Author Topic: Blown head gasket  (Read 2429 times)

Offline vwphillips

  • Moving Up
  • **
  • Join Date: Nov 2013
  • Posts: 23
  • Karma: 0
Blown head gasket
« on: 23.06. 2014 16:58 »
1959 A7 SS with1951 engine

Out on a run saturday a chirping sound started when pulling away after stopping for petrol(premium shell with additive)

before long it started to lose power and blowing from the RH side of the cylinder.

I removed the rocker cover and cylinder head and found a big split in the RH side if the gasket.

the center head bolts were not much than hand tight the others required medium force to remove

I can not find any reference to the torque settings in the haynes manual, is there any recomendation?

I removed one exhaust valve to see what it was like but as I was not sure what I was looking for I have taken the head to
a local firm that does motor cycle cylinder heads and he said it does not look too bad.

He also said that there were signs of blowing on the LH cylinder.

I have left the head with him for valve seating and skimming.

I have ordered a set of gaskets and a pushrod comb.

I am conserend what caused this

I am new to BSAs (well back after 50+years and knew little then)

I retimed the magneto points not long ago(after many attempts and still not sure)

All thoughts, advice would be welcome

including
 the the torque settings of the head bolts,
 do I wind the rocker gap out before refitting the rocker cover,
 and how best to use the pushrod comb and check the push rods have seated correctly

Thanks

Vic




Offline a10gf

  • Wise & Enlightened
  • *
  • Join Date: Sep 2006
  • Posts: 2804
  • Karma: 42
  • West Coast, Norway & Alpes Maritimes, France
    • A10 GF
Re: Blown head gasket
« Reply #1 on: 23.06. 2014 17:11 »
Quote
I can not find any reference to the torque settings in the haynes manual
The service sheets says 'real tight'  *smile*
Use the forum search (example: torque head etc ),dozens of posts with interesting discussions and recommendations available. Example http://www.a7a10.net/forum/index.php/topic,2452.0.html

How the search works: http://www.a7a10.net/forum/index.php?topic=1352.0

A10 GF '53 My A10 website
"Success only gets you a ticket to a much more difficult task"

Online bsa-bill

  • Wise & Enlightened
  • *
  • Join Date: Mar 2006
  • Posts: 5474
  • Karma: 64
Re: Blown head gasket
« Reply #2 on: 23.06. 2014 17:26 »
Hi Vic
Sorry to hear your problem
What kind of gasket was installed, I much prefer to the solid copper ones to the composite ones (asbestos type stuff sandwiched between thin copper sheet), I think they are more prone to blowing but will be taken to task by those who favour them  *fight*

Torque settings - I use 35 lb/ft, SS will have an alloy head (right) in which case make sure the correct washers are under the head bolts, and bolts need to be tightened up in the correct order - if you don't have that info shout and I'm sure we'll get ti in a reply

Ah now the pushrod tool - it's a help in aligning the pushrods while you drop the rocker box down onto the head, rarely goes exactly to plan so be prepared to jiggle the pushrods around with a finger or bit of bent wire, meanwhile the tool will be collecting as much gasket goo as it can just to annoy you, it can be a doddle or a pain just Keep calm

yes slacken off the rockers before removing the box, makes it a bit easier, leave them wound out then you can lift the rocker onto it's pushrod and then turn it down to keep it there
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline Briz

  • A's Best Friend
  • ***
  • Join Date: Apr 2013
  • Posts: 209
  • Karma: 7
  • West Norfolk UK
    • Custom cycle developments
Re: Blown head gasket
« Reply #3 on: 23.06. 2014 19:18 »
If you're skimming the head, the tappets would need resetting anyway.
Never use copper-asbestos head gaskets! They're junk.
Head bolt torque is related to the bolt strength so if 35 ft-lbs works on an ally head, it should work on an iron head.
Loose head bolts would definitely have caused gasket failure.
I never use a pushrod comb. More hassle than its worth, and it will disturb any gasket-goo you will have used.

Online orabanda

  • Wise & Enlightened
  • *
  • Join Date: Nov 2008
  • Posts: 1015
  • Karma: 21
Re: Blown head gasket
« Reply #4 on: 24.06. 2014 05:13 »
I use 32 ft lb.

very important that the surface underneath each bolt head washer is flat; often they need spot facing.

Also, the washers should be high tensile.

If the surface is not flat (dished), and / or the washers too soft, the bolts can work loose.

Shout yourself a new set of head bolts as well.

