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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Drivetrain losses are a PERCENTAGE. Not a hard number of HP's. Sure you can easily lose 100 HP in the drivetrain - if you are making 900+ CHP you will easily lose that much. Also has to do with the dyno operator, settings they used, what gear it was run in, and a host of other factors. Was it 100 degrees in the dyno bay that day? How many pulls did they do in a row? How much heat soak factor are we talking about?
You really have no idea what you are talking about and that just becomes more clear as you continue to respond to our attempts at educating you. Have YOU ever put a car on a dyno? I'm about to head down to MY performance shop and do some pulls on MY $150,000 AWD chassis dyno this afternoon. Do you suppose I *might* know a bit about this subject?
GD
75-100 HP isn't a hard number it's a ballpark. It's not a set ballpark for everything either, it's for automatic solid rear axle street cars. I'm sorry but I'm not terribly inclined to believe much of what you're saying when I can see someone else educating you on the subject in this same thread.
75-100 HP isn't a hard number it's a ballpark. It's not a set ballpark for everything either, it's for automatic solid rear axle street cars. I'm sorry but I'm not terribly inclined to believe much of what you're saying when I can see someone else educating you on the subject in this same thread.
Keep reading - no one is educating me in this thread kid.
Automatic, solid axle cars DO NOT lose 100 HP through the drivetrain. How f**cking stupid are you actually? There have been millions of such vehicles built by auto manufactures that didn't even HAVE 100 HP at the crank from the factory? How is it they are able to drive then genius? If you lost 100 HP on an automatic, solid axle, RWD car with a 4 cylinder or inline 6 cylinder that makes less than 100 HP at the crank then the car wouldn't be able to even move. Losses are a percentage. I have dynoed tons of cars with around the same power as your LG4 and they are going to lose about 20-30 HP through the drivetrain in their most direct-drive gear at peak HP RPM with the TC above it's stall speed.
As far as that silly Hot Rod article goes - they clearly f**cked up that test. Either that Ford's AOD was slipping, bad torque converter, etc or the car wasn't strapped properly or had traction problems on the rollers. Those numbers are WAY off base for the Ford. The Buick is much closer to reality with it's 18% figure - that was likely a loading dyno like a Mustang.
What? You think that because they publish it on the internet they are infallible? These are magazine editors relying on some shop with a dyno for their numbers and their explanations of said numbers. They are just as fallible as anyone else and subject to confirmation bias just as you are. Someone is in denial that his trans is shot.
I don't buy the whole "percentage" thing. The idea that a drivetrain robs 20hp from a 200hp engine, but that SAME drivetrain is gonna rob 100hp from a 900hp engine just defies all physics. I'm just not buying that the more power an engine produces, the more will be lost through the drivetrain.
At the same time, I don't buy that the drivetrain in a thirdgen is robbing 100hp from any engine. It's probably around 40 or 50 at most.
Obviously you can figure out the percentage of loss of a particular engine/drivetrain combination if you know the crank horsepower, but there's no given percentage that covers all engine/drivetrain combinations across the board...
Even if you are correct about drivetrain loss being set in stone at 18% that still puts every stock 305 I've seen on a chassis dyno at or over 200 crank HP including this 83 GMC that supposedly is all stock besides intake and carb. I would even dare to say that the intake and carb aren't helping much at all when compared to the stock aluminum intake and Q jet. If the truck is making 160 at the wheels and losing 18% on the way there then it's making 196 at the crank which matches up almost perfectly with the Hot Rod Magazine LG4 dyno test mentioned earlier that shows the engine making 197 HP with just tuning tricks and headers. In fact that's pretty good evidence right there that the GMC didn't gain anything number wise from that performer intake. It also shows that a stock 305 may not actually benefit much at all from headers, at least not in peak numbers. The 4 into 1 scavenging effect is probably improving the torque curve and drivability.
Anyhow my point is the evidence for 200 gross crank HP is there for sure, even going by 18% loss.
Last edited by Impact's Garage; Nov 16, 2019 at 01:59 PM.
