jevansio Posted January 11, 2009 Share Posted January 11, 2009 One small problem I have with my exhaust manifold is that 1 stud has stripped the thread, as you tighten the nut up it just draws out the stud, I have to check it every couple of weeks. This isn't the 1st time this has happened and another stud or 2 have had helicoils put in. What I want to know is, are there any issues with ditching the standard M10 studs & using M12 studs over the entire manifold? (I'm thinking along the lines of them becoming too close to the water jacket or oil galleries). Quote Link to comment Share on other sites More sharing options...
dandan Posted January 12, 2009 Share Posted January 12, 2009 Jay - are the helicoiled ones behaving perfectly? Quote Link to comment Share on other sites More sharing options...
TLicense Posted January 12, 2009 Share Posted January 12, 2009 I don't think there is enough material around some of the holes to go much larger. In particular the upper ones around the no.2 exhaust ports - if not those some of the ones in that area. Quote Link to comment Share on other sites More sharing options...
legendswraith Posted January 12, 2009 Share Posted January 12, 2009 (edited) Rather than using a metric thread have you thought about using an imperial one? The clearance drill of the original studs might fall into roughly the dia of an imperial one, that would then just be like cleaning up the hole rather than taking alot out. A 7/16 UNC thread uses a 9.65mm tapping drill so it would be close to removing the original threads and not take too much out. Its not ideal and it will also need the helicoil holes to be near too which they might not be. Only other thing i can think of doing is using studlock or filling the old holes with a thixotropic agent then retapping them, but thixo might be hard to come by. *edit* actually i forgot one method you can get a metal sleeve that works in a similar way to a helicoil insert but rather than just being wire it is a long sleeve that is threaded on the outside and inside. You put studlock on the outside and wind it in and the thread should be as good as new. We use then for strengthening aluminium holes that have high loads attached to them. http://fulltorque.com/ffb.htm thats pretty much what they are might be worth investigating Edited January 12, 2009 by legendswraith (see edit history) Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted January 12, 2009 Share Posted January 12, 2009 WHY are the studs pulling out? I am assuming you have a none stock, probably tubular manifold? Does it ever blow on the interface between itself and the head? Is the head flange divided, lengthwise, to minimise elongation expansion? How thick is the flange? 10mm should be a perfectly adequate stud diameter. has the head ever been on an engine that's overheated and gone soft? Quote Link to comment Share on other sites More sharing options...
TLicense Posted January 12, 2009 Share Posted January 12, 2009 I've seen a couple where the aftermarket exhaust manifold isn't flat, so the bolts are used to pull the mating surfaces together. I also saw one car that had a big blob of weld on the cylinder head around one of the bosses for the stud, the chap said that he'd "torqued" the stud into the head and cracked the head around the boss. Quote Link to comment Share on other sites More sharing options...
jevansio Posted January 12, 2009 Author Share Posted January 12, 2009 (edited) WHY are the studs pulling out? I am assuming you have a none stock, probably tubular manifold? Does it ever blow on the interface between itself and the head? Is the head flange divided, lengthwise, to minimise elongation expansion? How thick is the flange? 10mm should be a perfectly adequate stud diameter. has the head ever been on an engine that's overheated and gone soft? Yes Chris I have a tubular manifold. When the 1st stud started to come out it started blowing from around that area, the blowing was the thing that drew my attention to it. IIRC (it's been a long time) a helicoil was put in to fix that. The manifold flange has been divided (I assume you mean the flange isn't made from 1 piece of material). It was a two piece flange from the manufacturer (Sound Performance). After the 1st time it blew the infamous Dan Turner recommended that it be cut again, so I think it's something like #1, #2 & #3, #4 & #5, #6. The flange exactly the same as the HKS T4 manifold in terms of dimension. The head has been on another engine, I had the single turbo conversion done, & opted for a built block & head, a 2nd hand one supplied by Michel was used (not my own block & head). I'm pretty sure he said it had come from a car that had overheaded. The reason I'm asking is that when my GT4088R dies a death (as I know it's going to at some point), I'll be putting a new turbo & manifold on, if the head is fecked I want to know now so I can budget to replace that with a brand new one at the same time. But if I can avoid it I'd rather not be spending £4k+ unneccesarily when the only problem with the head is 1 stud being drawn out. PS the manifold isn't blowing at the mo even with the stud prob Edited January 12, 2009 by jevansio (see edit history) Quote Link to comment Share on other sites More sharing options...
jevansio Posted January 12, 2009 Author Share Posted January 12, 2009 I've seen a couple where the aftermarket exhaust manifold isn't flat, so the bolts are used to pull the mating surfaces together. I also saw one car that had a big blob of weld on the cylinder head around one of the bosses for the stud, the chap said that he'd "torqued" the stud into the head and cracked the head around the boss. Tony I'm pretty sure the last time I had the manifold off, I was told that it wasn't perfectly flat. At the time I just wanted it back together (TOTB was days away). Quote Link to comment Share on other sites More sharing options...
jevansio Posted January 12, 2009 Author Share Posted January 12, 2009 Jay - are the helicoiled ones behaving perfectly? Yes they are Dan Quote Link to comment Share on other sites More sharing options...