Richard

Online WozzA

  • Wise & Enlightened
  • *
  • Join Date: Nov 2011
  • Posts: 1307
  • Karma: 16
  • Melbourne Australia
Re: Blown head gasket
« Reply #5 on: 24.06. 2014 05:43 »
For my own information, should the head bolts be re-torqued after a certain  amount of miles / Kms?  *????*
'51 Golden Flash Plunger
'57 Golden Flash Swingarm

Melbourne
The biggest lie I tell myself is
"I don't need to write that down, I'll remember it"

Offline vwphillips

  • Moving Up
  • **
  • Join Date: Nov 2013
  • Posts: 23
  • Karma: 0
Re: Blown head gasket
« Reply #6 on: 24.06. 2014 10:50 »
Thank you for the feedback

orabanda

should all bolts have wyashers aqs only the four outer bolts had washers

Online bsa-bill

  • Wise & Enlightened
  • *
  • Join Date: Mar 2006
  • Posts: 5474
  • Karma: 64
Re: Blown head gasket
« Reply #7 on: 24.06. 2014 11:09 »
Quote
, should the head bolts be re-torqued after a certain  amount of miles / Kms

I'd say yes, head and bolts will settle after a few heat /cool cycles, was always the way although modern engines with finer tolerance and cooler running don't seem to need it.

I do torque mine up again after a couple of hundred miles sometimes you don't get much on a bolt (some bolts nothing) but the important thing is they should all be the same.

The washers come in sets to match the number of bolts Vic, so thereby maybe gives a clue to your head blow if the centre bolts had none and were slack
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online chaterlea25

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 3280
  • Karma: 47
Re: Blown head gasket
« Reply #8 on: 24.06. 2014 22:47 »
Hi VW,
Quite a few times I have found the washers embedded into the alloy head metal  *eek*
As Richard says the bolt holes will need spotfacing for the washers
I make my own washers 1/8th in. thick parted off from 3/4in. round stock, it  can take a while to do them as the parting  tool can flex and leave a tapered face  *doh*
chamfer the outer edge and deburr the bolt hole edges
Well worthwhile doing and theres never a budge on the head bolts afterwards  ;)

HTH
John
1961 Super Rocket
1963 RGS (ongoing)

Offline bikerboy

  • Valued Contributor
  • ****
  • Join Date: Dec 2011
  • Posts: 363
  • Karma: 4
Re: Blown head gasket
« Reply #9 on: 29.06. 2014 03:12 »
With an alloy head I torque to 30 leave it for 24 hours then torque it again. I personally have never taken the rocker box off to retorque the cylinder head and touch wood have never blown a head gasket. I do always use a copper head gasket never an asbestos type.

Online orabanda

  • Wise & Enlightened
  • *
  • Join Date: Nov 2008
  • Posts: 1015
  • Karma: 21
Re: Blown head gasket
« Reply #10 on: 29.06. 2014 05:57 »
Suggest you do (take a deep breath!) and take the rocker boxes off when re-torquing.

In my experiences, it is usually only the inner bolts that have loosened (the front two especially).

before using a new head gasket for the first time, I like to anneal them; sometimes they are too hard even as new.

I re-torque the head after 50 miles, again at 200, then at 1,000.

Well practiced at re-fitting the rocker box!

Richard

Offline vwphillips

  • Moving Up
  • **
  • Join Date: Nov 2013
  • Posts: 23
  • Karma: 0
Re: Blown head gasket
« Reply #11 on: 05.07. 2014 23:05 »
having to wait for valve guides and springs I had a closer look at the head gasket

In fact two were fitted(laminate type)

http://www.vicsjavascripts.org/BSA/HeadGaskets.jpg

any reason why two should be fitted.

The new gasket appears to be solid

annealing has been metioned, what temperature and how long?

I only have a domestic oven available.

Thanks Vic

Offline bikerboy

  • Valued Contributor
  • ****
  • Join Date: Dec 2011
  • Posts: 363
  • Karma: 4
Re: Blown head gasket
« Reply #12 on: 06.07. 2014 02:14 »
To anneal the ehad gasket heat it over the oven ring until it is cherry red then quench it on water, you normally have to do one cylinder at a time. after wards with some wire wool or something clean the black crud off and a slight scratch with your finger nail should show its soft enough

Online bsa-bill

  • Wise & Enlightened
  • *
  • Join Date: Mar 2006
  • Posts: 5474
  • Karma: 64
Re: Blown head gasket
« Reply #13 on: 06.07. 2014 08:08 »
two head gaskets - most likely to lower compression
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline The Artful Bodger

  • A's Best Friend
  • ***
  • Join Date: Dec 2013
  • Posts: 31
  • Karma: 3
Re: Blown head gasket
« Reply #14 on: 06.07. 2014 09:25 »
Or............. Back in the old days it wasn't an uncommon bodge to use two head gaskets when the head was distorted (quicker and cheaper than a head skim), I must confess I did it a few times on old banger cars to keep them running.
 Colin