Bolts? Studs?

[oregonjoe]

Originally Posted by Blackdog

Just wondering what the differance wld be between the ARP Head bolts and ARP Studs. Thanks

About $40

I have debated this a long while in deciding which way to go on my rebuild. When I tore the engine apart, one of the head bolts was severely damaged from a coolant leak that made it unusable – so I had to purchase a head bolt set. After much looking around I could not find OEM head bolts but only found ARP bolts or studs. ARP bolts were about $100 and ARP Studs were $140.

Then I talked to my machine shop guy who builds racers and he explained that Head studs were used to mainly make assembly and disassembly easier since studs do not have to removed all the time when they would take heads off which was on a weekly basis and that wears on the block threads. So I thought OK, Bolts would be fine since I am only going to this every 20 years!

Then he explained the advantage of studs was that they could be set all the way down into the block threads in relaxed state thereby getting more bite into he block when torque down. Head bolts can’t reach as far down into the block and the toque down starts to stretch them before they can reach full clamping force. As a result, studs can achieve more pressure on the gasket and mating surface. As the block and aluminum heads expand at different rates, over time they grind on the gasket to wear it down. Increased clamping force will limit head movement and reduce gasket movement. I asked what about too much torque to break the block threads or crack the block. He said there is more then enough structure in the block to take the extra 10 pounds of torque down that studs can achieve.

So not only can the head withstand higher compression – the gasket mating will last much longer and more importantly will compensate for surface defects that appear over time. All engine parts are new only once – they only deteriorate from there

Overall, since studs can be installed into the block in a relaxed state and then put under tension – more clamping force can be achieved on the gasket then bolts. At $40 difference on a $1200 project – I decided to go with the studs. Got them from

www.horsepowerfreaks.com
ARP 203-4202 ARP (86-92) Supra MK3 Head Studs - 7MGTE (includes nuts) $134

Ordered on Wednesday via UPS Ground – arrived on Thursday.

The only drawback is installing the head with the studs in place. Haven’t done that yet but others have. I figured since I got the hood removed, can’t be too bad?