L-88 Dyno results with stock exhaust and factory headers
04-25-2002, 02:26 AM
#1
Racer
Thread Starter
L-88 Dyno results with stock exhaust and factory headers
I hope it is ok to post this on both C3 and here. Please delete it if it is not appropriate. But, people on both boards have been so helpful to me and I don't know how much crossover there is.
====================================
The first leg of the long journey is almost over. I am getting really close to the light at the end of this tunnel. Hopefully after this motor is installed it will be nothing but wide open roads.
I got this car last August. I had put less than 300 miles on it when it spun a connecting rod bearing in my mechnanic's shop. And so the rebuilding process began....
The block was line honed, decked, and bored.
My car is an early '69 with a late '68 build date. The engine code is "IT." I have remained fairly true to spec but not totally. The biggest change is I had the motor built to late '69 specs, this means the open chamber heads and the later cam.
Here is a basic rundown of what is different from spec.
Block is bored .030 over
Late '69 "074" heads, rated at 118cc (actually 125 cc)
Late '69 Holley List 4296 850 CFM double pumper
3959180 cam, .575in/.615ex, 262in/272ex (made by Crane to GM spec)
JE domed pistons (instead of TRW)
H-Beam connecting rods (instead of the GM rods), all ARP bolts
Crank is 4340 instead of 5140 but otherwise built to spec
Hardened rocker arms (but NO rollers, just the traditional type)
Manley springs and valves, 4340 retainers
Protective splash guard beneath the intake manifold to keep the hot oil off of the bottom
The motor came in at 11.2:1 instead of the advertised 12:1. My machine shop Guru assured me that this was actually the high end of the norm for these motors and that advertised compression was never seen when new. Accept it or not, if you read the recent article in Hot Rod, the difference between 12 and 11.2 could cost 3% of HP.
The other thing that was not proper for the dyno run was the flywheel. (Mine did not fit the machine.) L-88's come with a smaller flywheel. It's lighter and makes for better revving. I don't know if that cost us 5 HP or not.
Finally the motor was dynoed without the benefit of the cold cowl induction. That has to be good for something. We did not even have the black base around the carb because it interfered with the machine's throttle linkage.
So here are the numbers:
With stock exhaust manifolds:
444 HP @ 5200 RPM
465 HP @6100 RPM
The torque was above 440 lb-ft from 4000 RPM to 5400, it peaked at 458 lb-ft @ 5000 RPM.
With the OK Kustom factory headers and the 4" side tubes installed, they have not been hot coated yet:
506 HP @ 5200 RPM
539 HP @ 6100 RPM
The torque was at least 500 lb-ft from 4000 RPM to 5400 RPM, it peaked at 515 lb-ft @ 5000 RPM
The timing for both runs was set approximately at 39 degrees. I think we could have gone higher and milked a few more ponies out of it. We never fiddled with the carb jets during the whole process.
So there you have it. :smash: GM advertised 430 HP @ 5200 RPM. I have read that that figure is low, that it is high, that it is accurate for the stock exhaust. I have read that the actual output is 560 HP with headers. There is no question that the GM number was rated below it's peak power. I think if we played with the timing some more (and maybe the jets) we could have gotten closer to the 560 figure. In any case I am thrilled, 540 is plenty for me. :chevy
Both exhausts were so loud I thought I was standing on a runway while planes were taking off.
I will post pics and the actual printouts of the Dyno runs tomorrow.
Thanks to everyone on this board who has answered my questions throughout this process.
:cheers:
[Modified by BAD-L88, 10:39 PM 4/24/2002]
====================================
The first leg of the long journey is almost over. I am getting really close to the light at the end of this tunnel. Hopefully after this motor is installed it will be nothing but wide open roads.
I got this car last August. I had put less than 300 miles on it when it spun a connecting rod bearing in my mechnanic's shop. And so the rebuilding process began....
The block was line honed, decked, and bored.
My car is an early '69 with a late '68 build date. The engine code is "IT." I have remained fairly true to spec but not totally. The biggest change is I had the motor built to late '69 specs, this means the open chamber heads and the later cam.
Here is a basic rundown of what is different from spec.
Block is bored .030 over
Late '69 "074" heads, rated at 118cc (actually 125 cc)
Late '69 Holley List 4296 850 CFM double pumper
3959180 cam, .575in/.615ex, 262in/272ex (made by Crane to GM spec)
JE domed pistons (instead of TRW)
H-Beam connecting rods (instead of the GM rods), all ARP bolts
Crank is 4340 instead of 5140 but otherwise built to spec
Hardened rocker arms (but NO rollers, just the traditional type)
Manley springs and valves, 4340 retainers
Protective splash guard beneath the intake manifold to keep the hot oil off of the bottom
The motor came in at 11.2:1 instead of the advertised 12:1. My machine shop Guru assured me that this was actually the high end of the norm for these motors and that advertised compression was never seen when new. Accept it or not, if you read the recent article in Hot Rod, the difference between 12 and 11.2 could cost 3% of HP.
