I must have missed the pump gas part. I have been running 116 octane on my 408 on all size shots, and all the different timing settings and plugs. It's a good safety net. We are loosing some power n/a but who cares, it's all about getting down the track to me. Start safe, with race gas, cold plug and low timing. You can always progressively get more radical with the tune when your ready. The power difference will be a tad, but when first flogging it's the smart way to proceed. My cam is slightly smaller and my comp is 11.25, but pretty close motors, as mine is also an LME. I haven't got it over 500hp n/a yet, but new heads may allow this and a little more aggressive cam. Anyway, that is a really nice combo you have getting 530hp n/a. Good luck
Robert

 

I'm just guessing as to the RWHP #'s, based off of my track times. I stood on the rev limiter at the 1000', had the wrong pushrods, pinion angle wrong, and was knocking (flywheel bolts came loose lol), and it still went 11.18@124.5mph, haven't been back since I got it dialed in. The race weight is 3850lbs. I figure it will go 10.80@130 N/A.

I am trying to do all this on pump gas, it's my goal. I want to be able to bust into the upper 130's on spray and run a bottom 10. All on pump gas and 17" radials. I REALLY want to do it without race gas. This is a 95% street car. I can barely afford the nitrous as a poor-broke-college-kid, let alone race gas.


The build sheet on the motor claims 11.5:1. With the pistons, gaskets, deck height, and heads it should be 11.3-5:1 or so, so if anything, it's less, unless they used a different gasket than specified. Patrick told me my DCR would be about 8.3:1 with the cam I've got now.



383LQ4SS - I was under the impression that you could put 80 ft-lbs on the iron block with ARP studs? I didn't install the heads, but they clicked the torque wrench at 50 ft-lbs when I was checking, so I moved it to 70 and it clicked again w/out moving.


1lejohn - Do you know the part number for the gaskets? I'm assuming they're for a 4" bore? Mine's a 4.03.

 

80 is probably ok. I am just making the point that you cant just crank down on them. At a certain point it will do more harm than good. You can tighten them down so much that the deck will ripple between every bolt hole and the gaskets wont even hold NA. I learned that lesson when i was about 18...lol. Everyone thinks head gaskets lose seal because of bolt stretch..its my opinion that its mostly aluminum deck movement (bending between each bolt hole)....especially under detonation.

If you really want pump gas...you really need to go over your static and dynamic compression stats, veryfy EVERYTHING yourself....a cam change may be in order. Maybe Patrick will help you there. You will have to use the coldest plug so its not a concern..a 7 should be ok...maybe an 8 for good measure.

Then youll have to log your runs and put the best tune you can on it. Stay on the rich side on juice. low 11,s AF ratio and pull as much timing as you need so there is NO detonation.

It is possible a cam change will be in order.

Another thing to do is adjust the rpm range you are spraying. The higher the activation point the less likley detonation is to occur. And who knows when your head gaskets where comprimised...it may have been messing around on the street when spraying right at 3000 rpm...and from there its all downhill once the gasket is comprimised. If you are spraying from 3000-7000 or something like that...try raising the activation point up a bit. Maybe even 4000 rpm on. That will reduce the cylinder pressure seen in a big way but not really slow you down at the track.
Its all in the details man. I think you should be able to run your numbers on GOOD 93 octane myself. But you will have a small margin for errors such as bad gas or mistakes on the tune.

 

I have the window set for 3600-6400, that's how I've been testing. I want to be able to run a 150 hit or more. 700rwhp sounds like a good number lol. I removed that 253/263 because I wanted a little more driveability, but now I know a lot more about tuning. The car would have quite a bit less DCR and maybe like the spray a little better. That cam has 34* of overlap.

The first weekend I had it going and hit the 100 shot 2-3 times I was ready to pill it up.

 

LOL, My first 100 shot run was at the track, went a new PB of 9.77 old best was 10.54 2nd run on the jug the 150 jets were in it.

 

It's thuper-fun. My car would hook on gas in 2nd on the street with worn out MT's, no progression on the shot, and 4.11's. Now I've got new Hoosiers and 3.73's, I can't wait to get it going again.

 

at 700 rwhp you will be on the ragged edge. Get your ducks in a row. You may even think about dual staging that 150 shot. 75 on at 3400 and another 75 on at 5500 or so. That will keep Tq/cylinder pressure more in check but result in the same rwhp at peak hp. Tq will be lower ( by design), but your track times should not really suffer.

