Jump to content


Photo
- - - - -

Head gasket and head..


  • Please log in to reply
40 replies to this topic

#1 miniman5

miniman5

    1 Gold star

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 3,135 posts

Posted 27 March 2005 - 03:37 PM

hello! my head gaskets gone, theres mayo in the rocker cover and there is presure commign throught the rocker cover. im going to hope fully do this next weekend, dad said that he had a 998 with an 1100 head on it as the ports are the same size but the valves are bigger, so where after an 1100 head,


ok i no theres leaded heads and unleaded heads but what is the differance is it the bronze valve guids or any thing liek that? if it is would it be had to get new valves etc and fit them in???

any tips on doing the head gasket would be much apreshated! and also where i could get a 1100 head, ive looked on ebay under, 1098 head, 1100 head, austin 1100 head any way you get the picture!!


guessworks i aint been able to get hold of you but have you got an 1100 head or block knoking about?? i also need trhe rocker gear to!

this is urgent! i want to do it this weekend iff i dont then itler never get done because of my gcse's that im about to take


Also if im keepign the block a 998 then do i need a 998 or a 1098 head gasket?
Thanks alot u lot! Tom!

#2 miniman5

miniman5

    1 Gold star

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 3,135 posts

Posted 27 March 2005 - 07:56 PM

arghh come on some one must have one...

#3 Dan

Dan

    On Sabbatical

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPipPipPip
  • 21,354 posts

Posted 27 March 2005 - 08:04 PM

998 and 1098 engines are exactly the same, except for the stroke of the crank and the piston height.

Your dad might mean that he had the head from an 1100, which was a model of car from BL and which did generally have better tuned engines (especially the MG version which had a better head but it's not to do with valve sizes, it's the actual casting which is better) but it's not a direct swap for the 998 head as you need to skim about 18 thou off the thing to get it back to decent compression.

Unleaded heads have steel valve seats and unleaded compatible valves fitted. Nothing to do with the valve guides. It's not a conversion you can do at home as it needs some pretty good machine tools and a skilled engineer. And some liquid nitrogen too.

There's no tips for changing a head gasket really, it's fairly easy. Just do what it says in the book. Only takes about two hours unless something goes really wrong!

Good luck.

#4 miniman5

miniman5

    1 Gold star

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 3,135 posts

Posted 27 March 2005 - 08:07 PM

hello i read that the ports are the same but the valves are bigger my dads mate had a 1100 head on hsi and it made it loads faster "went like poo of a shovel" lol

#5 Dan

Dan

    On Sabbatical

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPipPipPip
  • 21,354 posts

Posted 27 March 2005 - 08:19 PM

I run the MG1100/Cooper 998 head on mine. And yes the standard inlet is a little bigger (Mine are now a lot bigger, :grin: ), but the main benefit is the design of the combustion chamber.

But that's only an MG1100. An A series 1100cc engine from a Clubman estate uses axactly the same head as a 998 engine of the same age.

#6 miniman5

miniman5

    1 Gold star

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 3,135 posts

Posted 27 March 2005 - 08:20 PM

ok so what do i need to look for
??


i think dads mate had hsi head off an austin 1100

#7 Dan

Dan

    On Sabbatical

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPipPipPip
  • 21,354 posts

Posted 27 March 2005 - 08:39 PM

Heads with casting numbers 12G295 or 12G206. But like I said it's not a straight swap, these heads are designed for high crown pistons which actually protrude from the block face and into the head at the top of the stroke. So with conventional pistons which stay within the block they will have very low compression. You need to have the cylinders buretted to find out how big they are currently (they should be 28.3cc but many of these heads have been adjusted in the past) and then get the head skimmed down until the chambers are the correct size for the compression you are after. A standard A plus 998 has chambers of 25.5cc so you need to lose about 3cc which normally means skimming off about 18 thou. You might get lucky and find one which has already been skimmed down. These heads were not unleaded as standard so you may also need to get it converted to suit.

These heads are great. The chamber design is very open so it's kind of like a head which has been modified by someone for you, with the added bonus that extra work can still be done to it.

Any small bore head gasket will do but try to use the copper one which used to be called TAM2121 'because it's brilliant.

