Ls3 Max compression on stock pistons and heads
Thread Starter
Registered User
Joined: Aug 2017
Posts: 5
Likes: 0
From: Melbourne, Australia
Ls3 Max compression on stock pistons and heads Hi guys long time reader first time poster I have bought my self a hsv with a ls3 in it and am looking to put a big solid roller in it somthing like 240-250 @50" and about 650" lift and want to remove the heads to obviosly put some link bar solid lifters in it but while the heads are off I would like to put thinnner gaskets and deck the heads as much as possible to get as much compression I can without valve contact I will be piston to valve checking it but want to know roughly what comp have people been able to achieve without fly cutting pistons? Any advice much appriciated
TECH Regular
Joined: May 2011
Posts: 433
Likes: 1
Hi guys long time reader first time poster I have bought my self a hsv with a ls3 in it and am looking to put a big solid roller in it somthing like 240-250 @50" and about 650" lift and want to remove the heads to obviosly put some link bar solid lifters in it but while the heads are off I would like to put thinnner gaskets and deck the heads as much as possible to get as much compression I can without valve contact I will be piston to valve checking it but want to know roughly what comp have people been able to achieve without fly cutting pistons? Any advice much appriciated
Our previous LS3 had a CompCam 231 239 .617" .622" 113 which could not be fitted straight up due to clearance issues.
Last year I had the heads milled .075" which resulted in 57cc chambers, this was ~12.6:1 compression after flycutting .100".
Factory is 10.7:1 and even leaving the heads on you can't sneak much more than a 231-234 sized intake lobe in there without flycutting. In solid roller territory that's about 236-239 range.
Now the rolled valve angle PRC/trick flow/or MAST heads all allow more cam or that sized with more compression but seldom BOTH
Now the rolled valve angle PRC/trick flow/or MAST heads all allow more cam or that sized with more compression but seldom BOTH
LS1Tech Sponsor
Joined: Feb 2008
Posts: 300
Likes: 18
The stock LS3 has an intake valve drop of .140 in. Without fly-cutting, a standard head can be milled about .030 and still have enough piston to valve clearance with a 231@.050 style cam. I'll personally will take the compression bump over the few degrees of cam timing.
The TFS 255 LS3 heads have .180 intake drop. Basically it means you could mill the heads .030 and still run a cam in the mid 230 range and still not have to fly-cut.
The TFS 255 LS3 heads have .180 intake drop. Basically it means you could mill the heads .030 and still run a cam in the mid 230 range and still not have to fly-cut.
__________________
LS1Tech Sponsor
Joined: Dec 2014
Posts: 507
Likes: 106
The stock LS3 has an intake valve drop of .140 in. Without fly-cutting, a standard head can be milled about .030 and still have enough piston to valve clearance with a 231@.050 style cam. I'll personally will take the compression bump over the few degrees of cam timing.
The TFS 255 LS3 heads have .180 intake drop. Basically it means you could mill the heads .030 and still run a cam in the mid 230 range and still not have to fly-cut.
The TFS 255 LS3 heads have .180 intake drop. Basically it means you could mill the heads .030 and still run a cam in the mid 230 range and still not have to fly-cut.
Using a typical naturally aspirated LS3 intake centerline of 110 degrees ATDC, this leaves room for an intake duration of about 232 degrees @.050" on a typical hydraulic LS street camshaft lobe when using a stock, flat-top LS3 piston with no valve reliefs.
Every 1 degree earlier IVO or 2 degrees of intake duration measured @.050" costs about .006" of piston to valve clearance. So, if you mill .030" off of the cylinder head, you will need to open the intake valve about 5 degrees later to maintain similar piston-to-valve clearance. So, you would end up with a reasonable IVO of about 1.5-2 degrees BTDC @.050" lift or a camshaft intake duration of about 222 degrees @ .050" of lift on a 110 ICL to maintain the same piston-to-valve clearance you would have with an un-milled cylinder head.