The other thing that was not proper for the dyno run was the flywheel. (Mine did not fit the machine.) L-88's come with a smaller flywheel. It's lighter and makes for better revving. I don't know if that cost us 5 HP or not.
Finally the motor was dynoed without the benefit of the cold cowl induction. That has to be good for something. We did not even have the black base around the carb because it interfered with the machine's throttle linkage.
So here are the numbers:
With stock exhaust manifolds:
444 HP @ 5200 RPM
465 HP @6100 RPM
The torque was above 440 lb-ft from 4000 RPM to 5400, it peaked at 458 lb-ft @ 5000 RPM.
With the OK Kustom factory headers and the 4" side tubes installed, they have not been hot coated yet:
506 HP @ 5200 RPM
539 HP @ 6100 RPM
The torque was at least 500 lb-ft from 4000 RPM to 5400 RPM, it peaked at 515 lb-ft @ 5000 RPM
The timing for both runs was set approximately at 39 degrees. I think we could have gone higher and milked a few more ponies out of it. We never fiddled with the carb jets during the whole process.
So there you have it. :smash: GM advertised 430 HP @ 5200 RPM. I have read that that figure is low, that it is high, that it is accurate for the stock exhaust. I have read that the actual output is 560 HP with headers. There is no question that the GM number was rated below it's peak power. I think if we played with the timing some more (and maybe the jets) we could have gotten closer to the 560 figure. In any case I am thrilled, 540 is plenty for me. :chevy
Both exhausts were so loud I thought I was standing on a runway while planes were taking off.
I will post pics and the actual printouts of the Dyno runs tomorrow.
Thanks to everyone on this board who has answered my questions throughout this process.
:cheers:
[Modified by BAD-L88, 10:39 PM 4/24/2002]
04-25-2002, 08:55 AM
#2
Melting Slicks
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Re: L-88 Dyno results with stock exhaust and factory headers (BAD-L88)
BAD-L88,
that is an excellent story...there have been many documented L88's with minor tweaking that could pump 560hp easily. I have a few questions...what ignition and plugs were run...is there any intake/port/head matching and what intake is used....the Crane replica cam is hyd right?
As you are probably aware...560 hp is easily attainable out of this motor. I am curious if the dyno was operated by your builder or another shop...wondering if you had more time for more tweaking with the jets, or if you were on a timetable. You'd be surprised what experienced dyno operaters can get out of a motor...just when you think you are at the max, they squeeze another 20 or so hp.... :cheers: :cool:
that is an excellent story...there have been many documented L88's with minor tweaking that could pump 560hp easily. I have a few questions...what ignition and plugs were run...is there any intake/port/head matching and what intake is used....the Crane replica cam is hyd right?
As you are probably aware...560 hp is easily attainable out of this motor. I am curious if the dyno was operated by your builder or another shop...wondering if you had more time for more tweaking with the jets, or if you were on a timetable. You'd be surprised what experienced dyno operaters can get out of a motor...just when you think you are at the max, they squeeze another 20 or so hp.... :cheers: :cool:
04-25-2002, 12:14 PM
#5
Le Mans Master
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Re: L-88 Dyno results with stock exhaust and factory headers (BAD-L88)
back in the L-88 days i was a kustom header dealer and they sent me a ad to post on the wall that said the L-88 made 560 HP with their headers. their headers for BB chevys made more power than any other we tested at the drag strip. :chevy
04-25-2002, 01:55 PM
#6
Racer
Thread Starter
Re: L-88 Dyno results with stock exhaust and factory headers (topless68)
topless,
The plugs were Ac Delco rapid fire, I think they were the 44 XL's. We used a Moroso ignition and distrubutor that was part of the dyno bench since the K66 system failed, it was missing with it. I am going to have the guts of my original TI box upgraded. There has been no intake/port/head matching done. My machinist did not port the heads at all, he felt they had more than adequate breathing ability. It is the correct intake for the car with the plane between the plenums carved out. The Crane cam is a solid lifter cam, no roller anything, no hydraulic anything.
