[olrocker]

Originally Posted by Alan47717

Your point is well taken, however, you have to remember that the advertised horsepower ratings for most of that era's "King Kong" engines were pure fiction, mostly to pacify insurance companies. 430 hp for the L88? 375 hp for the Boss 429? Please.

Yes that’s true. If GM had the supercharged Gen V LT4 then they’d have rated it at “425” horsepower….

I can imagine Brock Yates in Car & Driver after taking a 2021 ZL1 on the track……

“If GM wants us to believe this thing has only 425 horsepower maybe the flat earthers should be taken seriously too”

[ZED SLED]

Originally Posted by olrocker

And that was using modern day SAE Net calculations?

lol, no idea. show was from 2007.

[Evergreen6]

Any estimate on how much modern "emissions equipment" robs horsepower these days?

Cats are generally already high-flow. Engines don't turn smog pumps anymore and haven't for about the last 30 years. EGR systems? What else?

[ctrlz]

Originally Posted by Evergreen6

Any estimate on how much modern "emissions equipment" robs horsepower these days?

Cats are generally already high-flow. Engines don't turn smog pumps anymore and haven't for about the last 30 years. EGR systems? What else?

Probably on the order of 1%.
I know that may be an unpopular answer. But even in the 90's people were saying deleting emissions equipment was more for looks than power gains. A/C compressors, alternators... all this stuff gets switched in and out as needed.

[Evergreen6]

Originally Posted by ctrlz

Probably on the order of 1%.
I know that may be an unpopular answer. But even in the 90's people were saying deleting emissions equipment was more for looks than power gains. A/C compressors, alternators... all this stuff gets switched in and out as needed.

I tend to agree, but would love to see any current data.

When I owned my 86 Iroc (60k orig miles) a few years back, people would ask if I had modded the 305 and pulled off all the "emissions crap". I hadn't, because the goal was to keep the car original. It retained the factory cat, belt-driven smog pump and secondary air injection system.

Even if I had done that, we're still talking turd-levels of horsepower from a 30+ year old LB9. It had 190 wheezing ponies from the factory, and I don't think that was under-rated.lol!!. It wasn't going to be a fast car even if you pulled all that stuff off and lit the car on fire. My answer was always, if I wanted a fast car, I'd buy one (an IROC by modern standards is....slow).

And that gets a lot of guys telling me "you just don't get it!" Uh, I do, and, I think it's stupid

[ctrlz]

Originally Posted by Evergreen6

I tend to agree, but would love to see any current data.

Without getting into tuning, most "honest" vendors will tell you to work the exhaust first, mainly by going to a higher flow cat. Not cheap, and requires welding. Much easier for sellers to push intakes, but gains may be close to zero as we have discussed here.
This site has data for LT2 corvette. They get a bump of 6 HP with their cats. Click on the graph in below link.
https://www.fabspeed.com/fabspeed-ch...ort-cats-2020/

[Evergreen6]

Originally Posted by ctrlz

Without getting into tuning, most "honest" vendors will tell you to work the exhaust first, mainly by going to a higher flow cat. Not cheap, and requires welding. Much easier for sellers to push intakes, but gains may be close to zero as we have discussed here.
This site has data for LT2 corvette. They get a bump of 6 HP with their cats. Click on the graph in below link.
https://www.fabspeed.com/fabspeed-ch...ort-cats-2020/

Thanks for sharing. That's more of a bump than I would have expected.

Gains of ~20hp up top, or about 6-6.5 at the wheel. On a 490hp car, that's a 4% increase, or just over 1% at the wheels.

For $3700+ before install...hmm. That's steep.

[m6-lt1]

Originally Posted by Evergreen6

Any estimate on how much modern "emissions equipment" robs horsepower these days?

Cats are generally already high-flow. Engines don't turn smog pumps anymore and haven't for about the last 30 years. EGR systems? What else?

It’s been proven on these boards that removing the primary cats gets us about 10-12 HP so a little over a 2% gain. Removing the secondary cats gains us nothing.