In these scenarios, the extra valve clearance afforded by an 11 or 12 degree cylinder head like the Trick Flow heads can make all of the difference if you don't have pistons with valve reliefs.
LS1Tech Sponsor
Joined: Dec 2014
Posts: 507
Likes: 106
Hi guys long time reader first time poster I have bought my self a hsv with a ls3 in it and am looking to put a big solid roller in it somthing like 240-250 @50" and about 650" lift and want to remove the heads to obviosly put some link bar solid lifters in it but while the heads are off I would like to put thinnner gaskets and deck the heads as much as possible to get as much compression I can without valve contact I will be piston to valve checking it but want to know roughly what comp have people been able to achieve without fly cutting pistons? Any advice much appriciated
Unfortunately, the LS3 is extremely limited in the piston-to-valve clearance department from the start. If you really want a serious racing camshaft in your LS3, consider procuring a Lindy fly-cutting tool and adding valve reliefs. Otherwise you will be quite limited on camshaft duration.
Trending Topics
LS1Tech Sponsor
Joined: Feb 2008
Posts: 300
Likes: 18
If you don't mind, I would like to contribute on this issue. The valve drop that I have measured on LS3 heads is about .130 to .135 with the cylinder head on a flat surface. If you add a factory head gasket thickness of .051" and subtract the positive deck height of about .006" you end up with an assembled valve drop measurment of about .175-.180" when used with flat top piston having no valve reliefs. This allows for an IVO (intake valve open) event of about 6.5 degrees before TDC @.050" and still have .055 to .065" intake valve clearance.
Using a typical naturally aspirated LS3 intake centerline of 110 degrees ATDC, this leaves room for an intake duration of about 232 degrees @.050" on a typical hydraulic LS street camshaft lobe when using a stock, flat-top LS3 piston with no valve reliefs.
Every 1 degree earlier IVO or 2 degrees of intake duration measured @.050" costs about .006" of piston to valve clearance. So, if you mill .030" off of the cylinder head, you will need to open the intake valve about 5 degrees later to maintain similar piston-to-valve clearance. So, you would end up with a reasonable IVO of about 1.5-2 degrees BTDC @.050" lift or a camshaft intake duration of about 222 degrees @ .050" of lift on a 110 ICL to maintain the same piston-to-valve clearance you would have with an un-milled cylinder head.
In these scenarios, the extra valve clearance afforded by an 11 or 12 degree cylinder head like the Trick Flow heads can make all of the difference if you don't have pistons with valve reliefs.
Using a typical naturally aspirated LS3 intake centerline of 110 degrees ATDC, this leaves room for an intake duration of about 232 degrees @.050" on a typical hydraulic LS street camshaft lobe when using a stock, flat-top LS3 piston with no valve reliefs.
Every 1 degree earlier IVO or 2 degrees of intake duration measured @.050" costs about .006" of piston to valve clearance. So, if you mill .030" off of the cylinder head, you will need to open the intake valve about 5 degrees later to maintain similar piston-to-valve clearance. So, you would end up with a reasonable IVO of about 1.5-2 degrees BTDC @.050" lift or a camshaft intake duration of about 222 degrees @ .050" of lift on a 110 ICL to maintain the same piston-to-valve clearance you would have with an un-milled cylinder head.
In these scenarios, the extra valve clearance afforded by an 11 or 12 degree cylinder head like the Trick Flow heads can make all of the difference if you don't have pistons with valve reliefs.
__________________
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Five Reasons the Camaro Was the Most Pivotal Player in the Pony Car Wars 2.0
Brett Foote Thread Starter
Registered User
Joined: Aug 2017
Posts: 5
Likes: 0
From: Melbourne, Australia
Great posts guys my plan with this was to get over 12:1 comp and try make 500rwhp with basically a stock motor just high comp big cam full exhaust and intake that's why I wanted to go solid cam to get tight clearances but looks like I will need to either drop in a set of pistons or fly cut I have allready tuned the car and put an Otr intake and I squeezed 422rwhp out of it with just intake and tune on a dyno dynamics dyno just want to break that 1.5hp per cubic inch barrier
PV Contact = EAP Hi Kika, good above tech from the other posters.
