78 Stock L-82/4 Speed-65,000 Miles-First Time on the Dyno!
10-10-2011, 01:19 PM
#41
Le Mans Master
I haven't seen a stock '78 L-82 dyno sheet as a baseline, nor a dyno sheet with exhaust only modifications on a stock '78 L-82 - so no, I can't agree with "very substantial" gains from exhaust only.
I'll continue to provide my perspective when the issue arises, as you will. The readers can then interpret and make their own decisions...the beauty of differing experiences
I'll continue to provide my perspective when the issue arises, as you will. The readers can then interpret and make their own decisions...the beauty of differing experiences
Last edited by billla; 10-10-2011 at 01:22 PM.
10-10-2011, 04:25 PM
#43
Drifting
It is interesting that headers or cam plus improved intake manifold and true duals get you something like 50+ horsepower gain on an L82. In my case I did not change the cam or the intake manifold or the exhaust manifolds and got a 30 hp gain. My numbers won't match yours because the guy who ran mine on the dyno he has uses different calibration techniques so you have to look at the net difference which I've reported above. In shorthand, factory for an L48 which did not have the slightly more advanced cam of the L82 was 180 hp sae net at 4,000 rpm and 270 ft lbs of torque at 2400 rpm sae net. The best pull I had Friday would translate that according to the dyno guy and his calibration and experience I used into: 210 hp sae net at 3750rpms and 285 ft lbs at 2900 rpms. In other words: a 30 hp gain and about 15 ft lbs of torque. We did not adjust carb, just ran baseline.
I would expect the L82 to do better with better breathing because everything I've read is that the stock L82 cam is a slightly more aggressive cam than the L48.
For whatever it's worth, your results and Mine and the other with the cam of unknown but not the headers keeps saying the same thing: advance the timing (13 degrees for me), more exhaust to let it breath....big changes...improve intake manifold then cam and then heads with bigger valves and porting and you can bring these engines back to late 60's muscle car status. The L82 is a better platform with different bolts in the bottom, etc. but every time someone does what we've done the answers come out the same..let 'em breath and they do better.
From what I've read there's another maybe ten hp available by going to a better intake...then perhaps headers to get a little more. After that I think with the l48 you have to get into the engine to do cam, compression ratio, heads, bigger valves and rollers to get more and if that, then bore it out and make it a 383. I'm fine the way it is but the L82 would have been a more robust engine to improve it looks like...started with more hp and gets more with similar changes.
Thanks for sharing.
Lance
Lance
I would expect the L82 to do better with better breathing because everything I've read is that the stock L82 cam is a slightly more aggressive cam than the L48.
For whatever it's worth, your results and Mine and the other with the cam of unknown but not the headers keeps saying the same thing: advance the timing (13 degrees for me), more exhaust to let it breath....big changes...improve intake manifold then cam and then heads with bigger valves and porting and you can bring these engines back to late 60's muscle car status. The L82 is a better platform with different bolts in the bottom, etc. but every time someone does what we've done the answers come out the same..let 'em breath and they do better.
From what I've read there's another maybe ten hp available by going to a better intake...then perhaps headers to get a little more. After that I think with the l48 you have to get into the engine to do cam, compression ratio, heads, bigger valves and rollers to get more and if that, then bore it out and make it a 383. I'm fine the way it is but the L82 would have been a more robust engine to improve it looks like...started with more hp and gets more with similar changes.
Thanks for sharing.
Lance
Lance
Last edited by LancePearson; 10-11-2011 at 03:53 AM. Reason: correct rpms
10-11-2011, 12:30 PM
#44
Safety Car
(It is interesting that headers or cam plus improved intake manifold and true duals get you something like 50+ horsepower gain on an L82. In my case I did not change the cam or the intake manifold or the exhaust manifolds and got a 30 hp gain. My numbers won't match yours because the guy who ran mine on the dyno he has uses different calibration techniques so you have to look at the net difference which I've reported above. In shorthand, factory for an L48 which did not have the slightly more advanced cam of the L82 was 180 hp sae net at 4,000 rpm and 270 ft lbs of torque at 2400 rpm sae net. The best pull I had Friday would translate that according to the dyno guy and his calibration and experience I used into: 210 hp sae net at 3750rpms and 285 ft lbs at 2900 rpms. In other words: a 30 hp gain and about 15 ft lbs of torque. We did not adjust carb, just ran baseline.)
