ARP Head studs in a N/A engine, necessary?

[Jimmi The Kid]

I'm building a highly modified 4A-GE, and wondered if a set of ARP Head studs will be waste of money, or a clever thing to do. The original Toyota parts are off couse top quality :wink:

Engine spec:
Smallport heavy modified head, with bronce valveguides, lightnen valves, underbucket shims, Toda valvesprings, Toda 304deg 10,5mm valves, Toda cam sprockets, Toda cambelt, Blacktop modified ITB's, T3 modified inletmanifold.
7rib 42mm block, TRD/Carillo Atlantic conrods, TRD/JE Atlantic pistons, Toda lightweight 200mm flywheel, T3 aloy underdrive pulleys.


Please speak up

[fax0815]

Well, probably not, BUT as you´ve spend all the money, I whouldn´t hesitate a second to buy them, think of all the grief if you need to change a headgasket, cause of one silly headbolt that decided to stretch. Dialing in cams... And as you´re changing the headgasket, worst case you might strip a thread in the block, and now you´re fucked.

Whould not have happended if you invested those 200Euro in the first place, whouldn´t it?

Thats one of the things I like the most about studs, if they´re in they´re in.

Done anything the main bearing bolts?

[ditn]

i have been thinking about it,but i dont like the fact they the reduce the oil flow on one side.
Thats why i wont use them.

[fax0815]

ditn Wrote:i have been thinking about it,but i dont like the fact they the reduce the oil flow on one side.
Thats why i wont use them.

How is that possible? Neither the head studs, or main bolts interfer with the oil galeries as far as I´m aware...

[Jimmi The Kid]

Well, he sell me both the studs and the main bolts for £100, this is a pretty sweat deal right? The are new off couse...

[fax0815]

Jimmi The Kid Wrote:Well, he sell me both the studs and the main bolts for £100, this is a pretty sweat deal right? The are new off couse...

Why do you even ask? Buy it!!! They´re about 230GBP new.

[Bean]

I went with OEM but then I'm running sub 12:1 static CR. But for that money I would go with both too... (I have ARP mains and rods)

PS: the oil supply to the head runs around one of the headbolts - assassin did the whole math behind it once and it basically boils down to the fact that there are other areas still smaller - but with the ARP it gets very shallow around the stud and therefor a slide build up of crud could get you in trouble. IMHO nothing to worry on a well maintained engine.
Also I assume/hope your are going to open the engine once a year for inspection - I think this is called for on a spec like yours.

[Jimmi The Kid]

Bean Bandit Wrote:PS: the oil supply to the head runs around one of the headbolts - assassin did the whole math behind it once and it basically boils down to the fact that there are other areas still smaller - but with the ARP it gets very shallow around the stud and therefor a slide build up of crud could get you in trouble. IMHO nothing to worry on a well maintained engine.
Also I assume/hope your are going to open the engine once a year for inspection - I think this is called for on a spec like yours.

Wich hole are that? do you have any pictures?

I don't think I will do more than 500km a year (100km @ full throttle), so if it aint broke - dont fix it :wink:

[ditn]

yeah but for me the engine will be oem 4AGZE so i dont see any reasons to update

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

So you are OK if using ARP headstuds. (But it sure was close in my mind and I was worried until I did the #'s)

Andrew

[Bean]

Beat me to it.
I agree for a daily/fun car for racing the saying is usually a bit different.
If you don't check regularly it might end a good season early. Most do it during winter brake. Considering the cost a powerful engine cost, checking it once a year is more sensible than fixing it because of neglect.