ARP head studs stripped block threads

[Zoom]

Got a call this morning from my mechanics (who's still re-assembling my 3.2l engine, long delays for Honda parts these times...) who was putting back the heads - while torquing the bolts (in proper sequence, with ARP grease..) one of the bolts started raising, meaning it was stripping the block threads. And That was half the final torque !
Was the block faulty from before ? history of that car is spotty at best, as I bought it from someone who had it maintained at a small independent shop, who did a really bad job on other parts of the car (wrong bolt sizes, over-torquing threads, etc.) .. who knows.

In any case, OEM Honda bolts are going in instead. But before we'll have to put a helicoil: do you guys think it will be ok with it ? Seems like they have a good machine shop who could do it (if there is enough metal around the hole to bore it to the helicoil diameter..).
Otherwise I'll have to find a new block :moody:
I kept the stripped threads as a souvenir. My mechanic is mortified.

 

[Honcho]

Sorry to hear this. Pulling threads is actually somewhat common on the aging NSX block. Most likely those threads were damaged during a prior service. Most mechanics (including Acura) do not take steps to clean the threads thoroughly before re-installing the bolts. You need all the old oil and trash out of those holes and shiny metal before putting torque on them. I will run a brass wire brush down there with some degreaser, drain, and then hit it with brake cleaner. Remember, the torque specs assume a clean, perfect bolt and a clean, perfect thread, like at the engine assembly plant.

ARP bolt torque is 85 lb/ft IIRC, which is at the upper limit of what even perfect aluminum threads can tolerate on the C30. Thus, the conventional wisdom is to install time-serts on all holes to ensure proper torque. A good machine shop can install them for you and your block will be fine.

 

[Zoom]

Thanks. Mechanic is a certified Honda mechanic, knows the NSX and has a few open engines around that he's working on (a CTR and S2k right now). He's extremely thorough and meticulous, and indeed he cleaned up the engine completely before re-assembly.
Block is going to a machine shop for helicoil insertion (no time-sert around here i'm afraid). Plan was to do only the one thread that's been stripped - would it be wiser to do all 16 of them in a pre-emptive manner ?

 

[Honcho]

Thanks. Mechanic is a certified Honda mechanic, knows the NSX and has a few open engines around that he's working on (a CTR and S2k right now). He's extremely thorough and meticulous, and indeed he cleaned up the engine completely before re-assembly.
Block is going to a machine shop for helicoil insertion (no time-sert around here i'm afraid). Plan was to do only the one thread that's been stripped - would it be wiser to do all 16 of them in a pre-emptive manner ?

I'd do all 16 and the run the ARP if it were me. This isn't an area where you want to have a failure.

 

[Zoom]

Good point. I'll phone them first thing tomorrow morning and see if they can do the 16 in a reasonable delay (I miss my NSX !).

 

[Valhalla]

i had a 3.2 that also pulled bolts on two different threads on the same head. It happens quite often. Timeserted all of them and went back in with the ARP bolts. No problem at all. Good luck.

 

[RYU]

Seems like the 3.2 blocks like to strip from head bolts. I might recommend time serting instead of the helicoil though

 

[RYU]

You can buy timesert kits directly from the company. They also sell on Amazon. They have a few different kinds... Might want to ask which is the best type to use. Or the guys here can help.

 

[Zoom]

Block is going to a machine shop - what will be done is what they have really, they are the specialists, "timesert" seems to be another brand name for helicoil ? I cant be picky at this point, and I wont ship the block to US and back just for that...

 

[Superhatch]

A helicoil is just a wire insert where a time-sert is a solid insert and is generally better overall but especially for softer metals. They might not have them in stock, but they can order them from many different locations online. Not sure why they would have an issue with getting/using them.

 

[RYU]

Timeserts are easy to install. If a machine shop can't do it, I'd be worried about anything else they claim to know.

 

[Honcho]

Timeserts are easy to install. If a machine shop can't do it, I'd be worried about anything else they claim to know.

Don't the time-serts require a special deck adapter to ensure a square bore when drilling the block? The machine shop might not have that adapter. I recall the internet debate between helicoil and time-sert is about at the same level of crazy as asking "what is the best oil" on a car forum, LOL. If the machine shop is experienced with helicoil, I'd probably go that route. The threads will be far stronger than the original aluminum. As with anything, it's mostly about the quality of the install rather than the particular product used. JMHO
That said, I too prefer time-serts.

 

[Zoom]

In doubt I ordered the time-sert kit from the US (that product is unknown in EU as it seems - there are quite a few other German brand names floating around)... great expense but I dont want to risk my block. They wont have the deck adapter though...

 

[RYU]

Don't the time-serts require a special deck adapter to ensure a square bore when drilling the block? The machine shop might not have that adapter. I recall the internet debate between helicoil and time-sert is about at the same level of crazy as asking "what is the best oil" on a car forum, LOL. If the machine shop is experienced with helicoil, I'd probably go that route. The threads will be far stronger than the original aluminum. As with anything, it's mostly about the quality of the install rather than the particular product used. JMHO
That said, I too prefer time-serts.

It comes in a kit. I've used them both. Much much prefer time serts

 

[MotorMouth93]

As others have said, pulling threads out of a C3x block isn't really uncommon especially if its been overheated. I would do all 16 head bolt holes for good measure, since it would really suck to start torquing the heads down again and have a different stud pull out and have to start all over.

If a machine shop is doing timeserts (or any other thread insert) they typically would do it on a mill (I would hope) so the deck adapter isn't needed to square everything up perfectly like it is if you're doing it on a 96 Camry in front of Autozone with a cordless drill. The mill will hold everything square so just line up the bit with the hole using whatever method you prefer and go.

If doing it at home, the timesert alignment tool won't fit in the large tapered holes in the C3x deck, its too small, so I had a machine shop make me a custom alignment tool when I did the timeserts in my last engine block. Even with that special tool though there's enough slop in the timesert installation tools that I ended up with some studs off by like 0.5-1 degree by my measurements, which is not enough to matter after everything is torqued up but enough to make it tricky to put the heads on after the studs. I had my 2nd block timeserted by a machine shop in mill and everything is perfect though.

 

[Zoom]

I'll pass these infos to the mechanic who's doing the installation, thanks (that's the kit I got: https://time-serts.com/store/7111/ + 10 extra inserts as there are only 10 in the box - looks like the box includes an alignment plate and a bushing + guide for the drill bit)

 

[Valhalla]

That is the one I've used in the past. Good luck.

 

[MotorMouth93]

I've used that kit as well, and unless they've updated it, the alignment tool is too narrow to be used with a C3x block. There are other reports of this here on Prime as well so it's not just me, @Mac Attack reported the same issue here: http://www.nsxprime.com/forum/showt...or-Headstuds?p=1575344&viewfull=1#post1575344

If anyone needs it, I can machine a suitable alignment pin if they still haven't fixed this issue.

 

[Zoom]

Well given the rarity of C3x blocks I would suppose they did not change that alignment tool. [MENTION=25419]Valhalla[/MENTION] did you get an updated one by chance ?

 

[Valhalla]

Well given the rarity of C3x blocks I would suppose they did not change that alignment tool. @Valhalla did you get an updated one by chance ?

This repair happened 6 or 7 years ago so I doubt it was the upgraded kit. But I took my time and measured everything multiple times to make sure I got it right. I had zero issues with reassembly.