TLicense Posted January 12, 2009 Share Posted January 12, 2009 Tony I'm pretty sure the last time I had the manifold off, I was told that it wasn't perfectly flat. At the time I just wanted it back together (TOTB was days away). If it's been cut between 1 & 2, 3 & 4, and 5 & 6, then it shouldn't be too much of a problem but doing so would put an additional strain on the weld joints (although probably very small) IIRC the tolerance for flatness on the exhaust manifold is something like 0.2mm, but I would have to check on that. It's the age old problem you've described there, sacrificing having something "right" for "right now". Quote Link to comment Share on other sites More sharing options...
and1c Posted January 12, 2009 Share Posted January 12, 2009 Why not remove the manifold and have the mating surface machined properly flat. and at the same time you can helicoil the troublesome thread. It will bea PITA removing it all but it may be the longer term solution. At least then if it still works loose when you put the manifold back on you know its the head 'most likely' out of interest, does the exhaust mani/turbo have a support bracket anywhere? Quote Link to comment Share on other sites More sharing options...
jevansio Posted January 12, 2009 Author Share Posted January 12, 2009 If it's been cut between 1 & 2, 3 & 4, and 5 & 6, then it shouldn't be too much of a problem but doing so would put an additional strain on the weld joints (although probably very small) IIRC the tolerance for flatness on the exhaust manifold is something like 0.2mm, but I would have to check on that. It's the age old problem you've described there, sacrificing having something "right" for "right now". Yeah I know, the next time this manifold comes off it's going to be replaced with a new item. With the manifold issue to one side, do you think there's anything that can be done to the head, I don't want to spend a load on a new manifold/turbo setup only to find it starts drawing stud out the head again, yet I don't want to replace a head that is working fine in all other respects unless I have to. Quote Link to comment Share on other sites More sharing options...
jevansio Posted January 12, 2009 Author Share Posted January 12, 2009 Why not remove the manifold and have the mating surface machined properly flat. and at the same time you can helicoil the troublesome thread. It will bea PITA removing it all but it may be the longer term solution. At least then if it still works loose when you put the manifold back on you know its the head 'most likely' out of interest, does the exhaust mani/turbo have a support bracket anywhere? It doesn't have a brace, it was something I was going to have done this time round. I bought a T51R manifold which has support for a brace built in, sadly I sold that and thought when I do get a new T4 manifold I would have some bracing added to that also. When this manifold comes off I'll be replacing it regardless, when I fix it this time I'm doing it right once (mainly because I can't do the work myslef so have to pay someone to do it). Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted January 12, 2009 Share Posted January 12, 2009 If the head's been got really hot it may have softened, in which case head gasket fire ring sealing may be compromised as the fire ring will just dig a hollow in the head material and clamping force will be lost. Stud threads may pull out, valve seats and guides may come loose, and the cams probably aren't running in bearings that are still in a straight line. You can have the cam bearings checked with an engineering straight edge, and the hardness tested various ways, commonest being by Brinnel testing where a hardened steel ball is dropped on the material under test, with a known and repeatable force, and the indent microscopically measured for size. I would just scrap an overheated head. i have 2 here, I use them to cut up and generally mess with. A poor manifold design, either in material or execution, will warp, and could warp powerfully enough to pull the studs out. GTS-t Skylines have a poorly designed cast manifold, over tight fitting studs. The elongation of the manifold unde duress is enough to snap 10 mm studs off, flush with the block, like rotten carrots. Oversizing the holes in the manifold to allow it to elongate without putting shear loads into the studs, and using only a stock, slip and slide gasket fixes it. Quote Link to comment Share on other sites More sharing options...
dandan Posted January 12, 2009 Share Posted January 12, 2009 Why not go with a cast manifold Jay? Quote Link to comment Share on other sites More sharing options...
jevansio Posted January 12, 2009 Author Share Posted January 12, 2009 If the head's been got really hot... Many thanks for all the info Chris. I think the best solution is to budget for a new head and put a new head/turbo/manifold all on at the same time Why not go with a cast manifold Jay? Mostly due to the szie of turbo I want to fit, I have the GT4088R currently and when that goes I'd look to move to T67 minimum, most likely a T51R/71DBB/74DBB, & I don't think the cats manifolds would support such a large turbo Quote Link to comment Share on other sites More sharing options...
dandan Posted January 12, 2009 Share Posted January 12, 2009 Hmmm a 74mm turbo does sound large - what sort of power will you aim to put down? SimonB runs a 67DBB on his as do a few over on SF. Apparently Jeff from Induction motorsport ran a 71mm turbo to well over 700bhp on one. I am building my kit now (67DBB) around one - but that isn't proof obviously as I am still doing it and it has not been on a RR. Quote Link to comment Share on other sites More sharing options...
bondango Posted January 12, 2009 Share Posted January 12, 2009 Fensport do a repair stud - M11 x 1.25 thread on the head side and a M10 x 1.25 thread on the manifold side, though they are £7 each Quote Link to comment Share on other sites More sharing options...
jevansio Posted January 12, 2009 Author Share Posted January 12, 2009 Hmmm a 74mm turbo does sound large - what sort of power will you aim to put down? SimonB runs a 67DBB on his as do a few over on SF. Apparently Jeff from Induction motorsport ran a 71mm turbo to well over 700bhp on one. I am building my kit now (67DBB) around one - but that isn't proof obviously as I am still doing it and it has not been on a RR. I'm hoping to see around the 700bhp mark with a T51R. The 67 would be a good choice but I may not see enough difference from the GT4088R I currently have. Fensport do a repair stud - M11 x 1.25 thread on the head side and a M10 x 1.25 thread on the manifold side, though they are £7 each Many thanks, may be worth a try considering it's coming out now & the head is most likely going to be ditched anyway. Quote Link to comment Share on other sites More sharing options...
jevansio Posted January 12, 2009 Author Share Posted January 12, 2009 Just ordered a couple, worth a shot. Saves ditching a head that is working perfectly fine in all other respects I guess. Quote Link to comment Share on other sites More sharing options...
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