 

Maybe look into a meth kit, there's a sponsor on here that says they work with nitrous.... if a standalone with good gas in it isn't an option.

 

I've got her on an FJO progressive right now, but I've got it setup with no ramp, just instant 100% (like a normal kit). I thought I was going to have bigger traction problems, but it looks like I may be right on the edge of spinning in 2nd instead of DEFINITELY spinning. After pilling it up I was planning on putting it on a 1-2 second ramp though.


I spent a ga-zillion bucks on my fuel system making it 1000rwhp worthy (maybe I'll put on an F1 one day), I guess a meth kit would work with that too lol.

I may just have to look into a standalone. I can get race gas about 10 minutes from my house if absolutely needed.




What about Octanium? $16 bucks extra per full tank doesn't sound bad. It may be just enough if I do still have problems. I've been doing quite a bit of research on it and it seems to have helped quite a few people get their detonation problems lined out. I haven't read much about it on here though.

 

dont mess with that ****. just put a standalone in the car and put some 116 in the cell. the cell will last several bottles and 116 is $10 a gallon. in the long run it will be cheaper. just say u use 1 tank of gas per week. thats $832 in gas additive. it would cost less then that to do a standalone and several gallons of 116.

 

fwiw i have used torco to get rid of some false knock (detonation) on the nitrous in my car and it def helped but i was using it as a band aid and its not something i would recommend to do on a normal basis. ur mixture will never be the same twice and its just too much damn hassle.

 

If a standalone is an option, I'd do that and put the best race gas in it you can get, it's only gonna be safer down the road. I assume you don't have any cats on the car to get screwed up, and I'm sure your rear o2's are turned off. Hell tune it in open loop and turn them all off, and never worry about a stupid exhaust sensor sending your tune haywire.

 

Nice info guys...

I have the same problem. On N/A its all fine and dandy but mid summer this past year, I noticed after I spray the 100 shot, I am loosing water and its not coming out of the radiator cap.

I believe I am at 24* of timing on the jug (26* total and used the 2* per 100 shot rule).

I am also at ~11.5.1 CR and running TR6 plugs.

So, I guess after reading this thread and after I fix the head gasket leak, I should retard my timing some more and put say a #7 plug in?

I plan on hitting the 200 shot and trying to squeak into the 9"s this year, thats my goal.

 

thats basiclly my issue i had. 24* of timing on a 150. all good on motor but once i hit that bottle its would start sucking that **** down. put in new gm gaskets and head studs and it was a ok. also at 11.5 cr and had tr6 plugs. ive since swiched to 8's.

 

You still stock bottom end?

Did you change the timing any? I have had ~20 bottles thru the motor on teh 100 shot and no signs of any issue other then losing water on the juice.

I try really hard to run 100 octane while spraying anywhere rather it be the track or the street. But, there was a few times over the summer where I was forced to get 91 octane and I did spray on it. So, I am guessing thats where I got my gasket leak and now it leaks no matter what octane I put in.

 

ya stock bottom end. never changed the timing. it doesnt take mauch to lift a head in these cars froim what ive seen.

 

Gotcha...

Assuming its only one side, how can I tell from looking at the plugs which head gasket is blown??

I dont think its both so why do both.

 

Hmmm. I think the lifting issue for most of us has more to do with the tune than anything. Hell, I have run 280rwhp shots through bonestock motors and never lifted a head. My 408 has already saw 300rwhp shots a few times, and no head lifting, and will be applying a 350rwhp soon. Though on the 408 I do run the ARP L19 head studs, and they allow 40% more clamping force than normal ARP. Also use the GM MLS gaskets.
Robert

 

I am just using a cometic .040" gasket and stock GM bolts.

Everything was cool till I sprayed using 91 octane.

 

I did some quick calculations. On a 150 shot with 93 in the tank and 116 in the standalone, my overall octane rating would be about 98.5. On a 200 shot it would be about 99.5. Is that problem? Is mixing leaded + unleaded a problem? I'm not running any O2's besides my wideband, plus I wouldn't be running enough leaded fuel to make a **** anyway.

I had no idea that the standalone tank would last so long as you guys are saying lol. 11.5:1 air/fuel by weight means I'd burn up a lot of spray before that fuel ran low, never thought about it before.


PS - I couldn't find much info on gapping TR-7 plugs either. .032" or so sound about right?