ARP head stud question

[TSITurbo95]

So, I have standard ARP's (torqued to 84ft lbs), with a oem composite head gasket in my 7 bolt. My question is does anyone know roughly the most boost you can run on standard ARP's and composite hg? I am at 28psi with the 20g pushing 47lbs a min. I am looking to get to about 50 (if possible). Will my hg and standard arp's suffice?

 

[ed1380]

you're getting close to the limit. L19's are recommended over 30, but with a good tune and no knock you can go a little higher. Another option is to overtorque the standard studs until you go with the L19's, but you won't be able to reuse them once they come out.

 

[richard33]

I was using standard ARPS with my hx35 on 38lbs with no problems. Plenty of people run 30+ lbs with standard ARPs. The only thing is most do it on 6 bolts where the studs are thicker. I just upgraded my turbo and threw some L19s in there.

You might as well run it and if the headgasket blows get L19s and a better headgasket.

 

[turboglenn]

I've been big on wondering this and the exact limits myself lately because i ended up with a turbo that doesn't get into it's efficiency range till past 35psi. Although i have come up with the same as what most say "30psi is the limit" i have personally run 32psi a few times with no knock, at 21* timing up top (rising from 18* where i finally spool into the 30+ range - and i admit timing is probably a little high) BUt anyway, it felt great but i've backed off it. Most people i've seen here on the forums that i've PM'ed to ask after seeing them post about being the the "excess of 30 zone" said that they have pushed 32-35psi on the plain ARP's but all of them say they were pushing coolant, which means the head was lifting.

Now, here's what i DON"T GET, 30psi in the manifold flowing into the head is NOTHING compared to the pressures of combustion. So with this in mind I would say with a good amount of certainty that it has less to do with boost pressure and more to do with the amount of air that is getting into the combustion chamber making for a bigger explosion where only THEN do cylinder pressures get high enough to start lifting the head. I would without fear run a 14b/16g on plain ARPs without a wastegate at all and have no fear of the head lifting (if it could even manage over 30 for long). But i think a lot of this baseline "30psi is the limit" is coming from people that are making a lot of power on turbos that require being past 30psi to push their airflow numbers

i.e. turbo "x" needs to be at 40psi to make 700hp - well does that mean if turbo "Z" could push the same air for 700hp at 20psi would the head be safe on one and not the other??? probably not, the results would most likely be the same on both situations, but turbo "Z" would probably be so much bigger than "X" that we'd never spool it on our cars there fore we'd probably never see the kinda power to make the plain ARP's yield at anything under a range in excess of 30+ psi.. because the force/energy needed for 700hp is what's lifting the head and not the boost pressure from the turbo, and this force is being created in the combustion chamber.

I hope that's clear, but basically what i'm saying is if there was no spark being generated you could probably push 100 psi through the manifolds and the valves and everything would probably be fine except the intake manifold gasket and such. (of course this is teory and in this case you'd be turning the engine through it cycles with an outside source just to spin it and perform this test)

Well, i hope that explains some things and clears some things up, but through all the past weeks of studying i've been doing that's the conclusion i come to, that at a certain amount of energy being created the cylinder pressures from combustion are actually what's too much for the ARP's to hold, and not the actual boost pressure, i would also estimate that this amount of energy beign created is probably enough for some where in the WHP range of 550 - 600 horses, and being that i never see anyone making over 600 with less than 30psi you can start to see where the boost pressure correlation comes into the factor. And i would safely ASSume that even with 10psi and enough nitrouse to surpass the 600 zone you would probably still be lifting the head in the same way. (i would give an NA scenario but i don't think that one is physically possible with the given RPM restrictions placed upon our engines)

EDIT: Richard33 chimed in while i was writing my post, great example (wondering what HG you were running though) but dyno numbers showing 527hp (but at 38psi) and the head was ok as far as he knew, yet some ii've talked to making 600 and more on 35psi or less said the head was lifting on a 6 bolt engine

 

[ckrell]

To get the most out of my 6bolt STD ARP's I've Oringed the deck then torqued the head on to the Orings with no gasket to leave a slite reciever groove in the head. .035" wire .024" deep with .002''or .003" in the head. Using felpro composite. It's also scary how dished the washer pockets are in the head. I made a spotfacer to flatten them with a slightly larger O.D. then that of the ARP washer. The nut faces and both sides of the washers get touched with a flat hone.

