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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!
You have now heard from several well respected members that have plenty of experience with these engines such as Fast355, as well as Sofakingdom who is actually a physicist - again with tons of SBC experience, and myself that owns a 305 car AND a dyno. None of us agree with you.
What is your analysis of that conundrum? Seems the consensus here is that you are wrong. Plain and simple. Given the opinion of respected members you have virtually zero chance of convincing anyone of these claims.
Rebuttal? I'm curious to hear your analysis of why you are now in this position?
GD
I actually feel quite satisfied and I'm even more convinced the LG4 is under rated now. Fast355 had to show me the link twice but the article he linked clearly shows a bone stock LG4 is capable of making 190 crank HP (assuming 18% loss) with full front accessories and stock single exhaust. That matches up pretty well with the 82 LG4 making 197 on the HRM dyno too. I'm 100% convinced those motors were mildly under rated, I never cared for them at all until I owned one but now I truly appreciate them.
I actually feel quite satisfied and I'm even more convinced the LG4 is under rated now. Fast355 had to show me the link twice but the article he linked clearly shows a bone stock LG4 is capable of making 190 crank HP (assuming 18% loss) with full front accessories and stock single exhaust. That matches up pretty well with the 82 LG4 making 197 on the HRM dyno too. I'm 100% convinced those motors were mildly under rated, I never cared for them at all until I owned one but now I truly appreciate them.
God could come down with the facts and you'd still be convinced that boat anchor is 'under rated.'
At no point was it under rated. The ratings from factory are accurate, and not 'short' by any means. Like most, to any vehicle, you can modify it from stock and eek more performance out of it.
Want to know a vehicle GM under rated from factory? The 89 Turbo Trans-Am. The factory HP rating was definitely shy...
That's ONE article from the 80's using an OLD dyno with analog everything. Can you imagine what it even had for a computer in 1987? LoL. It was probably a high reading dyno to make the magazine editors happy. Remember this is 1987!! The dyno said 142 wheel on a stock engine - trust me the drivetrain eats more than 3hp. The engine was absolutely NOT under rated.
Can someone please bring me a car with a stock early 80's LG4? I'll dyno it for free!
GD
Last edited by GeneralDisorder; Nov 18, 2019 at 01:27 PM.
That's ONE article from the 80's using an OLD dyno with analog everything. Can you imagine what it even had for a computer in 1987? LoL. It was probably a high reading dyno to make the magazine editors happy. Remember this is 1987!! The dyno said 142 wheel on a stock engine - trust me the drivetrain eats more than 3hp. The engine was absolutely NOT under rated.
Can someone please bring me a car with a stock early 80's LG4? I'll dyno it for free!
GD
I keep also trying to explain to him that the LG4 in that article was also a 170 hp crank rated LG4. Not the weaker 140 hp rated one. There is not a single piece in common between his LG4 and an 87 LG4. Different pistons, different cam, different heads, different intake manifold, etc.
Right - so the dyno probably read about 2-3% high. Engine made 170..... put 142 to the ground. That's 15% drivetrain loss just as I said. It was probably closer to 139 WHP and the losses were more like 18%. But 1980's dyno tech and high reading for magazine article happiness.
If you drive the car up a mountainside it loses some power
it you drive the car below sea level it gains power
since when does plus or minus 5 to 15 percent make any difference?
tire friction varies, technically daily it changes. Lubricating viscosity varies especially with temp. Wear and tear seems like it will lower pistonringdrag
being more well balanced creates less friction, frees up some power I bet humidity is water molecules as a gas state within a specific volume therefore reduces power because it lowers air density
even two identical engines may vary greatly, and the older you go the more variability there seems to be between identical specimens.
theres little 1 and 2 percents all over the place to gain or lose and that effect is compounded with aging the older, longer ago it was made from today
Last edited by Kingtal0n; Nov 18, 2019 at 05:41 PM.
In other words, your 145 is 200. 200 is the same as 120. 120 is 220. they are all essentially the same for the purpose of illustrating, clearly, the kind of vehicle we are talking about at 3800lbs the 200 might as well be 120. Whether or not it was done on a mountain, in the humid rainy season, with a dyno correction factor or not, is irrelevant...
