Head bolts: You decide.....

[oldeskewltoy]

I've been aware for about a decade that ARP head studs in a 4AGE are NOT something you need to bother with... I've heard this from Loynings on many occasions. Well, now from the "other" 4AGE engine gurus... Hasselgren speaks

from another forum Wrote:I have quoted the reply from Paul Hasselgren. Basically the ARP studs may represent a problem. He has some useful insight so when you make a decision about what bolts/studs to use I strongly recommend you consider the oil galley issue. My thanks are extended to Paul and Chester:

"Hello Alastair,

The oil does flow past the stud as you have observed, are you still using the VVT pulley? We restrict the oil flow on the race engines but for the street you need idle lubrication for the cams and tappets.

I think the ARP studs should be waisted to the minor diameter of the threads at the body of the bolt leaving a centering step at the top just like the standard bolt, which worked well for us past 230 hp and 13/1 compression, we never did use studs until we started turbo charging.

Paul Hasselgren
Hasselgren Engineering Inc."

oldeskewltoy from another forum Wrote:if it makes you feel any better... Loynings only NEEDS the ARP when the engine is a structural member... conventional builds will often times get bolts

When 2 reputable well known engine builders tell you you don't need something..... but you buy it anyway... what does that tell you??


(PS I posted this here... I had thought in the 4AGE engine info thread... but that is stock stuff... not modified)

[ditn]

thats what i have been saying for a while
stock are the best you can get for 99,9% of the people

[allencr]

Thanks.

oldeskewltoy Wrote:...Hasselgren speaks....

from another forum Wrote:I...

Mind naming the forum or a link?
Thanks again.

[oldeskewltoy]

allencr Wrote:Thanks.

oldeskewltoy Wrote:...Hasselgren speaks....

from another forum Wrote:I...

Mind naming the forum or a link?
Thanks again.

http://www.mr2oc.com/showthread.php?t=418874

[Lewy]

Wouls of been handy before i built my engine lol but i know for next time

[ditn]

repost from another post

if you want to read it,this is the post from andrew

Here is some info regarding using headstuds vs. stock head bolts and the issue oil flow & volume to the cyl head on the 16v 4A-GE engine.


After reading a post a couple months ago it stuck a thought in the back of my head, "Am I really going to hurt anything by using ARP headstuds instead of OEM headbolts due to the differences in diameter?"

I did run them for 3+ years on my old motor with no upper end issues. And many others have as well with no problems. But that's not to say there couldn't have been one we've all been lucky enough to avoid.


Since right now I've got my cylinder head and block back fresh & clean from the machine shop (basic rebuild, no perf parts - no spare $) I decided to take a look into this by measuring & calculating the area's where oil is flowing through to get the cylinder head, starting with where it comes out of the block and goes up around the head bolt/stud and into the cyl head oil galley/passage.


The measurements (starting with the important one - since it defines the smallest area oil flows through & dictates what the min. allowable area/volume will be):
1.85mm - head passage/galley I.D.
6.15mm - block passage/galley I.D.
8.5mm - OEM head bolt O.D.
9.95mm - ARP head stud O.D.
11.05mm - Cyl head opening (for bolt/stud) O.D.

Calculated area (approx.):
2.69mm - head passage/galley
29.7mm - block passage/galley
56.75mm - OEM head bolt
77.76mm - ARP head stud
95.90mm - Cyl head opening (for bolt/stud)

Now, don't forget since were working with oil under constant pressure flow dynamics aren't as huge of a deal. But having a 'minimum' of area for oil to flow through; equal to OR matching the smallest point it flows through in an OEM setup is the goal (IMO). In other words, don't choke off the oil supply volume/area. It's your engine's life blood. In this case that point is the passage/galley in the cylinder head that is supplied by the oil coming up around the head bolt/stud.


Since the only thing being changed here is the difference between the area (and volume) between the OEM bolt & ARP stud. Let's compare by subtracting the area the bolt/stud takes up from the available area in the cylinder head bore and you get the area oil can flow through:

39.15mm - OEM head bolt
18.14mm - ARP head stud

No worries yet, still plenty more than the minimum area necessary (the head passage/galley - see above) But, you also have to take into consideration the clearance available between the cyl head opening/galley & head bolt/stud as that can also bottleneck oil flow. I think this is where Dan/Oldeskewltoy was really concerned, and what has been stuck in the back of my mind.

Clearance's (not area's - that'll be important just a bit further down):
1.275mm - OEM head bolt
_0.55mm - ARP head stud

But don't forget, the oil is under pressure and will come in/up/around/through from ALL sides. So the real calculation that is important is the area around the passage/galley opening to the bolt/stud.

Area of clearance for oil to flow through:
7.41mm - OEM head bolt
3.19mm - ARP head stud

Calculated by taking the clearance between cyl head opening & bolt/stud x circumference of the cyl head oil galley. (The area that oil can flow into the galley is basically cylindrical for these purposes, since it's under pressure... I think.)


In the end it all boils down to:
3.19mm > 2.69mm

[FanIsHere]

Nice piece of information here since I am in the process of rebuilding my 16v.

I wanted to ask you guys if this information regards only the 20v (as I read above Hasselgren's answer including "VVT") or all of the 4AGs?

If it regards the 16v as well, then is that ok to reuse OEM head bolts or do I need new ones?

[Ivan141]

Wow, this is an old thread..
I believe I read somewhere that ARP adressed the issue with the headstuds a long time ago, but search around and dont just take my word for it.

[oldeskewltoy]

When using studs in a 16V you want to over drill the front, #1, exhaust side head bolt hole one step larger..... If you drill it down to just below the oil feed hole - blocking that hole is now impossible.

(11-10-2020 09:53 AM)FanIsHere Wrote:  If it regards the 16v as well, then is that ok to reuse OEM head bolts or do I need new ones?

FSM has a spec on headbolts.... if they measure up, and are not corroded, they should be able to be reused.