348 HP #s, need help BAD!!
Thread Starter
Racer
Joined: Nov 2006
Posts: 378
Likes: 0
From: Southside Alabama
348 HP #s, need help BAD!!
Need some help, just wanted to see what kind of numbers people are getting with their 348. Had one built but when it went to the dyno, the numbers were really low (in my opinion). Seem like most people are in the 450-500 range. This motor only made 402 rwhp. Below are the specs from the build, just trying to get some opinions and maybe a clue as to why the motor just isn't making the HP. Oh one more thing, we did find out the builder made a mistake with one of the pistions. They installed one pistion which was 0.010 smaller than the others. Thats been taken care of.
Mahle Forged Pistons
Callies Compstar Rods
Calico Coated Clevite Bearings
ARP main studs
ARP head bolts
FAST 90 intake manifold
230/232 x 112 cam
AFR dual springs w/ Ti retainers
Manley hardened pushrods
Stock GM LS1 block
Stock crank
11.49.1 compression ratio
AFR 205 heads
stainless steel rings
this in the NA set up and then it has nitrous but we've yet to spray since we've had these problems and didn't want to damage anything.
Mahle Forged Pistons
Callies Compstar Rods
Calico Coated Clevite Bearings
ARP main studs
ARP head bolts
FAST 90 intake manifold
230/232 x 112 cam
AFR dual springs w/ Ti retainers
Manley hardened pushrods
Stock GM LS1 block
Stock crank
11.49.1 compression ratio
AFR 205 heads
stainless steel rings
this in the NA set up and then it has nitrous but we've yet to spray since we've had these problems and didn't want to damage anything.
Drifting
Joined: Sep 2006
Posts: 1,757
Likes: 13
From: Stillman Valley Illinois
Actually that seems about right, maybe a bit low, but not much. How did you measure compression? what are the lift specs of the cam? What TB ar eyou running? Any additional head work? Whose headers? cats or catless? etc, etc, etc
Safety Car
Joined: Sep 2003
Posts: 3,558
Likes: 2
From: Cape Coral FL
A couple of things come to mind. Have you done a compression check, and a leakdown? The rings may not be sealing fully. Also, what about exhaust? Are you running headers? What kind? what kind of mufflers? A good port job on the FAST 90 could net ~ 8-10 more. What kind of trans? What gears? What was your AFR, timing, etc. Have you checked cam phase? What does the dyno graph look like? You may be getting some float. How about spark knock?
Thread Starter
Racer
Joined: Nov 2006
Posts: 378
Likes: 0
From: Southside Alabama
the compression test was done by proline. exhaust is kooks long tubes, x pipe and z06 ti exhaust. air intake is vararam, 3.73 gears. AFR was 12, not much timing was added and no knock. I'll post pics of the dyno run. keep in mind the run was with a piston which was 0.010 too small. Since then the new piston has been replaced.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Racer
Joined: Nov 2006
Posts: 378
Likes: 0
From: Southside Alabama
the motor is from GA, Proline built the motor but its being tuned here in AL by Speedsouth (very trustworthy). I'm just wondering if the motor got the wrong part or if something is wrong internal
Thread Starter
Racer
Joined: Nov 2006
Posts: 378
Likes: 0
From: Southside Alabama
that was my old car, it was sold about two years ago. This motor was built and it too is in a 2002. The old car had air intake, LG long tubes, x-pipe, no cats, slp loudmouth, thermostat, and custom tune very simialr to the set up on the new 2002. The old set up made 346 rwph. Comparing both set ups, its like comparing apples to oranges when it comes to money (about three times as much; not including install). Seems like the numbers on the built motor should be higher. Since the motor made 472 rwph orginally. It was taken out of a road course car but only had made a few passes.
Le Mans Master
Joined: Feb 2007
Posts: 9,296
Likes: 1,531
From: Oviedo Florida
2024 C5 of the Year Finalist - Modified
2024 C2 of the Year Finalist - Modified
2023 C2 of the Year Finalist - Modified
2021 C2 of the Year Finalist - Modified
2016 C5 of Year Finalist
pleased with your engine after a few passes at the track.
Safety Car
Joined: Sep 2003
Posts: 3,558
Likes: 2
From: Cape Coral FL
What kind of dyno was that? If it was a Mustang, they use a different method of obtaining power levels than a DynoJet and the numbers are about 10% lower. That could be where your power is.
If the piston issue was fixed before these runs I would do a leakdown, not just a compression test. If all the above has been verified I would look at the cam phase. I can't see the grid numbers where the torque peaks. It looks low. Just my $.02
I would think with that setup you should be seeing at least 440rwhp/400 rwtq.
If the piston issue was fixed before these runs I would do a leakdown, not just a compression test. If all the above has been verified I would look at the cam phase. I can't see the grid numbers where the torque peaks. It looks low. Just my $.02
I would think with that setup you should be seeing at least 440rwhp/400 rwtq.
