Hi guys...was a member a couple of years ago...this is such a educational forum.....I rebuilt my motor last year 86 C4 L-98 all new gaskets, Comp Cam--nothing too radical. Got a good deal on a Nitrous kit (Wet one for the L-98) Installed and check out all electrical--solenoids worked fine, etc. Ran a full bottle thru and man impressive power. But a couple days later I noticed the rad was shy a little coolant...but thought Oh well may have been caused by the heat from the Nitrous. Went up to the beach (Sauble Beach) and I was taking family members out to the back roads and showing them how well it worked. Midweek it was running hot when I came back to town. Started it up the next day and had steam (sweet tasting steam) coming out of both tailpipes. I shut it down and trailered it back to Guelph to my mechanics place. Both head gaskets where gone---and had taken the heads back to my engine builder to go over--OK. Now I am a little hesitant on switching on the juice again. The install sheets say nothing of retarding the timing 2 degrees per every 50 hp on jets....it says stock timing and premium gas!!! Thought maybe I could get some advice here----I am going to buy an MSD ignition kit with the variable time box also. ---gotta be cheaper than head gaskets!!!! Thanx

 

Weather you use 50 or 150 shot you still need colder plugs.
It is usually 1 1/2 deg timing for every 50 shot.
You were probely holding the nitrous for more than 15 seconds .
You should be using the copper gaskets or feld pro.Check your compression when replacing the plugs and see if any cylenders are below 10% of the rest before you use the nitrous.
Head gaskets are not something that usually blows first on a nitrous motor.The plugs usually burn the electrode.
A better spark is always good.
I use the msd dial on mine to retard the timing when I fire the juice.
Never use water in the radiator.I use distilled or coolent.
I think you had a head gasket problem and the nitrous just finished it off.

 

You could be right about the head gaskets----they where Feldpro gaskets but may have had a problem agrivated by the Nitrous. And I waited till car was well out of the hole and was only on the Nitrous for about 6-9 seconds tops.

 

Also did compression after heads went back on and all is fine. We do use coolant in system. Ahhh its good to be back on the forum for some opinions and answers!!! the more the better!!!

 

How big was the shot? Is the engine stock?

 

Basically motor is stock--Comp cam but that is about it--new pistons and rings all new bearings, trued the crank--basic stuff--but fresh--heads have been done twice now!! At the time I was running 150 shot jets--like I say it ran good when it was running--I was impressed with the power--less impressed with the steam!!

 

Let me see if I've got this right:

Stock components in the rotating assembly. Stock crank, rods, a small overbore, and stock replacement pistons.

Aftermarket cam of unknown specs.

Computer tune of unknown origin, with an unknown amount of timing advance.

My bet, is that some detonation or maybe even pre-ignition caused your failure. With a 150 shot, you should be pulling at least 3 degrees of timing off the stock tune, 5 or 6 would be safer. You might need to pull even more timing depending on the timing advance in the computer re-tune that was done for the cam.

Depending on cam specs, your dynamic compression ratio can also be really high. It's possible that with the right cam, and a 150 shot you just over powered the head gaskets with an extreme amount of cylinder pressure. Peak cylinder pressure needs to occur as close to 14 degrees ATDC as possible. Without knowing the cam specs and timing advance, it's impossible for us to even guess at where peak pressure is occurring. Since the engine was making good power, we can assume you are somewhere close to the 14 degree ATDC optimum, but we don't know for sure. If you were making peak pressure at say, 10 degrees ATDC, then it's not really the head gaskets fault that it let go. You could theoretically run the same head gaskets again, move peak pressure to 14 degrees ATDC, and be just fine. If you were making peak pressure at 14 degrees ATDC, then it is possible that you just over powered the head gaskets. If that's the case you'd need some better head gaskets, to go to head studs, or some other better method of sealing.

Like I said though, my bet is that too much timing contributed to a detonation problem, and that is what caused the gaskets to let go.

