I was never brave enough to do it. But a guy who was specialising in Stags back in the late issues. He replaced the studs with bolts. I had stainless steel.atuds.made and still applied anti corrosion. Not for the threads, that's not the problem. It's the shank against alloy head that the stud seizes.
I was under the impression the problem was corrosion between the stud and head within the hole it passes through. I will be using Castrol Optimal TA around the stud where it passes through the head. Thanks for pointing out the water gallery drain holes. 2 stags and thirty years in my garage and I never knew they were there!
Hi Tony Don t know if already mentioned , have you seen where guys are connecting the water from rear water transfer housing on the the Left hand head to the right hand head , then to heater .To help water flow though the right had head ?
Need to be shown or talk about the stud removal when one is in trouble ie the stud snaps. corrosion prevention once the jobs done is straightforward and yes in the event of having to do the head gasket again would obviously be easier...
Agree that there is no need to lube or corrosion protect the bottom threads, steel stud goes into iron block so no dissimilar metal corrosion there. Just nip up tight with a flathead screwdriver, the upward tension on the threads will ensure no movement until you need to remove it. The corrosion issue is indeed where the steel stud passes through the alloy head, this gives problems when trying to detach e.g. a big Jaguar XK head from the block. Cheers JM
Morning Tony ,one thing with reference to the head studs, Normfest are a maker of various automotive lubricants and service products,one of which is Offshore anti seize treatment, I've been using this on my rebuilding projects,for the last twenty years or so and it's brilliant stuff,that doesn't cost a fortune,and is easily available from Euro Car Parts, use it on most bolts and fixings that are exposed to the road and it's great on bushes,and handbrake levers on the shoes in the drums,and of course front pads to prevent sticking in the calliper one spray goes a long way ,so use sparingly Cheers.
Hi Tony, This my understanding for the reason the head studs becoming very difficult to remove after a long period of time. It has less to do with the actual threads seizing but the plain shanks of the studs corroding to the acutal bore they are located in, in the cylinder head itself. Couple of things can happen, one is electrolysis of dissimilar metals which can be exasperated by very slight weeping of coolant into the stud holes in the head overtime. Another good reason to keep the heads torqued and the coolant fresh. When I refitt my Stag cylinder heads I liberally coat the whole plain length of the stud with a good anti-seize compound. I've always used the loctite product. I've had the heads off after several years, and the studs are easy to remove. BTW, lubricating the THREADS on the studs with anti-seize is not always a good idea, and you did address this is your video, as it can give false torque readings when tightening down. Infact that goes for any critical fastener. Back to removing the studs/heads. It is why the the cylinder heads can only often be removed by physically cutting the studs at the face of the cylinder block, assuming you're lucky enough to be able to work the head up enough to get a hacksaw in between the head and block. I've have had to do this. It left the length of the stud(s) in the cylinder head which had be drifted out with with not insignificant effort. Once the stud was out the amount of corrosion was obvious and I was not surprised the stud would not just back out per the manual. I don't think this phenomenon was unique to just Stag engines. Many engines of the same time period that used aluminium heads and iron blocks suffered similar problems, even Ferrari! It was true that the odd setup of angled head studs used by the Stag engine didnt help matters. I have heard of people replacing the studs with regular bolts. I believe ARP have bolts that will work. It does take a little "thinking outside the box" on reassembly. Plus the ARP have a higher torque spec which is not a bad thing. Hope this helps shed a little more light on the vagaries of the Stag engine. If nothing more it gives you something to argue about down the pub, when Covid permits. Cheers Russ. Anyway, hope this helps you with a little more insight into
@@ArryTheStag Tony, I had a look at the ARP website. They list a head stud/bolt kit for the TR7, obviously two kits needed for the Stag. I little more research needed to find bolts to replace the studs, but their catalogue is extensive. What is interesting is that they recommend their fasteners be torqued down to 80ft/lbs. Quite a useful step up from the original Stag spec. I think the tighter the heads and gaskets are squeezed down to the block the better.
Russ, just for some added perspective, my studs were literally electrolytically welded into the head and nothing could raise the head sufficiently to even saw them. Solution? Electrical discharge machining (EDM) whereby an electrode emits a high-intensity spark to literally burn away the stud from inside. Once hollowed out, liquid nitrogen is poured into the generated cavity and what remained of the stud instantly collapses on itself. The only place I could find in Southern California that'd take the entire block and heads to perform the machining was an extremely expensive aerospace machine shop that supplied parts to McDonnel Douglas in Long Beach. Cost at the time for 8 studs? $1,750 in 1977 U.S. dollars. Ran out of money and never did complete the repair, selling the project soon thereafter. Which was a shame, since I loved that 1971 MK I manual.