The dyno was actually operated by a 3 time world champion pro stock drag racer who is a close friend of my mechanic who built the engine. He fiddled with the carb adjustments a little while it was up there. He also tinkered with the advance. We had free run of the place while we were there and there was no time pressure at all. I think we probably could have gotten close to the 560 if we really worked it.
They were svery impressed by the header gain. When I told them that the headers were rumored to add 100 Hp they brushed it off and said 10-20. One observer even guessed they would add nothing. Nevertheless, they were stunned with the 74 HP gain.
The plugs were Ac Delco rapid fire, I think they were the 44 XL's. We used a Moroso ignition and distrubutor that was part of the dyno bench since the K66 system failed, it was missing with it. I am going to have the guts of my original TI box upgraded. There has been no intake/port/head matching done. My machinist did not port the heads at all, he felt they had more than adequate breathing ability. It is the correct intake for the car with the plane between the plenums carved out. The Crane cam is a solid lifter cam, no roller anything, no hydraulic anything.
The dyno was actually operated by a 3 time world champion pro stock drag racer who is a close friend of my mechanic who built the engine. He fiddled with the carb adjustments a little while it was up there. He also tinkered with the advance. We had free run of the place while we were there and there was no time pressure at all. I think we probably could have gotten close to the 560 if we really worked it.
They were svery impressed by the header gain. When I told them that the headers were rumored to add 100 Hp they brushed it off and said 10-20. One observer even guessed they would add nothing. Nevertheless, they were stunned with the 74 HP gain.
04-26-2002, 12:14 AM
#7
Race Director
Member Since: May 2000
Location: Redondo Beach USA
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Re: L-88 Dyno results with stock exhaust and factory headers (BAD-L88)
The L-88 cam has a great amount of overlap, and it was specifically designed to enhance the torque curve in the upper half of the range with properly designed headers. The overlap also works to kill torque across the range with the production manifolds. The type of exhaust system is a major input to valve timing choices.
I'm suprised those guys wouldn't understand that if they have any experence with racing engines. When you design and engine properly, whatever the application, if you do your system engineering homework you pick components and architectures that are synergistic, and the whole is greater than the sum of the parts.
Those Chevy engineers knew what they were doing 35 years ago.
Duke
I'm suprised those guys wouldn't understand that if they have any experence with racing engines. When you design and engine properly, whatever the application, if you do your system engineering homework you pick components and architectures that are synergistic, and the whole is greater than the sum of the parts.
Those Chevy engineers knew what they were doing 35 years ago.
Duke
04-26-2002, 12:17 AM
#8
Re: L-88 Dyno results with stock exhaust and factory headers (BAD-L88)
They were svery impressed by the header gain. When I told them that the headers were rumored to add 100 Hp they brushed it off and said 10-20. One observer even guessed they would add nothing. Nevertheless, they were stunned with the 74 HP gain.
[Modified by 67HEAVEN, 4:58 PM 4/29/2002]
04-26-2002, 01:58 AM
#9
Racer
Thread Starter
Re: L-88 Dyno results with stock exhaust and factory headers (67HEAVEN)
Pics and dyno sheets up, pics #152 - #167, the dyno sheets are #164 - #167:
http://photos.yahoo.com/bc/badl88/vw...no.jpg&.view=t
&.done=http%3a//photos.yahoo.com/bc/badl88/lst%3f%26.dir=/My%2bPhotos%26.src=ph%26.view=t
God bless Mr. Kustom wherever he is!!!
I don't know if these guys ever dynoed anything with a stock exhaust. They get over 1000 HP out of a normally aspirated 368 cubic inch motor. I don't think it would last very long in San Francisco, especiallly with all of the traffic here.
http://photos.yahoo.com/bc/badl88/vw...no.jpg&.view=t
&.done=http%3a//photos.yahoo.com/bc/badl88/lst%3f%26.dir=/My%2bPhotos%26.src=ph%26.view=t
God bless Mr. Kustom wherever he is!!!
I don't know if these guys ever dynoed anything with a stock exhaust. They get over 1000 HP out of a normally aspirated 368 cubic inch motor. I don't think it would last very long in San Francisco, especiallly with all of the traffic here.
04-29-2002, 01:37 PM
#11
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Re: L-88 Dyno results with stock exhaust and factory headers (BAD-L88)
First time poster here, but when I read this I had to respond! THIS is the kind of thing I like to read about!
Those kind of numbers, through exhaust manifolds, may surprise some people, but not me. I did a similar test on the L-72 in my dad's Yenko Camaro, and it was slightly over the factory rating of 425hp, with the stock Camaro/Nova/Chevelle exhaust manifolds. This was with a DEAD STOCK rebuild (except for the .030" overbore). If the factory didn't do it, neither did I. Like your L-88, our L-72 was WAY down on compression, making just 10.2:1, and I have even seen STOCK rebuilt L-72s go as low as 9.8:1 actual compression!