If you drive the car up a mountainside it loses some power
it you drive the car below sea level it gains power
since when does plus or minus 5 to 15 percent make any difference?
tire friction varies, technically daily it changes. Lubricating viscosity varies especially with temp. Wear and tear seems like it will lower pistonringdrag
being more well balanced creates less friction, frees up some power I bet humidity is water molecules as a gas state within a specific volume therefore reduces power because it lowers air density
even two identical engines may vary greatly, and the older you go the more variability there seems to be between identical specimens.
theres little 1 and 2 percents all over the place to gain or lose and that effect is compounded with aging the older, longer ago it was made from today
While this is true, I have had occasion to dyno stock cars from the 80's and early 90's and they are usually quite close to factory specs. They may smoke or run like poo at low RPM/Cruise, but at WOT..... they really have to be SHOT or have serious fuel system issues or clogged exhaust or something to make significantly less than factory spec.
While this is true, I have had occasion to dyno stock cars from the 80's and early 90's and they are usually quite close to factory specs. They may smoke or run like poo at low RPM/Cruise, but at WOT..... they really have to be SHOT or have serious fuel system issues or clogged exhaust or something to make significantly less than factory spec.
GD
that is testament to factory SAE or OEM protocol (years of updates), the goal of modern autos is to minimize those differences between assembled units. The newer the car, the less variation in every part, ex. bearing clearance gets tighter and more uniformly controlled.
When we see cars that DO Produce exactly the number that it says on a sticker from some year forward, we can thank the factory's methods of generalizing auto parts production into repeatable, same type of unit construction "quality guarantee" more or less w/ respect to certain attributes by using manufacturing size/materials ranges and techniques for producing those parts. A benchmark for human society no question
That also happens to be the quality which gives us statistical interface for used parts, for example I can say with around 90 to 98.88888887% confidence that a random initially fully working alternator from years 2002-2008 certain van/trucks will work terrific and last a long time if installed properly.
But if I have a dyno on a mountain now we might see my car has lost some power. And this turns into an internet discussion called 305
GD, since you own a dyno, let me ask how much does rear axle gear ratio change results?
I've seen it explained before that the further a final drive is from 1:1, the less power will be registered on dyno. So a 3.73 gear ratio registers lower horsepower during testing then a 2.73 gear ratio (with same tires).
Is there a rule of thumb for comparing dyno runs with different gear ratios?
Numerically higher ("lower") gears increase losses due to friction and inertia and thus lower the dyno readings. The final drive is the major loss in the system and the major reason why drivetrain losses are an approximation. Changes in the final drive and tire sizes will change the dyno numbers. The farther you get from 1:1, the more losses you will have. When we say 12-18% it is because it largely depends on the final drive and tire size.
@GeneralDisorder Why are you referencing the test they did out of curiosity with the factory cold air package blocked off? Did you not read the article or are you just trying to stack the deck in your favor? Bone stock with factory cold air and single exhaust it made 190 at the crank assuming an 18% loss (and 183 @ 15%).
I love how you can just say "the dyno doesn't lie" until it says something you don't like and then all of a sudden they do lie.
Just like the way you instantly said that old dyno was way off until Fast355 had to remind you the 87 has different specs and then suddenly the dyno isn't nearly as far off anymore. I feel sorry for anyone close to you that has to put up with your condescending dogma.
I already mentioned the compression variation earlier which is the biggest difference but frankly it doesn't matter if the 82 and 87 LG4 aren't identical twins, they are both carbureted single exhaust 305's making the same ballpark of power at the same RPM according to dyno tests and those dyno tests all back up my hunch whether you guys like it or not. If nothing else we all learned that the factory cold air package can make these motors produce almost 20 more horsepower than advertised and that is the very definition of under rated.
In addition we've all seen proof that the early and late LG4's are indeed capable of 200+ HP with all stock internals and even single exhaust. Honestly I was hoping for proof they make 200 in full factory trim but 180-190 is close enough for something from that era with single exhaust. Even if we assume the early 145 HP rating is true the fact that my car came with the cold air package and I never got a chance to drive it before some genius cut up the Y pipe would be why my butt dyno so accurately told me it had somewhere closer to 200 HP.
