93 ZR1 no cats project

[8388]

Finally got around to replacing the ZF tranny in my ZR1. The original had a bad 2nd gear synchro. While the exhaust is off I decided to remove the cats. because 93s and newer have the cats bolted onto the manifolds. I started by fabricating the flanges which were made out of scrap steel plates over 3/8" thick. This thickness is needed in order to bolt the replacement pipe to the manifold flange with out the use of gaskets ( I hate gaskets ). The exhaust system is a cat back Desert Developement, which are no longer made. Here are a few pics.

This car made 411 rwhp SAE with just a Rippie chip, K&N filter and the DD exhaust with cats. I am curious to see if any more power can be made without the cats.

 

[SurfnSun]

Damn thats sweet Sam. Youre car is a freak I can't wait to see the results...I think you'll be around 430-435rwhp.

 

[JT ZR-Won]

Very cool setup. Your car is putting down some awesome numbers for that few of mods.

Jay

 

[8388]

From what I've been able to learn. 93 was when Merc. started port matching and degreeing the camshaft in order to meet the higher hp rating. I think some of these engines left the factory with a better combination of the two. I say this because this engine seems to make it's power higher in the rpm, which is in line with those types of improvements.

If this is true, this means that any LT5 is capable of producing these kinds of numbers with better port matches and cam degreeing.

 

[roadster]

I was thinking of doing the same thing when building an x-pipe cat back exhaust. I have the old type manifolds though, and some people have told me it´s not worth the effort, but maybe 5 hp on a fairly stock LT5.

Plz post your experience when done!

roadster

 

[EricVonHa]

How has the exhaust note changed without the cats?

More tacos to the wheels now?

 

[8388]

At idle you can barely tell the cats are off. Upon cracking the throttle open, you can definitely tell this car means bitness, and yes it does appear to have more tacos to the wheel :gap


BTW, I've heard that on a different vette forum, my Z was brought up in their rwhp discussion. As for the skeptics that may happen to read this, and for the record, this car has never had any porting or performance head work. I bought the car in 96 with 15,000 miles. The only thing that has ever been unbolted on the engine was the alt. which was replaced under warranty.

 

[8388]

Project completed

 

[dmrodco]

NICE work !!~!!!!

 

[JT ZR-Won]

Very sweet!

Jay

 

[8388]

Thanks Guys !

 

[SurfnSun]

That looks awesome, Sam. Thats the exhaust I need on my car

 

[Hib Halverson]

(snip)This car made 411 rwhp SAE with just a Rippie chip, K&N filter and the DD exhaust with cats. I am curious to see if any more power can be made without the cats.(snip)

Oh mah gawd be still my heart!
Am I embarassed or what. In fact, just about anyone with "top ended 350s" is going to be embarassed.

My stock block LT5 has ported heads, housings and plenum, a 63mm TB, reset cams, ported stock exhaust manifolds, cats, aftermarket cat-back exhaust, RC injectors, hot coils, cold plugs, Green Filter, 170-deg thermostat with a Fluidyne radiator.

It made 412 SAE at the wheels...just one hp more than 8388's stocker with just a DRM cal., K&N and a 3-in cat-back.

Either my engine is a big weak-suck or....

P.S. 8388. Please, please, leave your cats on or I'll be even more embarassed.

 

[8388]

Hib, you of all people should know how the 93 and newer engines where put together. And you of all people should be aware of the power variances when an engine is ported matched by hand along with cam degreeing ***at the factory*** so don't be too embarassed.

BTW the chip in the car currently, is the one I purchased from you.

Also the car is here in N. Texas and is available for inspection.

 

[SurfnSun]

Also the car is here in N. Texas and is available for inspection.

Hib looks like youve been called. Since you write for the mags....lets see a story done.

I can see the title now....

Sam's Stock Freak


FWIW....Ive seen ZR1s with just a p&p and exhaust put down numbers near yours. One man's car doesn't set the curve for the rest. BTW my stock Callaway w/o cats is making 406rwhp/536rwtq. Is that possible?

 

[Fort94z]

Sam, looks great!

 

[Hib Halverson]

Like I said, people--I'm embarassed.

All the time and money I've spent far exceeds what 8388 has laid out. My heads were done by VanDeventer and the motor was put together by Automasters. Those are two of the best.

Looking at your RWHP numbers, and considering my mods, my car ought to be about 450 at the wheels, rather than 412. That totally sucks.

Figuring the normal 18% loss, 411 SAE at the wheels is just a hair over 500 NET hp at the flywheel. Considering the engine was rated at 405, that's an oustanding performance with minimal bolt-ons. My compliments, 8388.

A magazine story on 8388's car? Well...in a perfect world, that's what I'd do but, currently, I don't work for any Corvette print media.

Nevertheless, the time's right for owners to appeal directly to the magazines. With four of them, now---Corvette Magazine, Corvette Enthusiast, Corvette Fever and Vette---looking for articles on cars in the hobby, there's lots of opportunities.

 

[8388]

Hib, as much as I'd like to, I can't take any credit for the #'s this engine is putting out. Trust me I wish I could. No, the ones responsible I'm afraid are those folks at Mercury Marine. As we all know, these engines were hand assembled which explains why some *stock* (meaning 100 % untouched) models dyno as little as 310 rwhp while others over 370. And these #'s come from an extremely small % of ZR1, and that's only because of the few owners out of the total out there that actually converse via some of the vette forums. There's literally thousands of other ZR1s that we know very little of.

Hib, have you dynoed your car without the cats ?
Also at what elevation was the dyno performed ?

P.S when the LT5 was still in developemental stages the engineers actually got some pretty impressive #'s. But the engine was detuned for production. Go figure.

 

[ZR1 MK]

Running without cats won't get much if any. If you are looking for results, go headers, cats and 3" system with x pipe. You will get considerable increase in power, pass emissions, be environmentally acceptable and get fewer fumes.
Many would like to see your dyno results. Scan or fax to someone so we can see. Are they SAE corrected etc.?
Mike

 

[8388]

Yes they are SAE. All I currently have are the Dyno sheets. I don't have access to a scanner.

I will be doing another Dyno soon. Hopefully I can get a diskette to download with the next one.

I'm currently running the desert Developement 3" exhaust with a crossover.