As far as that silly Hot Rod article goes - they clearly f**cked up that test. Either that Ford's AOD was slipping, bad torque converter, etc or the car wasn't strapped properly or had traction problems on the rollers. Those numbers are WAY off base for the Ford. The Buick is much closer to reality with it's 18% figure - that was likely a loading dyno like a Mustang.
What? You think that because they publish it on the internet they are infallible? These are magazine editors relying on some shop with a dyno for their numbers and their explanations of said numbers. They are just as fallible as anyone else and subject to confirmation bias just as you are. Someone is in denial that his trans is shot.
GD
The Buick has a clutch, that's why you think it's more in line with what you see normally. Also did you miss the part of the discussion earlier where we talked about the lighter duty automatics like the TH200 developed for less powerful engines at the start of the first oil crisis?
That truck has a 315 (60 over), intake and carb. Sounds like has exhaust also. Those are all absolutely worth additional power. That'a DynoJet they are using and it's certainly in Inertia mode without any loading being applied based on the sound of the run. So it's not at all a fair comparison showing more power than the "stock" rating from a 305. It's not even a 305 and if they went to the trouble to bore over a 305 (which is a hilariously bad idea), then they may have done a few other things on the inside of the engine in the process. It really demonstrates absolutely NOTHING in terms of the *STOCK* rating of your LG4. That "315" is modified and probably makes 30-40 HP over stock and is losing about 15-20% on that dyno. This makes total sense and does NOT show that your LG4 makes 50 HP more than GM claimed.
The Buick has a clutch, that's why you think it's more in line with what you see normally. Also did you miss the part of the discussion earlier where we talked about the lighter duty automatics like the TH200 developed for less powerful engines at the start of the first oil crisis?
The design of the auto has little to do with this discussion. The losses are in the torque converter unless the trans is slipping.
The Buick is closer to reality but without seeing the setup on their dyno you really can't say much about it other than it appears from those numbers that the Ford had drivetrain problems - slipping or a badly built torque converter. I've seen plenty of poor quality "performance" torque converters that slipped like that. That is not typical for an automatic to perform that badly.
Do you really think a stock 305 is taxing the abilities of a 750 CFM Q jet and aluminum intake? I don't think a non air gap performer and Holley carb has anything at all to offer an internally stock 305. Someone wasted their money putting that intake on that truck, it needed either the stock intake or an SP2P.
30-40 HP? 10 cubes isn't even worth 10 HP the exhaust is likely worth more than that
The POINT is that it's FAR from stock. They didn't come bored 60 over did they? So it's not scientific. They probably shaved the heads, shaved the deck, different head gasket thickness, certainly an aftermarket piston - maybe "stock replacement"..... maybe not. You can't tell from that video or the description and people who overbore 305's are immediately suspect because that's NEVER a good idea. Who knows what they have done. The point is that it;s a completely unfair comparison.
The design of the auto has little to do with this discussion. The losses are in the torque converter unless the trans is slipping.
The Buick is closer to reality but without seeing the setup on their dyno you really can't say much about it other than it appears from those numbers that the Ford had drivetrain problems - slipping or a badly built torque converter. I've seen plenty of poor quality "performance" torque converters that slipped like that. That is not typical for an automatic to perform that badly.
GD
You say it's not typical but it falls right in line with something experts three times my age told me. Not trying to be a jerk, just pointing out what I'm seeing.
Do you really think a stock 305 is taxing the abilities of a 750 CFM Q jet and aluminum intake? I don't think a non air gap performer and Holley carb has anything at all to offer an internally stock 305. Someone wasted their money putting that intake on that truck, it needed either the stock intake or an SP2P.
Again you don't know it's stock. Compression is likely higher than stock, timing is probably different than stock, and who know what they did to the heads while it was apart. Anyone that would overbore a 305..... I wouldn't trust a thing they say or do. That's an idiot move.
The POINT is that it's FAR from stock. They didn't come bored 60 over did they? So it's not scientific. They probably shaved the heads, shaved the deck, different head gasket thickness, certainly an aftermarket piston - maybe "stock replacement"..... maybe not. You can't tell from that video or the description and people who overbore 305's are immediately suspect because that's NEVER a good idea. Who knows what they have done. The point is that it;s a completely unfair comparison.