#8 miniman5

miniman5

    1 Gold star

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 3,135 posts

Posted 29 March 2005 - 07:44 PM

regardign the smokey start, since me n guessworks did the tappets it dont do it any more! :grin:

#9 miniman5

miniman5

    1 Gold star

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 3,135 posts

Posted 30 March 2005 - 08:11 AM

hello ive found a 12g295 head wich i beleive is a 998 cooepr head but! its just the head no valves etc...

ok in mini sport catalogue these are some prives i found

ok what would i need ?

i know ile need:

valves £17.50

valve guides £10.95

oil seals ??

valves springs (998 cooper double) do i have to have double? £23.95

collets can i use the ones i have already?

rockers??? could i use the rockers of my 998??

Do you think its best to do it like this or buy a complete head? but if i do that then itle need to be converted to unleaded, where as if i get all the parts then it wont? which would work out cheeper??

infact what can i salvage of my 998 head at the moment? to put onto this one if we get it?

from the bits i can think that ile need its guna be cheaper than buying one and gettign it converted to un leaded what you lot think?

#10 TimS

TimS

    Mini Doctor

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 2,712 posts
  • Local Club: TMF

Posted 30 March 2005 - 09:44 AM

you can use the existing rockers, no probs, collets should be interchangable but it depends on the valves you get as there are different types.

If you look around you will brobably find cheaper prices than minisport(im quite sure of it) i thinkl the best thing to do would be to go to an engieering shop like morspeed and speak with the person there, they will b able to supply you with all the parts and fit them. I had larger inlet valves put in while i waited :P

#11 Bungle

Bungle

    Original Spamster

  • Members
  • PipPipPipPipPipPipPipPipPipPipPip
  • 28,971 posts
  • Location: Cornwall
  • Local Club: cornish mini club

Posted 30 March 2005 - 09:46 AM

if you have got to buy new valves get some rimflo valves they flow much better

#12 TimS

TimS

    Mini Doctor

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 2,712 posts
  • Local Club: TMF

Posted 30 March 2005 - 10:47 AM

and alot more expensive.. do you understand how they work

#13 Bungle

Bungle

    Original Spamster

  • Members
  • PipPipPipPipPipPipPipPipPipPipPip
  • 28,971 posts
  • Location: Cornwall
  • Local Club: cornish mini club

Posted 30 March 2005 - 05:11 PM

rimflo valves flow better because of there shape , because of this you can use smaller valves that flow the same amount as a bigger valve .

my mini sport stage 4 head has valve sizes 35mm and 31mm

but a stage 3 head has 37mm and 29 mm

so why do you whant smaller valves ?

because the valves are smaller the air moves quicker and this you more torque .

#14 Dan

Dan

    On Sabbatical

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPipPipPip
  • 21,354 posts

Posted 30 March 2005 - 05:47 PM

Rimflo were the best valves available about 20 years ago. This is no longer true.
Like ISKY valve springs, were great, now just like everyone else. The best flowing valves available for Mini's at the moment are MED 6mm stem valves I think.

You will still need to get your casting machined to make it unleaded compatible Miniman5. The valve seats are a part of the head casting which need to be cut out and replaced. And it needs skimming like I said before, the Cooper 998 was a very different engine to your 998.

I agree with Flappy, take it to a good Mini engineer and ask them to fix the head up for you. They will also more than likely give you the best prices for the valves and stuff. You probably don't need double valve springs, these are to prevent valve bounce at high RPM in high compression engines. Without doing other work to your engine you can't go past 6500 rpm anyway so it doesn't matter. All they'll do is increase internal friction and valve train loading and so cost you power. Get some slightly stronger single springs instead.

If your current head is not unleaded then you don't want to keep the valves as they won't be unleaded compatible.

The casting you have is good and valuable core, so it's definitely worth getting it looked at. It will be just as good as a 'stage 2' (whatever that means) at least, without any porting or flow bench work due to it's better design.

Flappy, Simon has done an unleaded conversion and a skim on a 12G295 for me while I waited back when he worked for MED. He's good isn't he!

#15 miniman5

miniman5

    1 Gold star

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 3,135 posts

Posted 31 March 2005 - 03:48 PM

hello where jsut guna kleep the standard head ok do i use all the gaskets dry? or do i need sealant stuff? if i do what should i get???




1 user(s) are reading this topic

0 members, 1 guests, 0 anonymous users