Sealing up a nitrous motor?
 

I'm running a 300 shot of nitrous and blew the cometic gaskets on the center cylinders on both banks. It's an IA2 block and tiger heads. I know I was running too much timing but before I put it back together is there something I should know to do different?

Steve

How much timing are you talking about?

If you've got cometics and head studs already, the only thing you could do is O-ring it. That assumes everything is flat and square, deck height is good, oil control is good, enough octane, correct parts for the appp, yadda yadda.

But if you know you had a tuning mistake, then there's your problem. Detonation is going to pop the head gasket at that location. Only 4 bolts per cylinder, not much sealing area there, high temps from 2 exhaust ports, etc..

What did the rod bearings look like?

Do you have Step Washers/"L" Washers/Shoulder Washers (whatever you want to call them) on your heads (head stud holes)?


GTO George

Charlie a total of 25* timing and it should have been closer to 20*.


GTO George I do have the washers, ARP studs etc.


I'm having the heads resurfaced and will dis-assemble the block today and check the bearings.

I'm no expert but if your tiger head peaks power anything like a Ehead (I have no clue) which for mine is 34-35 degree's. That would be 10 degrees you took out right? I have a 461 ci with a 150 shot . I don't take out anything . I do take out 4 degrees with a 210 shot though ... Doesn't sound that far off to me. Are you certain your A/F is correct n/a? Do you free flow your regulator to your nitrous jet to 5 psi? Im just sayin, maybe it could be something else then timing?

How do the piston lands/rings look?

Wide band A/F meter?

Charlie, I pulled the motor down and the rod bearings showed too much timing. The valve relief scallops on the edges of the pistons, where it gets paper thin, was cracked and broken. I ground out the thin areas and polished to a smooth finish. I had 10 degrees pulled but will go to 16 and work it from there.


70 bird, I have a chassis dyno with a wide band showing 12.7/ 12.6 A/F. I will richen it up a bit. Strange thing is that on a 300 pill it only picks up 141 HP. Motor puts down 612 and on spray it put down 753. It is blowing through the converter though. I called PTC and they sent me a nitrous converter. So I am making changes.

Steve

Did you figure out the percentage of slip of the converter ?

What was the mph verse rpm with your spray dyno run?

What psi do you free flow your NOS regulator to?

Do you know what degree of timing the Tiger heads peak hp at N/A ?

Charlie,

Can't remember the slip % but 22 mph loss.

5 lbs. fuel flow

at peak power total timing is set at 34.8, initial is about 14.

Piston lands look good, tops of pistons had detonation marks. All the rings spin free, no friction. I went back on my dyno sheet and the A/F ratio was 12.3 and not 12.7 as I said earlier.

I thought I had a 12* module in the retard box but it was a 10*. I will put a 16* module next time and work from there.
Basically The shift light stayed mostly on the entire 1/8 mile run. (set at 6800) I just kept shifting it. It used to come on right before I cross the stripe on a 1/4 mi run.

Charlie, I ran a timed 1/8 mi run and it went 6.01 at 118. 60' was the same as on motor 1.38. It was turning over 6800 rpms at 118 mph. Probably close to 7000 rpms maybe a little more. On the motor it would be trapping 133-135 mph.

Steve

Check this out. Just thought I would share it with you .

http://www.robietherobot.com/nitrousjetcalculator.htm

12.3 12.7 if that's on spray , to me that's too lean.

I would try free flowing at 6 psi..

My motor with spry is in the 10's and 12.9 N/A

22 mph Is quite a bit of loss . Good idea to tighten it up..

Thanks Charlie, I will try the App.

WOW Charlie you don't take any timming out at all even with a 150 shot,
I take out 8* on any shot from 50-325 haven't sprayed any more than
that yet. A friend told me a long time ago with a 125 shot didn't need to
take any timing out so I tried it. Didn't even feel nothing. So I took out 8*
and what a differents. Try 8* on your 150 shot and let me know what you
think.

GT.

What do you mean you didn't feel anything? So you hit it with a 125 shot and it felt like just motor?

I shot a 210 and took out 4 degrees..

A 150 shot is a baby shot . As long as you have your motor tuned for good AFR and timing on motor with plugs looking good no need to taking any out.. My friend who shoots over 500 told me that , and I tried it and he was right .

With a 150 shot no timing taken out night and day difference in power with my car then N/A.....

I think your playing with fire going at it that way. It's not how much you pull from your base timing N/A, it's what your running down the track with a given amount of pph of nitrous. Monte Smith flowed our Big Shot plate and wanted us at no more than 29* going down track with a 150 shot. Our best runs with the E heads N/A is 41* timing. Steve Johnson suggested we start at 28*. We ran at 29* for 8 hits. Then we dropped to 28* and picked up another 1 mph. There were still a couple of plugs that were on the edge with that tune up. We have the Grid installed in the car so we are going to install then ICT fiber optic this winter so we can take out .5 to 1 more degree out of a couple of those cylinders. That "baby shot" put the car on the bumper twice at Norwalk this year. Needless to say we didn't jet up that weekend. We needed to get the suspension under control. We ran 145 mph lifting twice on the last run at 28*. That's with the 150 shot.

What fuel are you running with that 300 shot p4msi1? If it were me I'd be using C23. We are using C12 for the 150 shot.

Brian

The magic 27 degrees of timing number (or close to it) also applies to NOS, Charlie. LOL!

Tom V.

My car went its fastest at 34 degree's N/A. 41 degrees surprises me for a E head. I never said a 150 shot was nothing, just that its not a lot to worry about if you have the motor tuned right N/A . My car fly's on a 150. I have never tried it with timing taken out. Maybe ill try it next time and see what your talking about.. But 13 degrees for a 150 sounds like a lot..

Your missing my point (Montes point) Timing is for a given amount of nitrous running down the track regardless of what your base timing is. :(

Brian

While the engine is apart you may want to consider having the special alloy insert installed between the center exhaust ports in the deck. Calvin Hill, I believe is the source for the insert and installation. It's not going to solve the problem, but will give you a margin for error you don't have now. 300 HP is what I consider to be the beginning of "serious" N2O injection and fuel, timing, and jetting become really critical. Don't be afraid to take "too much" timing out of the engine as you develop your ideal tune for your engine package. The only real harm will be the car slowing down. You already know what too much timing does. On the Grocery Getter, we kept taking more and more timing out down track and it went faster and faster and killed fewer parts. Wide band O2 was in it's infancy in those days but we were able eventually spray 600+ HP without damage. At 600 HP, we took out 25 degrees of timing.