What can the 11mm ARP Head Stud take in terms of boost and power?

Is it really worth paying for the 14mm conversion which some builders offer?


Cheers

 

i blew my wad at approx 550 - 600

 

What engine type, 2 or 2.5?

 

2.33 actually.

 

Not yours, the OP's.

 

oops sorry.

 

Cosworth high tensile variant would be the better option if you don’t want to splash out on the 14mm conversion but want a more than the 11mm APRs have to offer.

 

I've heard the 14mm stud conversion would be needed over 500 but unconfirmed?

 

2.1 CDB Stroker.

I don't mind spending the money if it's definitely needed!? As eventually I will hopefully be going over 500.

 

enginertuner(alan) recommended the 11mm to me for my 2.1 stroker above the expensive 14mm headstud conversion however i've no idea of the power they can handle!!

 

What sort of power do you intend to run?

 

im not 100% but over 500 would require 14mm conversion to both block and heads, expensive - yes, but if you going 500plus, im sure you have the dollars as its not cheap to hit that target anyways lol

 

You can go way beyond 500bhp on a 2.5 for instance on ARP 11mm headbolts and Cometic gaskets.... the question is how much boost are you running and how much abuse do you give your engine, dictates how long the gaskets will last (assuming the engine has been built correctly). Mine lasted 9k of proper abuse at over 500bhp and with boost up to 2.5bar, but mostly at over 2bar.

However.... on a 2.1 you would have more meat around the tops of the cylinders and although the same issues *may* apply, I suspect the 2ltr / 2.1ltr or 2.2 blocks are the better choice in that area.

If I did this all again I would probably go with the Cosworth High Tensile bolts and Cosworth stopper Headgaskets on a 2.1 stroker, which is the set-up I moved to on my 2.5 build with the previous Spec C.

Keeping boost at sensible levels helps.

 

I would definately use the 14mm ones

 

450bhp tops!!!

 

I certainly would not disagree with what you have been recommended on your build then. I would not be looking to go to 14mm at that level on a 2.1 stroker either.

 

Why is that then Steve.... have you now been guaranteed not to have HG issues with 14mm bolts then!

 

Why not make it future proof by adding the 14mm studs, as im sure the boost bug may bite you later in the future

 

I am still on 11mm ARP's on my drag car, so 682bhp and 2.26 bar ! I am due to refresh this winter and I will use the Cosworth 260,000 11mm's. Just need to find some, no one seems to have them in stock.

However I will add in two years on this build most work has been drag, it did do a few track days @ circa 550bhp with no issues and Scoobysprint last season at 600bhp.

 

http://cgi.ebay.co.uk/Cosworth-Head-...item41490d0eb7

http://cgi.ebay.co.uk/Cosworth-Head-...item483ba5d493



...Are these suitable? Or do they only fit 2.5L heads and/or blocks?

 

Should be fine on any block them Joz

Banny

 

That's what I thought (all heads/blocks being the same for stud positions).

MH must have overlooked the ones on eBay then........

 

Didn't even think of looking there ! ta

 

Cheers for the advice guys I probably will got for the 14mm conversion as I will probably always be pushing for more power.

 

I know this is an old topic, but a very interesting read. I wonder if any of the thought process has changed from hands on experience with the builds over the past 9 years.

On the 2.5L I've been told it's all about Boost / CFM / Torque as to how much of a safety margin you have before head lift and that 11mm ARP very much have their limitations. 610NM torque or 450 Ft-lbs and you can expect to be lifting your heads on 11mm at least in the experience of this particular Subaru engine builder who prefers to remain on the cautious side as ultimately it's us paying for rebuilds not them!

 

my closed deck 2.5 runs 11mm and is speced for 500-550. Bear in mind there are different grades available for the studs.

 

Fair point, what torque are you running and what turbo / boost. I followed the thread about ARP, Cosworth high tensile and importance of how they are torqued.

 

low boost at min, around 1.3bar on an sc46x so only 380/390, once i have front mount and replaced exhaust manifold will be pushed to full potential so to 500+

 

Would be great to post here once you have it running to the full potential how the heads hold up at the new power, torque and boost levels .

 

wont be an issue, clinic have speced and built dozens if not hundreds