Righto. I have done some investigating into using late model evo 11mm head stud kits in our 6A13TT's
First concern I had was, were the evo studs the correct length?
I got my hands on a stock 11mm 4G63T head bolt and did some measurements. There is a minimum of 2mm worth of head room for bolt stretch before the evo bolt will bottom out in the threads in the block which means we can use the evo studs.
I am looking at getting multiple "ARP L-19" or "A1 Technologies H11" Evo head stud kits (10 studs) to create a 16 stud VR4 kit for myself and two other VR4 owners here in NZ
The stud kits I'm looking at are
The ARP Kit
http://www.amsperformance.com/cart/A...d-Package.html
275 USD per 10 studs which if we buy in multiples of 8 sets which will split into 5 exact sets of 16 (6A13TT kit) it will be 440 USD per person
The A1 Technologies Kit
http://www.maperformance.com/map-ult...evolution.html
250 USD per 10 studs which if we buy in multiples of 8 sets which will split into 5 exact sets of 16 (6A13TT kit) it will be 400 USD per person
So is anyone interested in joining in on this?
Now I have left a few questions unanswered so to hopefully curb any queries that anyone may have here I go...
#1
No this is not a direct fit both the heads and block require modification!
The threads in the block need to be chased with an M11x1.25 bottoming tap so the larger 11mm studs can be screwed into the block as factory the 6A13 engines have 10mm stretch type bolts.
The head bolt holes in the heads will need to be reamed/drilled from standard size to +1mm oversize to give appropriate clearance around the new 11mm studs (as some of the oiling to the heads passes up through past a head bolt). also the dowels will need to be removed, not that this matters as the new studs will locate the head onto the block instead.
#2
No the stock threads in the block are NOT roll formed, they are cut, just as you would cut a thread with a tap or die, so re-tapping the block from M10x1.25 to M11x1.25 will not weaken the thread. Cast Iron is not a material that can have threads roll formed into it. only malleable steels and other malleable alloys can have threads roll formed. Also over sizing head stud threads in blocks is common practice, At work we have an 800+hp SR20 drag engine with huge over size head studs with just tapped threads, and a 930RWHP RB30DET with +1mm OS head studs.
#3
Yes the uprated 11mm studs will be fine with the stock head gaskets, Its tight through the stock head gasket holes but they do fit.
#4
Yes the ARP Head studs are re-useable. because the ARP/A1-Technologies studs are not "torque to yield" this means they can be reused over and over again unlike the stock bolts
#5
Yes the L-19 ARP material is exactly the same as the A1 Technologies H11 tool steel. L-19 is just ARP's "Brand Name" for it.
#6
Yes the L-19/H11 material is probably overkill for your average joe. I myself and the other two people already interested however are building big power motors so we need that kind of a safety factor in our builds. Making the move to 11mm studs, especially with the L-19/H11 material will mean you will Never be in danger of lifting a head and failing a gasket unless you are going to be pushing 50+Psi of boost
I will be emailing suppliers and trying to get the price down on the kits. And if there is any Interest on this thread I will run a GB thread officially later on.
please if you have any more queries, post them up and I will do my best to answer them. And I can also post photos of what needs to be done to the heads/block to make them fit.