Quoted from LancePerson
So what did you get at the rear wheel? on my stock l-48 I did long tube header, 2.5'' true duals, xe262h, wieand action plus dual plane aluminum intake, edelbrock performer heads (64cc chambers with 185cc intake runners), comp 1.6 to 1 roller tip rockers & a 600 cfm holley vaccum secondaries, I got 260 rwhp w/ 300 rwtq. I think that if i had gone with afr or dart heads I could have sqeezed more powere out of it, although the performer heads were better than the 882's they just dont flow what better heads do. I just got my afr 195 eliminators in for my dart shp 400. The quality alone looks to be about 4 fold. just curious for the comparison being as yours being stock.
Quoted from LancePerson
So what did you get at the rear wheel? on my stock l-48 I did long tube header, 2.5'' true duals, xe262h, wieand action plus dual plane aluminum intake, edelbrock performer heads (64cc chambers with 185cc intake runners), comp 1.6 to 1 roller tip rockers & a 600 cfm holley vaccum secondaries, I got 260 rwhp w/ 300 rwtq. I think that if i had gone with afr or dart heads I could have sqeezed more powere out of it, although the performer heads were better than the 882's they just dont flow what better heads do. I just got my afr 195 eliminators in for my dart shp 400. The quality alone looks to be about 4 fold. just curious for the comparison being as yours being stock.
10-11-2011, 01:25 PM
#45
Drifting
blue dawg....Yes, yours is modified much more than mine....the heads and intakes are big things and a more aggressive cam is good too. The L82 stock engine I've read has a more aggressive cam in it than the l48 and it's a four bolt main versus two for ramping power up better.
The dyno guy had his calibrated in his own way so I'll give it all back to you in sae net terms.
Horsepower: sae net 180 at 4,000 rpm. After changes: would be sae net 210 at 3750 rpms
Torque: sae net 270 at 2400 rpms. After changes: would be sae net 299 ft lbs at around 2900 rpms.
The actual rear wheel dyno numbers on his dyno would not relate to other dynos the way he calibrated his but they are easily convertible to the above.
the intake I've read is worth maybe as much as another 10 hp and the tube headers a few more. After that you have to get into the heads to increase compression, larger valve sizes, cam and then rollers so it all spins faster now that it can breath all the way through. There is no reason to open my engine so I won't do all that as the engine runs fine if not as powerfully as yours which is now substantially more powerful than mine.
If you take yours forward with your estimate of drive train losses to sae net you have an engine pretty much like the 300-350 hp small blocks of the late 1960s now with yours it seems to me. Good on you, mate!
Lance
The dyno guy had his calibrated in his own way so I'll give it all back to you in sae net terms.
Horsepower: sae net 180 at 4,000 rpm. After changes: would be sae net 210 at 3750 rpms
Torque: sae net 270 at 2400 rpms. After changes: would be sae net 299 ft lbs at around 2900 rpms.
The actual rear wheel dyno numbers on his dyno would not relate to other dynos the way he calibrated his but they are easily convertible to the above.
the intake I've read is worth maybe as much as another 10 hp and the tube headers a few more. After that you have to get into the heads to increase compression, larger valve sizes, cam and then rollers so it all spins faster now that it can breath all the way through. There is no reason to open my engine so I won't do all that as the engine runs fine if not as powerfully as yours which is now substantially more powerful than mine.
If you take yours forward with your estimate of drive train losses to sae net you have an engine pretty much like the 300-350 hp small blocks of the late 1960s now with yours it seems to me. Good on you, mate!
Lance
10-11-2011, 01:28 PM
#46
Drifting
p.s. Is the 600 cfm Holley big enough for the way yours is set up now? I'd wonder if it can flow enough air to match the rest now and might be your new limit. Don't know, just have seen 700+ cfm carbs for the horsepower range you are getting into elsewhere. If you do anything further you might consider increasing carb cfm after researching it.
