Heads for Dummies
Thread Starter
TECH Enthusiast
iTrader: (2)
Joined: Aug 2008
Posts: 537
Likes: 4
From: MCB Quantico, VA
Heads for Dummies Could someone break down the specs on a set of heads? I'm not sure what the 59cc refers to or the 250cc refers to in a set of heads. or the ange degree 13, 16 etc. Or the flow charts listed under a particular set of heads. Just want to know what i'm looking at when shopping! thanks for the info!
59cc refers to the amount of volume the combustion chamber can hold.
This is the combustion chamber.
250cc refers to the intake port runners measured in the same fashion. Filled up and measured with the valves closed. Exhaust ports same way.
Intake Runner.
Exhaust Port.
As for the valve angle I believe it is measured in reference to the piston at TDC but I'm not certain on that. Different valve angles account for better flow and different characteristics of how the combustion process happens.
Flow numbers don't mean ****. Go by real world testing when looking for heads. A lot of companies skew the numbers and use pipes on the flow fixtures to inflate numbers. I had a set of 243s and they didn't flow over 300cfm on the intake side yet I ran 125 mph in the 1/4 and made more power than most LS1's with larger heads.
Did any of this help at all lol?
This is the combustion chamber.
250cc refers to the intake port runners measured in the same fashion. Filled up and measured with the valves closed. Exhaust ports same way.
Intake Runner.
Exhaust Port.
As for the valve angle I believe it is measured in reference to the piston at TDC but I'm not certain on that. Different valve angles account for better flow and different characteristics of how the combustion process happens.
Flow numbers don't mean ****. Go by real world testing when looking for heads. A lot of companies skew the numbers and use pipes on the flow fixtures to inflate numbers. I had a set of 243s and they didn't flow over 300cfm on the intake side yet I ran 125 mph in the 1/4 and made more power than most LS1's with larger heads.
Did any of this help at all lol?
Thread Starter
TECH Enthusiast
iTrader: (2)
Joined: Aug 2008
Posts: 537
Likes: 4
From: MCB Quantico, VA
DJFURY- your the man! thats exactly what i needed lol but now i have a few follow up questions....
does the bigger the combustion chamber always mean better?
same for the intake runner/exahust?
does the bigger the combustion chamber always mean better?
same for the intake runner/exahust?
No, the bigger the combustion chamber the less your compression ratio is.
I run the 317 casted head witch has a 72cc cumbustion chamber, this droped my compression down about 1/2 point. So now I'm around 9.4:1 from 10:1 compression. Stick a 59cc head on your moter and you'll start to bump the compression up to the 11:1 mark. This is all with a (stockish style) flat top piston.
Big combustion chamers = lower compression ratio, good for forced induction bad for a N/A motor.
For a N/A app you would want to bump up the compression, just watch the smaller cc combustion chambers heads can cause you piston to valve clearance problems depending on how big your cam is.
I run the 317 casted head witch has a 72cc cumbustion chamber, this droped my compression down about 1/2 point. So now I'm around 9.4:1 from 10:1 compression. Stick a 59cc head on your moter and you'll start to bump the compression up to the 11:1 mark. This is all with a (stockish style) flat top piston.
Big combustion chamers = lower compression ratio, good for forced induction bad for a N/A motor.
For a N/A app you would want to bump up the compression, just watch the smaller cc combustion chambers heads can cause you piston to valve clearance problems depending on how big your cam is.
Thread Starter
TECH Enthusiast
iTrader: (2)
Joined: Aug 2008
Posts: 537
Likes: 4
From: MCB Quantico, VA
what should be a good goal Compression for an NA car....
also, im okay with a smaller cc chamber as long as my pistons have some valve relief in them for the cam correct?
also, im okay with a smaller cc chamber as long as my pistons have some valve relief in them for the cam correct?
10.5:1 - 11:1 would make for nice throttle responce on the street (93/94 octane). If your pistons have valve relief in them that will give you some extra PTV clearance.
Do you have heads/cam yet or are you going to be ordering a package soon ?
Do you have heads/cam yet or are you going to be ordering a package soon ?
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
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 Thread Starter
TECH Enthusiast
iTrader: (2)
Joined: Aug 2008
Posts: 537
Likes: 4
From: MCB Quantico, VA
im ordering the 408 assembly this week and while its being assembled to my new 6.0 iron block i'm going to order the heads/cam
Thread Starter
TECH Enthusiast
iTrader: (2)
Joined: Aug 2008
Posts: 537
Likes: 4
From: MCB Quantico, VA