 

and if you are ever unsure of the timing or just would like a little security, don't hesistate to use a race fuel 50/50 mix. I never pulled timing on my 5.0s or 360mag, 100 shot with 50/50 mix. Since you are running 150 I tend to agree with a few degress of timing removed. Also make sure you get those plugs dropped a range or two. Heat kills.

 

Here is the skinny on the Camshaft--its a Comp Cam Grind #CS XE256H-12---Gross valve lift is .449 intake and .456 exhaust..Duration at 0.05 Intake 212 and exhaust 218--lobe lift is intake .299 and exhaust .304 lobe seperation is 112. Valve timing at 0.006 -Intake open-20 Close56-----Exhaust open-70 Close-18. Have added the recommended 983-Kit valve springs Timing was not altered from stock!!! And Eprom is stock from factory!!! This is great guys and I really apprieciate all the input!!! How will the colder range plugs and retarded timing effect day to day running of car---Canada you know --got to get in every day or driving!!! After it was back togeather I immediately took out the 150 shots and installed the 100 shot jets (scared to death)---but still have the fuse pulled for system till I gather lots of information on first motor Hiroshima!!!

 

I don't know if you are using iron heads or alum?
If alum I would install B8EFS NGK plugs .
The plugs are fine for all my driving condtions and I have had no problems.
Do you have an adjustable reg?

 

I have aluminum heads and a variable fuel regulator--one of those ones you buy off Mid america--it didn't seem to help the fuel pressure from before and after measurement---around 49 PSI. Thanx for tip on cooler plugs---would you knock back the timing also???

 

Pulling a few degrees of timing will take some power away from normal driving. It will probably be less than 10 RWHP though, so I doubt you'd actually feel it.

You could get an aftermarket ignition box like a Mallory, MSD, Crane, etc... These boxes will allow you to run your full timing advance for notmal driving, and then when you arm the nitrous system the box pulls a set number of degrees of timing. I have a Mallory 685 and really like it. It's got a built in window switch to turn the N20 on and off, automatic timing retard that is adjustable in .1 degree increments, N20 shut down 500 RPM's before the rev-limiter, and all kinds of other N20 friendly features. The cheapest place I've ever found it is www.centuryperformance.com.

A colder plug won't affect driveability at all, but they do tend to foul a little quicker, especially if the engine is running rich at all.

Good luck, and get some timing out of that sucker!

 

I would pull 2 degrees and lower the fuel presure with the vaccum line disconected to 42 lbs to start.
The plugs I gap at 32.You should not have a problem fouling the plugs you are not pulling enough timing .When I pull 6 degrees or more then you can see the sparks fly.
I highly recomend that you run Nitrous fuel addative,3 ounces per 3 gallons of fuel.You should always regardless of what any one says try to increase the burn time on the fuel.
106 is good if you want peek performance.
Your trans will last longer if you have a button and shoot above 3000 rpm's and shut off 500 rpms before the trans shifts.
Make sure you bottle presure is always around 87 to 90 degrees after your first shot.presure should be around 950 psito 1000psi.

 

He has an LT1, I don't think you can't just pull timing. There is no distributor to turn. He might be able to get the computer to retard timing with a resistor is the IAT connector, but I am pretty sure a real timing change will require a computer re-tune or a C/D ignition box.

Pulling fuel pressure is a bad idea at this point, in my opinion. Lean, and nitrous are a bad combination. He might have a failing fuel pump, clogged fuel filter, stuck injectors, or any of a hundred other issues where that extra fuel is what is keeping his engine alive. Pulling fuel, without knowing what his AF ratio is at WOT, is a bad idea right now I think. If he could get the car on a dyno with a wideband and spray it, then he could make changes based on that, but I don't think just dropping fuel pressure based on ??? is a really good idea.

What do you mean? You are saying when you pull 6 degrees of timing you can actually see sparks somewhere? If that's the case, you've got some problems going on.