GD
I must agree with you, we do not and likely will never know what's inside that trucks motor. I do know that machine work is expensive though and if I paid to have heads worked, block decked etc. I'd be VERY disappointed with those numbers.
@GeneralDisorder Putting the perspective history of that trucks motor aside don't you find it coincidental that it matches up almost perfectly with the HRM dyno test of the internally stock LG4 when accounting for an 18% drivetrain loss?
You say it's not typical but it falls right in line with something experts three times my age told me. Not trying to be a jerk, just pointing out what I'm seeing.
Look - I understand you are young and are trying to get a grasp on the fundamentals but between myself and the tuners that I work with we have about 60 years of combined dyno tuning experience. The stated percentages I have previously given ARE accurate. There are nuances with different dyno's, etc but that's just the way it is. It is virtually universally accepted that your are going to lose about 15% with a 2WD dyno run at peak power assuming your drivetrain is working properly. I have dynoed everything from a 1950's Volvo with 40 HP to a 2019 Hellcat Redeye with a race gas map pushing over 800 to the wheels. This is all well known and we use these general percentages day in and day out and they work, they are repeatable, and they jive with manufacturer stock ratings. I guarantee my 86 LB9 would stomp your LG4 in a race and it's a little over 210 CHP with mods on an engine that's rated at 190 CHP by GM. Dyno result doesn't lie - 185 RWHP.
@GeneralDisorder Putting the perspective history of that trucks motor aside don't you find it coincidental that it matches up almost perfectly with the HRM dyno test of the internally stock LG4 when accounting for an 18% drivetrain loss?
I did not see this test anywhere in this post. Other than an old article posted on an '87 Firebird. That was a later LG4 with a different (higher) rating. The LG4, much like the LB9 was not rated the same for every production year. Mine was about 190 HP in 86, but later in the early 90's they were about 215 HP from the "same" LB9 with TPI. They went to roller cams in 1987 so things changed dramatically across the lineup.
Look - I understand you are young and are trying to get a grasp on the fundamentals but between myself and the tuners that I work with we have about 60 years of combined dyno tuning experience. The stated percentages I have previously given ARE accurate. There are nuances with different dyno's, etc but that's just the way it is. It is virtually universally accepted that your are going to lose about 15% with a 2WD dyno run at peak power assuming your drivetrain is working properly. I have dynoed everything from a 1950's Volvo with 40 HP to a 2019 Hellcat Redeye with a race gas map pushing over 800 to the wheels. This is all well known and we use these general percentages day in and day out and they work, they are repeatable, and they jive with manufacturer stock ratings. I guarantee my 86 LB9 would stomp your LG4 in a race and it's a little over 210 CHP with mods on an engine that's rated at 190 CHP by GM. Dyno result doesn't lie - 185 RWHP.
GD
You just said they CAN lie based on variables though. And OF COURSE it would stomp it, it has almost a full point more compression and a better cam so that's a no brainer. I'm not here to discuss your LB9, I never said the LG4 was the best 305 just that it was under rated. Not sure why you would even feel the need to flex on me like that, I could pull two plug wires off my daily and still leave your little POS LB9 sitting in a cloud of tire smoke. Does that prove that it makes less power than you say it does? No it doesn't.
I don't buy the whole "percentage" thing. The idea that a drivetrain robs 20hp from a 200hp engine, but that SAME drivetrain is gonna rob 100hp from a 900hp engine just defies all physics. I'm just not buying that the more power an engine produces, the more will be lost through the drivetrain.
At the same time, I don't buy that the drivetrain in a thirdgen is robbing 100hp from any engine. It's probably around 40 or 50 at most.
Obviously you can figure out the percentage of loss of a particular engine/drivetrain combination if you know the crank horsepower, but there's no given percentage that covers all engine/drivetrain combinations across the board...
Well - I'm not a physicist...... but there *are* ways to get at the crank HP without actually knowing it directly. With a modern engine that has a MAF sensor you can quite accurately estimate crank HP by a simple formula. It's (grams per second) x (1.2) ~= CHP. It's amazingly accurate actually. Try doing some datalogs on modern cars and taking a peak MAF reading at WOT. Run it through a VE calculator to check VE on the engine and ensure it's in proper working order then multiply by 1.2 and you have your basic CHP number. Seems simple I know - but it's true. You don't even need a dyno except for tuning. On most any modern fuel injected engine - if you want CHP you don't need a dyno. Grams per second is about wheel HP, and grams per second * 1.2 is about crank. It just is.