With regard to the torque requirement of the nuts and bolts, you show the manual at 6:50 minutes section 12.29.27 which states 45 to 55 lb ft with the correct equivalent kgs m. I have told that this was a misprint in the book and it should be upto 65 ft lb. Unfortunately I can remember where I picked this up, but if you go to the service section page 10.00.09 para 19, you will note that it does in fact say 65 lbf ft, although the KGf m figure does not correlate. Hopefully an expert will be along soon to clarify?
@@ArryTheStag A bit more info. In the Feb issue of practical Classics they did some work on a TR7 and replaced the head. In the article is says ' Everything was torqued up to 60lb ft...not 55 lb ft as it says in the workshop manual. the '55' guidance was corrected by BL with a supplement in the late seventies, but this piece of paper was soon lost. Most original manuals still state the 55 figure - it is wrong and you risk further gasket failure by sticking to it' I obviously read this a few weeks ago and had the idea that the Stag would be the same. Not sure if it helps or confuses the issue. I would add that E J Ward did my engine using their special studs and told me they do theirs to 65 lb ft.
I have never heard of the studs described as stretch types. If this were the case, the nuts would be tightened to torque, and then a further angular amount. By definition they would have to be replaced every time too.
Thats fine of course if you wish to do that but there is no mention of such a requirement in the workshop manual. The usual reason to do so is because of electrolytic corrosion between the stud and alloy head, once the space between them gets some leaked coolant in there. I’ve done my heads a couple of times and only ever replaced corroded ones. Thing is that true stretch fasteners, also referred to as ‘torque to yield’, are permanently stretched after torquing so are single use, and there are none of these on the Stag
Hi Tony. I see this is a Mk2 engine from the location of the drain plugs. Mine (as you know) is a Mk1and it has a couple of butterfly valve screws which (allegedly) makes draining much easier.....and access is pretty easy too. No idea whay they changed this on the Mk2, as the origional looks much easier.
I was never brave enough to do it. But a guy who was specialising in Stags back in the late issues. He replaced the studs with bolts.
I had stainless steel.atuds.made and still applied anti corrosion. Not for the threads, that's not the problem. It's the shank against alloy head that the stud seizes.
i had 8 that were seized in the head made a tool up to pull heads off with studs in place worked a treat
I was under the impression the problem was corrosion between the stud and head within the hole it passes through. I will be using Castrol Optimal TA around the stud where it passes through the head.
Thanks for pointing out the water gallery drain holes. 2 stags and thirty years in my garage and I never knew they were there!
I have always wondered why the studs cannot be replaced with bolts.
Hi Tony
Don t know if already mentioned , have you seen where guys are connecting the water from rear water transfer housing on the the Left hand head to the right hand head , then to heater .To help water flow though the right had head ?
Need to be shown or talk about the stud removal when one is in trouble ie the stud snaps. corrosion prevention once the jobs done is straightforward and yes in the event of having to do the head gasket again would obviously be easier...
Agree that there is no need to lube or corrosion protect the bottom threads, steel stud goes into iron block so no dissimilar metal corrosion there. Just nip up tight with a flathead screwdriver, the upward tension on the threads will ensure no movement until you need to remove it.
The corrosion issue is indeed where the steel stud passes through the alloy head, this gives problems when trying to detach e.g. a big Jaguar XK head from the block.
Cheers
JM
Morning Tony ,one thing with reference to the head studs, Normfest are a maker of various automotive lubricants and service products,one of which is Offshore anti seize treatment, I've been using this on my rebuilding projects,for the last twenty years or so and it's brilliant stuff,that doesn't cost a fortune,and is easily available from Euro Car Parts, use it on most bolts and fixings that are exposed to the road and it's great on bushes,and handbrake levers on the shoes in the drums,and of course front pads to prevent sticking in the calliper one spray goes a long way ,so use sparingly Cheers.
Hi Tony,
This my understanding for the reason the head studs becoming very difficult to remove after a long period of time. It has less to do with the actual threads seizing but the plain shanks of the studs corroding to the acutal bore they are located in, in the cylinder head itself. Couple of things can happen, one is electrolysis of dissimilar metals which can be exasperated by very slight weeping of coolant into the stud holes in the head overtime. Another good reason to keep the heads torqued and the coolant fresh. When I refitt my Stag cylinder heads I liberally coat the whole plain length of the stud with a good anti-seize compound. I've always used the loctite product. I've had the heads off after several years, and the studs are easy to remove. BTW, lubricating the THREADS on the studs with anti-seize is not always a good idea, and you did address this is your video, as it can give false torque readings when tightening down. Infact that goes for any critical fastener.
