Dilemma; should I fit ARP head studs?

[Brazil]

My dilemma is that I had my head taken out cleaned skimmed and brought to new like condition we fitted SRD 264 exhaust cam and kept intake VVTI I also replaced my head gasket but I did not fit ARP head studs and still have the OEM.

 

I have a HKS T04Z turbo kit, big plenum & TB, 1000cc injectors and hope to achieve a power goal of 700 to 750bhp. I like to know if its essential to replace my OEM to ARP head studs?

 

The issue now is that the engine has been put together and its back in the car! What would be the most practical way to fit the ARP head studs? One at a time? If I did brake the head would I also need to replace my new head gasket?

[Chris Wilson]

There's absolutely no need for them, I wouldn't worry. A TO4Z won't make that sort of power, surely, and stock bolts torqued correctly should be fine. Personally I think 1000cc injectors are far too big, and a bigger TB will just compound drivavbility issues. If you take the head off you must renew the gasket. I'd leave it alone.

[Brazil]

There's absolutely no need for them, I wouldn't worry. A TO4Z won't make that sort of power, surely, and stock bolts torqued correctly should be fine. Personally I think 1000cc injectors are far too big, and a bigger TB will just compound drivavbility issues. If you take the head off you must renew the gasket. I'd leave it alone.

 

Thanks Chris..! That's what I wanted to hear...! What kind of drivabillity issue does it having a bigger TB create? My whole set up is prepared for the possibility of seeking more power in the future.

[JamieP]

It's not the bhp, it's the boost, if you plan to run much over 1.8bar I think I would change them.

 

I had head lift with stock head bolts and arp head bolts, I had to change to L19's in the end so I could run more boost.

[Kaan W]

I thought stock bolts were designed to stretch once torqued down leaving them useless when removed. I'm using arp anyway there not that expensive.

[Chris Wilson]

A too big a TB will give very un-progressive, almost uncontrollable low speed throttle control, with the last say 20% of throttle movement making virtually no change to engine power at all. It may also give issues when mapping. If in doubt stay stock and measure for pressure drop across the TB at peak torque, full boost. Just 2 el cheapo boost gauges off Ebay and two £1 fittings and you KNOW whether you need a big TB. Of course, there will be those to whom bigger = better. It's often the case a stock size TB will be preferable, with a bit of pressure drop, to a bigger one with other more unpleasant issues. Porsche got around this with a none linear throttle cable cam. Mazda, in the RX-7, by a small TB for the first 65% of throttle pedal movement, then two bigger ones adding in for the last percentage of movement. Of course, multiple TB's, up by the ports, is the ideal situation, like the Skyline RB26 and some straight six M Series BMW engines.

[Brazil]

It's not the bhp, it's the boost, if you plan to run much over 1.8bar I think I would change them.

 

I had head lift with stock head bolts and arp head bolts, I had to change to L19's in the end so I could run more boost.

 

James Do-Luck is running 1.6 bar @ 607bhp I am going to be on a similar set up 'same turbo' if I push for 1.8bar is there a way to guesstimate what kind of power it may achieve? i like to break into the 700bhp.

[JamieP]

You won't make a 100bhp with 0.2 bar raise on a turbo of that size, more like 50bhp I'd say.

 

jamesy has a Greddy intake and q45 also, when I fitted one to my car many years ago I gained 40bhp iirc.

[Chris Bailey]

My dads made 607bhp @1.6 bar at SRR with stock plenum, The TO4Z will run out of puff at around 700bhp.

[Brazil]

You won't make a 100bhp with 0.2 bar raise on a turbo of that size, more like 50bhp I'd say.

 

jamesy has a Greddy intake and q45 also, when I fitted one to my car many years ago I gained 40bhp iirc.

 

Maybe if Chris Bailey's old man made 607bhp on 1.6 with stock plenum I may reach my 700 with 1.8 bar plus bigger plenum and TB. Though to be in the safe side would probably be worth fitting th L19's. My head is already made up to the block and in the car so its been suggested to me to fit one head stud at a time which will save me having to brake it open and have to replace my new head gasket.

[Chris Bailey]

Maybe if Chris Bailey's old man made 607bhp on 1.6 with stock plenum I may reach my 700 with 1.8 bar plus bigger plenum and TB. Though to be in the safe side would probably be worth fitting th L19's. My head is already made up to the block and in the car so its been suggested to me to fit one head stud at a time which will save me having to brake it open and have to replace my new head gasket.

 

Also we are still on stock cams.

[JamieP]

Yeah maybe, you both got the right ECU for the job.

[Lee P]

As Jamie says its the boost that can lift the head, the Do Luck car is in stock cams so would be around 50hp more with cams in it

 

Its running about 1.5-1.6 so you should see 700hp no probs

 

I have had cars running 1.7 bar of boost on stock head bolts for some time but that was on an untouched engine.