But, I am envyous (sp?) of your 'Vette manifolds, which are a little better design than our "other" BBC manifolds. They aren't as free flowing as the Hemi's exhaust manifolds, but they aren't as bad as the other models had.
Just curious: What are your plans with the car/engine now? The reason I ask is, that I race in the Pure Stock Drag events every year with our cars, and us Chevy guys would LOVE to have an L-88 step up and handle some business! Right now, our L-72 Camaro is running high 12's @ about 109, FACTORY STOCK, on the Polyglass tires. There is a ZL-1 Camaro running 12.3x's (last I saw him, just got the car going!). In fact, there will be a write up in the new "Musclecar Review" spinoff, "Musclecar Power", in the premier issue, on my car/engine as well as the ZL-1 car/engine, and the rest of the Certified Stock competitors. For those that don't know, Certified Stock was a voluntary tear down by some of the competitors, to show that we WERE in fact Pure Stock. In the same issue will be a dyno test of the ZL-1, which is WAY under the factory specs, but made HUGE power in Factory trim. He then made a run with headers...but you'll have to wait until the magazine comes out to see the results!
Anyway, sorry about the lengthy post, but this is the kind of info/test that gets my blood boiling So, any chance of you bringing that baby to the strip for a little "test"? :D
Those kind of numbers, through exhaust manifolds, may surprise some people, but not me. I did a similar test on the L-72 in my dad's Yenko Camaro, and it was slightly over the factory rating of 425hp, with the stock Camaro/Nova/Chevelle exhaust manifolds. This was with a DEAD STOCK rebuild (except for the .030" overbore). If the factory didn't do it, neither did I. Like your L-88, our L-72 was WAY down on compression, making just 10.2:1, and I have even seen STOCK rebuilt L-72s go as low as 9.8:1 actual compression!
But, I am envyous (sp?) of your 'Vette manifolds, which are a little better design than our "other" BBC manifolds. They aren't as free flowing as the Hemi's exhaust manifolds, but they aren't as bad as the other models had.
Just curious: What are your plans with the car/engine now? The reason I ask is, that I race in the Pure Stock Drag events every year with our cars, and us Chevy guys would LOVE to have an L-88 step up and handle some business! Right now, our L-72 Camaro is running high 12's @ about 109, FACTORY STOCK, on the Polyglass tires. There is a ZL-1 Camaro running 12.3x's (last I saw him, just got the car going!). In fact, there will be a write up in the new "Musclecar Review" spinoff, "Musclecar Power", in the premier issue, on my car/engine as well as the ZL-1 car/engine, and the rest of the Certified Stock competitors. For those that don't know, Certified Stock was a voluntary tear down by some of the competitors, to show that we WERE in fact Pure Stock. In the same issue will be a dyno test of the ZL-1, which is WAY under the factory specs, but made HUGE power in Factory trim. He then made a run with headers...but you'll have to wait until the magazine comes out to see the results!
Anyway, sorry about the lengthy post, but this is the kind of info/test that gets my blood boiling So, any chance of you bringing that baby to the strip for a little "test"? :D
04-29-2002, 05:32 PM
#12
Re: L-88 Dyno results with stock exhaust and factory headers (Chevy454)
Chevy454.
Welcome to the Forum. Sounds like you're on the right track.
I'm 16 to 24 months away from completion of a complete body-off on mine.
Welcome to the Forum. Sounds like you're on the right track.
I'm 16 to 24 months away from completion of a complete body-off on mine.
04-30-2002, 08:37 PM
#13
Safety Car
Re: L-88 Dyno results with stock exhaust and factory headers (Chevy454)
Rob, can you tell me when Musclecar Power magazine will become available and where I could subscription info? Thanks
04-30-2002, 10:26 PM
#14
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Re: L-88 Dyno results with stock exhaust and factory headers (BAD-L88)
Taken straight from the email:
The first press run will be only 5,000 copies, so reserve your
Premier Collector Issue right now. Send $9.95 check or money order to
Musclecar Power, P. O. Box 6085, Lakeland, FL 33807-6085. Your issue will
arrive in this Spring, postage-paid and custom mailed in a protective
envelope with subscription information. If you love American musclecars
don't miss this opportunity. Musclecar Power will feature both the Factory
Stock Drag Race in May of 2002, and the Pure Stock Drags in September!