Back to removing the studs/heads. It is why the the cylinder heads can only often be removed by physically cutting the studs at the face of the cylinder block, assuming you're lucky enough to be able to work the head up enough to get a hacksaw in between the head and block.
I've have had to do this. It left the length of the stud(s) in the cylinder head which had be drifted out with with not insignificant effort. Once the stud was out the amount of corrosion was obvious and I was not surprised the stud would not just back out per the manual.
I don't think this phenomenon was unique to just Stag engines. Many engines of the same time period that used aluminium heads and iron blocks suffered similar problems, even Ferrari! It was true that the odd setup of angled head studs used by the Stag engine didnt help matters. I have heard of people replacing the studs with regular bolts. I believe ARP have bolts that will work. It does take a little "thinking outside the box" on reassembly. Plus the ARP have a higher torque spec which is not a bad thing.
Hope this helps shed a little more light on the vagaries of the Stag engine. If nothing more it gives you something to argue about down the pub, when Covid permits.
Cheers
Russ.
Anyway, hope this helps you with a little more insight into
@@ArryTheStag Tony, I had a look at the ARP website. They list a head stud/bolt kit for the TR7, obviously two kits needed for the Stag. I little more research needed to find bolts to replace the studs, but their catalogue is extensive. What is interesting is that they recommend their fasteners be torqued down to 80ft/lbs. Quite a useful step up from the original Stag spec. I think the tighter the heads and gaskets are squeezed down to the block the better.
Russ, just for some added perspective, my studs were literally electrolytically welded into the head and nothing could raise the head sufficiently to even saw them. Solution? Electrical discharge machining (EDM) whereby an electrode emits a high-intensity spark to literally burn away the stud from inside. Once hollowed out, liquid nitrogen is poured into the generated cavity and what remained of the stud instantly collapses on itself. The only place I could find in Southern California that'd take the entire block and heads to perform the machining was an extremely expensive aerospace machine shop that supplied parts to McDonnel Douglas in Long Beach. Cost at the time for 8 studs? $1,750 in 1977 U.S. dollars. Ran out of money and never did complete the repair, selling the project soon thereafter. Which was a shame, since I loved that 1971 MK I manual.
With regard to the torque requirement of the nuts and bolts, you show the manual at 6:50 minutes section 12.29.27 which states 45 to 55 lb ft with the correct equivalent kgs m. I have told that this was a misprint in the book and it should be upto 65 ft lb. Unfortunately I can remember where I picked this up, but if you go to the service section page 10.00.09 para 19, you will note that it does in fact say 65 lbf ft, although the KGf m figure does not correlate. Hopefully an expert will be along soon to clarify?
@@ArryTheStag A bit more info. In the Feb issue of practical Classics they did some work on a TR7 and replaced the head. In the article is says ' Everything was torqued up to 60lb ft...not 55 lb ft as it says in the workshop manual. the '55' guidance was corrected by BL with a supplement in the late seventies, but this piece of paper was soon lost. Most original manuals still state the 55 figure - it is wrong and you risk further gasket failure by sticking to it' I obviously read this a few weeks ago and had the idea that the Stag would be the same. Not sure if it helps or confuses the issue. I would add that E J Ward did my engine using their special studs and told me they do theirs to 65 lb ft.
I have never heard of the studs described as stretch types. If this were the case, the nuts would be tightened to torque, and then a further angular amount. By definition they would have to be replaced every time too.
Thats fine of course if you wish to do that but there is no mention of such a requirement in the workshop manual. The usual reason to do so is because of electrolytic corrosion between the stud and alloy head, once the space between them gets some leaked coolant in there. I’ve done my heads a couple of times and only ever replaced corroded ones. Thing is that true stretch fasteners, also referred to as ‘torque to yield’, are permanently stretched after torquing so are single use, and there are none of these on the Stag
Hi Tony. I see this is a Mk2 engine from the location of the drain plugs. Mine (as you know) is a Mk1and it has a couple of butterfly valve screws which (allegedly) makes draining much easier.....and access is pretty easy too. No idea whay they changed this on the Mk2, as the origional looks much easier.
The butterfly versions leak, probably due to the higher system pressure in the later engine
The block part starting with 888 also signifies Mk2 heads. Just as an FYI