engine performance
Thread Starter
Instructor
Joined: Oct 2007
Posts: 124
Likes: 1
From: baltimore ohio
engine performance
Hey guys , I built a 383 for the 76. It dyno at 425hp and 418 torque, I have 3:73 rear gear's and th350 trans with a 2700-3000 (jegs) stall. The car is not as fast as I would have thought. My first thought it was the cam, and a friend thought it was the convertor cause the motor made pretty good hp and tq. Just not getting it to the rear. Timing is 18 and all in at 50 at 2500-2700, the motor temp are 175-180 in the summer heat. A little more on the motor 10.5 comp. rpm air gap in take, pmb profiler alum. heads, 2.10 intake 1.600 exhaust, 210 intake runners, howards flat tap. cam .488 intake 509 exhaust intake 234 @50 and 244 @ 50 780 quick fuel vac. secondary. and thoughts Thanks
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
Hey guys , I built a 383 for the 76. It dyno at 425hp and 418 torque, I have 3:73 rear gear's and th350 trans with a 2700-3000 (jegs) stall. The car is not as fast as I would have thought. My first thought it was the cam, and a friend thought it was the convertor cause the motor made pretty good hp and tq. Just not getting it to the rear. Timing is 18 and all in at 50 at 2500-2700, the motor temp are 175-180 in the summer heat. A little more on the motor 10.5 comp. rpm air gap in take, pmb profiler alum. heads, 2.10 intake 1.600 exhaust, 210 intake runners, howards flat tap. cam .488 intake 509 exhaust intake 234 @50 and 244 @ 50 780 quick fuel vac. secondary. and thoughts Thanks
It should be a tire smoker with 418 ft/lbs of torque. I have always preached high stall torque converters with stall speeds above 2000 rpm are way too "loose" for street use. I think it would run a lot better with a stock 1200 rpm stall speed. High stall converters are beneficial for off the line acceleration but then hinder you once the car is in motion unless the throttle stays wide open the whole time. You can buy rebuilt torque converters for only $100 from any transmission parts supply house so I'd try one. A stock one!
Drifting
Joined: Oct 2005
Posts: 1,916
Likes: 48
From: Angier nc
How fast is it or are you going by the butt-meter?Try your timing with the vacuum advance plugged.No way you have 50 degrees timing.
Is it spinning the tires? Are you running headers and what exhaust system?
Is it spinning the tires? Are you running headers and what exhaust system?
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
He's talking about 50 degrees total at high engine speeds which is a combination of the initial advance, the mechanical advance AND the vacuum advance. The desired total is actually 52 degrees but 50 is close enough. With the 3.73's it would certainly spin the tires which would negate the need for a high stall converter.
Advanced
Joined: Feb 2007
Posts: 90
Likes: 0
Even if you can work out the tune someone picked the wrong parts for your combo. Heads are way to big and if your looking for power a hydrualic roller cam would be first choice. A 4 inch bore doesnt like a 2.100 valve on a street car. Your close to the power a good 350 would make.
Harry
Harry
Melting Slicks
Joined: Jun 2011
Posts: 3,114
Likes: 598
Hey guys , I built a 383 for the 76. It dyno at 425hp and 418 torque, I have 3:73 rear gear's and th350 trans with a 2700-3000 (jegs) stall. The car is not as fast as I would have thought. My first thought it was the cam, and a friend thought it was the convertor cause the motor made pretty good hp and tq. Just not getting it to the rear. Timing is 18 and all in at 50 at 2500-2700, the motor temp are 175-180 in the summer heat. A little more on the motor 10.5 comp. rpm air gap in take, pmb profiler alum. heads, 2.10 intake 1.600 exhaust, 210 intake runners, howards flat tap. cam .488 intake 509 exhaust intake 234 @50 and 244 @ 50 780 quick fuel vac. secondary. and thoughts Thanks
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
High stall converters are beneficial for off the line acceleration but then hinder you once the car is in motion unless the throttle stays wide open the whole time. You can buy rebuilt torque converters for only $100 from any transmission parts supply house so I'd try one. A stock one!