My observation is NO mention of the Camshaft Lobe Center.
There is a MAJOR difference in PV distance when a 112 L/C vs a 116 L/C camshaft.
The Hendric Head you have LOVES compression AND a Wide Lobe Center camshaft.
WOULD you PROVIDE the L/C value ?
Lance
My observation is NO mention of the Camshaft Lobe Center.
There is a MAJOR difference in PV distance when a 112 L/C vs a 116 L/C camshaft.
The Hendric Head you have LOVES compression AND a Wide Lobe Center camshaft.
WOULD you PROVIDE the L/C value ?
Lance
Hi Kika, good above tech from the other posters.
My observation is NO mention of the Camshaft Lobe Center.
There is a MAJOR difference in PV distance when a 112 L/C vs a 116 L/C camshaft.
The Hendric Head you have LOVES compression AND a Wide Lobe Center camshaft.
WOULD you PROVIDE the L/C value ?
Lance
My observation is NO mention of the Camshaft Lobe Center.
There is a MAJOR difference in PV distance when a 112 L/C vs a 116 L/C camshaft.
The Hendric Head you have LOVES compression AND a Wide Lobe Center camshaft.
WOULD you PROVIDE the L/C value ?
Lance
See post #6.
Thread Starter
Registered User
Joined: Aug 2017
Posts: 5
Likes: 0
From: Melbourne, Australia
Hey lance im looking at somthing along these lines in250@50" ex258@50" in612"lift ex634"lift @112lsa im thinking somthing like that should get me close to the 500rwhp mark
TECH Regular
Joined: May 2011
Posts: 433
Likes: 1
If you have an auto behind your LS3 I would suggest the Dyno Dynamics that your car is being run up on is a little "happy"
Thread Starter
Registered User
Joined: Aug 2017
Posts: 5
Likes: 0
From: Melbourne, Australia
Nah car is a manual and dyno was in shootout mode so no way to fake the numbers I tuned it and it made 315rwkw that's 422rwhp just has an otr intake factory hsv tri y headers and a stock 2.5" hsv exhaust
TECH Regular
Joined: May 2011
Posts: 433
Likes: 1
Without adjusting the straps I was able to make down to 320rwhp and up to 402rwhp by simply adjusting the hand controller and air temp sensor position.
428rwhp on a Dyno Dynamics in a 3,900lb car is good for 11.0 quarter mile times .
Thread Starter
Registered User
Joined: Aug 2017
Posts: 5
Likes: 0
From: Melbourne, Australia
Hate to disagree with you but a few years ago I experimented with our 243 headed LS1 on a friends Dyno Dynamics dyno.
Without adjusting the straps I was able to make down to 320rwhp and up to 402rwhp by simply adjusting the hand controller and air temp sensor position.
428rwhp on a Dyno Dynamics in a 3,900lb car is good for 11.0 quarter mile times .
Without adjusting the straps I was able to make down to 320rwhp and up to 402rwhp by simply adjusting the hand controller and air temp sensor position.
428rwhp on a Dyno Dynamics in a 3,900lb car is good for 11.0 quarter mile times .
Hello Kika may I suggest you take down limitations so you can go fast you see by denying the simple but important step of fly cutting the pistons you will be living lots of power off your build.
In my world taking off all limitations is a most fly cutters are not that expensive and you can later rent them or sell/trade them or whatever.
I did just what you are about to do with an ls3 by fly cutting the pistons I was able to kick up the compression from 10.7 to 14.1 the limitation on any ls3 head is the lower accessory bolt hole in from and rear of the heads.
I was able to flat mill 0.150 thous off and still manage to jussst stay off the accessory bolt hole threads.