Lance P.
Lance P.
10-11-2011, 04:32 PM
#47
Le Mans Master
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Scott,
OK! Let's just say then that a 78 L-82 4 Speed with the mods mentioned above and having never been internally apart was rated at the factory at 220 Net HP when new producing 233 RWHP today! What that 233 RWHP is in net or gross terms today is debatable but the figure has to be substantially more in Net HP than the 233 RWHP figure. Agreed?
OK! Let's just say then that a 78 L-82 4 Speed with the mods mentioned above and having never been internally apart was rated at the factory at 220 Net HP when new producing 233 RWHP today! What that 233 RWHP is in net or gross terms today is debatable but the figure has to be substantially more in Net HP than the 233 RWHP figure. Agreed?
If you take a close look at L82 specs, what you find is pretty interesting.
1.) It has a pretty big cam, for a factory engine.
2.) It has a pretty decent intake manifold, for a factory engine.
3.) The heads may not be much to write home about, but they do have the 2.02/1.60 valves.
4.) 9:1 static compression ratio, not too shabby.
5.) Pretty much the same crappy, restrictive exhaust system that a station wagon of the same era had. (The twin tailpipes don't do squat for exhaust flow after that big, heavy, restrictive catalytic converter.)
So, I am not in the least surprised to see what some people might consider pretty dramatic power increases from allowing such an engine to breathe, by freeing up the exhaust. It's just that the dyno numbers that you measured are the only numbers that really mean much of anything. Trying to figure out the net HP from the rear wheel measured HP is quesswork, at best. And the factory HP rating? Gimmee a break!
I would love to see some chassis dyno numbers from a stock L-82, and then another run after installation of a nice dual exhaust system with headers. That would be comparing apples with apples. Or would it be oranges with oranges? Whatever.
Scott
10-11-2011, 05:05 PM
#48
Le Mans Master
some time back super Chevy did a dyno run on a stock L-82 engine and came up about 312 h.p. i have no reason to doubt those numbers, that's about what we figgured back in 78 when that engine was a few years old. as a point of interstate i knew a girl with a 70 LT-1 and her dad complained about the solid lifters being noisy so we put the cam we took out of a L-82 in it with little loss of performance on the street. i put her old cam in my L-82 and wasn't great put my stock cam back in advanced 4 degrees like the cam was designed and it ran best like that.
10-11-2011, 05:40 PM
#49
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I absolutely agree with this statement!
If you take a close look at L82 specs, what you find is pretty interesting.
1.) It has a pretty big cam, for a factory engine.
2.) It has a pretty decent intake manifold, for a factory engine.
3.) The heads may not be much to write home about, but they do have the 2.02/1.60 valves.
4.) 9:1 static compression ratio, not too shabby.
5.) Pretty much the same crappy, restrictive exhaust system that a station wagon of the same era had. (The twin tailpipes don't do squat for exhaust flow after that big, heavy, restrictive catalytic converter.)
So, I am not in the least surprised to see what some people might consider pretty dramatic power increases from allowing such an engine to breathe, by freeing up the exhaust. It's just that the dyno numbers that you measured are the only numbers that really mean much of anything. Trying to figure out the net HP from the rear wheel measured HP is quesswork, at best. And the factory HP rating? Gimmee a break!
I would love to see some chassis dyno numbers from a stock L-82, and then another run after installation of a nice dual exhaust system with headers. That would be comparing apples with apples. Or would it be oranges with oranges? Whatever.
Scott
If you take a close look at L82 specs, what you find is pretty interesting.
1.) It has a pretty big cam, for a factory engine.
2.) It has a pretty decent intake manifold, for a factory engine.
3.) The heads may not be much to write home about, but they do have the 2.02/1.60 valves.
4.) 9:1 static compression ratio, not too shabby.
5.) Pretty much the same crappy, restrictive exhaust system that a station wagon of the same era had. (The twin tailpipes don't do squat for exhaust flow after that big, heavy, restrictive catalytic converter.)
