Factory Exhaust Manifold horsepower data

[tgonyaw]

I found an advertisement from Lingenfelter showing the 368 ci LT-5 at 530 hp. Is that number before the factory exhaust manifolds and cats are installed? The add has an EPA number for this configuration. How much horsepower do the stock exhaust manifolds with cats support?

Thanks for any opinions and insights.

http://lingenfelter.managecontent.com/engine-packages/corvette-1990-2013/c4-zr1-1990-1995/530-hp-368-cid-lt5

[Karl]

Since it has a carb # and no description of headers I am going to say the engine is advertised with factory exhaust manifolds.

[Paul Workman]

Since it has a carb # and no description of headers I am going to say the engine is advertised with factory exhaust manifolds.

Sounds reasonable, Karl.:thumbsup:

tgonyaw: Based on my 350 cid LT5, I picked up 20-25 over top-end porting and a canned tune by switching to LT headers, no cats, and flow thru mufflers (with a 2.5" choke on the inlet.

So, based on that, it would be an estimate at best, but the stock manifolds and cats, etc. are prolly costing you ~ 30 hp or maybe more. Marc Haibec's (http://www.zr1specialist.com/HAT%20Web/products/major%20engine%20upgrades.htm) site can give you some more info, far as mix and match goes (headers, a tune, aluminum FW, etc.) With his treatment including exhaust, porting and tuning shows 540 HP. So, if you're getting ~ 530 w/ stock exhaust manifolds and cats, I'd say your right in the ball park with a typically well tuned 368 with stock exhaust manifolds and cats, etc.!

[efnfast]

But why would you build a 368 with stock exhaust?

[Karl]

But why would you build a 368 with stock exhaust?

To be 50 state emission compliant, especially California. I believe Lingenfelter sells, or use to sell these packages with a warranty also.

That is something not seen today. Building a 500 - 600+ hp car with a tuner warranty.

[tgonyaw]

Thanks for the replies.
My car is emissions exempt here in Virginia. It still must pass a visual test for the safety inspection each year. It has a ported top end with Corsa exhaust and deleted secondaries. The shop replaced everything under the plenum except the AC compressor. Ran well for about 400 miles after new fuel pumps and 2nd tune completed. It now acts like an old carb car with a faulty accelerator pump.
I will contact Marc after the holidays to craft a plan. His 510 package makes the most sense because I would get new head gaskets and could add all new hoses while fixing 2 oil trips, etc. while the engine is out.
This sight has 100?s of years of data and knowledge. Can not be duplicated.

[Vette73]

I found an advertisement from Lingenfelter showing the 368 ci LT-5 at 530 hp. Is that number before the factory exhaust manifolds and cats are installed? The add has an EPA number for this configuration. How much horsepower do the stock exhaust manifolds with cats support?

Thanks for any opinions and insights.

http://lingenfelter.managecontent.com/engine-packages/corvette-1990-2013/c4-zr1-1990-1995/530-hp-368-cid-lt5

Holy crap $22,500 for this package ? You can probably get a high mileage C6 Z06 for mid to high 20's....There around 505 HP but 300 lbs lighter than a C4 Z...Not cheap to really up displacement in these cars....Pete's 391 is a better bet...

[tf95ZR1]

https://www.zr1.net/forum/showthread.php?t=32159&highlight=carb

Esp post #8

[32valvZ]

I think with the new "political climate" those of us not having to worry about it will not have too long to enjoy "emissions exempt".... just sayin':fahne:

[Karl]

Holy crap $22,500 for this package ? You can probably get a high mileage C6 Z06 for mid to high 20's....There around 505 HP but 300 lbs lighter than a C4 Z...Not cheap to really up displacement in these cars....Pete's 391 is a better bet...

You are paying for the 24 month/24,000 mile warranty.

I was talking with Pete about his 391 and if the factory crankshaft is offset grind from 3.66" to 3.76" you will get a 402.

So tempting!!!!!