Max safe compression 4.155" stroke 4" bore, 91 Octane?
#1
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
I am starting to finalize the parts list for my build, and I am trying to decide what pistons I want to get. The motor will be 4.155" bore and 4" stroke, with LS7 style heads. I will also have piston oil squirters installed by Katech.
So, what does everyone think will be a safe compression with 91 octane gas? I think that I read somewhere that 12.5:1 was the max, but that was on a smaller bore motor. I think that the piston oil squirters should allow higher compression too.
So, what does everyone think will be a safe compression with 91 octane gas? I think that I read somewhere that 12.5:1 was the max, but that was on a smaller bore motor. I think that the piston oil squirters should allow higher compression too.
#2
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
Oil being squirted underneath Pistons helping with Compression and Pump gas...Wow never thought of that.
Fake News.
Your cam shaft dictates what's allowable.
91 octane and 12.5 =
A cam with more than 260 degrees @ .050
Top of my head math from reference builds.
Oil Squirter's 🤣
Fake News.
Your cam shaft dictates what's allowable.
91 octane and 12.5 =
A cam with more than 260 degrees @ .050
Top of my head math from reference builds.
Oil Squirter's 🤣
#3
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
93 octane is what's being used with anything above 12 points of comp and sometimes with a
Fuel additive
Got Corn fuel?
And or a thicker head gasket to lower compression.
Fuel additive
Got Corn fuel?
And or a thicker head gasket to lower compression.
The following users liked this post:
G Atsma (03-15-2021)
#4
TECH Senior Member
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
I think the real reason The LSA/LS9 use piston squirters is to keep the pistons cool enough to stave off being barbecued under lean conditions, not so much for low octane tolerance.
But that is just me speculating....
But that is just me speculating....
#5
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
Sounds Correct to me! Read this around the time GM High tech was around.👍
The following users liked this post:
G Atsma (03-15-2021)
#6
TECH Senior Member
The following users liked this post:
Corona (03-15-2021)
#7
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
Oil being squirted underneath Pistons helping with Compression and Pump gas...Wow never thought of that.
Fake News.
Your cam shaft dictates what's allowable.
91 octane and 12.5 =
A cam with more than 260 degrees @ .050
Top of my head math from reference builds.
Oil Squirter's 🤣
Fake News.
Your cam shaft dictates what's allowable.
91 octane and 12.5 =
A cam with more than 260 degrees @ .050
Top of my head math from reference builds.
Oil Squirter's 🤣
The following users liked this post:
Corona (03-16-2021)
Trending Topics
#9
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
Thing is 8000+ rpm is needed with 12.5 on 91 octane.
#10
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
Lower comprescompression or
Meth injection...
Best thing I came up with in a Pinch 😉 like U.
Use a thicker head gaskets Till u ready for a better fuel...
Winning either side of the coin flip 🙃👍
Meth injection...
Best thing I came up with in a Pinch 😉 like U.
Use a thicker head gaskets Till u ready for a better fuel...
Winning either side of the coin flip 🙃👍
The following users liked this post:
Corona (03-16-2021)
#12
TECH Enthusiast
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
I’m at 12.3 : 1 and specked the cam so I could run on 98. It’s borderline in the hotter months but have flex fuel as back up
as stated earlier your cam will dictate how high compression so mayb 1st work i out how big a can you can live with and work from there
as stated earlier your cam will dictate how high compression so mayb 1st work i out how big a can you can live with and work from there
The following users liked this post:
Corona (03-16-2021)
#13
On The Tree
iTrader: (6)
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
We spec'ed my 403ci build with 11.8:1 in mind. Tony said anything more and I would have to detune it with regards to timing, which defeats the purpose of more compression. He also said during the heat of the summer it might be good to toss some octane booster in for good measure.
#14
ModSquad
iTrader: (6)
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
Oil being squirted underneath Pistons helping with Compression and Pump gas...Wow never thought of that.
Fake News.
Your cam shaft dictates what's allowable.
91 octane and 12.5 =
A cam with more than 260 degrees @ .050
Top of my head math from reference builds.
Oil Squirter's 🤣
Fake News.
Your cam shaft dictates what's allowable.
91 octane and 12.5 =
A cam with more than 260 degrees @ .050
Top of my head math from reference builds.
Oil Squirter's 🤣
The following users liked this post:
tblentrprz (03-16-2021)
#15
TECH Enthusiast
iTrader: (1)
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
I run 11.9 on 93 with about 21-22 degrees of timing and the cam is 246 / 258 on a 114 with an intake closing at about 80 degrees. Its a 454 - 4.185 x 4.125 with Brodix LS7 heads done by Advanced Induction. Car is light at 3,100 pounds with half tank no driver. I think I could run more timing but I kept is lower to factor in some cushion and or bad batch of gas. Cam timing, gearing, transmission, car weight and how good your head is are all factors.
#17
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
The young man with the thread came up with the plan of the Century.. Get pistons that lowers the Comp.
As is with the pistons listed he could:
Later with E85 have the heads Milled $ vs removing the Thicker gssket and going with a thinner gasket that gets the 12.5 compression back Cheaper and not having to send the heads out 🤔😱