So, I am not in the least surprised to see what some people might consider pretty dramatic power increases from allowing such an engine to breathe, by freeing up the exhaust. It's just that the dyno numbers that you measured are the only numbers that really mean much of anything. Trying to figure out the net HP from the rear wheel measured HP is quesswork, at best. And the factory HP rating? Gimmee a break!
I would love to see some chassis dyno numbers from a stock L-82, and then another run after installation of a nice dual exhaust system with headers. That would be comparing apples with apples. Or would it be oranges with oranges? Whatever.
Scott
10-11-2011, 06:29 PM
#50
Drifting
well said
I absolutely agree with this statement!
If you take a close look at L82 specs, what you find is pretty interesting.
1.) It has a pretty big cam, for a factory engine.
2.) It has a pretty decent intake manifold, for a factory engine.
3.) The heads may not be much to write home about, but they do have the 2.02/1.60 valves.
4.) 9:1 static compression ratio, not too shabby.
5.) Pretty much the same crappy, restrictive exhaust system that a station wagon of the same era had. (The twin tailpipes don't do squat for exhaust flow after that big, heavy, restrictive catalytic converter.)
So, I am not in the least surprised to see what some people might consider pretty dramatic power increases from allowing such an engine to breathe, by freeing up the exhaust. It's just that the dyno numbers that you measured are the only numbers that really mean much of anything. Trying to figure out the net HP from the rear wheel measured HP is quesswork, at best. And the factory HP rating? Gimmee a break!
I would love to see some chassis dyno numbers from a stock L-82, and then another run after installation of a nice dual exhaust system with headers. That would be comparing apples with apples. Or would it be oranges with oranges? Whatever.
Scott
If you take a close look at L82 specs, what you find is pretty interesting.
1.) It has a pretty big cam, for a factory engine.
2.) It has a pretty decent intake manifold, for a factory engine.
3.) The heads may not be much to write home about, but they do have the 2.02/1.60 valves.
4.) 9:1 static compression ratio, not too shabby.
5.) Pretty much the same crappy, restrictive exhaust system that a station wagon of the same era had. (The twin tailpipes don't do squat for exhaust flow after that big, heavy, restrictive catalytic converter.)
So, I am not in the least surprised to see what some people might consider pretty dramatic power increases from allowing such an engine to breathe, by freeing up the exhaust. It's just that the dyno numbers that you measured are the only numbers that really mean much of anything. Trying to figure out the net HP from the rear wheel measured HP is quesswork, at best. And the factory HP rating? Gimmee a break!
I would love to see some chassis dyno numbers from a stock L-82, and then another run after installation of a nice dual exhaust system with headers. That would be comparing apples with apples. Or would it be oranges with oranges? Whatever.
Scott
Lance P.
10-11-2011, 07:29 PM
#51
Race Director
I haven't seen a stock '78 L-82 dyno sheet as a baseline, nor a dyno sheet with exhaust only modifications on a stock '78 L-82 - so no, I can't agree with "very substantial" gains from exhaust only.
I'll continue to provide my perspective when the issue arises, as you will. The readers can then interpret and make their own decisions...the beauty of differing experiences
I'll continue to provide my perspective when the issue arises, as you will. The readers can then interpret and make their own decisions...the beauty of differing experiences
78 Corvette with GW350 motor, same cam as a stock L48, smog-like heads with 1.94/1.50 valves.
A series of 5 0-60 tests at each step in the process.
Started at avg 7.4, with stock exhaust, timing dialed in.
7.1, with stock manifolds, 2.25" true dual exhaust with cats.
6.6, after adding 1 5/8" long tube headers
6.2, upgrading to dual 2.5" exhaust.
The exhaust issue is very real - the headers provided a very big SOTP difference, along with the numbers to back it up.
10-11-2011, 07:49 PM
#52
Le Mans Master
The L-82/L-46 cam is still a great cam today for a 4-speed car with fairly deep gears (3.55-3.70), but more cam with the stock heads isn't going to have a huge impact as flow tops out between .400 - .500...right where the cam is at
10-11-2011, 08:45 PM
#53
Le Mans Master
Thread Starter
I can.
