ARP questions

[link16]

Head studs or Main studs, what is the difference?

I also can't find any other places to buy ARP products for the 420A, the only site I have found is www.howellautomotive.com. Can someone point me in the right direction? I am getting a full bottom end rebuild with forged internals for my turbo, listed in a post called "A different turbo question"

 

[VelocitàPaola]

Headstuds secure the head to the block, and mainstuds secure the bedplate to the block. The primary advantage is that they're much stronger than OEM TTY bolts, and they can, in most cases, be reused. Personally, I optimistically thought that I will never have to remove the bedplate again, so I just used OEM TTY bolts. The head, however, will have to come off several times, so I used ARP hardware there.

Concept Illusions sells ARP hardware in addition to Howell Automotive. I believe you'll receive your bolts a little quicker if you purchase through CI (that's been my experience).

 

[drivemusicnow]

Headstuds secure the head to the block, and mainstuds secure the bedplate to the block. The primary advantage is that they're much stronger than OEM TTY bolts, and they can, in most cases, be reused. Personally, I optimistically thought that I will never have to remove the bedplate again, so I just used OEM TTY bolts. The head, however, will have to come off several times, so I used ARP hardware there.

Concept Illusions sells ARP hardware in addition to Howell Automotive. I believe you'll receive your bolts a little quicker if you purchase through CI (that's been my experience).

I agree with you (which is a pretty common occurence) and used similar reasoning behind my purchase of new OEM main bolts, with new ARP head studs for my engine.

The other reason is that when you replace the mains with ARP studs, you need to line hone the mains. (a machining process that requires fairly specialized tooling) I didn't feel any benefit to the added expense, which lead me back to the OEM main bolts.

 

[VelocitàPaola]

Where did you hear that from? I'm not necessarily doubting you, I'm just curious...

The block has two dowels that align the bedplate, so line honing shouldn't be necessary.

 

[drivemusicnow]

Where did you hear that from? I'm not necessarily doubting you, I'm just curious...

The block has two dowels that align the bedplate, so line honing shouldn't be necessary.

The reasoning behind it is because of the different forces applied with a stud compared to a bolt. From what I've seen the dowels still leave quite a bit of freedom, especially when you look at the torque involved on those bolts.

I've heard the a variety of responses from "absolutely neccesary" to "I've never heard of that" from different machinists, however I believe I first heard about it from Mitch Ruso. (I don't want to put words in his mouth and in case I did not hear this from him, you may want to PM him and see what he thinks.)

 

[VelocitàPaola]

Perhaps it's because of the differences with the 4G63 then... we don't have main caps, but rather one integral piece called the bedplate. The dowels don't allow for any play at all, and I can't imagine the ARP hardware making any difference.

 

[Locke]

I had to tap the bed plate down with a mallet. The dowels seemed to provide an interference fit. No play.

I, personally, see no reason line honing would be necessary because of switching to main studs on the 420a.

 

[drivemusicnow]

... This is the problem with me surfing the forums using the "new posts" button. I am not familiar with the rebuild on a 420A, and that is probably why we had the confusion. I have rebuilt other motors with alignment dowels that still left enough play that when you torqued the main bolt down the plate could still flex a little bit.

 

[link16]

Well, thank you all for your input, I will be ordering my head studs now and OEM main studs. Thank you guys.