Disappearing Horsepower
Thread Starter
Staging Lane
Joined: Apr 2003
Posts: 70
Likes: 0
From: Texas
Disappearing Horsepower First of all my mods:
LS6, ported heads, 2.02/1.60 valves Isky 295's, vararam intake, LGM headers, magnaflow x pipe, borla stingers, no cat's, TNT wet kit, 3:42 gears, F1 cam 230/226 592 569 112.
The car pulled
426 rwhp 408 rwtq. Motor
538 rwhp 578 rwtq. 100 shot
Fast foward 3 months.
410 rwhp 397 rwtq.
Decided to make a few changes. Replaced cam with a comp cam
232/236 595 601 114, 3.90 gears.
395 rwhp 373 rwtq motor
492 rwhp 510 rwtq 100 shot
The car still feels strong. No codes, tuned by Chris R.
Tonight I performed a compression check.
1 185
2 180
3 185
4 187
5 180
6 185
7 185
8 185
This was with 4 compression strokes. After 8 strokes they were around
210 each.
Pulled the rockers and push rods, no problems. Tomorrow will be the leak test.
After that what??
So much for the train of thought that a "nitrous cam" needs to have more duration and lift on the exhaust side.
LS6, ported heads, 2.02/1.60 valves Isky 295's, vararam intake, LGM headers, magnaflow x pipe, borla stingers, no cat's, TNT wet kit, 3:42 gears, F1 cam 230/226 592 569 112.
The car pulled
426 rwhp 408 rwtq. Motor
538 rwhp 578 rwtq. 100 shot
Fast foward 3 months.
410 rwhp 397 rwtq.
Decided to make a few changes. Replaced cam with a comp cam
232/236 595 601 114, 3.90 gears.
395 rwhp 373 rwtq motor
492 rwhp 510 rwtq 100 shot
The car still feels strong. No codes, tuned by Chris R.
Tonight I performed a compression check.
1 185
2 180
3 185
4 187
5 180
6 185
7 185
8 185
This was with 4 compression strokes. After 8 strokes they were around
210 each.
Pulled the rockers and push rods, no problems. Tomorrow will be the leak test.
After that what??
So much for the train of thought that a "nitrous cam" needs to have more duration and lift on the exhaust side.
Last edited by Wire Dog; Apr 15, 2004 at 06:21 PM.
A compression check is not always the most conclusive means of determining an engines condition. You really need to do a leak down test and see if the motor is holding it's compression.
You can have two different cam profiles and they will show different cranking compressions in the same engine. This is due to variation in valve timing events.
Check back in after a leak down test!
You can have two different cam profiles and they will show different cranking compressions in the same engine. This is due to variation in valve timing events.
Check back in after a leak down test!
Thread Starter
Staging Lane
Joined: Apr 2003
Posts: 70
Likes: 0
From: Texas
I performed the leak down test. Here are the results:
Cyl Comp Leak
1 185 28%
2 180 10%
3 185 10%
4 187 6%
5 180 18%
6 185 25%
7 185 6%
8 185 10%
The car is not using oil, only down on power according to the dyno.
I am going to reassemble the top end and perform the test with the engine warm.
Any thoughts??
Cyl Comp Leak
1 185 28%
2 180 10%
3 185 10%
4 187 6%
5 180 18%
6 185 25%
7 185 6%
8 185 10%
The car is not using oil, only down on power according to the dyno.
I am going to reassemble the top end and perform the test with the engine warm.
Any thoughts??
Typically, I would take a look a cylinders 1,5, and 6. Those numbers are a little high for my personal liking. Ususally, you want no more than 10% leak. I would double check the figures.
Theres the problem! That numbers are way to high! You should be less then 5% on all cylinders.
The ones over 10% are the big problem. Sounds like the rings and cylinder walls are glazed over.
A re-ring job is the cure.
The ones over 10% are the big problem. Sounds like the rings and cylinder walls are glazed over.
A re-ring job is the cure.
TECH Fanatic
Joined: Nov 2001
Posts: 1,248
Likes: 0
From: Kansas City, MO
Yes, you need a rebuild. That is why a lot of nitrous guys keep upping the spray as the year goes on. You can drive it, but I would lay off the spray.
cheapest cure:
get the block align bored, honed, and decked, decent 3.905 pistons and rings, get the stock rods reconditioned with ARP rod bolts. New bearings all around, have the crank balanced, polished, or whatever it needs.
Problem solved, you now have a good motor, spray away.
cheapest cure:
get the block align bored, honed, and decked, decent 3.905 pistons and rings, get the stock rods reconditioned with ARP rod bolts. New bearings all around, have the crank balanced, polished, or whatever it needs.
Problem solved, you now have a good motor, spray away.
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Brett Foote Buck,
Did you leakdown the motor yet? It's the number one causer of loss of power with no changes!
Wiredog, if you plan on spraying the car a lot. Now is your chance to build the motor to take it without hurting the motor.
Did you leakdown the motor yet? It's the number one causer of loss of power with no changes!
Wiredog, if you plan on spraying the car a lot. Now is your chance to build the motor to take it without hurting the motor.
TECH Junkie
Joined: Dec 2001
Posts: 3,242
Likes: 0
From: Lakeland, FL
Ouch those #s are bad for the leakdown, One questiong though on the cylinder that were above 10% where did you hear the air coming out of? Maybe you have a bent valve or something like that and not necessarily bad rings or pistons.
Thread Starter
Staging Lane
Joined: Apr 2003
Posts: 70
Likes: 0
From: Texas
Thanks for the replies guys..
Never heard any air through the intake or exhaust. Sure was trying to though
Ok so its time to forge the bottom end.
What are your opinons on a 382 stroker? With the new Eagle cranks it's only another 1000.00
What could I expect over stock cubes?
Never heard any air through the intake or exhaust. Sure was trying to though
Ok so its time to forge the bottom end.
What are your opinons on a 382 stroker? With the new Eagle cranks it's only another 1000.00
What could I expect over stock cubes?
its all good and it all costs money.
go with a good set of moly rings and build your bottom end strong for the juice, don't spare any expense.
strokers add torque and torque is a good thing, makes daily driving more fun.
any more ?'s just use the search button.
go with a good set of moly rings and build your bottom end strong for the juice, don't spare any expense.
strokers add torque and torque is a good thing, makes daily driving more fun.
any more ?'s just use the search button.
If you decide to do a stroker, be prepared to also put some money into the heads. My opinion would be to build an "all bore" motor and leave the stock stroke. Build a Darton 4.125" bore with stock stroke. You'll make more power in the long run!
I have not been too impressed with the 382 strokers. To make these motors run you really need to unshround the valves by opening up the bore size.
I have not been too impressed with the 382 strokers. To make these motors run you really need to unshround the valves by opening up the bore size.