Drifting
Joined: Jun 2012
Posts: 1,990
Likes: 183
From: Port St. Lucie Fl
Hey guys , I built a 383 for the 76. It dyno at 425hp and 418 torque, I have 3:73 rear gear's and th350 trans with a 2700-3000 (jegs) stall. The car is not as fast as I would have thought. My first thought it was the cam, and a friend thought it was the convertor cause the motor made pretty good hp and tq. Just not getting it to the rear. Timing is 18 and all in at 50 at 2500-2700, the motor temp are 175-180 in the summer heat. A little more on the motor 10.5 comp. rpm air gap in take, pmb profiler alum. heads, 2.10 intake 1.600 exhaust, 210 intake runners, howards flat tap. cam .488 intake 509 exhaust intake 234 @50 and 244 @ 50 780 quick fuel vac. secondary. and thoughts Thanks
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Thread Starter
Instructor
Joined: Oct 2007
Posts: 124
Likes: 1
From: baltimore ohio
it will not spin the tires, it squits and goes and yes I have the dyno sheet from the engine dyno, I have hooker header and side pipes. The tire are nitto's very sticky. I'm going by butt feel. I would like to put a roller cam in but won't I have to check clerance's?
Drifting
Joined: Jun 2012
Posts: 1,990
Likes: 183
From: Port St. Lucie Fl
before you start throwing money at it, lets find whats wrong. If you can post the dyno sheet it will help us get a better idea of whats going on. I have the same cam in my 406 and its alot of fun.
Last edited by Kacyc3; Nov 26, 2015 at 11:27 PM.
Safety Car
Joined: Jan 2009
Posts: 3,736
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From: anchorage ak
Spinning ain't winning.
Drifting
Joined: Jun 2011
Posts: 1,704
Likes: 27
CAn you post up a dyno chart? That might be helpful when you are talking about trying to calculate converter efficiency.
But when you are talking about TH350's and TH400's, they are not dyno queens. My '98 Firebird has a 408" LS motor and an old school TH400 (wanted to put it up there and forget about it). It turns my face red everytime I dyno it. Embarrassing. But boy it runs good at the track. 10.60 @ 126. And that is no power adders, 93 octane pump gas, and a heavy 3680 lbs with me in it. I'm proud of those numbers.
But when you are talking about TH350's and TH400's, they are not dyno queens. My '98 Firebird has a 408" LS motor and an old school TH400 (wanted to put it up there and forget about it). It turns my face red everytime I dyno it. Embarrassing. But boy it runs good at the track. 10.60 @ 126. And that is no power adders, 93 octane pump gas, and a heavy 3680 lbs with me in it. I'm proud of those numbers.
Le Mans Master
Joined: Oct 2007
Posts: 7,445
Likes: 971
From: Tennessee/Rhode Island
I see 2 problems with the build right off the bat, if you are looking for tire burning low end torque:
1. As stated all ready, the heads with 210 CC's are too big for the 383 which will kill low end grunt but will produce high rpm power which they seem to do
2. The howards flat tappet cam with 234/244 duration pushes the power into the mid to high rpm range....again killing low end power. I could not find your exact cam on howards website but found similar grinds with your duration and lift which pushed the power into the 3,000-6,500 RPM range, meaning not much power being made down low in the rpm range.
As a comparator, my L-82 355 with AFR 180 heads, 10.2:1 compression, Howards Roller cam (219/225 duration, Lift .525/.525, LSA 110) has an operating range of 1,500-5,600 RPM making big power and torque from off idle, very strong mid range torque, along with high rpm power to 6,000 RPM.
Looks like the combination of parts is not matched to your indented use on the street. Something like this flat tappet cam or a roller with 195 CC heads would give you what you want:
110041-12 CL110041-12 279 289 225 235 .465 .488 112 108 Hyd. Hyd. 1
1800-6000 Street Force™ 3, Noticeable idle, Hot Street & mild Bracket Racing.