The first press run will be only 5,000 copies, so reserve your
Premier Collector Issue right now. Send $9.95 check or money order to
Musclecar Power, P. O. Box 6085, Lakeland, FL 33807-6085. Your issue will
arrive in this Spring, postage-paid and custom mailed in a protective
envelope with subscription information. If you love American musclecars
don't miss this opportunity. Musclecar Power will feature both the Factory
Stock Drag Race in May of 2002, and the Pure Stock Drags in September!
05-03-2002, 02:37 AM
#15
Racer
Thread Starter
Re: L-88 Dyno results with stock exhaust and factory headers (Chevy454)
Chevy454,
My plans are to drive it and have fun. If I were near you I would be happy to bring it over and see how it runs. I don't know if I am a good enough driver to extract the most out of it buut I would give it a try. Maybe I can find someplace out here in Northern CA to give it a go.
Thanks for the Yenko link. I need to dig into that site some more.
[Modified by BAD-L88, 10:38 PM 5/2/2002]
My plans are to drive it and have fun. If I were near you I would be happy to bring it over and see how it runs. I don't know if I am a good enough driver to extract the most out of it buut I would give it a try. Maybe I can find someplace out here in Northern CA to give it a go.
Thanks for the Yenko link. I need to dig into that site some more.
[Modified by BAD-L88, 10:38 PM 5/2/2002]
05-03-2002, 02:33 PM
#16
Melting Slicks
Re: L-88 Dyno results with stock exhaust and factory headers
Rob,
Good to see you over on this forum... Maybe we can to turn you to the "dark side" and get you running a Corvette in the Pure Stock drags!
What's the deal with the new magazine? I sent my check off several months ago when the address was posted on the Supercar forum... Now I hear that the cost has been increased. Are they going to bill me for the difference or do I need to get another check off to them? I'm really looking forward to the return of Tom Shaw and would prefer not to miss an issue.
Regards,
Good to see you over on this forum... Maybe we can to turn you to the "dark side" and get you running a Corvette in the Pure Stock drags!
What's the deal with the new magazine? I sent my check off several months ago when the address was posted on the Supercar forum... Now I hear that the cost has been increased. Are they going to bill me for the difference or do I need to get another check off to them? I'm really looking forward to the return of Tom Shaw and would prefer not to miss an issue.
Regards,
05-14-2002, 12:16 AM
#17
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Re: L-88 Dyno results with stock exhaust and factory headers (Rowdy Rat)
Stan:
The $9.95 is for the premier issue, and to help get the magazine off the ground. The "other" amount you have saw is the actual subscription price of the magazine. I think this magazine is gonna be a winner...I can't wait for it to arrive. Nice choice for the premiere cover as well...;)
BadL-88:
I would LOVE to see that thing go down the 1/4! Hemis beware...
The $9.95 is for the premier issue, and to help get the magazine off the ground. The "other" amount you have saw is the actual subscription price of the magazine. I think this magazine is gonna be a winner...I can't wait for it to arrive. Nice choice for the premiere cover as well...;)
BadL-88:
I would LOVE to see that thing go down the 1/4! Hemis beware...
05-17-2002, 06:11 PM
#18
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Re: L-88 Dyno results with stock exhaust and factory headers (BAD-L88)
For comparison sake. Just went through the same drill with my rebuild:
67 427 4 bolt 351
bored 30 over
hardened orig crank
11:1 TRW pistons
closed chamber 391 iron heads
double valve springs
new original type valves and pushrods and solids
L88 type cam and water pump
stock exhaust manifolds
stock orig carbs and intake manifolds (tripower)
DYNO
496 HP @ 6200 RPM Gross
400 HP @ 6200 RPM rear wheels
67 427 4 bolt 351
bored 30 over
hardened orig crank
11:1 TRW pistons
closed chamber 391 iron heads
double valve springs
new original type valves and pushrods and solids
L88 type cam and water pump
stock exhaust manifolds
stock orig carbs and intake manifolds (tripower)
DYNO
496 HP @ 6200 RPM Gross
400 HP @ 6200 RPM rear wheels
05-17-2002, 06:25 PM
#19
Melting Slicks
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Re: L-88 Dyno results with stock exhaust and factory headers (dhendo)
Welcome aboard, dhendo! Always nice to have 'new' blood around. Those are healthy looking numbers as well!!
Are you running the 427 in a coupe or roadster?
Are you running the 427 in a coupe or roadster?
05-20-2002, 04:21 PM
#20
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Re: L-88 Dyno results with stock exhaust and factory headers (Mac)
Convertible. Would like to add headers but have to resist temptation due to originality. I think it would spin 520-525 HP with headers.