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  #1   IP: 174.242.83.90
Old 01-30-2020, 03:17 PM
Sculldog1 Sculldog1 is offline
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Replacing head studs when doing head gasket

I am replacing the head gasket and need to know if new studs should be purchased or if the current ones will be ok to reuse. I had one stud come out with the nut but all others seem ok. Just want to get some feedback about the issue. Also is it necessary to take out the remaining studs before reassembling or just clean mating surfaces with studs in and replace only the stud that had come out with nut. (Threads look o.k. to me) any advice is appreciated. Thanks
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  #2   IP: 155.186.124.219
Old 01-31-2020, 10:09 AM
Dave Neptune Dave Neptune is online now
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Sculdog, first welcome to the MMi Afourian Forum.

I would remove the studs for 2 reasons. First a good inspection of the threads holding the studs in the block.. Studs are cheap and a good investment especially if you have a raw water cooled engine.

Second it will make cleaning the surface of the block much easier thus insuring a good gasket seal.

I recommend using Av grade permatex on the head. Really helps seal out water for a cleaner and longer lasting seal. Although it is a bit tougher to get back apart if necessary.

Dave Neptune
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  #3   IP: 32.211.28.40
Old 01-31-2020, 10:25 PM
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Al Schober Al Schober is offline
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Let me add a bit to Dave's suggestions (all good). The block is a high nickel alloy and is somewhat corrosion resistant - the studs are not. The end of the stud exposed to raw water coolant will tend to go away. This also applies to the 3 studs holding the manifold. The only way to check them is to pull them. Consider this a plug for glycol coolant/heat exchanger.
As for sealant, what I use is Permatex 2A - this is the brown stuff with the consistency of peanut butter that comes in tubes.
The purpose of the studs is to be in tension, holding the head against the block. When you torque the nuts, the amount of corrosion affects the amount of tension developed. Rusty studs/nuts should be replaced or at least cleaned up. The ID of the nut and the face against the washer should be lubricated - I use the silver Permatex anti-seize (comes in a 4 oz tub with brush - lifetime supply). Some A4 owners go with stainless washers and acorn nuts - building a 'show quality' engine.
When cleaning the top of the block and the face of the head, don't try to get it too smooth - the gasket holds better to surfaces with a bit of 'tooth'. 60 grit is good, I wouldn't go finer than 80 grit.
Original head gaskets on the A4 were asbestos with a copper jacket - top and bottom. I've measured the original gaskets after removal, and found them to be a solid 1/16". Gaskets available today are 1/32" hence you need 2 of them. If the head/block have been surfaced, you might even need 3 to retain the original compression ratio.
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Old 02-11-2020, 12:16 PM
Sculldog1 Sculldog1 is offline
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Head gasket replacement

Thanks to Al and Dave. Just want to be clear though. After removing head studs and cleaning up block surface with say 60 or 80 grit to give good mating of head I should clean stud hole threads and apply the av 2 to threads. Then tighten them in to till the tops of the course threads are no longer seen. 2 gaskets (dry) then the head placed and torqued following diagram. Three steps of increasing tightness until at specified torque in mm overhaul manual. Then washers and head nuts with anti seize on fine threads. This is my intended procedure as I understand it.
One question about product for coarse threads is that overhaul manual recommends jb weld, another person recommended loctite red and now you fellas say av2. Are these products interchangeable or is any one more appropriate? Thanks for all the help.
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  #5   IP: 155.186.124.219
Old 02-11-2020, 01:39 PM
Dave Neptune Dave Neptune is online now
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Exclamation Opinion on studs

Sculdog, as far as setting studs goes you will find many opinions and most do work quite well. Some of those are short term like for selling once running again, you know the PO thing.
Most important no matter what you seal with is the prep! The threads should be chased with a fresh tap using a paint thinner, acetone or such. A brush can be used to apply your choice. Once the tap is in the hole spin it back and forth a bit to really clean the threaded hole. Once dry blow out with air.

Only use new studs if you can afford them and clean them with the thinner so no oil residue is left.

Now the studs are ready to be sealed with your choice.

The JB Weld is strong but the epoxy tends to break away from stressed areas once the torque is applied. It will help hold but does not do as good job of sealing.

Sealing with malleable sealers works great but adds no strength. The malleability of the Permatex products or the non hardening grades of Lock-Tite will not "break away" when torqued thus a better "seal". I have always used the Permatex on engines and the Lock-Tite on dry applications. I prefer the aviation grade on the studs and head gasket as it can be easily brushed on. The #2 works just as well for studs but not on a head gasket.

