When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Great work.! Really enjoyed reading the thread. I had a 91zr1. They are awesome cars!
as far as the secondary butterflies wire them open. The car might lose a little low end torque but the system is complex and this will save you time and money going forward.
Trivia -- How many rat nests can a single ZR1 have when left for a couple years in a barn?
I finally pulled the radiator cover off today and pulled the old radiator out of the hole. There was a dead rat between the radiator and the condenser... what I could not see was that there was a full rat nest also in there. In other words, its a wonder the car cooled at all! So for those who are counting... I've pulled 6 nests and 2 dead rats.
Getting the radiator housing cover off was ... fun. The forum articles were an enormous help. I probably would have wrestled with the cover for a while had I not read about the process figured out by those before me... mainly 'popping' the cover with a crow-bar pushing the bottom corner. Below is what I found after getting the cover off. Yeah.
Once I pulled the radiator out, it took a while to clean out all the rat, and rat nest. It was a mess. In the end, it was easier to push the car out into the driveway, and get a hose. As expected, there was a layer of oil and grime covering the condenser and oil-cooler. That in turn collected a layer of hair and other junk. And... of course... there was a thick layer of rat urine at the bottom of the enclosure. I used a prodigious amount of Awesome Orange (and a hose) to clean everything up.
The new Dewitt radiator was a breeze. I had to trim the rubber mounts at the top of the housing down to fit the wider radiator. Dewitts also sent a couple of spacers that go between the fan shroud and the radiator housing. You need these to also accommodate the wider radiator. Dewitts also sends longer bolts to attach the shroud to the housing with the spacer. In other words, putting the new radiator in was super simple.
Next came the rest of the fun... fixing the error codes. Thanks to the comments above, this was also a breeze. Yes... I did bend a pin on the large connector at the back of the plenum. Added to that was a crack (leak) in the vacuum canister. Jerry came through with expedited shipping for a replacement. Being that this was the THIRD time putting a plenum back together... I can almost do this blind-folded. I did make sure to test all the vacuum lines with my new vacuum gauge and tester before putting it all back together. I really don't want to take this apart again!
After getting it all back together, I refilled the coolant, and started it up. All error codes fixed. Temp stayed right around 195 while idling in the garage. Next came a drive...
Ok... NOW the full-power kicked in. We finally had the power I remember from driving a ZR1 ~28 years ago. It moved! And even better... the temps never went above 200 degrees. FINALLY... this is a fun car with ALL the problems worked out. And... it's finally ready to be smogged. Going in on Monday to get this done... along with a new set of Nitto 555 tires all-around.
Wow! Thats an amazing amount of crap in that radiator area. I pulled my shroud 2 weeks back to see what might be in there... it wasnt really much at all..... just a decent sized mud wasp nest, some good sized bugs and a layer of tan dirt on everything. I just hit it with a hose and it was cleaned up. I removed the fans and such for a good cleaning also. Nothing like what you pictured though. Hats off to ya for all the hard work and money spent bringing the beast back up to snuff!
Finally took the car on a ~30 mile 'get to know you' trip. First surprise... on the highway, this thing gets right around 29mpg at ~75-80 mph! Great Schnikes that's amazing. Of course, I then dialed in full power and had a little more fun on the 30 mile trip home... and saw about 15mpg. Still not all that bad considering my '65 gets 10mpg whether I drive like a ninny, or racerX. For perspective, this gets even better highway mileage than my 2012 Porsche 911 GTS with all it's fancy computer software (~26mpg) AND the performance for the 2 cars is more or less the same. Who knew?
Also paid extra attention to the temps... which I'm happy to say was a waste of time. The temps lived between 92C and 97C (197F - 207F) regardless of how I was driving. In other words - I basically had the same Dewitt experience I did with my '65... overheating becomes a thing of the past that requires zero-attention going forward. Tom Dewitt is the man. I know folks say 220-230 with occasional blips of 240 is just fine for these cars... but I just couldn't get past the pucker factor and spent most of my pre-Dewitt driving scanning the temp gauge ... which is a little fatiguing. I probably would have been fine with the stock radiator (after cleaning out the rat nest), but am happier knowing I don't ever need to worry about this again; especially since I had to take apart the whole system anyway.