You just said they CAN lie based on variables though. And OF COURSE it would stomp it, it has almost a full point more compression and a better cam so that's a no brainer. I'm not here to discuss your LB9, I never said the LG4 was the best 305 just that it was under rated. Not sure why you would even feel the need to flex on me like that, I could pull two plug wires off my daily and still leave your little POS LB9 sitting in a cloud of tire smoke. Does that prove that it makes less power than you say it does? No it doesn't.
My point is you are claiming 200 CHP on an early LG4 that's bone stock and if that were the case you would be neck and neck with my LB9 WITH mods. Does that seem likely to you?
I did not see this test anywhere in this post. Other than an old article posted on an '87 Firebird. That was a later LG4 with a different (higher) rating. The LG4, much like the LB9 was not rated the same for every production year. Mine was about 190 HP in 86, but later in the early 90's they were about 215 HP from the "same" LB9 with TPI. They went to roller cams in 1987 so things changed dramatically across the lineup.
GD
Curved stock replacement MSD distributor and headers, they think the headers were worth 30 HP but I think it's more like 5 or 10 at the most as 30 HP from a set of headers seems a bit optimistic for such a low output engine. https://www.hotrod.com/articles/ccrp...-engine-build/
I don't buy the whole "percentage" thing. The idea that a drivetrain robs 20hp from a 200hp engine, but that SAME drivetrain is gonna rob 100hp from a 900hp engine just defies all physics. I'm just not buying that the more power an engine produces, the more will be lost through the drivetrain.
At the same time, I don't buy that the drivetrain in a thirdgen is robbing 100hp from any engine. It's probably around 40 or 50 at most.
Obviously you can figure out the percentage of loss of a particular engine/drivetrain combination if you know the crank horsepower, but there's no given percentage that covers all engine/drivetrain combinations across the board...
That is simple physics and it happens for two reasons. One the more HP you make the more quickly the whole driveline has to accelerate. This means the drivetrain eats more hp just to accelerate itself. Also energy is also not created or destroyed but changes form. What that means is for every action there is a reaction. You have gears in mesh and bearings holding these meshed gears into place. The more power you push into them the more friction between the parts and more force the bearings see. It is ABSOLUTELY a percentage of loss. Some things are fixed loss like a water pump, transmission hydraulic pump or power steering pump but most driveline components lose more and more power as more and more power are directed through them.
Well - I'm not a physicist...... but there *are* ways to get at the crank HP without actually knowing it directly. With a modern engine that has a MAF sensor you can quite accurately estimate crank HP by a simple formula. It's (grams per second) x (1.2) ~= CHP. It's amazingly accurate actually. Try doing some datalogs on modern cars and taking a peak MAF reading at WOT. Run it through a VE calculator to check VE on the engine and ensure it's in proper working order then multiply by 1.2 and you have your basic CHP number. Seems simple I know - but it's true. You don't even need a dyno except for tuning. On most any modern fuel injected engine - if you want CHP you don't need a dyno. Grams per second is about wheel HP, and grams per second * 1.2 is about crank. It just is.
GD
Funny thing is on the GM trucks I have messed with. 1 gm/sec is roughly 1 rwhp time and time again.
My point is you are claiming 200 CHP on an early LG4 that's bone stock and if that were the case you would be neck and neck with my LB9 WITH mods. Does that seem likely to you?
GD
I think the LB9 and the L69 were both under rated as well and made over 250 crank horsepower. I find this "rough" horsepower calculator actually tends to give you a fairly accurate ballpark for gross HP. http://www.bgsoflex.com/roughhp.html To be honest the under rating I'm referring to is mainly attributed to the difference in net VS gross. These 305s were rated in NET and everyone I'm aware of in the American performance scene with a dyno or chassis dyno is still going by gross numbers these days so it's cause for confusion.