As you can see the power gains on an NA car are minimal. It’s when you’re making big boy HP that things like going catless or adding headers net you some decent gains. The primary benefit of removing cats is when you’re making big boy HP not having to worry about your cats melting and clogging the exhaust/getting damaged. Of course the car won’t be smog legal now but just wanted to explain the benefits and who really benefits from removing emissions equipment on modern vehicles.

[Kamero6]

Originally Posted by olrocker

Just thinking about the old SAE gross ratings of the original muscle car era and I had a real mind blower…..

If our 455 hp LT1s were rated in gross circa 1963-71 it’d have been rated about 570 hp!!!

Those of you with the 650 hp supercharged LT4? 810 hp!!!!

Take that Chevelle SS396, Charger 440 Magnum and 426 Hemi, and Ford 428 Cobra Jet

Nice topic to discuss.

Actually, based on my research and opinion (based in data also), its the other way around.


The old SAE gross HP methodology, was made to inflate numbers and probably twist the HP marketing war between brands.

They would Dyno the engine (in an engine dyno), making the following adjustments.

- Ignition and fuel adjustments for each RPM. (Basically play with distributor and jets until you get the max power at that particular RPM, then draw the dot in the graph).
- No drag. This means no belt, alternator, no water pump, fan, etc.. The only things driven were oil pump, fuel pump (maybe), and distributor.
- No air filter or exhaust, and I doubt they used the production exhaust manifold.
- Standard SAE room temp and water coolant temp, etc... that's described in the standards.


That gave a boost of around 15% in power, but it is a gross estimation because you would have to travel in time and do back to back test to get it right.

Now our engines, with modern control systems, adjust spark and fuel for each rpm and condition, they have low drag belt systems, electric water pumps, electric fans, alternators stop generating at WOT, low drag oil pumps, Super efficient air filters and exhausts... and so on.

A 1960's engine with a moder control pack, will most probably dyno SAE Gross numbers on the street, means the difference will be gone or be very narrow.

To clarify, I mean a 425 GROSS HP car from 1969, with a modern spark & fuel control system, modern accesories, modern intake and exhaust, will dyno that installed in the car. It is basically replicating the SAE gross testing method on the street.

[Kamero6]

Originally Posted by Evergreen6

Any estimate on how much modern "emissions equipment" robs horsepower these days?

Cats are generally already high-flow. Engines don't turn smog pumps anymore and haven't for about the last 30 years. EGR systems? What else?

EGR doesn't work at WOT. Cats also muffle a lot of sound, so in case the factory would ditch EPA regulations, they would still have to add another muffler/resonator to make the car pleasant. That would also rob power.

[Evergreen6]

Originally Posted by m6-lt1

It’s been proven on these boards that removing the primary cats gets us about 10-12 HP so a little over a 2% gain. Removing the secondary cats gains us nothing.

As you can see the power gains on an NA car are minimal. It’s when you’re making big boy HP that things like going catless or adding headers net you some decent gains. The primary benefit of removing cats is when you’re making big boy HP not having to worry about your cats melting and clogging the exhaust/getting damaged. Of course the car won’t be smog legal now but just wanted to explain the benefits and who really benefits from removing emissions equipment on modern vehicles.

For track use I don't disagree at all. Tenths of a second matter and 1% whp gain is meaningful, and like you said, you can actually destroy a cat converter.

It's that crossover point, big boy HP on the street, or in my example above, my 190hp IROC. My perspective on that leans pragmatic, what are those gains worth.

[GearheadSS]

Originally Posted by ZED SLED

I saw a show on Speed channel several years ago where a team built a 1964 era 426 hemi, a Pontiac 421, a 409, Ford 427 and an L88 supposedly to original specs and dyno tested to see if they lived up to the advertised HP from back in the day. 409 came in at 409 as advertised, 421 was close to what it was advertised. The 426 was supposed to be rated at 426 but was way off. Came in around 830. Ford 427 was 600ish and L88 was like 530. Found part of it: