Low Dyno.. What's Wrong?
Thread Starter
TECH Apprentice
Joined: Jun 2007
Posts: 362
Likes: 2
Low Dyno.. What's Wrong? Ok, so the crate motor was supposed to make 620 hp/tq crank...
Block
4 Bolt Main .060 over block
Two piece rear seal, drivers side dipstick
Square and parallel decked
Align honed main bearing bore
Cylinders honed on computer controlled machine to within .0002
straightness and roundness
Cylinders are sonic tested for thickness
Rotating Assembly:
New SCAT forged steel crankshaft internally balanced
New SCAT 4340 forged H-beam connecting rods
150,000 psi rod bolts
Probe forged flat top pistons
Hastings moly rings
Rotating assembly balanced to within 2 grams
Melling high volume oil pump
Hydraulic roller cam
Jesel shaft rocker system
Cylinder Heads:
AFR aluminum rectangular port cylinder heads
305cc runners and 119cc chambers
1.509 dia. Valve springs w/ damper Hardened retainers & keepers
2.25 swirl polished intake valves
1.88 swirl polished exhaust valves
Comp cams hardened push rods
Jessel rocker arm system
Edelbrock performer RPM airgap intake manifold
10.0 to 1 compression
Milodon cad plated oil pan
Brass freeze plugs
Professional Products harmonic balancer
TRANS is a Th400 with 2300 Holeshot converter
REAR is a 12 bolt with 3:08s
3rd gear at 6000 RPMs was 139.1 mph, so I would figure it's about 8% slippage on the converter. I plan to have an FTI custom built, but could this converter really be the reason for me being so low on power?
All input welcome
Block
4 Bolt Main .060 over block
Two piece rear seal, drivers side dipstick
Square and parallel decked
Align honed main bearing bore
Cylinders honed on computer controlled machine to within .0002
straightness and roundness
Cylinders are sonic tested for thickness
Rotating Assembly:
New SCAT forged steel crankshaft internally balanced
New SCAT 4340 forged H-beam connecting rods
150,000 psi rod bolts
Probe forged flat top pistons
Hastings moly rings
Rotating assembly balanced to within 2 grams
Melling high volume oil pump
Hydraulic roller cam
Jesel shaft rocker system
Cylinder Heads:
AFR aluminum rectangular port cylinder heads
305cc runners and 119cc chambers
1.509 dia. Valve springs w/ damper Hardened retainers & keepers
2.25 swirl polished intake valves
1.88 swirl polished exhaust valves
Comp cams hardened push rods
Jessel rocker arm system
Edelbrock performer RPM airgap intake manifold
10.0 to 1 compression
Milodon cad plated oil pan
Brass freeze plugs
Professional Products harmonic balancer
TRANS is a Th400 with 2300 Holeshot converter
REAR is a 12 bolt with 3:08s
3rd gear at 6000 RPMs was 139.1 mph, so I would figure it's about 8% slippage on the converter. I plan to have an FTI custom built, but could this converter really be the reason for me being so low on power?
All input welcome
Last edited by CamaroKidZ28; Feb 27, 2010 at 05:15 PM.
Man, you need to know one thing, a automatic can give some WAY off readings, i have seen cars make 450 RWHP out of a big block but still nail down low tens to the wall, meaning the readings were fals, only use the dyno for maximum tuning purpose and not for the actual power read out, use a calculator and the track to get the estimate with your MPH and race weight, ti is WAY more accurate for me.
-Z
-Z
Thread Starter
TECH Apprentice
Joined: Jun 2007
Posts: 362
Likes: 2
Man, you need to know one thing, a automatic can give some WAY off readings, i have seen cars make 450 RWHP out of a big block but still nail down low tens to the wall, meaning the readings were fals, only use the dyno for maximum tuning purpose and not for the actual power read out, use a calculator and the track to get the estimate with your MPH and race weight, ti is WAY more accurate for me.
-Z
-Z
Thread Starter
TECH Apprentice
Joined: Jun 2007
Posts: 362
Likes: 2
two things stand out to me. the first is the flat top pistons, flat top pistons and open chamber heads at 119cc usually result in low compression. i would think it needs a small dome to achieve 10:1. second is the rpm i would think an AFR headed big block with a roller cam would turn 6500-7000 rpm and the pull stopped at 5800. i would double check the timing and look at all eight plugs for clues. hopefully someone with more knowledge will chime in here.
Trending Topics
two things stand out to me. the first is the flat top pistons, flat top pistons and open chamber heads at 119cc usually result in low compression. i would think it needs a small dome to achieve 10:1. second is the rpm i would think an AFR headed big block with a roller cam would turn 6500-7000 rpm and the pull stopped at 5800. i would double check the timing and look at all eight plugs for clues. hopefully someone with more knowledge will chime in here.
