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 like the 243 heads on a 5.3. Figure for the effort it'll net you 20-30 from idle to redline.

 

I have the 799/243 heads milled 0.030" on my 05 truck with the 0.051" mls gasket and stock cam. It dose have better power and really can tell it above 2500rpms. One thing i would suggest is if you could only mill the heads 0.020" and usea the 0.041" comet gaskets to get a better quench and lower the predetonation chance. Problem with that is those gaskets are like $120ea.

Ether route should net you close to 10:1 compression.

 

thanks for the help guys and yes thats one thing i want is more compression to make this cam pop but also give me some good gains through out the power band any one else wanna help

and those gaskets really that much **** lol

 

Slim, bobfig knows his stuff, and he's giving you great advice.

FWIW, I've seen 4.8s with 243 heads beat 5.3/706 trucks that were otherwise identical gearing tires transfer etc.

It's a smart upgrade.

 

thanks guys and what length pushrods would i need?

 

did u use 5.3 or 5.7 head gaskets?

 

always measure first. just use what you find as a guideline.

mine have 7.350" push rods on a stock cam. from what i can tell im right at .080-.090" preload on new ls7 lifters. if i went with 7.325" rods i would be around .050-.060" preload

i had these used and that's for 2
http://www.briantooleyracing.com/che...8544-bulk.html

 

thanks man

 

Since it's a somewhat old thread, I'll add a question in a hi-jack kind of way lol...

I added a set of milled .030 243 heads and .040 (3.910 bore) Cometic Head MLS gaskets to my 5.3 w/ ls6 cam and intake. I'm in the process of measuring for pushrod length and have read some discouraging information about the head gaskets I used and them being prone to leaking if the block is not at a certain grade/finish.

I previously rebuilt with new fel-pro gaskets (blue head gaskets) and didn't have one issue with leaks. The block wasn't deck but cleaned as I did this time...

What are the odds these Cometics leak and I wasted $140 on HG's?

Thanks,
Justin

 

Guess I'll find out when it's fired up...

 

you'll be OK if it worked on the fel-pro MLS. For good measure, you can take a sanding board and 400 grit paper and smooth out the block deck.

 

Thanks for the tip!