Smog appt (and new tires) is setup for a week from Monday.
TWO QUESTIONS -
Is there a specific driving style I should have for re-calibrating the map sensor ahead of the smog test?
What should I do before dropping the car off for a smog test? I know to race the heck out of it before dropping the car off for the smog test to heat up the cats. Anything else? Should I put some 110 octane race gas in it (sold by a station down the street)? Maybe get some other additive? I run Chevron 91 with Techron. Would love whatever advice people have.
When you do headers, full exhaust , ported intake and heads with intake cams: then, you will be at full power....
Well, than again a 391 or 415CI LT-5 is a lot of full power.....Good luck with the CA smog test..
I don't get that state...In NY its only a safety inspection for a veh 25 years or older I believe..
Than again I guess its a trade off for all that nice weather you guys get...
I asked about a pretest. According to my local shop, anytime they turn on the tester, it connects to Sacramento. There's no way to pretest. That said, my local shop says its not a big deal to fail, and retest.
As for the test; remember what others have said,i.e. keep the switch at normal not full power, in fact remove the key.
Temperature.
Went to a show last Sunday about 50 miles away.
Drove home in 83 degree temp with air on the entire time.
Temp stayed at 197 the entire trip.
Original stock cooling system with 20k miles, green coolant, original t-stat and cap.
Was quite happy with the 25 year old ZR-1!
Marty
I disagree that 240 is acceptable also. Read articles from haibeck the stock gasket slowly crushes and doesn't recover after many heat cycles from near 240
I like a max of 220 and "less variance". now marc has the MLS which really helps and helps this problem. You now hold a record for most dead animals on a single car (just kidding).
for emissions, the techtron works well and you can disconnect the secondary fan and run the car HOT and get the cats heated with a few runs.
get a friendly dyno operator and do it right on the dyno. the lt5 is a bit of a carbon machine and after sitting, that stuff has to clear out to get good solid readings.
I have spiked the gas with a bit of alchy as sometimes that helps. race gas NO not going to work.
The bad news - I failed the visual inspection for smog. My car has 2 sets of cats (4 total!). Turns out there is a GM service bulletin that recommends this, and makes it legal for CA emissions, but the normal smog shop can't do anything with this until I get a ref to sign-off ... which I've been told is a rubber-stamp since this is an official GM bulletin. Of course, I would love to speak with the old owner about this, but that's not possible. So... I'm getting an appt with the referee on Wednesday (CA DMV computers need a few days to update).
I was told that the GM service bulletin is for all GM cars to add a 'close-coupled converter' to reduce tail-pipe emissions earlier in the operating cycle. The problem is that the way the CA law is written, the car is now considered 'modified', and therefore needs a stamp from the referee. I was also told that there wasn't always a visual test... and that this car likely passed fine the last time it was smog'd because of the extra set of cats. With a little luck, the ref will register this mod with the car, and I won't need to go through this dance again.
Have any of my CA ZR1 brethren heard of this? The bulletin number I have is #06-06-01-010D. This apparently replaces #06-06-01-010C to include all GM cars through 2019, but I cannot find the original 'C' bulletin to know when it was written.
Ok... everything in this post is preliminary, and not 100% confirmed yet, but I hope to have it all confirmed with all the detail by the end of tomorrow.
It APPEARS the mod in the GM bulletin for the 'close-coupled converter' (i.e. another set of cats) IS recognized by CA smog officials, and does not need a trip to the referee. That is the last piece to confirm definitively. Equally cool... the car passed the emissions portion of the smog test with flying colors! My guess is the extra set of cats zap about 10hp... but I can pass an emissions test and drive my car.
The shop I've been working with (Woodside Auto and Tire) intimated that they have a short list of collectors with ZR1s that will be elated to hear this news. Apparently, there's more than a few guys with Corvette collections that have had to register their ZR1s as no-op, and just store these cars away. One specific example they mentioned only has ~1300 miles!!! Hopefully this will mean a few more of these cars will get back on the road in CA.