I would not take any kind of abrasive to the block deck as it is assembled. Any grit getting down to the pistons and rings will chew things up until it gets flushed out. Ok on the head as there are no moving parts and you can really clean up after or on a stripped block. Just be very careful so you don't hollow out anything. Personally I only use a scraper and a medium wire brush to prep the surfaces on cast iron.

Do as Al says for the nuts and washers. Do remember to torque incrementally and retorque after the first few run cycles especially with two gaskets. If you choose to put the head on wet (with sealers) it will last far longer and it will be a bit more trouble removing if the need arrises. Also if you do assemble wet you will need to retorque at each increment a few times as the sealer squeezes and the gaskets compress. I go 10lbs at a time for increments.

Dave Neptune
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Old 02-12-2020, 09:46 AM
Sculldog1 Sculldog1 is offline
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Thanks a million Dave for the help. I just got the head back from the machine shop who magna fluxed and resurfaced it. As all but one of the studs stayed in the block I guess I will remove them and do as you describe to prep the threads and thread holes in the block. As I am doing the job in the cramped Pearson 30 and am fearful of breaking off any bolts or manifold studs what is your opinion as to should I attempt to remove water jacket side plate and manifold to clean them or just reassemble the head and acid flush the engine.
I have cleaned out as much as possible the ports in the block from above with stiff wire and wire brush thingies and shop vacuumed with a straw down through the ports and removed quite a bit of debris. I am inclined to reassemble without going deeper into things for now and saving for transitioning to fresh water cooling and a total rebuild once I have put aside funds to do so. Many other jobs to complete on this boat separate from the engine so time and funds need to be balanced. Thanks again for good advice.
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  #7   IP: 155.186.124.219
Old 02-12-2020, 03:59 PM
Dave Neptune Dave Neptune is online now
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Sculdog, if you are going to FWC I would not "acid flush" until you are setting it up. If you have knocked most of the stuff loose a vinegar soak which is far more subtle should suffice very well.

When you do convert freshen up everything and check the side plate and the diverter. The side plate can turn into a bigger job quickly if the threads are rusted out.

Dave Neptune
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  #8   IP: 208.114.165.87
Old 08-06-2020, 10:22 PM
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Stud Leaking Water onto Head

Hello, I'm wondering what can happen when a head stud is leaking water on top of the head? I have a stripped thread of one stud in the block and need to drill a tap it, but am wondering if I can run the engine for a 5-day trip or will that cause water to get into the pistons etc. and seize the engine? Or is it more a problem in the long term due to corrosion?
Thanks!
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Old 08-07-2020, 03:57 PM
Sculldog1 Sculldog1 is offline
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Talking Stripped stud threads

I would not be confident giving advice regarding the problem you describe and would hate to hear of you doing any damage based on my thoughts. I will say that tapping the threads in the A4 block is not a terribly difficult task. I ran a tap into all the holes before I replaced my head with no troubles and also on a manifold stud. If you do decide to run the motor with the stud leaking I would definitely check the oil for water before leaving and at frequent intervals as water in the crankcase while running for very long could be disastrous. Risk v reward comes to mind. Good luck.
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  #10   IP: 208.114.165.87
Old 08-07-2020, 07:35 PM
Amphibiographer Amphibiographer is offline
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Quote:
Originally Posted by Sculldog1 View Post
I would not be confident giving advice regarding the problem you describe and would hate to hear of you doing any damage based on my thoughts. I will say that tapping the threads in the A4 block is not a terribly difficult task. I ran a tap into all the holes before I replaced my head with no troubles and also on a manifold stud. If you do decide to run the motor with the stud leaking I would definitely check the oil for water before leaving and at frequent intervals as water in the crankcase while running for very long could be disastrous. Risk v reward comes to mind. Good luck.
Thanks for the feedback! We'll be tapping with the head on inside the cramped confines of a '72 C&C 27. The stud currently does not tighten and we tried another stud in it from closer to the front and it didn't tighten either so we figure the thread must be stripped. Running a same size tap into it wouldn't work would it? Or could it clean out any corrosion or metal flilings? Don't we need to drill it out then use a larger diameter tap?

Did you use the tap on a power drill or by hand?

Last edited by Amphibiographer; 08-07-2020 at 08:00 PM.
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