I sincerely thank everyone that took this thread seriously. Especially Fast355 for adding to my heap of evidence and helping me understand that drivetrain losses may not always be as great as I thought. I wish you all the best for the coming holidays. Now I must go, my Oldsmobile 260 budget build is in dire need of attention.
I'm gonna say this ONE last time: The 1984 LG-4 (which is what the O.P. has) DID NOT produce 190hp at the crank. It was NEVER "underrated", nor was any other American car engine during the 1980s.
PERIOD. End of story...
just say "the dyno doesn't lie" until it says something you don't like and then all of a sudden they do lie
Not really.
Dynos don't lie; but people claiming to "interpret" the numbers "for you", DO.
In the immortal words of Samuel Clemens, "there's lies, DAMN lies, and STATISTICS." Dyno output "interpretation" falls into the last category.
The 145 HP LG4s were NOT under-rated. Those of us who WERE THERE at the time, and avoided those cars (and CFI too) because of it, can be completely confident in telling you that. We don't need to argue about dynos. Track numbers correlated quite reasonably,
Since the energy a moving car has is its mass times the square of its velocity, and it's ALSO the product of time spent putting the energy of motion into it and the average power (power = energy, aka "work", per unit of time) over the length of time it took to accelerate it to that velocity, it's SOOOOOOOOOOOPER EEEEEEEEEZY to weigh a car, find its velocity at the end of the quarter, time how long it takes to run the quarter, and then crank the handle and watch RWHP fall out of the machine. Then one can apply almost ANY reasonable estimate of drive train loss percentage, with numbers in the 18 - 22% range being "reasonable", and back into crank HP. You'll find that the track numbers from back in the day correspond quite nicely to 120ish RWHP, which is around 145 - 150 HP at the crank in a 3400 lb car.
You can "believe" whatever you want, or attack the credibility of the witnesses, or attempt to maintain plausible deniability, or postulate something else and try to get everybody else to disprove that instead of you disproving the original hypothesis (aka the "straw man" logical fallacy), or whatever else you want; won't change THE FACTS.
I've seen people try to say it has more to do with the nuances of the dyno algorithms, but never provide a good exlanation. Does that hold any water?
What kind of difference are really talking about here? I've never seen real numbers comparing two gear ratios.
It's nothing really to do with the dyno algorithms. It's just that lower gears are requiring more input do to their greater multiplication and the forces at work between the gears are causing more losses due to friction (more tooth contacts per rotation). I've seen it stated that a good approximation is to take the percentage difference between the gears ie: 2.72 and 3.73..... 27% additional reduction. Then take the "usual" 15% loss rate and add 27% of it, or 4% additional loss. So going from a 2.72 to a 3.73 would add about 4% additional drivetrain loss. That's about as good of an approximation as anything I've seen and seems about right from experience. 15% for a high geared car vs. 20% for a low geared car. Bigger tires are doing the same thing in effect - more circumference equals more friction per rotation. As HP goes up, gearing usually goes down (lower numeric) - both because you don't need the mechanical advantage of high numeric gears, and because low numeric gears tend to be stronger due to the larger pinion diameter. This may account for why I tend to see smaller drivetrain losses on my dyno - we have a lot of cars with numerically low gearing because they have over 400 HP at the wheels. Many have over 600. Numerically lower gears tend to be advantageous with very powerful cars - otherwise you just smoke the tires and it's hard to get off the line.
GD
Last edited by GeneralDisorder; Nov 19, 2019 at 04:20 PM.
I agree w GD about "guessing" drive train loss; the best you can do is make an educated guess. His "guess" method makes about as much sense as any of them, and stays within the bounds of "reasonable".