 

[turboglenn]

Before i finished the sentence i thought you were gonna say you torqued the head on with no gasket and ran it that way

I see you're in kearny, if i can get some slicks i'm going to come out there and run in a week or so ( a drag bike i helped build and tuned runs up there when there's points events and i do his pit work sometimes, and wanna run my car in the 1/4 with the new turbo and everything else i've put on since i last visited the 1320 (years ago, like 8 or more )

 

[TSITurbo95]

OK, thanks for the info, it was very informational, and Turboglenn, that makes sense that it's not the boost per say, but the force caused by the combustion. Ok, I guess I will take my chances and if it fails, it fails. Prob just to be safe, I suppose I can over torque the headstuds to about 88ft lbs.

 

[richard33]

EDIT: Richard33 chimed in while i was writing my post, great example (wondering what HG you were running though) but dyno numbers showing 527hp (but at 38psi) and the head was ok as far as he knew, yet some ii've talked to making 600 and more on 35psi or less said the head was lifting on a 6 bolt engine

I use Flat Out metal headgaskets and never pushed a drop of coolant except once I barely blew one because of a user error. I did pick up L19s but haven't used them yet since I got the hx40.

 

[99gst_racer]

Now, here's what i DON"T GET, 30psi in the manifold flowing into the head is NOTHING compared to the pressures of combustion. So with this in mind I would say with a good amount of certainty that it has less to do with boost pressure and more to do with the amount of air that is getting into the combustion chamber making for a bigger explosion where only THEN do cylinder pressures get high enough to start lifting the head. I would without fear run a 14b/16g on plain ARPs without a wastegate at all and have no fear of the head lifting (if it could even manage over 30 for long). But i think a lot of this baseline "30psi is the limit" is coming from people that are making a lot of power on turbos that require being past 30psi to push their airflow numbers

This is true. This is exactly why there can never be an accurate "PSI" limit for any part, because "PSI" doesn't take into account compressor size. A more accurate limitation would be airflow (mass flow).

Properly torqued 12mm ARPs are at their limit at around 60-65 lbs/min. I'd put the 11mm ARPs at around 10% less than that. These are just my personal estimations based on what I've accomplished, what I've seen others accomplish, and basic metalurgy math.

Ok, I guess I will take my chances and if it fails, it fails. Prob just to be safe, I suppose I can over torque the headstuds to about 88ft lbs.

Leave them where they're at. Over-torqued studs are weaker than properly torqued studs. You have room for a bit more boost/airflow before you'll be at the limit of thse studs, BUT you're already very close to maxing out your compressor, so I don't see you gaining much more power with a bit more hot air. Consider leaving boost alone and looking for more power in your tune.

 

[TSITurbo95]

Ok thank's Paul. And by power in the tune, meaning adding timing?

 

[99gst_racer]

Yup, adding timing where you can, and playing with fueling. And degree those cams if you haven't already.

 

[TSITurbo95]

Don't have adjustable cam gears, and psh, my max timing I can get so far is 7-8 up top, with afr's around 11.1ish. Ill be messing around with meth here shortly to help me get some of my timing back.

 

[gixrman]

Does'nt your C/R have bearing on this also? Really the end result that your concerned about is final cylinder pressure? As a motor with 8:1 running 30psi compaired to lets say a E85 setup running 10:1 at 30psi is going to be completely different cylinder pressure and stress on head studs. Or am I missing something?

 

[Yamaharyder600]

I have been helping a friend build a 4g63 swapped conquest. We are currently using a standard 6 bolt with l19 studs and a cheap 30$ head gasket from advanced. We made around 450hp consistently with 28lbs of boost and a 60 shot of nitrous. No issues with a head gasket.

 

[99gst_racer]

Does'nt your C/R have bearing on this also? Really the end result that your concerned about is final cylinder pressure? As a motor with 8:1 running 30psi compaired to lets say a E85 setup running 10:1 at 30psi is going to be completely different cylinder pressure and stress on head studs. Or am I missing something?

Makes sense to me.

Though I dont know enough about it to factor in how CR affects head stud limitations.

 

[TSITurbo95]

Ok, so either way I should be alright with my current setup? My upcoming build, I will get a set of L19's.

 

[99gst_racer]

Ok, so either way I should be alright with my current setup? My upcoming build, I will get a set of L19's.

Yup, you're alright. Just don't re-torque them. I don't recommend anything over 80 ft/lbs (with moly) for the studs that you're running.

And for what it's worth; I was flowing 47 lbs/min on factory 7-bolt head bolts and a composite gasket, and I wasn't pushing a drop of coolant. So, you shouldn't have anything to worry about with those studs.

 

[TSITurbo95]

Ok, that's reassuring . Thanks boss!

 

[ALBurgundy]

Ok, that's reassuring . Thanks boss!

Yes, yes it is
Seems the next step in making the power is going to be the meth to add timing.

 

[TSITurbo95]

^ Yessir, I have my new meth kit coming this week