 

If they have reused the old head bolts then they should have measured them to make sure they havnt stretched too much.

[Brazil]

My dads made 607bhp @1.6 bar at SRR with stock plenum, The TO4Z will run out of puff at around 700bhp.

 

As Jamie says its the boost that can lift the head, the Do Luck car is in stock cams so would be around 50hp more with cams in it

 

Its running about 1.5-1.6 so you should see 700hp no probs

 

I have had cars running 1.7 bar of boost on stock head bolts for some time but that was on an untouched engine.

 

If they have reused the old head bolts then they should have measured them to make sure they havnt stretched too much.

 

The guys at the shop did take the OEM bolts off since my head went away to be machine cleaned so at least I would imagine that the threads are clean and should make easy to take them off and to have an accurate torque when replacing it with L19's ARP head studs one by one with the head made up.

 

I found this interesting post about replacing them with the head on and doing them one by one; what do you think? My head gasket is brand new so would it be a bit risky?

 

Someone here has done the 'one at a time' swap before with no issues. I've replaced OE head studs (with the head on) with ARP's twice on Porsche 944 turbos but I use the same torque pattern starting at the center not the edges. The ARP's get torqued to a higher value than OE so you would not want to work from the edges out and build stresses at the center of the head. The most important thing is knowing the condition of the HG first; if it's a high mileage HG or has no history of age I would not do it. If it's a recent warrantyreplacement HG I wouldn't be as concerned. Make sure the threads in the block are very clean and the correct lube is used on the ARP's.

[Brazil]

Would I need to remove my cams to take off the OEM head studs one at a time?

 

What would be the domino effect if the head lifted and I blown a head gasket under boot?

 

I am starting to think better to to stick with the OEM head bolts and boost 1.7 max.

Edited May 11, 2013 by Brazil (see edit history)

[Chris Wilson]

The cams need to come out You can do one bolt at a time without the gasket getting disturbed. Personally i think you are just making work and expense. An engine that stretches stock bolts through sheer cylinder pressures is not a road car engine and will be generally HUGELY demanding in maintenance, with a VERY short between rebuilds time. Peole just get carried away on the back of patently ludicrous rolling road BHP figures.

[Brazil]

The cams need to come out You can do one bolt at a time without the gasket getting disturbed. Personally i think you are just making work and expense. An engine that stretches stock bolts through sheer cylinder pressures is not a road car engine and will be generally HUGELY demanding in maintenance, with a VERY short between rebuilds time. Peole just get carried away on the back of patently ludicrous rolling road BHP figures.

 

Yes... I am going to give it a rest..... when Ryan come over to tune it I will ask him to do the best he can with what I have...!

[Brazil]

I forgotten to add a bit of history too; one of the main reasons why I started the single turbo project was because I had my fan shroud catch the fan blade and I blew a head gasket also after investigating the mechanic found that the thermostat was also not working? So I am not sure if this is a domino result of the engine getting too hot?

 

With that being said is that a even bigger reason to change the head studs could they have been stretched due to the heat etc?

[Chris Wilson]

There's NO WAY it will have got hot enough to affect the metallurgy of the head bolts and ever function as an engine again. What you SHOULD have been concerned about is whether the head was warped, or if the head had gone soft. It doesn't take much heat to change the metallurgy of a cast alloy head. If the head was warped or softened it is not suitable for re use, IMO. Are you using the head that saw an over heat situation? Was it tested for hardness? I test EVERY aluminium alloy head for hardness on every engine I build. It's surprising what "stories" customers suddenly remember when you tell them it's soft as toffee A soft head can suffer head gasket failures as the fire lands dig into the softened material, and they can suffer oil leaks down the outsides of the guides, and valve seat inserts coming loose. Engine building is 85% preparation, measurement machining and checking, and 15% chucking the bits together

[Brazil]

There's NO WAY it will have got hot enough to affect the metallurgy of the head bolts and ever function as an engine again. What you SHOULD have been concerned about is whether the head was warped, or if the head had gone soft. It doesn't take much heat to change the metallurgy of a cast alloy head. If the head was warped or softened it is not suitable for re use, IMO. Are you using the head that saw an over heat situation? Was it tested for hardness? I test EVERY aluminium alloy head for hardness on every engine I build. It's surprising what "stories" customers suddenly remember when you tell them it's soft as toffee A soft head can suffer head gasket failures as the fire lands dig into the softened material, and they can suffer oil leaks down the outsides of the guides, and valve seat inserts coming loose. Engine building is 85% preparation, measurement machining and checking, and 15% chucking the bits together

 

Thanks Chris, I've passed all this on to the lead mechanic I will wait to see what he has to say about it.