max psi on stock heads?
 

in the middle of a turbo build and was gonna do a forged 5.3 with 317s for heads. i was told that if i wanted to run 14lbs of boost i would need diff heads because they will lift and blow heads gaskets from the thickness of the head being to thin. anyone have any luck running 14 lbs or higher with stock heads and it not blowing head gaskets every thousand mile?

I ran upwards of 23 psi on my 706 castings with ARP bolts and MLS gaskets.

14 psi should be no problem if the tune is good.

31+ psi, people do crazy shit these days

Mls gaskets lasted for approx. 3k+ miles on my set up 11-12 psi. A lot of spirited driving on it as a daily driver. Turns out I was hitting 17-18#'s overboosting and #7 cylinder side of head gasket leaked out.
LS9 head gaskets are on now on the same 317's and with a very mild tune I was spinning out on the dynojet to 922whp/860wtq on 91 octane no meth.
A good tune goes a long way literally.

Wow those are some big numbers for a 364ci on pump gas! what is your CR, Cam And are those 317s ported?


Slow93z, I think you would be safe under 20psi. I believe it also depends on your CR.

19-20 psi here on 317s. A good tune helps a lot.

Also curious what people are putting down on unported cathedral heads. I am in between using stock 5.3 heads or 317 heads for the larger valves and lower compression.

@gimmeluvin

8.5:1 cp's
72cc PRC stg. III 2.08/1.60 ported from TSP. (317's)
Comp 236/242 .610/.612 lift 114 lsa 12.5 degrees of overlap IIRC.
103# hi imp. injectors.

I really never intended to hit 18#'s. Was a mistake actually. lol.
13#'s for -DD

nice dude, at what rpm do you see 13psi?

6,500. Was set at 7k but on the street past 4,500 it really doesn't matter anyway once its in boost.

sorry what i meant is at what rpm do you start to see boost and when are you making full boost. Have you had to the track?

lol. Yeah, after I read your last post again I realized that. 5k I am seeing 12-13#'s and no track times yet till I get a second vehicle. I can't risk breaking stuff right now. I still have 150 progressive NX system I am eagerly waiting to try out.

lol, thanks for the info. I better stop Hijacking this thread, someones going to get pissed. lol

If you or anyone has some questions just pm me. Sorry to the OP.

Tim

cool! thanks guys. but a far as running 14lbs. can it be done reliably? or do you blow head gaskets every couple thousand miles? and i guess the ls9 gaskets are the go-to gasket now..?

I built hot parts for friends swap, it uses a tnetics tc78 and has seen over 15psi daily for about 2yrs now. It's a stock everything bottom
end, stock heads milled .005 ls9 gaskets.new stock headbolts. Hell it's got a cl find tq converter we found for 50$. It's using s rebuilt th350. Runs hard everyday no problems. Excellent SD tune and 60lb injectors. Also using a 100$ C5 intake manifold

right on! sounds like i will be sticking with the plan then. anyone have some 317s they want to get rid of?

Shoot for a HP/TQ goal. It's easier that way. Too many variables with boost. You can accomplish a certain boost goal but from my experience, the less air flow resistance from said parts the more power you can get per amount of boost.

I have a set of 317s, pm me we'll talk!

I have heard 241's are good because they have a thick deck. Correct me if I'm wrong. I got a lq4 390 sitting in my living room right now haha. I'm putting my ls1 heads on it which are 241.