Do you really think a stock 305 is taxing the abilities of a 750 CFM Q jet and aluminum intake? I don't think a non air gap performer and Holley carb has anything at all to offer an internally stock 305. Someone wasted their money putting that intake on that truck, it needed either the stock intake or an SP2P.
The stock manifold is terrible. Performer RPM intake woke up my 80s 305 up by a good amount especially when the tach ran up over 3,000.
I think the LB9 and the L69 were both under rated as well and made over 250 crank horsepower. I find this "rough" horsepower calculator actually tends to give you a fairly accurate ballpark for gross HP. http://www.bgsoflex.com/roughhp.html To be honest the under rating I'm referring to is mainly attributed to the difference in net VS gross. These 305s were rated in NET and everyone I'm aware of in the American performance scene with a dyno or chassis dyno is still going by gross numbers these days so it's cause for confusion.
If you removed the accessories, cats, muffler, air intake, air filter and ran a 230 HP LB9 on the engine dyno I am sure it would make over 260 hp. However the net rating is much more realistic of the engines actual power installed in the vehicle.
Absolutely not. My LB9 had a MAF when stock and it never approached anything like 250 grams per second. And I have seen plenty of stock L98 engine dynos that show they make about 255 HP with no accessories and engine dyno open headers. That's a well established fact. When installed with log manifolds, full exhaust, and accessories they make the factory claimed 235 HP. There is no way the LB9 was more. The 350 is a larger, more efficient air pump. Your claims are outrageous, stupid, and just plain wrong.
The early LG4 was "rated" at 145 HP, as we all know. It had dished pistons. The L69 had flat-tops, and later LG4s did as well. The LG4 "rating" as well as its actual output changed accordingly.
In the earlier years such as 84, the LG4 had the same heads as L69. 416 casting mostly. The intake manifolds were also the same AFAIK. L69 exhaust is MUCH bigger than LG4; the cam is different; L69 had electric radiator fan (probably 15 HP right there), better gears, and the lighter "composite" hood, which shed around 30 lbs off the nose. The gears and hood didn't add power of course, but weight reduction and gearing can make a car MUCH faster, even if HP is the same.
Drivetrain losses are always there. Even at no load, it takes power to spin it, totally independent of power applied, due to things like bearing friction. Then once load is applied, losses begin to increase, due to friction on the loaded parts like gear teeth. The REAL formula for drivetrain loss would therefore look something like road speed x some amount of HP per mph, PLUS HP x some percentage. For a typical moderately fast street car (let's say, 300 crank HP), at typical power levels with a typical drivetrain, the typical losses at typical peak HP RPMs and mph are typically around 18% for a stick and 22 - 25% for an auto. The converter affects the measurement method as much as, or more than, it affects actual loss.
However all that may be, as far as I could tell at the time, the 145 HP "rating" for the SHOWROOM FLOOR STOCK LG4 was substantially reasonably accurate. It is quite easy to improve it, particularly with exhaust and cam, so comparing one with ANY modifications WHATSOEVER, to the STOCK "rating", is meaningless.
And FWIW, I AM a physicist, and mathematician. (not marketable skillz )
Funny thing is on the GM trucks I have messed with. 1 gm/sec is roughly 1 rwhp time and time again.
Yup. I've discussed this at length with many tuners and they ALL agree. It's kinda spooky and if people knew about it and believed in it the way we do they wouldn't bother with baselines on a dyno other than to see the power curve. Peak HP is no mystery for us tuners. LoL.
Absolutely not. My LB9 had a MAF when stock and it never approached anything like 250 grams per second. And I have seen plenty of stock L98 engine dynos that show they make about 255 HP with no accessories and engine dyno open headers. That's a well established fact. When installed with log manifolds, full exhaust, and accessories they make the factory claimed 235 HP. There is no way the LB9 was more. The 350 is a larger, more efficient air pump. Your claims are outrageous, stupid, and just plain wrong.
GD
If you are talking about what I said the G92 LB9 305 absolutely makes as much HP as the 350 L98. It was well documented that the speed density 305 engines made as much hp at the wheels as the 350 cars did. The L98 was more choked from a breathing standpoint than the LB9 and they used the same cams. The 350 may have had a 5-10 hp advantage. On a gross dyno I would expect a 240 hp speed density 350 to run about 270 hp. Its also been proven the 300 net hp LT1 made more hp than the 370 gross rated LT-1.
