Horsepower - Reading, Research,Options,Information
The topic of this is NOT a "How to reach XXX RWHP" thread, its merely trying to show members some basic insight on how to reach certain power levels the desire. Additionally, The thread is meant to have a good overview of general information on several popular topic's or questions.
-Compression
-Great flowing Cylinder heads
-Great flowing Exhaust system
-Great flowing Intake system
-Losing the "Extra" systems
-Camshaft Selection
-Nitrous
-Stroker Engines
-Fuel pumps, injectors
-Difference's in LS1/LS6
Compression -
One way to squeeze out a few more horsepower even after porting. Accomplished by milling the cylinder head deck surface to decrease the chamber volume. There are many compression calculators out there, but usually the normal going rate is around 11ish/1 on 91 or higher octane. This of course can depend on your camshaft and other parts of your setup. Shoot for around 11ish/1 compression on a naturally aspirated LSx engine. When milling the cylinder heads you are in turn bringing the valves closer to the piston, decreasing PTV ( Piston to Valve ) clearance. You must take this into consideration when buying a aftermarket camshaft. You can also sway your CR by different thickness head gaskets. Stock is .053" Non stock valve sizes will greatly reduce PTV. (Stock LS1 valve sizes are intake 2.00" and exhaust 1.55") Flycutting is an option when you have less then the desired .080 intake and .100 exhaust clearance. Flycutting will remove material from the piston to make room for the valve. Raising your static/dynamic compression will increase torque output. Roughly 1 point in raised compression will increase torque 3%-4%. Intake valve closing point decides dynamic compression. Trading your flat top piston for a domed piston will increase CR greatly. That's a another whole topic though, as it goes into replacing many parts. 5.3 heads will give a bump in compression immediately. A good thread to read on compression. http://www.gmhightechperformance.com...ion_ratio.html
Static Compression - The SC RATIO is defined as the Volume of the Combustion Chamber when the piston is at the very bottom of it's travel (called "bottom dead center" or BDC) DIVIDED BY the Volume of the Combustion Chamber when the piston is at the very top of it's travel (called "top dead center" or TDC) For NA purposes, you can get away with low/mid 11:1 SCR. For Forced induction, it will depend on many factors of your build, but anywhere from 8.5 to low 9.0's SCR is usually the numbers guys are going for.
Dynamic Compression - The Compression Ratio (CR) of an engine is the ratio of the cylinder volume compared to the combustion chamber volume. A cylinder with 10 units of volume (called the sweep volume) and a chamber with a volume of 1 has a 10:1 compression ratio. Static Compression Ratio (SCR) is the ratio most commonly referred to. It is derived from the sweep volume of the cylinder using the full crank stroke (BDC to TDC). Dynamic Compression Ratio, on the other hand, uses the position of the piston at intake valve closing rather than BDC of the crank stroke to determine the sweep volume of the cylinder. For NA setups, you should shoot for mid 8's. High 8's are attainable with the right parts and a very solid tune. Cant stress the tune too much there.
Compression calculators -
http://www.angelfire.com/fl/procrastination/motor.html
http://www.csgnetwork.com/compcalc.html
http://www.zealautowerks.com/
Cylinder Head Milling - A easy way to bump compression. But milling too much can hurt head flow greatly. Welding the chambers properly is a known effective way to raise compression and keep flow. Subtracting .080/.100 from measured PTV clearance will tell how much is safe to mill. At a certain point of milling, the intake is not going to line up. There are maximum amounts of milling that can be done. It takes approx .007" to remove 1CC from a LS1 cylinder head.
Cylinder Heads -
Cylinder heads vary. And you usually get what you pay for. AFR, TFS, WCCH, ETP all do a SUPERB job in flowing great numbers. The contenders are PRC and Patroit. Both cheaper heads that will still get the job done for most applications. When looking at cylinder heads you must look at the valve angle. It not only means better air flow, but usually will mean a different valvetrain setup is required, ie Pushrods, rocker arms etc. Of course you can always get your stock heads ported. 243 casting being the top head that came stock. You can find your casting number stamped onto the head in one of the corners on either head. Companies like TEA,CarTec, do port work, along with many others. Make sure you have a REPUTABLE porter do the work. 4 bolt VS 6 bolt heads. A stock LSx block will have a 4 bolt design. For most applications this will suffice. For High HP using Nitrous or FI, A 6 bolt block might be needed to prevent pushing water. Cylinder heads STUDS are better then any bolt. ARP studs are nice pieces.
