FD3SLS1

iTrader: (1)

Do to my current motor issue I'm have to put a motor together from spare parts. I have a 6.0l short block and the 59cc stage 2 ls6 heads off of my 5.7 and the compression will be about 11.2:1 with a .060 headgasket. Will that be too much for 93 octane or should I get a .075 headgasket to lower it to 10.9:1. The only other thing I can do is to put my stock 5.7 heads on it but I would really like to have my ported heads on it.

howard wolf

Here's my experience with an LS6 427 running 11:1 compression at the
dragstrip. I use a 50/50 mix of 93/100 octane. I had the engine apart after a couple of hundred runs and no sign of detonation on the piston tops.

Brian2001SS

iTrader: (1)

I run 11.0-1. If tuned right, pump 93 is ok. In the extreme heat at Road Atlanta, I do run 98 to help.

SUTTERERMAN85

iTrader: (42)

i at 10.98:1 here in Texas. 93 is what i run. it also has a lot to do with how high you DCR is. if its in the high side will be more prone to knock, but your F13 you should be fine.

getusum

iTrader: (42)

I'm 11:25.1...running 93...every third tank I run ms 109(unleaded) just to help on the cleanng side

Camaro99SS

iTrader: (4)

There are some here such as Patrick running close to 11.5:1 on pump gas even with a mild cam. To safely run this high, you need to be careful to details such as quench and cam overlap. A tight quench allows more compression because the burn is more complete.

Jason

ArcticZ28

iTrader: (14)

Running 11.6:1 here and no signs of detonation b/c my DCR is around 8.1:1.

FD3SLS1

iTrader: (1)

Well I'm going to give it a shot and see what happens. Any idea what my DCR will be with a stock 6.0l shortblock, 59cc ls6 heads and a FM13 on a 112 ica.

Thanks

Josh

ArcticZ28

iTrader: (14)

Need to know the valve events at .006" but I'm sure someone on here has them.

pewter 01 SS

iTrader: (5)

I Run 12:1 With 91 Octane Gas Here In Cali, No Problems

PREDATOR-Z

SCR is not what affects the ability to run at a certain octane.
It has to do with DCR/quench/quench area.
I run 11.75 on 93 and I shoot 100 dry on top, no issues.

racer7088

It depends on the cam but with the larger ones I run 11-11.25 all the time with no issues. On the smaller cams I wouldn't run quite as much.

PREDATOR-Z

That is because smaller cams have a higher DCR.
BTW, running colder plugs help too

ringram

You can retard the cam a little to help. As mentioned go with thinner gaskets not thicker and choose your cam timing carefully.

BlackHawk T/A

iTrader: (3)

What about 92 octane pump gas? That's the best here.

TAQuickness

iTrader: (28)

I'm running 11.38:1 static, 8.46:1 dynamic on pump 93 with no problems. I don't imagine 92 would make much of a differnece, but, then again, I haven't tried it.

PREDATOR-Z

Guys, just so thaT it is clear:
DCR- DYNAMIC COMPRESSION RATIO
Is the determining factor, not SCR (not completely)
You could have a 13:1 motor run on pump gas if the DCR is low enough.

On average:
<8.5 OK on 91
8.5>8.7 Higher octane recommended (but not absolutely necessary)
>8.7 93+ Octane

Ways to combat detonation and run higher compression:

> Colder plugs
> tighter quench (squish)
> More quench area (dual like AFR )
> Tuning

91Z28

If 8.7 requires 93, what is the limit to what 93 octane will be sufficient for? I've never found this kind of info before.

hammertime

iTrader: (1)

The 'limit' is going to vary from car to car. Two cars running the same heads, cam, octane and tuned to the same timing may or may not have the same tolerance for detonation. Other factors that can effect octane tolerance:

Coolant Temps
Ambient Air/Inlet Air Temps
Underhood Temps
PCV System - Oil/Carbon deposits in the combustion chamber
Coatings on the valves/pistons/combustion chambers

I'm sure there's more than that - but there's lots of good reading in these two articles.

http://www.popularhotrodding.com/tec...power_squeeze/
http://www.popularhotrodding.com/tec...ression_ratio/

z-ya

iTrader: (1)

Im running 11.6 compression with .027 quench and a smaller cam. No observed knock
on wot runs,get a little cruising at low rpm on accel.