My estimates came from a guy I knew that had a Mustang chassis dyno (old one, quite different from what you see around these days), who had a friend with a Superflow engine dyno. He consistently saw numbers like what I quoted earlier on, for motors that went on the stand in VERY CLOSE TO the same condition as they would go into the car... with a water pump, exhaust system, the same carb & air cleaner and cooling fan, and so forth. There's a good 100 HP of engine dyno tricks you can use to make the number read higher without "lying" sometimes, but that won't tell the truth about "drive train loss", even though the numbers you get appear to tell the difference between "the same" engine on the stand vs in the chassis. DAMN lies and STATISTICS.
In the same vein, putting a "cold air package" on a motor is, BY DEFINITION, making it something other than "stock", aka, MODIFIED; and comparing some kind of MODIFIED engine's numbers to the FACTORY spec for a STOCK one is the very DEFINITION of something in between a DAMN lie and a STATISTIC.
The factory's 145 HP "rating" for those turds is NOT "under-rated". In STOCK trim, that's what they did. No matter WHAT ELSE they might have done after being MODIFIED.
Last edited by sofakingdom; Nov 19, 2019 at 05:18 PM.
What if I were to tell you that in the late '70's, while GM Powertrain engineers were dynoing LG4s for the up coming 3rd gen F-car, they were shocked to see that they were actually producing 310 horsepower at the flywheel. It was an "oh $h!t" moment! These guys were in trouble! The Feds would never go for that!
So started a clandestine program, deep within the bowels of GM, to bleed off 170 horsepower and make the LG4 useable and safe for consumer consumption. They added a secret restricter plate on the Q-jet to reduce flow to 70 CFM and delivered all cars with clogged cats.
Please don't share this with anyone as this is still top secret. It's just between us guys.
What if I were to tell you that in the late '70's, while GM Powertrain engineers were dynoing LG4s for the up coming 3rd gen F-car, they were shocked to see that they were actually producing 310 horsepower at the flywheel. It was an "oh $h!t" moment! These guys were in trouble! The Feds would never go for that!
So started a clandestine program, deep within the bowels of GM, to bleed off 170 horsepower and make the LG4 useable and safe for consumer consumption. They added a secret restricter plate on the Q-jet to reduce flow to 70 CFM and delivered all cars with clogged cats.
Please don't share this with anyone as this is still top secret. It's just between us guys.
this is absolutely true even if it was an accident
I know that because
305x5800/3456*.069*.88 = 31lb/min or 310brake horsepower at 88% VE with a 5800rpm redline near sea level
predicts what any healthy 305cid engine would produce under those circumstances
this is absolutely true even if it was an accident
I know that because
305x5800/3456*.069*.88 = 31lb/min or 310brake horsepower at 88% VE with a 5800rpm redline near sea level
predicts what any healthy 305cid engine would produce under those circumstances
I was looking for something to kill some time this morning and this thread did not disappoint. It has all the great components, 305, newbs, Kingtalon (always a joy reading his garbage on LS1Tech), etc.
I was looking for something to kill some time this morning and this thread did not disappoint. It has all the great components, 305, newbs, Kingtalon (always a joy reading his garbage on LS1Tech), etc.
FWIW, 305's are turds.
I don't agree that 305s are turds. I mean it's a smallblock Chevy. Maybe the early '80's LG4s were a little turdy, but that doesn't cover all 305s, including later LG4s and L69s and various LB9s including L98 cammed, N10 equipped ones which on anyone"s scale are far from turds.
I don't agree that 305s are turds. I mean it's a smallblock Chevy. Maybe the early '80's LG4s were a little turdy, but that doesn't cover all 305s, including later LG4s and L69s and various LB9s including L98 cammed, N10 equipped ones which on anyone"s scale are from from turds.
Agreed. Hell, there were a lot of 350 and other "good" engine turds back in the smog era. It's like saying the 350 is garbage based solely on the L48 engine.
Now, that doesn't mean someone should throw good money at hopping up a 305 because it does have some serious design limitations.
Regrettably I have no 305 yarns to tell. In lieu of such compelling arguments as driveline losses, altitude correction, and can't be having the 305 compete with the Flagship Corvette, please accept these humorous images.
Regrettably I have no 305 yarns to tell. In lieu of such compelling arguments as driveline losses, altitude correction, and can't be having the 305 compete with the Flagship Corvette, please accept these humorous images.
