Might as well start planning for 'em..
05-13-2008, 07:49 PM
#1
Might as well start planning for 'em..
I want to go heads to compliment my cam and figure I might as well see what figure I should expect so I can start saving up, haha. I have a 4.8 with a Lunati 221/221 .558 .558 114LSA. I want heads with more compression cuz Im looking to stay N/A. I want to be able to run 91 tho, so if we can keep the CR shy of NEEDING 110 I would be happy 
Thanks for any suggestions guys I appreciate them.
Thanks for any suggestions guys I appreciate them.
05-13-2008, 09:28 PM
#2
243's are pretty easy to find in the classifieds and on eBay...might be something to look into. $300-400 spent on milling them with a good port and polish will bring them to life for sure, ask hirdlej, he's a member on here. 10.5:1 compression will still allow you to run 89-90 octane easily because I'm planning on using crappy 87 octane on 10.2-10.3:1 compression on my motor.
$300-400 for the used heads and another $3-400 for machine work. I'd save $1000 so you have plenty left over for a new head gasket and whatever else you can think of while the motor is apart.
$300-400 for the used heads and another $3-400 for machine work. I'd save $1000 so you have plenty left over for a new head gasket and whatever else you can think of while the motor is apart.
05-13-2008, 10:49 PM
#3
**** that much huh? well I guess thats pretty decent tho, Ill have to pick some up and let them hang around for a bit before the machine work. Thanks alot tho, I appreciate it. What would u think the compression on my truck is now? I know I have 862 heads
05-14-2008, 08:54 AM
#10
With your current combo now, you're running 9.5:1 compression ratio. To get the most out of your setup you will want to open those heads of yours up a bit. Quite frankly I see a more economical approach to your build would be taking the heads off your truck that're currently on there. Bringing them into a good local reputable LS1 performance shop, having them ported with a level or stage 1 port job, have new springs installed where they can check the installed height and adjust accordingly and then mill the deck surface down for a fresh new surface. You'll want to measure your piston height out of the hole before reassembly and then choose your head gasket accordingly. The thickness of the gasket minus the height out of the hole the pistons are = your quench. You will want to stay somewhere between .037-.042 for a street app. This way you can get your compression up, but yet squish the air fuel mixture better (like sqeezing on a tube of tooth paste) towards the center of the combustion chamber. This resists knock and provides a cleaner more efficient burn. The other option would be just to save yourself the dicking around, call up Patriot Performance, and get these heads:
Our custom 5 axis CNC machined new GM castings make these heads a must have for any performance oriented GM LS series engine. These heads provide are specifically for 97-98 LS applications. Custom designed runners flow up to 60 cfm over stock OEM versions.Based on other modifications, gains of up to 30 rwhp can be expected. These are a great choice for naturally aspirated engines and applications where 75-150hp nitrous systems will be used. The Stage II heads feature 21-4N 2.02”/1.57” stainless steel valves, our Original Patriot Gold Dual .650” Lift springs, titanium retainers, Super 7 machined locks, custom honed bronze guides, machined spring bases, and viton rubber seals.
*Sold as Pair
Technical Specs:
Combustion Chamber: 67cc
Intake Runner: 220cc
Exhaust Runner: 67cc
Intake Valve: 2.02"
Exhaust Valve: 1.57"
Max. Valve Spring Lift: 0.650"
Spring Pressure Closed: 135 lbs. @ 1.800"
Spring Pressure Open: 375 lbs. @ 1.090"
Retainer Material: Titanium
Valve Seal Material: Viton
Valve Guide Material: Manganese Bronze
Valve Job: 5-angle
All the fancy trick work is done for you, no down time on your truck and they are truly ready to bolt on. For a small 4.8L I don't see a benefit in ported 243 heads, they will flow too much and your intake and exhaust port velocity will slow down too much. Leaving you with shitty and soggy throttle response. I'm waiting for the "nay sayers" to come in here and flame me for that last comment. Been there, done that. Also since you went with a semi donkey dick cam for that 4.8L, you lost quite a bit of cylinder pressure and now you need that back. First, 243 heads have a larger combustion chamber than your 862's or patriot's 5.3L heads. 64cc for a 243 head and 67cc for a 862 head. The only logical way I see for you to regain compression would be run a thinner head gasket and mill .028 off the heads. Assuming you can run a .040 head gasket and mill the heads no more than .028, you should gain a half a compression point. Please don't put 243 heads on your combo, you won't know what you're missing out on. Never forget, when building a venomous street combo, usually less is more.
Our custom 5 axis CNC machined new GM castings make these heads a must have for any performance oriented GM LS series engine. These heads provide are specifically for 97-98 LS applications. Custom designed runners flow up to 60 cfm over stock OEM versions.Based on other modifications, gains of up to 30 rwhp can be expected. These are a great choice for naturally aspirated engines and applications where 75-150hp nitrous systems will be used. The Stage II heads feature 21-4N 2.02”/1.57” stainless steel valves, our Original Patriot Gold Dual .650” Lift springs, titanium retainers, Super 7 machined locks, custom honed bronze guides, machined spring bases, and viton rubber seals.
*Sold as Pair
Technical Specs:
Combustion Chamber: 67cc
Intake Runner: 220cc
Exhaust Runner: 67cc
Intake Valve: 2.02"
Exhaust Valve: 1.57"
Max. Valve Spring Lift: 0.650"
Spring Pressure Closed: 135 lbs. @ 1.800"
Spring Pressure Open: 375 lbs. @ 1.090"
Retainer Material: Titanium
Valve Seal Material: Viton
Valve Guide Material: Manganese Bronze
Valve Job: 5-angle
All the fancy trick work is done for you, no down time on your truck and they are truly ready to bolt on. For a small 4.8L I don't see a benefit in ported 243 heads, they will flow too much and your intake and exhaust port velocity will slow down too much. Leaving you with shitty and soggy throttle response. I'm waiting for the "nay sayers" to come in here and flame me for that last comment. Been there, done that. Also since you went with a semi donkey dick cam for that 4.8L, you lost quite a bit of cylinder pressure and now you need that back. First, 243 heads have a larger combustion chamber than your 862's or patriot's 5.3L heads. 64cc for a 243 head and 67cc for a 862 head. The only logical way I see for you to regain compression would be run a thinner head gasket and mill .028 off the heads. Assuming you can run a .040 head gasket and mill the heads no more than .028, you should gain a half a compression point. Please don't put 243 heads on your combo, you won't know what you're missing out on. Never forget, when building a venomous street combo, usually less is more.