AHA! Makes more sense. So the restriction is the terrible angle the oil has to take to get there and the design that in effect turns the link there in to a poor flow banjo bolt like design. . . I'm picturing this better as time goes by. Hold on I'll eventually catch up here

dsm-onster said:

AHA! Makes more sense. So the restriction is the terrible angle the oil has to take to get there and the design that in effect turns the link there in to a poor flow banjo bolt like design. . . I'm picturing this better as time goes by. Hold on I'll eventually catch up here

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That's pretty much it, along with the restriction created by the small clearances. Mainly, the ARP studs are somewhat larger in diameter than the stock head bolts. They reduce the clearance to .005 (.0025 from the stud to head) or less and further restricts the oil flow to the head. So this mod, along with the other oil port mod linked in the first post, should increase oil flow significantly. Doing both mods should be particularly beneficial to someone who is running ARP head studs and has had the head surfaced.

a91talonAWD said:

even If I am using the 6 bolt head with the 6 bolt block?

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Yes. I think that is a 6 bolt head that he is machining in the first post. Are you using ARP studs as well?

300dollarGSX said:

Yes. I think that is a 6 bolt head that he is machining in the first post. Are you using ARP studs as well?

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no studs, just new bolts. the reason I asked was I thought he was saying to do this mod #2 if you are using the 7 bolt block with a 6 bolt head cause the 7 bolt bolck has bigger diameter head bolts.

I see. You probably wouldn't need to ream the bolt hole, then. The 6 bolt holes are already larger and the stock bolts have a smaller outside diameter. You probably have the clearances this mod was meant to create with head studs. You could measure your bolt hole size and bolt diamter, then subtract to determine clearance. Please post your findings if you do so.

Edit: Check to see if your bolt hole has the small ridge or step just before the feeding hole (like the pic I posted). Removing that ridge should improve oil flow even with using stock head bolts. Honestly, it's all up to what you want to do or try.

300dollarGSX said:

I see. You probably wouldn't need to ream the bolt hole, then. The 6 bolt holes are already larger and the stock bolts have a smaller outside diameter. You probably have the clearances this mod was meant to create with head studs. You could measure your bolt hole size and bolt diamter, then subtract to determine clearance. Please post your findings if you do so.

Edit: Check to see if your bolt hole has the small ridge or step just before the feeding hole (like the pic I posted). Removing that ridge should improve oil flow even with using stock head bolts. Honestly, it's all up to what you want to do or try.

Click to expand...

just got the head back from the machine shop... they did not do either mod as I suggested to them(they said it was all "in spec"...) so I will be doing MOD #1... I will post if this eliminates lifter knock while still using stock lifters (not 3g lifters)

before mod#1

a91talonAWD said:

just got the head back from the machine shop... they did not do either mod as I suggested to them(they said it was all "in spec"...) so I will be doing MOD #1... I will post if this eliminates lifter knock while still using stock lifters (not 3g lifters)

before mod#1

Click to expand...

LIFTER KNOCK SOLVED thanks to oil Mod. NUMBER 1!!! no 3G LIFTERS...just the one with the pin holes
sorry no "after pics"...looked like the one posted at the beginning of the thread. We'll see how long this lasts only 10 miles one the newly built head...

glad that oil port mod #1 helped you out!!

Sorry to bring this thread back, but I recently just had my 2g head seize up on a 6 bolt block after installing 6-bolt ARP head studs. I believe this was my problem and will be performing this mod on my next head.

Mph said:

Sorry to bring this thread back, but I recently just had my 2g head seize up on a 6 bolt block after installing 6-bolt ARP head studs. I believe this was my problem and will be performing this mod on my next head.

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Did you have the 2g head stud holes inlarged to fit the 6 bolt studs. The 2g heads need to be inlarged 1/2" as oil flows around one of the studs feeding the head and the turbo.
If the studs bind when installing this will also restrict oil to the head. They should go in smooth as glass by hand with a T handle allen wrench.

I did drill the one stud hole that oil comes through to 1/2inch. The other holes I reamed to fit snug. Finally got my new head installed today and had it running for a long time with no problems!

so let me get this strait, for a 6 bolt block, and a 7 bolt head, i use the 6 bolt head bolts, and i just need to re drill the bolt hole for the one that the oil goes tru because 6 bolt bolts have thicker head bolts, and i dont need to drill all of the rest right? and to be safer do a head oil port mod as well. that should be it right?

and 1/2 inch is all i need to drill it out to?

Vancho.. ALL the head bolt holes need to be reamed to .500 to fit a 7 bolt head on a 6 bolt block

Bogus,
I am in the proccess of putting a 7 bolt head on my 6 bolt. My arps fit snug in all the bolt holes. Will I be ok just drilling out the one bolt hole? Or is there some other reason they all need to be 1/2"?

bigbird94 said:

Bogus,
I am in the proccess of putting a 7 bolt head on my 6 bolt. My arps fit snug in all the bolt holes. Will I be ok just drilling out the one bolt hole? Or is there some other reason they all need to be 1/2"?

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Read the post above yours

Arrowhead why dont you read MY post before quoting it. Both myself amd another member have been able to fit our 12mm studs exactly where bpgus said we COULDN'T. There is obviously something wrong there. My question involving WHY the others would need to be drilled if the stud fits was absolutely not answered in this thread.

Have you ever tried to remove a cylinder head that has not been drilled out? You will find out why you need to enlarge the holes real quick.

No biglady, that is not something ive had to do. Considering I can remove all the studs with an allen I not in the least bit worried about that issue.

Maybe somone else can chime in with a mechanical/oiling reason to drill the other nine holes?

If you have no problems great. We have never had a head that would just slide over the larger studs. There is no mechanical advantage however.

bigbird94 said:

Arrowhead why dont you read MY post before quoting it. Both myself amd another member have been able to fit our 12mm studs exactly where bpgus said we COULDN'T. There is obviously something wrong there. My question involving WHY the others would need to be drilled if the stud fits was absolutely not answered in this thread.

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Of course I read your post, otherwise how could I have answered, and I also read the one above yours, and all the others.

The other benefits are also easier placement of head as sometimes it gets very difficult to place or remove the head without a little bit of extra clearance.
I dont see a post of Bogus saying you could not.


If the head gets a little warped, it would be very hard to remove it or the studs, make things easier for yourself.
This also applies to many other engines in general, as it is a standard machine shop practice when going to studs and in particular going oversize.

If you feel that you dont have to, well go at it.

Ok thanks for the answer biglady. It looks like ill just drill the one hole

Arrowhead, In my last post I just said thet the studs can be removed via the top allens and wont be an issue. Thanks for trying asyer realizing that it was valid.