Sincerely...
GM made the 305's rotating assembly out of tungsten as well as the axles and then filled the driveshaft with depleted uranium to increase the mass and slow down the 305 powerhouse (along with the restrictor plates and clogged catalytic converters chazman mentioned) as to not embarrass Formula One who cut General Motors a check for an undisclosed (reportedly huge) $$ amount. Everyone knows this.
displacement is meaningless. Don't read the truth. Its how well built and what technology has been invested that determines capability and efficiency.
The 1989-1992 nissan and toyota stuff closely resembles 99-02+ chevrolet engines in terms of seals, girdle, pan support, oil control, pcv activities, and 99-01 was an uncertain time for chev, trying new things and figuring out how it all worked SEQEFI electronics had their own nuances and a stable platform for all vehicles was developed properly by around 02. The Gen3 is considered the first and earliest, simplest platform of the desirable variety. You may notice the 99 or 98 stuff was sometimes weird to deal with and undesirable. And luckily the plentiful 02' engines are nearly free 4.8L 5.3L. Which is why I currently recommend LS motors made from 02+ where years 04-08 seems ideal for the basic swap (get gen4 rods) into the 3000-4000lbs vehicle.
scrap
junkyard
I don't agree that 305s are turds. I mean it's a smallblock Chevy. Maybe the early '80's LG4s were a little turdy, but that doesn't cover all 305s, including later LG4s and L69s and various LB9s including L98 cammed, N10 equipped ones which on anyone"s scale are far from turds.
I should have said in stock form by today's standards. My N10 equipped LB9 isn't a complete turd, but my 2019 Ram would run right with it and honestly probably get it in the 1/4. My LB9 is a little tired though. I guess I got used to racing/driving an 800+ hp Camaro that went 5's in the 1/8. I do enjoy driving my stock 3rd Gen no matter how slow it is though.
I should have said in stock form by today's standards. My N10 equipped LB9 isn't a complete turd, but my 2019 Ram would run right with it and honestly probably get it in the 1/4. My LB9 is a little tired though. I guess I got used to racing/driving an 800+ hp Camaro that went 5's in the 1/8. I do enjoy driving my stock 3rd Gen no matter how slow it is though.
I think it's hard to enjoy cars of the past, be that from the '80's or '60's or whenever, if you don't appreciate them for what they are/were. My daily driver has an LS3 and TR6060, but I still enjoy driving my 3rd gens.
I think it's hard to enjoy cars of the past, be that from the '80's or '60's or whenever, if you don't appreciate them for what they are/were. My daily driver has an LS3 and TR6060, but I still enjoy driving my 3rd gens.
I certainly appreciate cars from the past and have really enjoyed my 91 Z. I actually enjoy driving it more than I did any of the 4th gens I owned and none of them were stock. I would even dare to say I enjoy driving it more than my Dad's 2016 SS and those cars are amazing IMO. Eventually the 91 will have more power and be even more fun to drive.
I actually feel quite satisfied and I'm even more convinced the LG4 is under rated now. Fast355 had to show me the link twice but the article he linked clearly shows a bone stock LG4 is capable of making 190 crank HP (assuming 18% loss) with full front accessories and stock single exhaust. That matches up pretty well with the 82 LG4 making 197 on the HRM dyno too. I'm 100% convinced those motors were mildly under rated, I never cared for them at all until I owned one but now I truly appreciate them.
Show us the TRAP SPEED of a completely stock LG4....the try to tell us how it's under rated. Until then...Give up.
@GeneralDisorder Why are you referencing the test they did out of curiosity with the factory cold air package blocked off? Did you not read the article or are you just trying to stack the deck in your favor? Bone stock with factory cold air and single exhaust it made 190 at the crank assuming an 18% loss (and 183 @ 15%).
All this theoretical nonsense is stupid. Let's take it back to the real world and find the truth.
.
Real World: You're 50 years old and drive a LG4 3rd gen, and still eat at Arby's.
Real World: About 20 minutes earlier you ate a family pack of jalapenos poppers all by yourself, with bronco berry sauce, because that's what 50 year old 3rd gen owners do.