Went with LLSR cam spec'd by Patrick G and ground Cam Motion specs are .240 .246 667/667 113 lsa + 3
I fly cut 0.125 to both intake and exhaust ended up with .075 .065 ptv clearance.
I honestly don't recommend .240 duration with less compression if you are going to drive it on the streets 20 degree overlap is quite a bit on an ls3
Note in the heads and cam ls3 mention above the heads used are the Trick flow 255 cc intake ports heads not the factory heads as I meant to get as much power out as I could.
In my world taking off all limitations is a most fly cutters are not that expensive and you can later rent them or sell/trade them or whatever.
I did just what you are about to do with an ls3 by fly cutting the pistons I was able to kick up the compression from 10.7 to 14.1 the limitation on any ls3 head is the lower accessory bolt hole in from and rear of the heads.
I was able to flat mill 0.150 thous off and still manage to jussst stay off the accessory bolt hole threads.
Went with LLSR cam spec'd by Patrick G and ground Cam Motion specs are .240 .246 667/667 113 lsa + 3
I fly cut 0.125 to both intake and exhaust ended up with .075 .065 ptv clearance.
I honestly don't recommend .240 duration with less compression if you are going to drive it on the streets 20 degree overlap is quite a bit on an ls3
Note in the heads and cam ls3 mention above the heads used are the Trick flow 255 cc intake ports heads not the factory heads as I meant to get as much power out as I could.
Last edited by CAMSTER; Aug 23, 2017 at 12:25 PM.
P/V Distances Kika Hi Kika, thank you for your cam data.
These are the engine specs used for the EAP "P/V" distance measurement.
#1 LS-3 with "0" deck (not stated) AND when measured, if a +, you may need to subtract from the results.
#2 The HG used is a FelPro 1041 at .041"
#3 The Valve Drop of .140", a NON MILLED head.
#4 The Flat Piston Crown with NO Valve Notches. (add distance if found)
Your Camshaft with a 112 C/L
352* Exhaust Valve/Piston = .030"
360* Split Overlap = .56"
368* Intake Valve/Piston = .033"
Your Camshaft with a 117 C/L
352* Exhaust Valve/Piston = .063"
360* Split Overlap = .081"
368* Intake Valve/Piston = .080"
Thus I too agree with the above "tech"of a .125" Fly Cut Requirement.
Lance
These are the engine specs used for the EAP "P/V" distance measurement.
#1 LS-3 with "0" deck (not stated) AND when measured, if a +, you may need to subtract from the results.
#2 The HG used is a FelPro 1041 at .041"
#3 The Valve Drop of .140", a NON MILLED head.
#4 The Flat Piston Crown with NO Valve Notches. (add distance if found)
Your Camshaft with a 112 C/L
352* Exhaust Valve/Piston = .030"
360* Split Overlap = .56"
368* Intake Valve/Piston = .033"
Your Camshaft with a 117 C/L
352* Exhaust Valve/Piston = .063"
360* Split Overlap = .081"
368* Intake Valve/Piston = .080"
Thus I too agree with the above "tech"of a .125" Fly Cut Requirement.
Lance
A note I like to add tho nobody asked is when fly cutting the pistons tape the entire top of the block you are going to be working on living out only the bolt holes you are going to use, I use 3 at the time at about 40 lbs torque sense you can only do one valve at a time and use only center holes with a used 0.051 compressed head gasket sense gasket is used has already been compressed.
The cutter itself will cut the tape and make a clean cut when head is removed
no metal shavings can possibly enter the block I remove the metal shavings with a vacuum cleaner then slid a clean line to have air go in as you turn the block to bring up the next piston which has to be exactly at top dead center..
The cutter itself will cut the tape and make a clean cut when head is removed
no metal shavings can possibly enter the block I remove the metal shavings with a vacuum cleaner then slid a clean line to have air go in as you turn the block to bring up the next piston which has to be exactly at top dead center..