To Mill or Not To Mill....

[Phish]

Long story short the new build is a LQ4 with ported 862 heads and a 232/234 595/598 112LSA cam. Nitrous motor. Should i have the heads milled to up the compression a bit or should i just leave the 862s stock height.

[APPLES355]

I am not sure what the factory 862 head have for cumbustion chamber cc's, but the main question that needs to be answered is what would you like your dynamic compression ratio to be? The camshaft you are running, gasket thickness, cylinder head cc, etc.. will dictate what your DCR will be. I havent really done extensive research on the ls1 and what people have pushed the DCR to, but if i recall correctly we had ours between 8.5:1 and 8.7:1 with unported 59cc 243's and 236/240 streetsweeper cam. The static was between 11.25:1 and 11.5:1. I dont have the numbers in front of me to give you exact values. The car made 410rwhp and 380 rwtq.

[sparkles]

Mill them suckers down, spray it with a 250 shot, and run some corn squeeze.

[slow ride]

You should figure out the current DCR and move forward. I always run 8.4-8.5:1 in case I would have to run 91 octane, etc. In Des Moines thats about all you can get unless you go with e85 full time. What is the ICL on that cam? I see it's 112 LSA and uses XER lobes, but does it have advance or not? You might need to flycutt as it sits, but if you mill it will probably be for sure. You should run more exhaust duration if it's mainly a nitrous engine, but it will still work fine.

[Phish]

On the cam,I called comp and they suggested something extrememlly close to this. Then i found a steller deal on this one BNIB on LS1tech. Its identical excapt the duration on these are just a tick longer.

cam specs : http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=1093&sb=2

From what i have figures on a LQ4 with 862's i will be running 10.5:1 compression without milling. 862's only have a 61.15cc chamber

Again this is a NA car which will run some spray when out playing around. Most likely a 150 shot unlessi get crazy and go up another 50.

I would also really like to keep running 91 through this turd since there is no 93 within 40mi from my house.

[Phish]

This is what i am getting off of the calculators.

Stock height would be a 10.7:1 Static and a dynamic of 7.9:1
Milled .020 would be 11.19:1 Static and a dynamic of 8.26:1

Thoughts?

[slow ride]

Quickly running the average numbers since I don't have the hard parts in front of me I got a 8.2:1 dynamic for your parts as is. Mill the heads to 58cc and it should be around 8.5:1 and thats where I'd put it. I forgot you had the dished pistons already in my post above, but I'd still check piston to valve clearance.

[z06-tt]

This is what i am getting off of the calculators.

Stock height would be a 10.7:1 Static and a dynamic of 7.9:1
Milled .020 would be 11.19:1 Static and a dynamic of 8.26:1

Thoughts?

NA??? boost??

91 will support around the 11.3-11.8 static in the LS world.

[Phish]

NA nitrous motor.

[z06-tt]

wet nitrous??

[Phish]

yes sir... plate kit

[z06-tt]

Go higher compression. E85 or 91?? If e85 don't worry. With 91 u could do extra tank of say 116 for when u hit the juice.

[BGjohnson]

If you are driving on the street and want to use 91, I would not. Nothing like being on the edge of what pump gas can do and getting a shitty tank of 91. knockknocknock.

You aren't gaining a ton by upping the compression .5-.7, what maybe 5-8hp. I'd rather be safe then on the edge.

[slow ride]

Our numbers don't jive for some reason, but you will be fine on 91 with the heads at 58cc. Not sure what calculator you are using, but you can get all sorts of different numbers depending on the calculator, etc. Some caculators use numbers based off .050" numbers and that don't cut it. Most of these cam lobes used on ls stuff are faster than the average.

[Phish]

Now if i milled the heads to a 58cc chamber, would that have an effect on the nitrous shot i could put into the motor "safely". I am shooting for an occasional 200 but would prolly roll around with 150 pills in the plate.

[Phish]

Second question would be my PTV clearance. Curious if i would need to fly cut the pistons with the 232/234 cam. The LQ4 dish should help, but from research i hear that the side of the valve will hit the ring around the piston before the valve hits inside the dish. That being said thats with the 2" valves in in other heads and not the 1.89 diamater of the Intake valves in the 862s like i have.

[slow ride]

Thats a measurment you'll have to make. Not a huge deal. To really know the DCR of the engine you should measure every single thing you can rather than taking the general number. Something little like cam timing could make a big change in DCR if the cam is not degreed in, etc.

If you run race gas on the bottle you should be fine either way. Are you going to run a stand alone fuel system or just T in at the rail?

[Phish]

Take it off the rail. I belive the pump shoule support the amount of fuel. I know (believe) does not sound to confident lol. Its an aeromotive stealth

[slow ride]

The nice thing about stand alone is not taxing the cars pump and the fact you know exactly what the fuel is that you are adding with the nitrous. If it's a 91 pump car and you mix 116 in at the track it's hit or mis what octane you end up with.

[Phish]

So your saying it would not hold up to a 200 shot for long if its just ran straight 91 through the car while spraying.

[slow ride]

I'm far from a nitrous expert. I just know a lot of guys that run it run race gas when spraying. Lots of guys on here would be better at making that judgment than me, but if you are maximizing the NA part you will need to pull a decent amount of timing on nitrous if running 91 octane only. Fuel does have it's limitations.

[derek072887]

So your saying it would not hold up to a 200 shot for long if its just ran straight 91 through the car while spraying.
you should get a small 1-2 gallon fuel cell with its own pump for race fuel that is only sprayed with the N2o

[APPLES355]

The LS1 we built two years ago is running 91 with around 11.5 static compression and 8.5 dynamic compression with the 236/240 streetsweeper cam. With the deck height and gasket thickness we are running around 0.035" for quench. We havent had any issues with detonation since we have had it. The only complaint is the lack of torque from the 347!

I am with everyone. if you want to be safer you can have a stand-alone fuel system with a higher octane fuel if you want to run nitrous. If you run a smaller shot you shouldnt have a problem with the stock system as long as it can handle the extra demand, but pulling timing would be a necessity.

If we would have opted to keep the stock ls1 piston we would have had to fly cut the tops with the 59cc heads. I am not sure if that would be needed with the lq4 dish, but the best way to ensure you wont have problems is to check. Your going to want to check anyway if you end up having to flycut the pistons in the end.

[Phish]

150 pills it is then :-)

[AutoMods]

do you have a tuner/logger like hptuners or efilive? i'd recommend one to adjust timing and log knock and afr's among the many other benefits. low counts of knock would appear on my stock ls1 with 100 shot, you'll have to monitor it and pull timing as needed.

i haven't read much about nitrous and meth injection but I wouldn't see why it wouldn't work and its a cheap way to get high octane .

I can get you efilive v1 for $500 if your interested

[Phish]

Yeah timing will definately be pulled when spraying. Car will be tuned with HP tuners if things go as planned. If not i may hit you up on that efi live

[sparkles]

All this technical talk. Just spray it down. You'll know when you have a problem. The motor will tell you.

[CROWN]

What Sparkles said. Unleaded Fuel and Leaded Say Race gas, they don't mix together. They seperate.