Newbie Here

[QMCMSS]

Hello all, I am an avid car guy and just purchased a 1991 ZR1, I am a decent wrench but my other cars are carbureted and no computer. So I'm in a new world here and after spending the last few days on this site I still have some pretty basic questions regarding the ZR1. First some background on the car. 1991 ZR1 with 51k original. It has Corsa cat back exhaust, Hailbeck Chip,and the top end has been ported and polished. It's a California car and after changing O2 sensors it passed smog. It failed on high NOx before changing the sensors. It has a high RPM miss (above 5500RPM) and seems to run a little hotter than I would like (around 220). I will be surprised if I put 5k miles a year on it with no racing expected. I do however have a heavy foot and love the way she responds.

So here is the direction I am heading

First change spark plugs to AC Delco plugs the cheapos, but one step colder than stock. Hopefully this will help with the heat and top end miss. Anyone know the part # or had experience with them. I don't know what plugs are it or when they were last changed.

Change Coolant this is my first aluminum block and want to treat it with some love any suggestions here would be much appreciated.

Change the oil and Filter to either Mobil one synthetic or Red line. Any input here much appreciated.

Thanks in advance for your wisdom.

[efnfast]

Plugs, I run NGK iridium, one plug cooler.
Coolant, good old fashion green coolant.
Oil filter, Delco AC970C seems to have a good anti drain back check valve.
Oil, I run Amsoil, Mobil 1 is also very popular.
Congratulations on the find. You'll find everything you need for your car here, and some really bright fellas.

[QMCMSS]

Thanks this is consistent with the other postings and reassures I'm going in the right direction.

[Vette73]

GOOD LUCK with your 91...I too purchased a 91 back in November.....Im running Mobil 1 high mileage oil and a bosch filter, its black in color....The Mobil 1 high mikeage you can get on sale at auto zone and its recommended for the LT-5..Amsoil is also recommend.a little more money but Mobil 1 is easier to find....

[We Gone]

Congrats and welcome to the brotherhood....

[PhillipsLT5]

Welcome. I have 91 #1258. what are the last 4 of your VIN

[Mystic ZR-1]

Master Chief
Welcome aboard!
There's a few "bubbleheads" here!
ex-TM2(SS)
SSBN657G
ret GD/EB 37yrs
90 #2282
PS: check for debris between radiator and AC condensor also on the forward side of the radiator. Use a good flashlite and look in near the oil cooler lines on the stbd side (I mean passenger side...) you can see well enough to determine if it's clogged.

[HAWAIIZR-1]

Welcome and congratulations (I think I know which car you bought). Great to have another ZR-1 in the local area. I'm in Pleasant Hill and work right down the highway from you at the old Concord Naval Weapons Station. Tomorrow some Z owners are meeting at Blackhawk Museum Cars and Coffee if you have time. I just moved to the area less than a year ago so still trying to meet all the Z owners in the area.

Besides what has already been mentioned, check out all the information on Marc Haibeck's website with all the presentations he has, there is a wealth of good info.

http://www.zr1specialist.com/

You can buy the AMSOIL from Marc and anything else you need. For parts, etc. contact Jerry's Gasket: http://jerrysgaskets.com/ (you can call him and he will also give you good advice and point you in the right direction.

Then you have the brotherhood here that will give you the shirt off their back. I have a lot of the special tools too if you get into a bind. I'll offer you the same that others have done for me when I got my Z some years ago.

Best wishes and congrats again.

[Paul Workman]

Whenever someone says "use Mobil 1", I can't help but roll my eyes, just a little. Which one??????

See link...

https://mobiloil.com/~/media/amer/us...ecs-guide.ashx

It is the Mobil 1, "HIGH MILEAGE" oil...but there are several. I use Amsoil AMO 10W-40 myself - and have for the past 7 years in the z. But, I also use Mobil 1 15W-50 in my wife's flat tappet 1969 motor (after a cam went flat on that relatively low ZDDP in API "SM" Mobil 1. The 15W-50 High Mileage is a full synthetic and has the higher phosphorous/zinc additive flat tappets desire.).

220ºF is "normal" for the stock LT5, although Marc does provide a calibration that turns both fans on at ≈ 205ºF and then off at ≈ 200ºF

The miss above 5000+ rpm" could be a few things:

I'd want to look at the plugs (especially if it misses under a heavy foot...which I assume is the case! (ohming out the plug wires is always a good idea too.) Marc recommends an NKG plug w/ rare earth electrodes, but I've been running the AC Delco copper core 41 602s which have been working fine for a lot less money and cheap enough to replace for the cost of a couple craft beers at the local pub!

Plugs OK would have me looking at the fuel pressure next (easiest ≈ 53 psi at WOT).

That being OK, it could be the "accordion" air duct between the filter housing and the air horn collapsing (they've been known to get soft with age and heat). Marc can supply some wire hoops to insert in the tube to support it and keep it from collapsing. OR, (like I did) fashion an aluminum liner to be placed on the inside of the tube.

That being OK, I'd be checking the resistance across the injectors (HOT) to see they're all w/in a window of about 1.2 ohms. Depending on the injectors installed, the resistance would average around 12 ohms, or 14 ohms, I've found. But, if you have one that is a couple - 3 ohms low, that one is going south. And if it is in the 8 ohms or less, it's time for a new set!

I was experiencing a miss when it got up to operating temp which turned out to be a coil(s) issue. A new set from GM fixed that; been good ever since. I know you said the miss was rpm-related; NOT temperature. But, I threw that in b/c it also caused me to have a miss at the higher end of the tach.

More in-depth info is available, but these are some of the "new to me" glitches I had to deal with when I first got my Z. Nothing out of the ordinary for a 25 year old car, and NONE of the problems have returned...Well, except for the injectors that a dealer replaced with NOS parts when I bought it. (Yep...the originals were susceptible to ethanol, and so were the "new, old, stock" ones they replaced the originals with!)

I've been fussing with carburetors since the late 60s, up until recent times. Armed with a scanner or laptop, I'd take the computer over dealing with "the black art" of carbs any day!

Welcome to the Brotherhood of the Beast!

[QMCMSS]

Last 4 #s of the vin are 0989