Real World: Now suddenly you have a serious attack of diarrhea and you're still 10 miles from home. (Do I even need to explain why again?)
Truth or Dare: You've got to have at least 180 Hp to get home in time before shitting your pants. Are you going to trust your LG4 to get the job done?
Now you know there's somebody here reading this saying to themselves, "Ya, totally happened to me." But that's not the point. The point is nobody in their right mind would run the gauntlet with an LG4 305.
All this theoretical nonsense is stupid. Let's take it back to the real world and find the truth.
.
Real World: You're 50 years old and drive a LG4 3rd gen, and still eat at Arby's.
Real World: About 20 minutes earlier you ate a family pack of jalapenos poppers all by yourself, with bronco berry sauce, because that's what 50 year old 3rd gen owners do.
Real World: Now suddenly you have a serious attack of diarrhea and you're still 10 miles from home. (Do I even need to explain why again?)
Truth or Dare: You've got to have at least 180 Hp to get home in time before shitting your pants. Are you going to trust your LG4 to get the job done?
Now you know there's somebody here reading this saying to themselves, "Ya, totally happened to me." But that's not the point. The point is nobody in their right mind would run the gauntlet with an LG4 305.
I wouldn't mind running this LG4 before they blew it up. Well it started life as a LG4 short block anyway. On the 150 shot it would have lived long enough for some track abuse.
IDK what ^that^ means exactly, but a funny thing is that I scanned your sig and saw the "Stickies: 82-92 FR-Body 1/4 mile times list" and clicked on it....since I've referenced trap speeds to the OP numerous times. Although the "Fast list" is serisoulsy lacking in participation, there is ONE LG4 on the list, and it ET'ed 16.2 and trapped 79 mph weighing 3370 lbs. That is about exactly what my '83 TA LG4 ran several decades ago. Plug in 79 MPH and 3570 lb (200 lb driver) into the WALLACE CALULATOR and what do you get? 137 FW hp. Not over rated, OP.
That's pretty much what I recall from back in the day. They et'd all over the map, depending on tires and such, never below 16.0 that I ever saw; but had real trouble breaking 80 mph no matter what else. You could get to 137 RWHP just by removing the air duct off of the air cleaner, if it was a nice cool night and you ran the car cold, and didn't hallucinate that a "burnout" would somehow make those super crappy 215/65-15 turds "sticky".
This is about as as we can to get to having a "social" forum I'd say.
If we had a social subforum it'd be exactly this kind of shitposting and moreso. Looking back it was fairly corny. Look at any older forum that still has a general discussion forum, it's all mouth breathing window lickers, and trolling.
I prefer the tech side of 3rd gen. Every so often we (as in we collectively) will throw in a personal anecdote or side story but the "chat room" thing has little appeal for me.
Threads like this one are certainly amusing to read and there are some real gems when it comes to replies (thanks QwikTrip) but overall I'd rather read than write.
Thanks for listening.
...there is ONE LG4 on the list, and it ET'ed 16.2 and trapped 79 mph weighing 3370 lbs. That is about exactly what my '83 TA LG4 ran several decades ago. Plug in 79 MPH and 3570 lb (200 lb driver) into the WALLACE CALULATOR and what do you get? 137 FW hp. Not over rated, OP.
My 50k mile L03 was 144 on the dyno this past fall. So that calculation is right on, and the LG4 and L03 were NOT under rated.
Originally Posted by Drew
If we had a social subforum it'd be exactly this kind of shitposting and moreso. Looking back it was fairly corny. Look at any older forum that still has a general discussion forum, it's all mouth breathing window lickers, and trolling.
That's ENTIRELY on the forum owner and mods. If left alone, it does become that. I run a forum, with strict rules, and have no such issues with our general or off-topic section. You just have to be clear about what the rules are, then enforce them. It's not rocket science, but it IS additional work.
i just sold recently a 83 trans am with a lg4 , 5 speed and 3.73 factory gears with 33k miles on it .. fresh tune up and ran great .. but one thing i can tell you for sure is it was a total dog as far as performance goes .. might have been the slowest thing i have ever driven in my life ..
