the heads have been milled .035. gonna use stock mls gaskets. also the intake and exhaust ports are gonna be cleaned up along with unshrouding the valves for stock ls1 valves. which are 2.00 and 1.55 i believe. can't remember on them exactly. three angle valve job. i am gonna run 7.035" pushrods. heads should flow roughly 280 and 215 cfm vs 225ish stock.

so in a nutshell, the heads are being worked but not hogged out. if i do decided to move up to a 6l then the heads will still be plenty good for that motor as well.

 

How close are those heads going to be the stock 317s?

i thought I might try the 317s with my stock 5.3l and the 224! I have not look into to it that much yet, though!

 

i haven't looked much into it as far as comparing stock 317's vs what i am having done. maybe someone that knows a little more about the 317's will chime in am enlighten us.

 

317s flow a little less stock than what you are having done (which is almost exactly what I have done to mine). The big problem with running 317s on a N/A 5.3 is the 72cc chamber. You'll lose a lot of compression with them, which would be great for a boosted application. Flyer actually ran 317s with his Radix.

 

Could you mill the heads to up the compression?

 

i'm sure doing that would help as well as running a thinner gasket. i wonder about the chamber size and what effects it will have though. i'm a noob when it comes to cylinder heads and all that so i'd really like it explained if someone don't mind.

 

Just going by may experience, but the porting of my heads brought the chamber volume up from 61cc to 65cc, then they were milled .045, which brought the chambers back to 58.8cc. That was the max that WCCH would mill them without fear of intake manifold fitment problems. I'll also be running a Cometic .045 gasket. This will put my SCR at 10.02:1.

A stock 317 head has a 72cc chamber, so it would have to be milled way more than .045 to even get it back to a stock 5.3 head chamber volume so you wouldn't loose compression. I don't see them as a viable option for a N/A 5.3, no matter what has been done to them.

 

Goshawk wouldnt the lower compression help you since you spraying nitrous?

 

as far as i have read and can understand nitrous will do just fine in a low compression motor or a higher compression one. plus i'll have the added benefit of running slightly more than stock cr when not spraying. to be honost i am following a path that was tested by bigKID. he did a heads/cam nitrous 5.3l and had great results. only difference is i am using a slightly larger cam and a wet shot vs his dry.

but i'll state this again, i am a noob when it comes to cylinder heads and we have way more technical people on the board that could answer that question. but i don't think compression ratio hurts nitrous like it can boosted apps.

 

no with higher compression u just don't run as much timing and run a better fuel nos just speeds the burn in the cylinder.