Sealer for cylinder head

[essexgp]

Just about to fit my newly rebored barrel (185 to 200) and reprofiled head courtesy of JB (thanks for getting it done John) but forgot to ask him what sealer to use on the head as it has a metal base gasket and no head gasket .

[Craig H]

Wellseal or loctite 5910

[WINTERMODEL150]

I use 5910 and its sold in Halfords for around £5.50 .

Dean

[nelson pk]

In theory your cylinder head shouldn't need sealant and it wont stop a major head leak. Its generally used to seal tiny marks around the head seal.
Make sure you torque the head up to say 17-20 foot pounds. If you haven't got a torque wrench, dont guess, buy one!
This is the main reason for head leaks etc. Also dont forget to retorque after a few miles. Its a pain but well worth the effort.
Dont use spring washers, just use flats.
I use threebond 1104 on heads (used to be called yamabond. kawabond etc) and find its the best stuff available for making good seals (apart from the chaincase as its too sticky for that!).

[essexgp]

Thanks for all your help and advice

[Adam_Winstone]

"Dont use spring washers, just use flats.", I keep reading this but most of the guys I've known to have heads come loose have only had the problem after taking this advice from one of 2 major dealers. I tried it once and had it fail so have returned to thick flats and thick split washers and have not had a failure since.

A great example of this was a mate on here had blowing/seal issues with his TS1, resulting in a strip down on the campsite at Euro Lincoln. He stripped it, rebuilt it with flats and soon had it blowing again, so we stripped it down and I refitted the head again with a smear of sealant + decent flats + chunky splits that a dealer was selling for wheel rim nuts. The motor didn't blow again and got him home without issue, and when I asked him about it several months afterwards he said that it was still going strong... now that it had decent split washers in it! To me it makes complete engineering sense that split washers should help as without them the heating of long studs and nuts will result in the assembly expanding, which without the physical pressure of spring washers will simple result in the nuts coming loose, which is exactly what this bloke, myself and many others have experienced.

I'm not saying that this is right or wrong, just that my own experience and those of others that I know to have tried it, resulting in failure, has resulted in me deciding that this is one of those issues that makes me think.... "Do whatever works for you."

Adam

[nelson pk]

I've never had a head failure since using a torque wrench with only flats and then re-torqueing after a few miles (once everything has expanded and bedded in).
My personal opinion is that if your studs are tight in the casing and the head and barrel have been flatted/skimmed correctly and you have used a torque wrench which i believe is vital and you have not over-tightened the nuts and then re-torque (again vital) it will not come loose.
I've done several engines like this and have not had a head come loose or the slightest leak since i've used this method.
Could it be that people who do not use a torque wrench find spring washers better as if you haven't got even pressure on each stud it will come loose and spring washers could help in that situation?

[Adam_Winstone]

^... the head and rear hub are the only things that I do use my torque wrenches for but even with the re-torqueing suggested in the 'flat only' text that I've read, the outcome of trying just flats has not been satisfactory. I also try to configure all my engines to do away with head gaskets and make sure that barrel and head surfaces are lapped flat prior to assembly. In doing so I cannot remember the last time (eek... tempting fate!) I had a motor blow, other than when trying the 'flat only' method.

However, I'm really not trying to convince anyone to use my method or anyone else’s, it was more picking up on the point that I keep reading this but personally have had poor results from it and know of a number of others that have read it, tried it, regretted it too. I really do think that it is a case of finding what works for you and sticking with it.

As they say... don't knock it until you've tried it... but there are things that I draw the line at!

Adam

[a.lo.v2]

i think the critical aspect of this is the type of split washers, i cannot seem to get the really strong original type. i am having trouble with a vespa head as the washers keep splaying out. have not had the lambretta top end off or tightened in 5/6 years (no gasket, bathroom silicone).

[Adam_Winstone]

^... Agreed. Many of the thin ones abuot these days are simply not man enough for the job. I tend to use bathroom sealant too, and have done for decades after having a respected racer laugh at me for spending money on more expensive products and stating that the head/fit must provide the seal, with the sealant being nothing more than an extra measure. This advice has worked for me ever since.

Adam