78 Corvette with GW350 motor, same cam as a stock L48, smog-like heads with 1.94/1.50 valves.
A series of 5 0-60 tests at each step in the process.
Started at avg 7.4, with stock exhaust, timing dialed in.
7.1, with stock manifolds, 2.25" true dual exhaust with cats.
6.6, after adding 1 5/8" long tube headers
6.2, upgrading to dual 2.5" exhaust.
The exhaust issue is very real - the headers provided a very big SOTP difference, along with the numbers to back it up.
78 Corvette with GW350 motor, same cam as a stock L48, smog-like heads with 1.94/1.50 valves.
A series of 5 0-60 tests at each step in the process.
Started at avg 7.4, with stock exhaust, timing dialed in.
7.1, with stock manifolds, 2.25" true dual exhaust with cats.
6.6, after adding 1 5/8" long tube headers
6.2, upgrading to dual 2.5" exhaust.
The exhaust issue is very real - the headers provided a very big SOTP difference, along with the numbers to back it up.
Excellent! More verification and validation of the substantial increase that my exhaust changes had on the RWHP on the dyno!! I still can't fathom claims by some that my L-82 is not basically a stock internal engine. Holley 650 spreadbore- no hp increase over the Oem Q jet:roller tipped 1.5 rockers- no increase in hp over stock rockers, hyptech hei coil-no increase in hp.
Btw-I have decided at this point with 65,000 miles on the L82 to advance the cam 4 degrees this winter since the timing chain should be replaced having a nylon cam gear currently. We will see in the spring on the dyno if the hp/torque numbers just move down by 500 rpm or if there is a substantial increase or decrease on the dyno. It may be interesting- no other changes!
10-11-2011, 08:57 PM
#54
Safety Car
p.s. Is the 600 cfm Holley big enough for the way yours is set up now? I'd wonder if it can flow enough air to match the rest now and might be your new limit. Don't know, just have seen 700+ cfm carbs for the horsepower range you are getting into elsewhere. If you do anything further you might consider increasing carb cfm after researching it.
Lance P.
Lance P.
10-11-2011, 08:57 PM
#55
Drifting
That's very interesting and a 16% decrease in times with the modifications. On my l48 something similar happened with a 16.6% increase in hp on the dyno runs done last week with similar but not the headers or 2.5" exhaust...just 2.25" exhaust. Might be within the range of variability but it sure makes me want to think about tube headers instead of the cast ram's horn exhaust manifolds that are stock along with a better intake manifold as well.
In 0-60 you don't go through many gears but it sure shows relative change.
Thanks.
L.P.
In 0-60 you don't go through many gears but it sure shows relative change.
Thanks.
L.P.
10-11-2011, 08:59 PM
#56
Le Mans Master
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I can.
78 Corvette with GW350 motor, same cam as a stock L48, smog-like heads with 1.94/1.50 valves.
A series of 5 0-60 tests at each step in the process.
Started at avg 7.4, with stock exhaust, timing dialed in.
7.1, with stock manifolds, 2.25" true dual exhaust with cats.
6.6, after adding 1 5/8" long tube headers
6.2, upgrading to dual 2.5" exhaust.
The exhaust issue is very real - the headers provided a very big SOTP difference, along with the numbers to back it up.
78 Corvette with GW350 motor, same cam as a stock L48, smog-like heads with 1.94/1.50 valves.
A series of 5 0-60 tests at each step in the process.
Started at avg 7.4, with stock exhaust, timing dialed in.
7.1, with stock manifolds, 2.25" true dual exhaust with cats.
6.6, after adding 1 5/8" long tube headers
6.2, upgrading to dual 2.5" exhaust.
The exhaust issue is very real - the headers provided a very big SOTP difference, along with the numbers to back it up.