One thing I can say when I drive this around the Bay Area... people get VERY excited about seeing an original ZR1. I'd go so far as to say that people (... who know Corvettes...) get more excited about my ZR1 than they do about my '65 Stingray. I didn't expect this kind of reaction for the car. My assumption was that no one would know what it was. That said, I can't even remember when the last time was that I saw a 90's ZR1 on the road... which is odd given the incredible car culture of the Bay Area. My neighbor owns multiple Pagani's... he wants to drive my ZR1!
Once I have everything documented, I will post all this to a new thread for ZR1 emissions testing in California. I'll also get the car back on the lift to snap a few pics for those who are curious.
If you ask me this TSB is being taken totally out of context with regard to 1990 -1995 LT5 powered ZR-1’s. A “close coupled converter” meant something different back then. It simply referred to the proximity of the converter to the engine. The LT5 set a new standard of proximity. It’s even referenced in the book “The heart of the Beast”. Today, it refers to the use of two converters, one small one very close to the engine and one behind that. To my knowledge there has never been GM provided two cat system for these cars.
But, hey, if they want to accept it I hope it works for all the CA owners.
H
Ok... everything in this post is preliminary, and not 100% confirmed yet, but I hope to have it all confirmed with all the detail by the end of tomorrow.
It APPEARS the mod in the GM bulletin for the 'close-coupled converter' (i.e. another set of cats) IS recognized by CA smog officials, and does not need a trip to the referee. That is the last piece to confirm definitively. Equally cool... the car passed the emissions portion of the smog test with flying colors! My guess is the extra set of cats zap about 10hp... but I can pass an emissions test and drive my car.
The shop I've been working with (Woodside Auto and Tire) intimated that they have a short list of collectors with ZR1s that will be elated to hear this news. Apparently, there's more than a few guys with Corvette collections that have had to register their ZR1s as no-op, and just store these cars away. One specific example they mentioned only has ~1300 miles!!! Hopefully this will mean a few more of these cars will get back on the road in CA.
One thing I can say when I drive this around the Bay Area... people get VERY excited about seeing an original ZR1. I'd go so far as to say that people (... who know Corvettes...) get more excited about my ZR1 than they do about my '65 Stingray. I didn't expect this kind of reaction for the car. My assumption was that no one would know what it was. That said, I can't even remember when the last time was that I saw a 90's ZR1 on the road... which is odd given the incredible car culture of the Bay Area. My neighbor owns multiple Pagani's... he wants to drive my ZR1!
Once I have everything documented, I will post all this to a new thread for ZR1 emissions testing in California. I'll also get the car back on the lift to snap a few pics for those who are curious.
-Gonzo
Okay. I spoke (wrote) too soon. within a couple hours of hitting send, I heard from the shop (who heard from the fine folks representing CA) that yes, this solution should be fine, but they need to still see the car and register it in their system as having this mod. Once they do that, it will forever be in the system, meaning that when I get the car smog tested in another two years, I can have it tested at any smog testing station (like normal folk!). My hope of having this process completed by the end of this week is proving a little too optimistic. I'm hoping to call the referee tomorrow and get an appt for next week. We'll see. Still looking positive, but with an extra step I hoped wasn't needed.
Good question on what mod's I can do (if any) to the car now that it passes emissions with a healthy margin. I can tell you right now that headers will not pass the visual inspection in CA. Porting is an interesting one. I want to believe it would... but I need to research this some before signing up. I predict a phone call with MarkH at some point. For now, I'm wholly focused on just getting the smog testing behind me.
I can honestly say - this is my first and last post-1975 collector car. This is a far bigger PITA than I ever would have dreamed. If I had not been lusting after this car for the last ~30 years... I would have sold it and moved on. Never again. I believe I have a front-row perspective for why the (CA) collector car market has largely ignored these cars. Comparatively speaking... this car should have an $80-120k price tag in today's market.
This post has been a long time coming… but I wanted to wait for a defining event to happen first… and that’s taken me quite a while.
