To upgrade head bolts or not?

Tapps33

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I'm in the process of rebuilding a 5.0 SC engine and I have a decision to make. As I'm not a machinist by trade I thought I would float this out there to those who have more experience in this area than me.

Upon disassembling my engine, I discovered I have the original style M10 size bolts. A little later LR upsized these bolts to M11. I have read several threads about guys boring and re-tapping the original M10 holes to accept the newer M11 bolts, but I wonder if it's worth it?

I have run into issues boring and re-threading blocks before, and I'm wondering if it's riskier to use the smaller M10 bolts or to machine, helicoil and use the M11 bolts?

Full disclosure, I plan un upping the HP of this engine as soon as I can afford it...probably looking to make close to 600HP or so. (Assuming I can find someone to re-VIN my SC ECU so I can fit it into my LR4....but that's a whole other thread!).

Anyone out there done this before? Pros - Cons?
 

avslash

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Not a machinist here, but would lean towards "do it once, do it right". Especially on a boosted application.

I doubt LR incurred the cost to up the bolt size for no reason.
 

Tapps33

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Yeah, that's kinda what I was thinking....

Plus, I've heard People have had issues re-torquing head bolts in these aluminum blocks. If I have to go in and use the head kit anyway, I might as well upsize!

FYI, this is the kit I'm planning on using:


A few guys on a different forum have used them with great success. I like it because it comes with a jig and everything you need to do the job right!
 

greiswig

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Does ARP make a set of studs for this application? If so, I'd use those over bolts. I've had great success with them in several different aluminum engines.
 
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Stuart Barnes

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Studs over bolts any day as long as you have enough clearance to get the heads on and off, and you have enough space for appropriately sized washers and nuts of course.
 

Tapps33

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Yeah, I'm trying to find some ARP studs that'll work, but dealing with them is a bit of a headache. They don't list anything by its' specs anymore, it's all vehicle based....which they "don't make anything for a LR 5.0 engine." Actually, I'm trying to track down ARP studs and bolts for the main caps, heads and conrods....all of it is difficult....unless money isn't an object....but it TOTALLY is!

However, someone found these might work...but I don't know if I can stomach the cost!


I'm trying to measure the existing bolts and see if ARP will make an M11 size head stud. The biggest concern I have is clearance to get the socket into the machined port in the head....the head bolt removal tool barely fit and that fits inside the bolt!

Not gonna lie, I do worry a little bit about the expansion and contraction rates between the aluminum block/heads and an ARP steel head stud. I know that's the theory behind the stretch head bolts....but I've run serious pressures through ARP studs on many a diesel....and Honda...so, I'm sticking with them....if I can afford them!
 

Stuart Barnes

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Have you scoured the jag forums yet? I’m sure one of those guys has gone down this path, or at least decided one way or another.
 

Tapps33

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Actually, yes, that's where I found the Porsche studs....but even he couldn't stomach the $$ ARP wanted for them.

That said, I think the Porsche ones are M10 and I want to put M11's in there....so hopefully a Honda stud will fit or something! LOL!
 

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