Scott
10-12-2011, 10:13 AM
#57
Drifting
The change from 2.25" diameter pipe to 2.5" pipe is 23% increase in cross sectional area so a significant change in exhaust max flow rate. At some point I've read that the pipe gets too big and it actually becomes a negative as a modest amount of back pressure is necessary for the pump that is the engine to keep flowing at its max.
10-12-2011, 11:06 AM
#58
Le Mans Master
As for stock internals, the power potential of the L-82 is clear and no disagreement - with the right combination of parts, which has always been my perspective and experience
0-60 times can vary dramatically for a variety of reasons - great times to be sure, and a great improvement, but I see this as yet another "proof" that is very subjective.
Certainly exhaust velocity up to about 18" behind the header collector can have an impact, which is primary tube size is something to be careful of, but past that there's no benefit to a smaller exhaust - and often a benefit to a larger one. This article does beautiful work of validation with what seems to be to be a pretty comprehensive and methodical approach:
http://www.hotrod.com/techarticles/e...tem/index.html
"In theory, the larger the engine's displacement and the higher the rpm where peak horsepower occurs, the better it should respond to the reduced backpressure of a larger-diameter exhaust. Conversely, it's been said that a mild engine with too much exhaust flow may fall on its face with not enough backpressure, though we've never seen that to be true and can't even imagine how backpressure could help performance in a four-stroke engine."
"...it came as no great surprise that our test revealed more power everywhere with the 3-inch system compared to the 2.5-inch system. "
Finally carb sizing is pretty straightforward for the street; the formula CFM = ((CI x RPM)/3456) x VE works pretty well in most cases - if you work the numbers, you'll find that a 350 has to make a fair bit of power or turn some serious R's to outbreathe a 600-650 CFM carb
Last edited by billla; 10-12-2011 at 01:41 PM.
10-13-2011, 01:34 AM
#59
Safety Car
Finally carb sizing is pretty straightforward for the street; the formula CFM = ((CI x RPM)/3456) x VE works pretty well in most cases - if you work the numbers, you'll find that a 350 has to make a fair bit of power or turn some serious R's to outbreathe a 600-650 CFM carb [/QUOTE]
So what do you use to determine ve? I only ask because I have been pondering that for about 3 years. I mean if the average bone stock engine is only @ about 80% ve, what do they use to determine this, is it total flow or horse power to cubic inch, is 100% ve all that's achievable with a naturaly aspirated engine. I truly figure that when the current set up I'm running starts to decrease on power gains its due to either valves starting to float or the cam shaft is just not running to the peak rpm that comp says its good for. I'm not for sure.
[/QUOTE]So what do you use to determine ve? I only ask because I have been pondering that for about 3 years. I mean if the average bone stock engine is only @ about 80% ve, what do they use to determine this, is it total flow or horse power to cubic inch, is 100% ve all that's achievable with a naturaly aspirated engine. I truly figure that when the current set up I'm running starts to decrease on power gains its due to either valves starting to float or the cam shaft is just not running to the peak rpm that comp says its good for. I'm not for sure.
10-13-2011, 11:50 AM
#60
Le Mans Master
Sorry for the OT excursion - should take this to PM for anything else.
For engine building and tuning I use HP/CID for almost everything from carb sizing, power potential from heads/intake to build budget estimates. I put a bone stock engine at around 75% (at peak power) moving towards the high 90's at around 1.4 HP/CID. I use DDA 5 for initial design for builds, tops, etc. and this provides a decent estimate for VE.
For carb sizing specifically it's important to look at not only peak flow but also at what RPM the secondaries will kick in. But intake velocity is key...a bit small is far better than a bit big for a street engine
For engine building and tuning I use HP/CID for almost everything from carb sizing, power potential from heads/intake to build budget estimates. I put a bone stock engine at around 75% (at peak power) moving towards the high 90's at around 1.4 HP/CID. I use DDA 5 for initial design for builds, tops, etc. and this provides a decent estimate for VE.
For carb sizing specifically it's important to look at not only peak flow but also at what RPM the secondaries will kick in. But intake velocity is key...a bit small is far better than a bit big for a street engine
Last edited by billla; 10-13-2011 at 06:20 PM.