1. As stated all ready, the heads with 210 CC's are too big for the 383 which will kill low end grunt but will produce high rpm power which they seem to do
2. The howards flat tappet cam with 234/244 duration pushes the power into the mid to high rpm range....again killing low end power. I could not find your exact cam on howards website but found similar grinds with your duration and lift which pushed the power into the 3,000-6,500 RPM range, meaning not much power being made down low in the rpm range.
As a comparator, my L-82 355 with AFR 180 heads, 10.2:1 compression, Howards Roller cam (219/225 duration, Lift .525/.525, LSA 110) has an operating range of 1,500-5,600 RPM making big power and torque from off idle, very strong mid range torque, along with high rpm power to 6,000 RPM.
Looks like the combination of parts is not matched to your indented use on the street. Something like this flat tappet cam or a roller with 195 CC heads would give you what you want:
110041-12 CL110041-12 279 289 225 235 .465 .488 112 108 Hyd. Hyd. 1
1800-6000 Street Force™ 3, Noticeable idle, Hot Street & mild Bracket Racing.
Last edited by jb78L-82; Nov 27, 2015 at 07:28 AM.
Burning Brakes
Joined: Nov 2011
Posts: 1,170
Likes: 201
From: Willoughby Ohio
I agree that a 195 head with a little smaller valve would work better for what you are doing.If you know anyone with a annular booster carburetor I would give that a try.IMOP the 2.100 intake valve needs a 400 based build.
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
My CrossFire Injected '82 with 3.54's will burn about 25 to 30 feet of rubber in 1st gear so if yours won't there is something drastically wrong.
Le Mans Master
Joined: May 2002
Posts: 5,086
Likes: 786
From: Lebanon Township New Jersey
What is the total advance,without vacuum advance? You mention 50 degrees as total but you don't say how you're measuring it. You want approx 36 deg. total, by 2,500 rpm, with the vac line plugged. I have a 383 with TH350, 3000 stall and 3.73 gears and it spins the street tires, off idle, like the engine was in neutral. Even from a 15 mph roll, they spin so bad I have to get off the gas. With your dyno numbers, converter and gear you should do the same. Make sure that timing is set up correctly.
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
It should be a tire smoker with 418 ft/lbs of torque. I have always preached high stall torque converters with stall speeds above 2000 rpm are way too "loose" for street use. I think it would run a lot better with a stock 1200 rpm stall speed. High stall converters are beneficial for off the line acceleration but then hinder you once the car is in motion unless the throttle stays wide open the whole time. You can buy rebuilt torque converters for only $100 from any transmission parts supply house so I'd try one. A stock one!
OP :
Does it launch hard ? One thing you want is no spin and all the power to be applied in such a way that it instantly translates into forward momentum .
Drifting
Joined: Jun 2011
Posts: 1,704
Likes: 27
Anyway, I noticed you have a jegs converter. I found out the hard way you get what you pay for when it comes to converters. There's no way around it, you want a quality stall you have to pay for one.
I switched from a "budget" converter to a YANK (same stall speed) and picked up a 1/2 second in the quarter mile.
Drifting
Joined: Jul 2013
Posts: 1,299
Likes: 93
From: Tri-Cities TN
Even if you can work out the tune someone picked the wrong parts for your combo. Heads are way to big and if your looking for power a hydrualic roller cam would be first choice. A 4 inch bore doesnt like a 2.100 valve on a street car. Your close to the power a good 350 would make.
Harry
Harry
If the combo is LAZY then it is the combination of parts.
Racer
Joined: Jan 2015
Posts: 293
Likes: 43
From: Vernon B.C.
Without doing some track testing or getting it on a chassis dyno we are all just speculating. Everyone`s seat of the pans meter is calibrated differently. Even if the combination is out a little it still made some power and torque. Id like to see the dyno sheet to if you have it handy. Short of getting it to the track, get some regular street tires on it and see what happens. It might just roast them like you think it should. Remember that Corvettes have great weight distribution and with the sticky tires it might be all she has. If you get it to the track and it runs in the 12s you should be happy. Just my 2 cents.....