Newly built motor, complete lack of power and out of ideas
Member
Joined: Nov 2016
Posts: 207
Likes: 7
From: Connecticut
Car: 1991 Camaro RS
Engine: Hot 355ci
Transmission: Beefed TH350
Axle/Gears: 4:10
Re: Newly built motor, complete lack of power and out of ideas
I had a 1983 Camaro with a 355 th350 and a B&M converter, maybe 2800 or 3400stall or something.
The rear gear was 2.77:1 , you know it sucked,
The car was an absolute slug. The slowest thing I ever drove in my life. The trans and converter were new, shift kit, etc...
I took all that out and put in a 4-speed manual trans and the car ripped, was nice and fast with the same engine.
The combo of th350 and high stall with the shitty rear gear was the reason it was terrible. Woulda been fine with a 3.73 or something but they dont make it easy on those 9-bolt rears.
The rear gear was 2.77:1 , you know it sucked,
The car was an absolute slug. The slowest thing I ever drove in my life. The trans and converter were new, shift kit, etc...
I took all that out and put in a 4-speed manual trans and the car ripped, was nice and fast with the same engine.
The combo of th350 and high stall with the shitty rear gear was the reason it was terrible. Woulda been fine with a 3.73 or something but they dont make it easy on those 9-bolt rears.
Supreme Member
Joined: Dec 2002
Posts: 1,592
Likes: 31
From: IL
Car: 1988 Formula
Engine: 421 Little M block
Transmission: TH400 w/brake
Axle/Gears: 9" 4.30s, Wilwood discs, 28X10.5-15
Re: Newly built motor, complete lack of power and out of ideas
You still don't know what you don't know...and that's OK this hobby has a pretty steep learning curve. I am still learning something new in this hobby which I have embraced since before I had a drivers license, over 30 years for me.
My issue is when people insist they are 100%correct in diagnosing a car's performance symptoms based on descriptions over the internet, having never driven or tested the car, yet dismiss possible causes to the problem which are sound and based on real world experiences.
OP made a engine/cam swap but makes no mention of the transmission or rear gearing. OP says the engine starts idles and revs just fine.
My basic point is if the engine starts, idles, and revs alot of the variables can be eliminated and OP can move on the other possible causes.
https://www.rodauthority.com/tech-st...-to-your-ride/
Matt Kehoe from B&M explained the cam/converter relationship this way. “Cam cards are helpful. We generally need to know the exhaust and intake duration at .050-inch lift before we are able to provide an accurate converter recommendation. Generally, a 2,000 or 2,400-stall converter is a good choice for advertised cam durations up to 248 degrees. For advertised cam durations up to 268 degrees, a 2,400 or 3,000-stall converter is the way to go. Advertised cam durations over 272 degrees, will require a 3,000 to 3,600 stall converter for optimum performance.”
In terms of torque and its effect on converter choice, as mentioned above, when the torque curve of the engine is raised, you need more stall speed in the converter to allow the vehicle to accelerate at lower RPM.
Trent understands camshafts, and helps explain the connection with the converter, “The camshaft plays one of the most critical roles in converter choice, as it is one of, if not the biggest factor in the powerband of the given engine combination. You must have a torque converter with the right amount of stall to allow the engine to get into that powerband for optimum performance, even in a daily-driver street car. If you have a bigger than stock camshaft, you must get the right stall to allow the engine to also idle in gear, and make the car function as it should.” As Trent said earlier, too much stall can create heat, and you don’t want that either.
Good luck OP...
My issue is when people insist they are 100%correct in diagnosing a car's performance symptoms based on descriptions over the internet, having never driven or tested the car, yet dismiss possible causes to the problem which are sound and based on real world experiences.
OP made a engine/cam swap but makes no mention of the transmission or rear gearing. OP says the engine starts idles and revs just fine.
My basic point is if the engine starts, idles, and revs alot of the variables can be eliminated and OP can move on the other possible causes.
https://www.rodauthority.com/tech-st...-to-your-ride/
Matt Kehoe from B&M explained the cam/converter relationship this way. “Cam cards are helpful. We generally need to know the exhaust and intake duration at .050-inch lift before we are able to provide an accurate converter recommendation. Generally, a 2,000 or 2,400-stall converter is a good choice for advertised cam durations up to 248 degrees. For advertised cam durations up to 268 degrees, a 2,400 or 3,000-stall converter is the way to go. Advertised cam durations over 272 degrees, will require a 3,000 to 3,600 stall converter for optimum performance.”
In terms of torque and its effect on converter choice, as mentioned above, when the torque curve of the engine is raised, you need more stall speed in the converter to allow the vehicle to accelerate at lower RPM.
Trent understands camshafts, and helps explain the connection with the converter, “The camshaft plays one of the most critical roles in converter choice, as it is one of, if not the biggest factor in the powerband of the given engine combination. You must have a torque converter with the right amount of stall to allow the engine to get into that powerband for optimum performance, even in a daily-driver street car. If you have a bigger than stock camshaft, you must get the right stall to allow the engine to also idle in gear, and make the car function as it should.” As Trent said earlier, too much stall can create heat, and you don’t want that either.
Good luck OP...
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