Starting the mods
 

First mod I'd like to attack will be headers, so here are the questions...


Will Stainless Works Headers/Cats bolt up to the stock exhaust?
I want to keep the nice "quiet" stock exhaust.


I'm pretty good with a wrench, but is header install a one man job?


I thought I read somewhere that there are 2 different size resonator internal ID's.


Which years had the larger internal ID?


Mark's chip is also in the plan, but the top end porting will have to wait until next year. Maybe by that time I'll have saved enough for a 415...


Enough questions for now.

Re: Starting the mods
 

SS works header will bot up to stock exhaust.

Can be installed by one person. Removing and reinstalling exhaust may be challenging.

I think 93 and later Zs have larger resonator internal diameter.

Re: Starting the mods
 

The toughest part of the header job is getting the OEM exhaust manifolds and associated emissions hardware out. I’ve done several by myself. It’s tight especially on the passenger side. If your patient and take your time is pretty straight forward. Removing the engine mount nuts and K members and lifting the engine slightly helps a lot. Inspect the engine mounts while your in there dollars to doughnuts one or both are broken. The 90-92 exhausts had a restricted resonator. If your keeping the stock exhaust swap that out for a later one, x pipe or Dynomax Ultraflow Welded X resonator. Exhaust system fabrication to some degree is unavoidable when your doing headers.
Have fun.
H
:cheers:

Re: Starting the mods
 

A 415 build will cost more than what you paid for the car....I think I saw that Vettes Drs.wanted like $22,000 for a ZR-1 build ...Better off contacting Pete, Haibeck or evolution motorsports if you want to build HP...

Re: Starting the mods
 

If I had the bucks I’d be doing Pete’s 391...
H
:cheers:

Re: Starting the mods
 

Everything is tight in there...…..
What other emissions hardware gets removed? AIR plumbing? Can I keep that stuff?
I've been looking for a stock replacement 93-95 resonator, but they seem to be non-obtainable. Hopefully something like the Dynomax will keep the "drone" out.

Re: Starting the mods
 

when do you need the 93-95 resonator. I am quite sure I still have one, however I will not be able to get at it for a while.. due to a medical issue with my right foot..

Re: Starting the mods
 

It’s really the air injection plumbing mostly. It runs under the engine to the passenger side. You can also remove the air pump in the driver side well next to the radiator. Good spot for an oil catch can when the air pump is out. I think Dominic (Xfirez51) is (or was) running the Dynomax resonator. Keep in mind stock pipes are 2.75” diameter, an unusual size. Most aftermarket exhaust items are either 2.5 or 3.0”s. Requires some adaptation. Unless your good at welding it’s best to let an exhaust shop do it. I’m a terrible welder. I usually cut all the pieces, fit everything together, spot weld it in place and let a shop do the final welding.
H
:cheers:

Re: Starting the mods
 

I second the vote for a 391 from Pete. Very, very happy with mine, and the best $/HP you can get from an engine build. Honestly though, if your engine doesn’t need a rebuild, your best route is headers and ported top end.

Re: Starting the mods
 

Will not be needed until sometime in the spring. Unheated garage up here, so I'll wait for milder weather before taking things apart.

Re: Starting the mods
 

that works.. as soon as the Doc okay's me for a ladder I can check the attic

Re: Starting the mods
 

Had a tough time getting it out of your mouth again Jeff? :cheers: --Bob

Re: Starting the mods
 

Looks like you have gotten some good answers here, as I would expect. The 93-95 resonator is in fact larger in internal diameter, less of a neck down. Here is a article Marc did on that:

http://www.zr1specialist.com/HAT%20W...rly%20Cars.pdf

Shops like Marc Haibeck's and others who have take off exhausts may be able to supply one if you can't find it from one of the other members, although of course there weren't too many made originally. There are quite a few posts here about exhaust characteristics and variations that might be interesting reading for you. After 20 years of mostly Corsa systems on the '93 and '95, I finally went back to a stock system (behind SW headers, no cats, with Haibeck 510 pkg.) for the quiet and lack of resonance. But I also added Quick Time Performance electric cutouts in front of the mufflers with a rocker switch hidden under the passenger side console carpet. (Tony Davila had done this with manually operated cutouts and it looked doable to me).

I had Marc do the cutout installation and I did the switch but any competent muffler shop could also do it with proper guidance. I like the ability to go from stock quiet to wide open pipes when I wanted to (like at the NCM track) or something in between with a little rumble for around town. While Marc normally installs cutouts where the stock exhaust pipes curve out from the center, that position eliminates the spare tire carrier, which I wanted to preserve, so we figured out how to put them just in front of the mufflers instead and I kept my spare. I don't believe there is a big difference in performance in either location as they are so far down the exhaust.

Here is a link to one of the very long posts on exhausts but there are many; just search "exhaust cutouts" : http://www.zr1.net/forum/showthread....utouts&page=16. This page is discussing cutouts, and shows both Marc's preferred installation spot as well as mine. But here also are a couple of pics of mine-Bob

Re: Starting the mods
 

Lmao, I wishAttachment 8837


Sent from my iPhone using ZR-1 Net Registry

Re: Starting the mods
 

I toyed with the idea of cutouts, but probably won't do it initially.

What I'd like to try is to have a straight through pipe installed in the stock muffler with a cutout supplying the pipe somehow.

The muffler would have 2 inlets and the single stock outlet. Not sure if there's enough room to do that.

Re: Starting the mods
 

If that’s your plan don’t bother with the expense. The stock mufflers are not particularly restrictive. Simply have the resonator removed and replaced with an X pipe. You can add the cutouts to bypass the muffler later.
H
:cheers:

Re: Starting the mods
 

FYI, removal of either the stock mufflers or the resonator will cause an increase in audible resonance. The LT5 creates significant resonance frequencies at two rpm points, about 1800 and 3400. The mufflers deal with one frequency and the resonator handles the other. Forget which is which. --Bob

Re: Starting the mods
 

Sorry to see that Jeff. My wife had foot surgery a few years ago and it was not fun for quite a while. Hope you are better soon--Bob

Re: Starting the mods
 

Interesting.. I will say my LT4 catback with Watson long tubes and bullet cats is quiet. If I could get the sound of Corsa at cruise without the screaming Banshee at WOT that wouldl be perfect for me

Thanks Bob, this is round 2, last year was the Clutch foot, this year to go pedal foot.. hopefully only another week in my cast.. Had surgery on Dec 12th

Re: Starting the mods
 

Typically resonator takes care of low RPM and muffler the higher RPM resonance.

Re: Starting the mods
 

I’ve done exactly that, swapping the resonator for an X pipe on an otherwise stock system. There was no resonance that I could perceive. As we know exhaust tone, noise and resonance tolerance is a subjective thing to some degree.
H
:cheers:

Re: Starting the mods
 

Agree!