ok I'm thinking about doing some 243s soon milled .030 and whatever gasket is best from my understanding 3.91 bore ls1 gaskets are best.. this is in a crew cab 06 silverado..

the set up is full bolt ons 222/226 595 605 112+4 cam built tranny with 3400 circle d 245mm converter 4.56 gears with 30'' tire..stock 706 heads and dual springs and a ported tbss intake with ls3 tb. its a strong setup for a big truck but want to do more on a budget.

questions are, will this be worth the time and effort compared to the gains.. what gasket? what push rods, what about piston to valve clearances

i know my intake is flowing more than my heads and they are whats holding me back

 

i have 243's milled .040 with a .040 thick cometic ls1 gasket, im right around 10.3:1 CR with my 5.3, deff feel a difference with the bump in compression and the heads.

I used a 7.350 length push rod and had no problem with clearance. that being said you should never take anyones word, you need to measure with a PR length checker. everyones setup will be different.

 

I like the cometic with LS1 bore size. Use the 051" if the slugs are out of the hole, use the 040" if they are at zero deck. Milling the 243s 030 will give about a 59cc chamber. That's about 9.75:1 depending on gasket and piston deck clearance. I'd mill them .040 if you were going to use .051" gasket for 9.85:1. Assuming stock 9CC dished pistons.

Extra compression and 20CFM headflow increase vs 706 will be worth the head swap.

 

thanks for the help guys think I'm going to mill them .030 and use the cometic 5.7 gasket at .041 for better quench and the bump in compression..

 

the pistons are 8cc stock. had my 799/243 heads milled .030" and the .051" gasket. that put me right at 9.9:1 compression.

with that set up should net you with a 10.2:1 compression.

 

but really the pistons are 6.5/7cc

 

When I plug the stock numbers into the Summit compression calculator, it takes 8.8CC dish to get 9.51:1 compression.

I assume
pistons are 5 thousands above deck.
051 gasket
61.15 chamber volume
9CC dish
stock bore, stock stroke

 

 

so how much would this net me to the tires over stock heads is the swap even worth it on a 5.3 or should i just use the money for a 150 shot

 

i want to say a good solid 10-20hp threw the whole rpm range. the thing is once this is done other mods you do become more "potent" and all just keeps piling on. the 243/799 heads just flow better and if milled have a compression bump which helps with torque all over the power band.

now for the money a 150 shot would be more power and generally more fun for cheaper, until you keep filling the bottles every week.

i only really replaced mine because my old 706 cracked on me so i figured why not add a little power to it while i was there.