To the OP your A/f is way down dipping below the 12's in the middle of the pull and barely above 12 at the peak of the pull. It needs to be a bit leaner and you might see more power.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Thread Starter
TECH Apprentice
Joined: Jun 2007
Posts: 362
Likes: 2
The motor is a crate motor. (Mostly wanted a warranty honestly..)
http://www.blueprintengines.com/popu...specs&pc_id=64
http://www.blueprintengines.com/popu...specs&pc_id=64
Thread Starter
TECH Apprentice
Joined: Jun 2007
Posts: 362
Likes: 2
The motor is a crate motor. (Mostly wanted a warranty honestly..)
http://www.blueprintengines.com/popu...specs&pc_id=64
http://www.blueprintengines.com/popu...specs&pc_id=64
Well, i am sure they dyno with zero accessories and a huge *** set of headers, but still seems low, like i said, dont trust the dyno, but you got drug by a cam car...maybe the weight would be a factor but damn.
496 chevy, 8-71 blower, 12 psi, 4l80e, 3.50 rear gear, heavy tires, steel wheels.
disappointing chassis dyno #'s = 520 rwhp, 580 rwtq
3800# (plus driver) => 10.62@127 (foot brake, 91 octane, hacked stock converter)
I don't claim to be any sort of chassis dyno expert, but I have a suspicion that if you put the same setup with 4.56 gears would see significantly higher numbers.
disappointing chassis dyno #'s = 520 rwhp, 580 rwtq
3800# (plus driver) => 10.62@127 (foot brake, 91 octane, hacked stock converter)
I don't claim to be any sort of chassis dyno expert, but I have a suspicion that if you put the same setup with 4.56 gears would see significantly higher numbers.
TECH Enthusiast
Joined: Jul 2008
Posts: 577
Likes: 1
From: League City, Tx
Dont put much stock in the rwhp dyno numbers....A TH400 is a horsepower killer, as is the mechanical accessories etc...All that really matters is how it runs....
When I dynoed my 496", we gave it the best possible conditions to make good power....(no accessories, no water pump, hot oil temp, cold water temp, big 2" shop headers with no exhaust, dyno carb hat, well ventilated dyno room etc...) mine made a corrected 657hp/675q.
But in the car I have full mechanical accessories, smaller headers, full exhaust, no carb spacer etc, Th400 w/10" converter, IRS rear end etc...so I only expect about 430hp to the wheels or so....a total turd right???
Last weekend I made one soft pass and it ran 11.14@122 with only a 1.69 60' at 3730lbs then got restricted to 1/8 mile....I made 3- 1/8 mile passes and it kept getting quicker...ended up at a 7.05 1/8 at 99.36mph....
This is a heavy, stock suspension, highway geared, weekend cruising 71 Vette with AC on a 255/60 drag radial..... No one would suspect it being even remotely fast....yet if I was to dyno it I would have been very disappointed with my low-mid 400s.....
Get it to the track....you'll be happy if the motor really made 620hp at the crank...
When I dynoed my 496", we gave it the best possible conditions to make good power....(no accessories, no water pump, hot oil temp, cold water temp, big 2" shop headers with no exhaust, dyno carb hat, well ventilated dyno room etc...) mine made a corrected 657hp/675q.
But in the car I have full mechanical accessories, smaller headers, full exhaust, no carb spacer etc, Th400 w/10" converter, IRS rear end etc...so I only expect about 430hp to the wheels or so....a total turd right???
Last weekend I made one soft pass and it ran 11.14@122 with only a 1.69 60' at 3730lbs then got restricted to 1/8 mile....I made 3- 1/8 mile passes and it kept getting quicker...ended up at a 7.05 1/8 at 99.36mph....
This is a heavy, stock suspension, highway geared, weekend cruising 71 Vette with AC on a 255/60 drag radial..... No one would suspect it being even remotely fast....yet if I was to dyno it I would have been very disappointed with my low-mid 400s.....
Get it to the track....you'll be happy if the motor really made 620hp at the crank...
I doubt that thing is 10:1 with flat tops and open chamber heads. your lucky if its 9:1 really. (not trying to be a dick)
I dont understand why they have all that duration and then a 112 LSA on a carbed motor...no sense except to have a smoother idle....dumb.
What size are the headers and carb?
I'd like to see some 2" headers and a nice 850 DP Holley on there.
I dont understand why they have all that duration and then a 112 LSA on a carbed motor...no sense except to have a smoother idle....dumb.
What size are the headers and carb?
I'd like to see some 2" headers and a nice 850 DP Holley on there.
With a 1/4" dome and 119 heads, it works out to about 10.25. At least that's what my wifes 489 is. She has a 1000 Holley, TH400, 3200 stall and 3.90 gears with a small mech flat tappet and in runs 10.80's with mid 1.5 60' times. Weight with her is 3200.
I doubt that thing is 10:1 with flat tops and open chamber heads. your lucky if its 9:1 really. (not trying to be a dick)
I dont understand why they have all that duration and then a 112 LSA on a carbed motor...no sense except to have a smoother idle....dumb.
What size are the headers and carb?
I'd like to see some 2" headers and a nice 850 DP Holley on there.
I dont understand why they have all that duration and then a 112 LSA on a carbed motor...no sense except to have a smoother idle....dumb.
What size are the headers and carb?
I'd like to see some 2" headers and a nice 850 DP Holley on there.
and some gear.
Chad