I'd also verify the pushrod length. They seem a tad short with the roller rockers unless you've milled a ton off the heads.

That 3200 stall isn't helping you. Similar driving characteristics doesn't mean it's as efficient uptop or that it has the same shift extension as a larger converter. Have you logged the slip on the top end to see how much power it may be eating? I don't know if it's a 258mm converter or one of those 278mm "stock like" converters?

Also, a 3.15 doesn't really have much to do with track times with a converter. Guys run 2.73s and 4500 stalls and do well at the track. The issue is the tall gear makes the car lug around on the street with a big stall, but a 3200 isn't a big stall.

Also, the headers/exhaust might be choking you out a bit. What's the primary size of the OBX headers? Collector size?

 

I think with that dyno your shift point should be 5800. youre losing all your torque at 6300

 

Headers are 1 3/4", but it still has dual cats. Exhaust is twin 2.5".

The converter is a 258MM billet front. We're not slipping at high RPMS. The tuner said it's one of the most efficient converters he's ever seen.

7.4" pushrods were too long. Both the block and heads were cut. I used an adjustable pushrod to find the right lenth.

Cam is installed dot to dot.

Frank

 

So the tuner liked the converter, but did he/she not comment on the flatlining up top? AFR looks ok but without knowing anything about the tune I am afraid we may be spinning our wheels...and apparently not fast enough.

I love throwing **** at the wall but to me, asking the tuner is your obvious next step.

 

Who ported the heads? Could be a poor port job?

Looks like possible valve float up top to me...very rough graph up there for smoothing 5. I bet it runs better with stock rockers.

I agree that gears probably aren't going to help you much.

 

Lloyd Eliiot did the heads. It's still pulling hard at 6500 at the track.

Frank