Yup. I've discussed this at length with many tuners and they ALL agree. It's kinda spooky and if people knew about it and believed in it the way we do they wouldn't bother with baselines on a dyno other than to see the power curve. Peak HP is no mystery for us tuners. LoL.
GD
Actually you don't even have to do that. Just build an excel file and graph MAF vs RPM. You can see the HP curve. If you graph the GM/CYL airmass you can graph the torque curve.
If you are talking about what I said the G92 LB9 305 absolutely makes as much HP as the 350 L98. It was well documented that the speed density 305 engines made as much hp at the wheels as the 350 cars did. The L98 was more choked from a breathing standpoint than the LB9 and they used the same cams. The 350 may have had a 5-10 hp advantage. On a gross dyno I would expect a 240 hp speed density 350 to run about 270 hp. Its also been proven the 300 net hp LT1 made more hp than the 370 gross rated LT-1.
No I was referring to Impact Garage's assertion that the LB9 and L69 made over 250 CHP.
'Sorry, NO1980s American car engine power output was "underrated"...
I never said it was. Net ratings are just net ratings. Gross ratings are gross ratings. When you start tearing parts off a net rated engine and run them the same way a gross rated engine was run, the net rated engine becomes gross rated. Just the same as if you took a gross rated engine and started putting parts onto it would become net rated. GM once upon a time even had both power measurements. I think in some of the old Corvette literature I read on a 1957 Corvette. They had both Gross and Net power ratings.
Yup. I've discussed this at length with many tuners and they ALL agree. It's kinda spooky and if people knew about it and believed in it the way we do they wouldn't bother with baselines on a dyno other than to see the power curve. Peak HP is no mystery for us tuners. LoL.
GD
This was a L31 with 1.6 rockers, thorley tri-y headers and a muffler/tailpipe swap. With the little restrictor lip removed off the throttle body. Dyno'd 220 hp at the wheels.
Actually you don't even have to do that. Just build an excel file and graph MAF vs RPM. You can see the HP curve. If you graph the GM/CYL airmass you can graph the torque curve.
True. A little time consuming but could be done manually. Dyno is a heck of a lot more convenient.
No I was referring to Impact Garage's assertion that the LB9 and L69 made over 250 CHP.
They did not.
GD
Agreed!
I think I once read for SCCA racing the L69 would make 230 hp with the cam retarded 4* and the cat & smog removed. With a L82 cam it would make 260 hp.
If your 86 LB9 has a 700r4/7.5 in it the thing loses right at 18%. 185/0.82 = ~225 crank HP.
The first thing I did to my old 83 carb 305 rated 165 hp was ditch the factory manifolds, stock y-pipe, and stock pellet cat and cheap muffler shop 2" single outlet muffler and tail pipe. In its place I put a set of factory stainless 1-ton tubular manifolds and the stainless 2.5" dual exhaust piping off an 85 G30 350. I added a universal X-pipe that fit the factory exhaust spacing practically perfectly and replaced the OEM mufflers with a pair of magnaflow magnapacks. The exhaust modifications gave about 20-25 hp. Muffler shops 2" muffler and tailpipe probably cost 5-10 hp compared to the OEM 2.5" single in/dual 2" out factory muffler. I swapped the stock intake for a performer rpm at the same time, ditching the EGR and rejetting the Q-Jet at the same time. I went from ~125 rwhp to 170 rwhp with those changes. The 268 cam and thorley tri-ys into the same exhaust system gave the other 21 hp to 191.
Factory stainless 1-ton tubular manifolds??? Need input. And pictures!
Factory stainless 1-ton tubular manifolds??? Need input. And pictures!
LOL OK # Johnny FIVE.
How is this for input?
These are the dorman replacement ones. I got mine off a junkyard van back around 2002 or 2003. I grabbed the matching exhaust at the same time. Replacing the 2" outlet cast iron logs that were cracked and the 2" to 2.5" Y-pipe and rotted out 2.5" pellet style cat.
