Project Thread Supercharged Supra

[hungryforinfo]

I love the PVC cams, LOL.... Sometimes my family thinks I am some sort of kook, I remanufactured an entire sump to get a couple more litres of oil capacity and a little more engine clearance, althought it wasn't entirely necessary, the vehicle was driving around, I just wanted to do that when I added the oil return.

 

[Cobber]

John,

It might be worth crack testing the heads too.

 

[cribbj]

John,

It might be worth crack testing the heads too.

Thanks for the reminder Andy; we did a coolant pressure test on this motor before the dyno and it was good then. Think I'll do another, and then possibly a dye pen test as well.

 

[cribbj]

Took the left bank head off yesterday, and had a poke around inside. The colors of the tops of the pistons are all similar (of course these were coated from PolyDyn, so it’s hard to judge.) In this photo, cylinders are 1-7 from left to right:



During the last dyno on this motor, we blew the insulator, and part of the side electrode off the #1 plug, and this was the result:



Fortunately the cylinder wall wasn’t scored too badly (those scratches look bad, but should polish right out), but it does look like the head gasket was leaking a bit in #1 and let some coolant in. This is a real p*sser ‘cause this motor has M12 head studs, and I couldn’t break them loose with a ½” ratchet; I had to put a 2’ cheater pipe on it:



Next I had a look at the head itself, and again, the coloring looks fairly equal, and you can certainly see the effects of all the methanol we ran through it. (Cylinders 7-1 from left to right) You can also see where the spark plug tip dinged the head a bit on its way out of the motor, but this should buff right out:





I took the head over to Dennis’ and we dropped the valves out of #1, and I was surprised to see how rough their surfaces were, and the surfaces of the seats. We both feel it was the methanol that did this. We also found both exhaust valves slightly damaged due to the exit of the spark plug tip.
If all cylinders’ valves and seats are like this, it well explains why there’s so much leakage. Good reason for making sure we spend some time doing a no boost cooldown with no M/W injection to flush all the meth out of the engine.

 

[cribbj]

Here's some info for those of you interested in getting rid of those wimpy M10 head studs, and putting some big, meaty M12 studs in your motors. I'm not a fan of upgrading from M10 to the 7/16" hardware because there's simply not enough "meat" left in the 10mm stud bore to drill & retap to 7/16". If 7/16" hardware is going to be used, it should be installed in the block with a Helicoil or Timesert kit.

These are ARP P/N 151-4201 studs, and they're intended for a Ford Pinto. Their OAL is 116.87mm, and they have an M12x1.75 thread on the block side, and a M12x1.25 thread on the nut side; unfortunately there's only 25mm of thread on both sides (I know the nut side looks like it has more thread, but it's an illusion):



81.26mm sticking out of the block:



Now if you've done the math, you may be wondering how did we get 116.87 - 81.26 = 35.61mm of stud in the block with only 25mm of thread? Well, we cheated, and put a 0.500" counterbore 11mm deep in the block to "sink" them in:



It's really unfortunate that ARP didn't put longer threads on these, but after all, they were designed for the Pinto iron block application; I've been in touch with them to see about modifying this existing design to add another 10mm or so of thread for our ally blocks. We'll see what they say.....

As a point of interest, the bores for these studs can go really deep without hitting the water jackets:



Other mods necessary to make these big studs work are enlarging the holes in the head, and enlarging the holes in the head gasket slightly, which we had Cometic do for us.

Once these are installed, since they're the standard 190,000 / 200,000 PSI ARP hardware the nuts "can" be torqued down to as much as 86 ft-lbs if ARP's moly lube is used. This is over twice as much clamping as the stock M10 fasteners and 30% more than 7/16"!

With this much clamping, the cylinders are going to be "pulled", so boring/honing with a torque plate is definitely a good idea.....

 

[JustenGT8]

Some good info on the head studs Cribbj. It has come to light with my new build than the "lextreme' ARP studs are a bit light on for thread engagement....only 17mm, so even less than your pinto versions 25mm. No evidence to say this will cause issues but seems marginal don't you think?

 

[cribbj]

What size & thread pitch are those studs, Justen?

I'd be wary of only 17mm thread engagement in these ally blocks, and would be considering Helicoil, Timesert, or Keensert.

In my #2 motor, which came with 7/16" hardware in rethreaded holes, Dennis remachined the holes, installed either Timeserts or Keenserts and then we reused the 7/16" hardware. I don't remember how much thread engagement there was, but it seemed like it was more than 17mm?

 

[JustenGT8]

Here's some measurements John. Stud size and thread pitch are as stock, these are the ARP ones suggested for the UZ (ie the ones sold on here).

Stud length - 117mm
stud thread - 24mm
block hole depth - 68mm
thread starts - 11.5mm down.

Threaded section looks even worse than i thought, with only 12.5mm of thread engagement?

 

[cribbj]

Justen, these are the ARP replacements for the stock M10 x "something" head bolts?

And you're saying that although the stud has 24mm of thread available, you think you're only getting 24 - 11.5 = 12.5mm of engagement because the block thread begins 11.5mm down the hole? Have you determined how deep the actual thread goes (not just the depth of the hole, but the depth of the thread)? Interesting that you measured 68mm for the hole depth, when I measured 55mm. Guess the depth of the holes isn't consistent - in my case I measured the depth of a hole "on top" or close to the intake side. Perhaps the holes on bottom, or close to the exhaust are deeper? I'll reconfirm this point on my motor.

