Head keeps blowing - advice please

[Knowledge]

Ok, so the engine is back together. This is what I have done.

The P200 studs have been reversed, so the long thread is at the bottom. The stud holes have been tapped to the bottom of the hole. This allows the stud to sink to 18mm deep, not 15mm as before. Loctite on threads at the bottom.

Three bond on the paper gasket at the bottom of the barrel.

Cylinder head now sealed with Three bond, 3mm thick steel steel washers, wavy washers and ali nuts. Tightened down evenly and tightened (I don't own a torque wrench). The whole set up has been left to cure.

I started to make a leak-down kit using a blood pressure gauge, but it doesn't work. I might have another go at making it work today, but I am keen to get the engine back in the frame today as it is cluttering up my workshop.

Thanks for the advice, some of which I have taken, and some of which I have declined, but I feel more confident, especially as I think the issue was at the bottom of the studs and the work I have done in that area looks to be a step forward.

[HxPaul]

You say you dont torque the head nuts down.Maybe that is your problem,your possibly tightening the head nuts,but not wanting to over tighten your maybe subconciosly not tightening them enough,either way without using a torque wrench theres no way that you will be able to tighten each head nut to the same torque.

[Knowledge]

I remember that I had a head gasket blow on an old Vauxhall Nova. The factory recommendation on tightening the nuts was to get them all tightened down in a relevant order until they were all just biting, and then turn them all by a quarter turn (again in a pre-described order) and then go round again with another quarter turn again.

This is the principle that I have used since. However, it is coming around the Christmas and people will be asking me what I want.

Dear Santa......

[Nick-j]

Must admit it seems I must of had my studs round the wrong way - long end up, you live and learn. Why do you not like the Blue Hylomar mr W tornado? What is considered the best option for this situation as I have been using Hylomar.
Nick

[CHRIS in MARGATE]

No torque wrench !
Answered your own question.

[johnnyXS]

Must admit it seems I must of had my studs round the wrong way - long end up, you live and learn. Why do you not like the Blue Hylomar mr W tornado? What is considered the best option for this situation as I have been using Hylomar.
Nick

I cannot speak for others experience but I wrecked a newly rebuilt 6x cylinder engine many years ago due to using Blue Hylomar.
When I stripped the engine I found that several key oilways had been blocked by tiny beads of Hylomar which had been squeezed off the gasket surfaces and fallen into the sump.

You cannot go wrong using Threebond 1104 Neo or Hermatite both of which are liquid gaskets but whatever you do ...do not use Blue Hylomar or any silicon based gasket cement.
Good luck

[Knowledge]

Update.

I had another think about how I could get my leak down test kit to work. I fitted the exhaust stub and stretched a cut-off of inner tube (with a valve in the middle) and secured it with a jubilee clip. The gauge is fitted to a bung in the inlet rubber. I can now get air into the cylinder.

I rather wish I hadn't, as it showed up a number of leaks, especially on the gasket faces of the reed valve. I have addressed these by getting them smooth on my plate, and refitting with Three bond. I then found air escaping up one of the four main studs. This is probably due to a repair I made after I broke through to the stud whilst fettling the transfers. More three bond on the fat washer at the top, and re-tighten the four nuts.

It is being allowed to cure before repeating the leak-down test.

I'm washing my linen in public here, so you all don't have to.

[Warkton Tornado No.1]

Unread postby Nicodemus » Sun Nov 20, 2016 4:16 pm

Must admit it seems I must of had my studs round the wrong way - long end up, you live and learn. Why do you not like the Blue Hylomar mr W tornado? What is considered the best option for this situation as I have been using Hylomar.
Nick

My experiences with Blue Hylomar made me believe it is Witches Snot! Despite it's claims, it just rolls away. It may be due to the oil in a two stroke, but bathroom silicone sealant doesn't migrate like that crap....

I really wanted it to work because "as used by Rolls-Royce" carried some kudos (once upon a time) to me. Conversely, Rolls-Royce do Helicoil their threads in alloy from scratch, & they are faultless if fitted properly.

Hylomar failed in every attempt I made. In fact, grease is better. I kid you not!

Green Hermetite is brilliant if you can find it, but there are more 'modern' equivalents @ more 'modern' prices.