^^^ This is true. I remember the intake test article, either Car Craft or CHP, that proves it.
There was actually more than one article confirming this. The performer intake itself was worth a solid 20 hp on a car with banks headers and exhaust back when these cars were new. It also showed solid gains in the article I linked above.
Also for reference these are the Thorley Tri-Ys I put on my LE9 and had on both the 350 and later 383.
Probably the best street headers you could ask for.
These are the dorman replacement ones. I got mine off a junkyard van back around 2002 or 2003. I grabbed the matching exhaust at the same time. Replacing the 2" outlet cast iron logs that were cracked and the 2" to 2.5" Y-pipe and rotted out 2.5" pellet style cat.
There was actually more than one article confirming this. The performer intake itself was worth a solid 20 hp on a car with banks headers and exhaust back when these cars were new. It also showed solid gains in the article I linked above.
Backed up by the simple fact that they still sell them and people still buy them - likely their sales would have tanked and they would be long out of production by now if they didn't work and people didn't see significant gains from them. Dyno's are common enough now and word spreads quick on the internet. Especially bad reviews.
Also it is WELL ESTABLISHED that the stock GM exhaust manifolds and especially the "Y" pipe (that was actually a T) flows VERY poorly and they are absolutely worth somewhere in the neighborhood of 20 HP. I know my Dyno Don's picked up a significant amount of power on my LB9. Those along with 1.6 rockers put me within striking distance of the '89+ LB9 with the L98 cam and roller lifters. Of course if you do the same mods to one of those...... I'm quite certain you could see stock L98 performance or possibly more.
GD
Last edited by GeneralDisorder; Nov 16, 2019 at 04:46 PM.
I never said it was. Net ratings are just net ratings. Gross ratings are gross ratings. When you start tearing parts off a net rated engine and run them the same way a gross rated engine was run, the net rated engine becomes gross rated. Just the same as if you took a gross rated engine and started putting parts onto it would become net rated. GM once upon a time even had both power measurements. I think in some of the old Corvette literature I read on a 1957 Corvette. They had both Gross and Net power ratings.
@Tom 400 CFI Even if you are correct about drivetrain loss being set in stone at 18% that still puts every stock 305
Impact. WHERE DID I SAY THAT?? Please quote where I said that so that I can correct it, would you?
Originally Posted by Impact's Garage
I've seen on a chassis dyno at or over 200 crank HP including this 83 GMC that supposedly is all stock besides intake and carb.
I believe you....mostly. As stated earlier, the LG4 is extremely responsive to exhaust mods, b/c the stock exhaust is SO BAD. I don't doubt that you can find an LG4 that produced "better" numbers than stock, that had an exhaust replaced. No news flash there.
You've still convinced NO ONE, that a STOCK LG4 was 200 hp...because it wasn't.
Last edited by Tom 400 CFI; Nov 16, 2019 at 05:16 PM.
Also it is WELL ESTABLISHED that the stock GM exhaust manifolds and especially the "Y" pipe (that was actually a T) flows VERY poorly and they are absolutely worth somewhere in the neighborhood of 20 HP.
GD
I always referred to it as a Y-pipe, but you're absolutely right; it's a T. So what about the H.O. T-pipe? It's gotta be a little better, isn't it?...
@Tom 400 CFI Even if you are correct about drivetrain loss being set in stone at 18%
Impact....here is what I ACTUALLY said.
Originally Posted by Tom 400 CFI
^^^^This is TRUE. People always seem to grab at large "%" numbers in order to bolster their opinion of CHP. I'd go further and say that the actual loss in most cars is 10-12%. Here are a few examples of my own, to support this:
My stock 06 C6. We know that it's 400CHP. Mine did 366 RWHP. What % is that?
My wife's '05 CTS-V, we know that's 400CHP. Hers did 340 RWHP. What % is that?
My stock '92 LT1. We know that's 300 CHP. Mine did 279 RWHP. What % is that?
My stock-except-for-exhaust '89 'Vette Kart. We know that 89 L98 TPI's w/exhaust are about 255-260hp. The Kart did 240 RWHP. What % is that?
8.5%
15%
7%
8%
....so, ImportGarage, there is one place where you math is way, way off.
) 