So, I assume the problem is that the stud has a shoulder that stops it at the the deck of the block?

Why not counterbore the stud holes a bit bigger so the stud shoulder will pass through the deck, and stop at the top of the thread, instead of the deck? These studs are essentially the same length as mine, and with full engagement in the block (well, the studs were backed off 1/2 a turn), I had full engagement on the nuts.

 

[JustenGT8]

hey John, that's what i was thinking but i was wrong, i blame my failing memory.

The top section of the bolt hole is already out to 11mm so you end up with approx 21mm of thread engagement before the shoulder of the stud bottoms out. Sorry for the confusion of numbers early as i tried to recall without checking.

Seems that this amount of thread engagement has some engine builders with more experience than i a bit excited...basically not enough for an alloy block?

My shortblock is assembled so options are a bit limited? All i really want is an M10 ARP equiv stud as per what they currently do but with 35mm of thread instead of 25mm of thread?

BTW my hole depth was the full hole, not just the threaded part if that makes a differece? Also, it's the VVTi 1UZ block.

 

[Zuffen]

Whilst I see a potential problem with the shorter thread engagement and I posed aquestion on Ed's Site about this and never had an answer.

My question was "has anyone pulled the thread out of a block regardless of how much boost they're running?"

Probably the biggest boost I've heard of is Justen's and Ive been running over 21.5psi and never pulled a stud.

Are we running from shadows.

I know Wayne Smith will be looking for the absolute best possible equipment in any engine he builds (he didn't get his excellent reputation by building duds) regardless of cost or necessity. After all he's the guy who warrants his engines so he wants to be 150% sure of everthing.

 

[JustenGT8]

That's the $64K question eh Rod?

I simply don't know never having built a tough alloy block before? I sure don't want it all to go wrong though

 

[Zuffen]

I think we are over emphasising the potential problem.

I'd like more thread engagement but I can have it with ARP studs.

If I go to lower grade studs/bolts I can have almost any amount of engagement but at the risk of stretching them.

Whilst not 100% happy with what I have I'm more than content to use them and see what happens.

If you look at my last engine it detonated itself to death. If any engine was going to pull a stud out of the block it was that engine.

I think I can sleep well and not worry about the studs pulling.

 

[JustenGT8]

It's not the studs pulling out that i'm worried about but i can see some chance of the threads deforming.....it would only take a few thou of 'thread stretch' to then cause gasket sealing issues?

I'm leaning towards them being OK, particularly as ARP are aware of their application, but there's still a niggle of doubt that can hopefully be put to bed with an alternative.

 

[Zuffen]

Justen,

I hear where you're coming from.

Like you it does niggle away in the back of your mind but as I can't do anything about it I have to live with it.

When you think about it there's been a lot of discussion and enquiry from/to numerous suppliers through Ed's Site and we've made no progress so unless ARP starts making 1UZ specific stud sets David's are the best we can hope for.

 

[cribbj]

I heard back from ARP on getting longer threads on that M12 stud I have, and they simply said "we don't have anything with a longer thread". Hmmmm.

Since they didn't really answer my question, I'll have to give them a ring tomorrow morning.

 

[stevechumo]

Please keep in mind that too big of a stud may weeken the block.

 

[cyberdiamond]

John, did the head gasket need modifying or were the holes already large enough for the 12mm studs?

 

[cribbj]

I thought they had to be modified by Cometic, but after putting the head back on the block the other day, I'm now thinking they were nearly large enough before, and once they were mounted on the deck, and the threaded portion of the studs passed through them fine, and their threads engaged in the block, the non-threaded portion of the studs simply pulled themselves through, and enlarged the gaskets the rest of the way. Not very scientific, and it may have caused a tad bit of distortion, but it seemed to work OK.

 

[cribbj]

Decided to consult the collective brain trust for some thoughts on wiring harnesses. First, I'm making my own off the wall, milspec type engine harness, but it will start & stop on the engine. There will be two large milspec type connectors, one on each valve cover, which will interface to the OEM wiring harness coming from the other side of the firewall.

My intention is to purchase a new, or nearly new OEM harness from either Toyota (for the 2JZ), or Lexus (for the 1UZ in the SC400) and adapt it to my needs.

If I buy a Supra 2JZ harness, it’ll already have conductors for 6 coils, and 6 injectors, so I'd only have to find a few more conductors, and its ECU connectors will fit my AEM ECU. Disadvantage is that it’ll be setup for an inline six cylinder engine, so the layout may not be optimum.

If I purchase an early SC400 harness, it’ll already have the correct V8 layout, but the injectors will e setup for four groups of two in batch fire, plus it’ll be setup for 2 distributors, not 8 COP’s. Really the only things it’ll have going for it, is its layout for a V8 engine, its ECU connectors will fit my AEM, and I think it'll be setup to penetrate the firewall in the same place as in the Supra.

If I purchase a late model (VVTi) SC400 harness, it’ll be setup for 8 individual injectors, 8 COP’s, but its ECU connectors are completely different from the earlier models, and so I’d need to fabricate a jumper harness for it to work with my AEM.

LS & GS400 harnesses are non starters because their ECU connections are different, and I believe the location of their firewall penetrations are also different.

A 2UZ harness out of Tundra was an idea, but its ECU connectors are completely different, and are more like the VVTi 1UZ in the SC400.

Any words of wisdom from those who've been there & done it already?