Engine Rebuild - 12G295 Cylinder Head Strip Down
Turbo Mini Forums

Hi everyone!

I am going to rebuild the 998 engine from my first mini build. It was quickly rebuilt about ten years ago with a 12G295 head and a Kent 266 cam and after three years of abuse was switched out for a rebuilt 1330. It has since been standing in the garage in the way!

I am going to start with the head. Here are some pictures of what it looks like at the moment.









Any recommendations on what to do with the bypass take of? I was thinking about doing away with it by screwing it out and threading it for a plug but am a bit nervous about it destroying itself on the way out. Anybody done this?



I managed to get all of the studs out exept one....



One of the thermostat bolts sheared off I have been applying penetrating oil and have ordered a left hand drill bit and an easy-out- The easy out doesn't fill me with confidence and I am hoping that if I heat the area a few times with a heat gun and then use the left handed drill bit to drill a hole through the center it will bite and come out without the easy-out! Any tips? Is this the best way to get it out?

Edited by kitch on 5th Sep, 2014.

pics dont seem to work mate

not sure if you mean the bypass to the water pump under the head at the back?
if so they can be a real bastard to get out ive got then out by gently die grinding it till the threads just brake thew then grab it with some ling nose pliers if you do it right it comes out in a spiral like a helicoil

as for the stud if you have a tig perhaps weld a nut on it? altho all the oil may make it hard to get a solid weld with all that nasty boiling up lol

maby if you can get the drill nice and center it may weaken the wall thickness enough that the heat and cooling may shrink the bolt

Hopefully the pics work now! The stud has snapped off just above the mating surface! Can't get anything on it...

Is it really necessary to have the bypass to the water pump? Is it advisable to get rid of it?

Evan with a stud broken flush with some skill it can be plug welded to something that can be grabbed with vice grips of something

the factory bypass is to keep coolant flowing while the engine heats up from cold to the temp of your thermostat with out it you may have problems getting to flow and open the stat

if it was to be blocked off you need to drill some holes in the stat to allow the pump to push coolant threw the engine but this will make it take a bit longer to heat up imo

drop an oversize nut on and spadge a load of weld down the middle and try undoing it?

looking at that stud if may be possible to thread a nut on by hand?

coolant jacket looks nice n clean !

Edited by Turbo This.. on 30th Aug, 2014.

I am going to strip the head down before I attack the snapped stud and was wondering whether anyone has seen the collets retained using wire like this?



Anything to watch out for when removing them or just compress the spring, unwrap the wire and remove collets.

I've never seen the collets retained like this before!

Edited by kitch on 5th Sep, 2014.

well thats a new one on me, normally these collets have a spring clip on them, one of these...

http://bullmotifminispares.com/2043/clip_valve_collet_2a12

When I block off that bypass stub all I do is grind it flat and then tap a thread and put a short bolt in there -with some JB Weld.

Did you ever have the engine rr'd last time round kitch? If so what power was it running?

Jack Jones

I would just use the bypass rather than try to block it.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I never use the by pass hose -- and no problems so far.

you standard head will make some good power if you get your compression right, but a modded one will be a fire breather, the bodge wire on the collets need to be removed if you want the original clips please pm me as i have many.

those top caps look lightened too perhaps someone was on a mission

Hi guys,

Thanks for the replies to my previous questions!

I'm still getting some work done but on a spare head to practise before properly starting on the 12G295.

I have been looking out for parts for the engine and am not sure whether to source a HIF38 or HIF44 carb....

The plan is to rebuild the engine with a 266 or SW5 cam with 9.5:1 CR and standard reconditioned rockers. Which carb should I go for?

Edited by kitch on 19th Sep, 2014.

Hi guys,

Been a while since I posted here but have recently started tinkering with the engine again.

I have stripped the timing cover down as it was a bit manky. Was wondering what the bracket is for in the lower half of the picture (not the bracket with the teeth). Ii is really rusty and I am wondering whether it is worth the hassle of cleaning it up or should I grind it off?



Looked at all the alloy offerings and they only have the toothed markings....

Cheers,
Mark

I have just dug out the timing chain and the crank damper. I have three crank bolts and am not sure which one to use. Why are the hexagonal bolts different? One has an extra shoulder...why and which is better?

Also I am not sure whether to just get a new chain and leave the sprockets? Any opinions?

https://drive.google.com/folderview?id=1Run...tueKmQhcuEvZkKc

Edited by kitch on 15th Jul, 2019.