I have used Three Bond a couple of times simply because I was gifted it, but can't say that it is better than the correct Hermetite which I tend to use.

[Warkton Tornado No.1]

Post by Knowledge » Sun Nov 20, 2016 8:30 pm

Update.

I then found air escaping up one of the four main studs. This is probably due to a repair I made after I broke through to the stud whilst fettling the transfers. More three bond on the fat washer at the top, and re-tighten the four nuts.

Porting can often result in blow by up the stud. Ooer!

To get around that, I fit some stainless tubing up the barrel hole.

I have some to hand that you can have, as long as you return any spare. How else can I keep up my expensive coke habit without my snort tube?

[Knowledge]

Thanks WT1, but I have already done that repair, but it hasn't worked completely. Next time the barrel is off (and that might be soon, the way things are going), I will treat the repair to a bit of epoxy glue to make sure it is fully sealed.

Thanks for the offer though.

[johnnyXS]

Update.


I'm washing my linen in public here, so you all don't have to.

there isn't a single owner reading this that hasn't either had a leak or some sort of fault due to not being quite meticulous enough during assembly .
I think this post is a valuable reminder to all of us Knowledge .

Well done for persevering and especially carrying out the diy leakdown test ...we are all learning from threads like this

[Knowledge]

That's the idea Johnny.

Every day is a school day. Fettle, learn, share

[Phil D]

I'm washing my linen in public here, so you all don't have to.

I thought that was a very humble post .
Great thread great philosophy .
What could we achieve if we all were prepared to accept we can all learn something and we don't know as much as we think we do .
Thanks Knowledge .

[johnnyXS]

I'm washing my linen in public here, so you all don't have to.

I thought that was a very humble post .
Great thread great philosophy .
What could we achieve if we all were prepared to accept we can all learn something and we don't know as much as we think we do .
Thanks Knowledge .

I thought for a minute he was offering a laundry service ...I was bagging up me smalls

[Adam_Winstone]

I'm washing my linen in public here, so you all don't have to.

I thought that was a very humble post .
Great thread great philosophy .
What could we achieve if we all were prepared to accept we can all learn something and we don't know as much as we think we do .
Thanks Knowledge .

Phil,

He was only playing for sympathy

Adam

[Phil D]

Doh
I was gonna launch a torque wrench crowd funding thingy.

[EddieStone]

I'm happy to be corrected here, but I thought the stud holes in the casing were deliberately not tapped to the full depth? This allows the stud to 'bite' into the shallower threads at the bottom so it doesn't come undone again...

[Warkton Tornado No.1]

Post by EddieStone » Mon Nov 21, 2016 3:50 pm

I'm happy to be corrected here, but I thought the stud holes in the casing were deliberately not tapped to the full depth? This allows the stud to 'bite' into the shallower threads at the bottom so it doesn't come undone again...

That’s not my understanding, limited as it is. However, I'm not aiming to 'correct' anybody & only to share what I hope is useful information.

In fact, in my time, I have had to produce drawings of studs that do ‘bottom out’ for TWR Nissan amongst others.

They comprise an extended portion of Ø6.8 mm in the case of M8 x 1.25 with a conical end 118° that does the bottoming out.

The V*spa cylinder studs with their rolled threads would be ideal to modify to such purposes using the 'long' end.

They work well as they do not apply load to the threaded portion of the hole.

[Storkfoot]

..... The factory recommendation on tightening the nuts was to get them all tightened down in a relevant order until they were all just biting, and then turn them all by a quarter turn (again in a pre-described order) and then go round again with another quarter turn again.
......

This made me smile My Dad, who fixed planes in the war, taught me something very similar which I still do to this day on hubs, gearbox endplate and loads of other things.

I do have a torque wrench for the cylinder head and rear hub though, Martin

[Phil D]

In fact, in my time, I have had to produce drawings of studs that do ‘bottom out’ for TWR Nissan amongst others.

They comprise an extended portion of Ø6.8 mm in the case of M8 x 1.25 with a conical end 118° that does the bottoming out.

The V*spa cylinder studs with their rolled threads would be ideal to modify to such purposes using the 'long' end.

They work well as they do not apply load to the threaded portion of the hole.

Just trying to get my head round the modified stud WT1 wont an ordinary stud have more thread area and bottom out the same but be stronger