Don't take this the wrong way, but the NOS brand fuel additive is a joke, all store bought octane boosters are a joke. The 'points' they refer to are tenths of a point of octane. IE, "Brand X will raise octane by 7 points!" They mean it will take you from 91 to 91.7 octane. None of them add sufficient quantity of anything to increase the gasoline's resistance to detonation/pre-ignition. While I don't think it's necessary at your power level with nitrous and the proper timing retard, some guys do like to run higher octane fuel when on the bottle. The best way is to find a station that sells 100 octane at the pump. If you can't find one, there are some paint additives you can add to gasoline to help raise the octane. However, 3 oz per 3 gallons is a ridiculously low amount and won't do anything. You can add straight Xylene or Toluene (those, or their derivatives are the main components of most store bought octane boosters) and 1 Oz per gallon won't do ****. I'm not going to get a ton deeper into it here, but adding anything at 1 Oz per gallon of fuel isn't gong to change the octane enough to do anything. Do some research on some of the turbo car websites (www.gnttype.org comes to mind) about DIY race gas. After you do some reading on what octane means, and how to increase it, you'll see that the store bought stuff is crap.

106 Octane? Are you sure? With the store bought octane booster you might think you are at 106, but I promise you aren't. I don't think he needs anywhere near that kind of octane to run a 150 shot on a basically stock engine. You typically want to run the lowest octane possible that still allows you to get your full timing advance.

I agree with not spraying through the shifts, but I've never ran N20 on an automatic so that's just what I've read. I don't have any personal experience with it.

Lol, 87-90 degrees will make different amounts of bottle pressure depending on how much is in the bottle. With 3 lbs of nitrous in a 10 lb bottle, 97 degrees would be lucky to get you 700 PSI. You are right though, bottle pressure around 1K usually leads to the best performance. There is no set temperature that will get you that 1000 PSI though, it will vary depending on the amount of N20 in the bottle, and even from bottle to bottle. I've had 2 or 3 NOS brand bottles that wouldn't heat for ****. They'd have be 130 degrees before the pressure would start to come up. Other NOS bottles I have had worked fine. Some NX bottles heat very well, others don't. My point is that there isn't a universal temperature that will yield the ~1,000 PSI you are looking for.

 

Sorry for the mis understanding guys--as per opening post motor is a L-98--still distributer and variable timing. This is all very good stuff--wish I had talked to you guys all before we cooked the head gaskets---it appears that the 2 biggest contributing factors where A/ knock timing back 2 degrees and B/ run one range cooler plugs. But Neat is correct I may have had a head gasket problem to start with--Nitrous just boosted it along!!! All excellent idea's.

 

Sorry for the mis understanding guys--as per opening post motor is a L-98--still distributer and variable timing. This is all very good stuff--wish I had talked to you guys all before we cooked the head gaskets---it appears that the 2 biggest contributing factors where A/ knock timing back 2 degrees and B/ run one range cooler plugs. But Neat is correct I may have had a head gasket problem to start with--Nitrous just boosted it along!!! All excellent idea's.

 

The bottom line is ,you just need to read some of the info out their and make your own desission.

http://www.go-fast.org/z28/new_to_nitrous.html

http://www.robietherobot.com/NitrousJetCalculator.htm
If you want more info I have lots.

 

Most nitrous Power settings are dependent on bottle presure and humidity.
Making mistakes with nitrous can be many ,you just want to keep them
to a minium.
Explosions and engine problems with nitrous can usually lead to something the person did wrong .Their are exceptions like NX and their junk solenoids.
They build them in house now?so they say.

 

This is what nitrous can do if the Manufacture builds lousy parts!!



Yes I put it back together it is the silver /blue vet in my sig.
I use 106 race non leaded race fuel in my red corvette and a 125 shot.
On the B/S vet 300 shot and C17 or C16 race fuel.I run almost 15 to 1 compression.

 

Hey guys those sites are just awesome!!! Thanx again for all the info!! Wished I had talked to all of you before I hooked up Nitrous---at least now I can make some helpful decisions before I fire up the Nitrous again!!--all you guys are the tops!!