65fury

well i didn't do the o-rings on my head when the engine was out, due to needing to get this truck driving asap and can't find anyone close enough (didn't want to ship it out) , but i have been talking about doing it and now im wondering, with just 12mm studs and a marine head gasket hold for the twins???


jason

blackdiesel

gasket and studs will only hold about 50psi on the safe side. maybe 55 on a single. running twins you have higher drive pressure, and that is the big factor in blowing a HG

caleb c.

55 psi. If your lucky! I wasn't, mine blew with studs and a stock turbo at 34psi. But maybe mine was just a freak deal or something!

Forrest Nearing

mine let go w/ 50psi, but it had a fair amount of miles on the twins, and like 175k miles on the factory gasket

ratsun

Can you please explain this?
As a general rule (someones always outside the box) I understood this to be opposite. I can see the TIP being lower on some of the big singles but most singles on guys trucks I know are running are way outside their map at 55psi
IMO you will have to be more careful with your timing than the TIP levels at moderate fuel levels

65fury

thanks for the feed back, im guess i was just lucky or something because on my 1990 engine i could hit 55 psi and never had any problems and i didn't even have any upgrades like studs or head gasket. well i guess i will just have to play it safe with twins until im able to o-ring it. any more opinions and thoughts are welcome. thanks again

jason

John DiMartino

warm it up real good before going over 10psi of boost,and hope for the best.Ive seem the blow at 40-and I have a friend who's making 525 to the ground now at 53psi for 2 yrs + bone stock HG,over 140K on the truck. My guess is if the head and block are flat,retorque,and you should be ok at 50psi.

blackdiesel

well say you blocked off you waste gate, and was running 45 psi of boost with a hx35, you would have 45 psi of HOT THIN air, well a set of twins gated at 45 psi, is still 45 psi of air but it is denser, cooler and alot more volume. so all that extra air makes more cyl. pressure, more drive pressure, more HP and more pontential to blow the head gasket

Forrest Nearing

excellent point

signature600

Also remember that drive pressure is a big killer of HG's...45psi on a HX35 could take as much as 80psi drive pressure with the gate blocked!

Chris

ratsun

Hmmm....
I don't understand this as you see it.
45psi out of a hx35 is a recipe for disaster, your drive pressures would be thru the roof.
As far as your analogy with the twins gated at 45psi I don't know but with my set the HX35/14 gated at 22-25 when I get to 45psi I'm no where near 1-1 yet. As I said with a large single designed to operate at 45+psi I can see slightly lower DPs than with twins but not with the small singles that most guys are running.
As I understand it HG failure is generally a result of timing, no matter if it comes from mechanical advancement/electronic advancement or from TIP (drive pressure being to high) A small single running way out side its map is slowly in effect advancing timing as long as its held there so if you hold to long, POP! You are correct that higher cyl pressure from the cooler air that a set of twins can supply over a single designed to run at the same PSI could make a difference if the engine in question was run at or near its limits for HP and timing but.......
I would rather run 50psi from a set of twins on a engine with no studs or orings than 40psi from the same engine with the stock turbo any day, come to think of it I have on both my trucks

BigBlue

What about using a stock 3rd gen gasket with a set of studs? Gate the twins down to around 50-55psi. Yall think that would hold long term or would it be better to just go ahead and o-ring the head while you've got it off.

Captain

think a stock hg and studs can hold a sps62 at like 40-43psi? or twins with the same pressure?

BigBlue

My stocker is holding 48psi with stock bolts and has been for about a year or two. Knock on wood though.

blackdiesel

im running a sps 62 and pushing 47-48 everyday