Stock valve angles are 15*. That's the angle of the valve STEM and the cylinder bore centerline. When you DECREASE this angle ( in degrees ' * ' ) you gain piston to valve clearance. Having a valve angle such as a ETP head produces will allow you to run a smaller chamber ( More compression ) to a point of not having PTV issues. Lets get valve angles straight for those that don't know.
Stock LS1 - ( 241, 243, 853, 799, 862, 317) angle - 15*
Trick Flow - 13.5*
AFR - 15*
ETP - 11*
West Coast Cylinder Heads - 12*
Some reading can be done. Ive searched so many sites, Ive forgotten most. Here's a few that touch on the valve angle ideology. http://speedtalk.com/forum/viewtopic.php?t=3080
Stock Combustion chambers are -
241 - 66CC
243 - 64CC - LS6 Head
317 - 71CC
L92 - 70CC
853 - 66.67CC
862 - 61.15CC - 5.3 Head
706 - 61.15CC - 5.3 Head
873 - 71CC - Cast Iron
035 - 71CC
799 - 66.67CC - LS2 Head, Same as 243
Runner port volume vary. Stock Port volume is 205CC. The AFR 205's are hard to beat on mid lift airflow and horsepower. 225CC ports should be consider 402 CI or higher territory.
*** Read this webpage on basic LS1 cylinder head specifications - http://www.smokemup.com/tech/ls1.php ***
L92 heads are a great head. Based off the LS7 head design, they flow huge numbers right out of the box. And for a very nice price. *** Read this page for L92 information,
L92 valve size -
2.160" intake valve
1.590" exhaust valve
http://www.gmhightechperformance.com...ads/index.html
http://corvetteactioncenter.com/spec...ls3_page1.html
Want a general review on the top main brand heads? CLICK HERE FOR REVIEWS
Stock valve guides are sintered iron. Most ( if not all ) aftermarket heads are bronze valve guides. Match that with a non-stock valve angle and a high lift camshaft (.610"+) and you will have increased valve guide wear that will lead to smoking upon start up and hard acceleration or high RPM deceleration. An adjustable rocker arm should always be considered when going to a non OEM valve angle, bronze valve guided head, or a high lift camshaft as all can cause increased valve guide wear.
Firing Order -
1 - 8 - 7 - 2 - 6 - 5 - 4 - 3
Rocker Arms -
Stock rocker arm ratio is 1.7. This number is important for figuring out your final camshaft lift. For example, my camshafts lift on intake is .337". ( 1.7 x .337 = .5729) and for exhaust ( 1.7 x .340 = .578 ) So increasing your rocker arm ratio will increase your net valve lift. Simply input your camshafts lobe lift and multiply it by your rocker arm ratio for your final lift. If you have no future plans of adding an aftermarket camshaft, then a higher ratio rocker arm ( 1.8 ) might be for you. It will add approx 10 HP with supporting modifications. Now, with your higher ration rocker arm, that will limit your future camshaft choices as it increases your lift by multiplying. Its better to keep a stock ratio and buy a camshaft with the lift you desire. There are many brands to choose from and many retailers. Harland Sharp, Yella Terra, Crane, Jesel, Scorpian rebuilt stockers. The stock rocker arms are the lightest, and very strong. If your applications does not require an aftermakret rocker, stick with the stock piece and maybe have them rebuilt. Harlan Sharp rebuilds them and COMP sells a rebuilt kit. Stock rockers are NON adjustable. Just tighten them down to 22 ft lbs, turn the engine over a few times and re-check. Pull the two connectors going to your coil packs and your fuel pump fuse. This will allow you to turn the engine over and not start the car. Here's a diagram on torquing the rocker arms. Ive never personally done the diagram's procedure on my setups, but maybe you will.
A good link on rocker arms - COMP CAMS ROCKER ARM FAQ
Link to Harland Sharps stock rocker upgraded rebuild found here -
http://www.harlandsharp.com/conversion%20kit.htm