This morning, I FINALLY got the ZR1 registered in CA. As I’m sure can be inferred… this was not an easy path to success. Truth be told, it was a giant PITA!
First – the Chevy bulletin I referenced before is worthless. The CA Referee program uses a very specific set of bulletins that are attached to the make, model, and year of the car. There are a couple for the 1991 ZR1, but nothing pertaining to passing smog.
With that, the referee I went to failed me immediately for having the extra set of cats. They totally acknowledged that removing the cats would make the emissions for the car worse, but that’s what they require (???).
Off to the exhaust shop…
$300 to get the extra cats removed, and weld in straight pipes.
Back to the smog station…
Car PASSED, but not nearly by the margins it had with the extra cats. Unreal. So, yes, I pollute more, but that’s the way the CA DMV wants it. My guess is that without all the work we’ve done in the last few months, the car would have failed.
The good news is I’ve been driving the car a lot (most of it unregistered). My gosh this thing is fun. With the weather a tad cooler (California cold is <55 degrees), this will become my daily driver instead of my ’65 hotrod. I’m surprised each time I plant the pedal at how much oomph this thing has. It’s not the steal-toe-boot to the spine of the ’65, but it’s at least as fast… and with handling and breaks (and heat). Also funny is that everyone looks at this car as a 1991 250hp Corvette. The other day I think I made a 997 911 driver cry.
Since driving it more, I’ve now thrown a ‘service suspension’ code. Being that the suspension is still riding in at least sport mode, my guess is that it’s one of the actuators. Gonna grab the code and take it apart today. Hopefully I can get this fixed without needing to rebuild the shock, or worse… throw the shock out.
Also interesting… I seem to have accidently moved from ‘Corvette enthusiast’ to ‘Corvette collector’… and remained married! Somehow I now have one each of my favorite C2, C3, and C4 cars. I now have a ’69 427 in the third bay of my garage. Gonna start taking that apart this week. Looks like I’ll be starting a thread in the C3 forums.
I’m sure there will be a few more posts here, but in case I haven’t already made it clear… Many thanks to all who’ve helped me getting the ZR1 back on the road. The forums were of critical help in my efforts.
Okay. I spoke (wrote) too soon. within a couple hours of hitting send, I heard from the shop (who heard from the fine folks representing CA) that yes, this solution should be fine, but they need to still see the car and register it in their system as having this mod. Once they do that, it will forever be in the system, meaning that when I get the car smog tested in another two years, I can have it tested at any smog testing station (like normal folk!). My hope of having this process completed by the end of this week is proving a little too optimistic. I'm hoping to call the referee tomorrow and get an appt for next week. We'll see. Still looking positive, but with an extra step I hoped wasn't needed.
Good question on what mod's I can do (if any) to the car now that it passes emissions with a healthy margin. I can tell you right now that headers will not pass the visual inspection in CA. Porting is an interesting one. I want to believe it would... but I need to research this some before signing up. I predict a phone call with MarkH at some point. For now, I'm wholly focused on just getting the smog testing behind me.
I can honestly say - this is my first and last post-1975 collector car. This is a far bigger PITA than I ever would have dreamed. If I had not been lusting after this car for the last ~30 years... I would have sold it and moved on. Never again. I believe I have a front-row perspective for why the (CA) collector car market has largely ignored these cars. Comparatively speaking... this car should have an $80-120k price tag in today's market.
-Gonzo.
Send it to Pete or Dempsey and do a 391 build on the motor.....Even without headers you will be in the upper 500 HP.....375 HP is boring in these cars...
Congrats on passing emissions in the Z and for taking us along for the ride! Your thread going to help as I bust into my 91' dark red metallic car I recently bought (9,300 miles) and my fathers 91' Quasar Blue metallic Z (19,200 miles) . BOTH suffer from bad injectors. Fuel pumps/filters already replaced.
I really enjoyed reading this thread. You've done an excellent job with that car and I can only hope to find a Z in the manner you did and enjoy it as I do my 86 with my sons. Its been one of my dream cars since I was a kid. Thank you for sharing the pics along the way!! What a fantastic car!!
10-08-2018, 06:06 AM
