machining pockets
Turbo Mini Forums

Wondered if anyone had a template for machining pockets into 998 block to accept 12g940 head?

cheers

998 turbo in progress.... DONE..........KNACKERED LOL

there was one floating around on MF a year or so ago (maybe more), one you could print off and use as a template i think.

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

right oh cheers bud

998 turbo in progress.... DONE..........KNACKERED LOL

Set your 1275 head onto it, and let the valves mark the head with some sort of marking compound ( remove springs obviously )

I ground mine out using dopey grinding stones and a drill. First time around I didnt seal off the cylinders properly, and after a few miles, my rings were knackered :S

Didnt do that again !!! I taped off the cylinder, twice, to ensure no grinding dirt got anywhere near the pistons.

Or you could just grind as far to the 1275 gasket line as you can, smoothing a lot bigger than the valve head itself, Might help de-shroud the valve from the bore.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

thank for that, the university technician and i are going to use the CMM machine to measure the centre distance and diameter of the pocket in relation to the centre of the bore on my knackered block to get the accurate offset. taking the a tangent of the bore as a datum. I've only used the machine once before so i'm not really confident i'll get it right Was hoping there would be a template on the web i could just input the co-ordinates into the vertical mill and go for it.

998 turbo in progress.... DONE..........KNACKERED LOL

On 5th of Feb, 2007 at 09:29pm chappers said:
thank for that, the university technician and i are going to use the CMM machine to measure the centre distance and diameter of the pocket in relation to the centre of the bore on my knackered block to get the accurate offset. taking the a tangent of the bore as a datum. I've only used the machine once before so i'm not really confident i'll get it right Was hoping there would be a template on the web i could just input the co-ordinates into the vertical mill and go for it.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

The Des Hamill book states that you should use a 35mm dia flycutter and cut between 5 and 6mm into the bore wall, depending on valve size.

Depth of cut depends on valve lift.

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."

The pockets are off centre from the bore though. Luckily i have a block to take measurements from. When i get some i'll post a template on this website.

This week i put some new cam bearings in the new block, i'm going to tap the 1/4" holes on the underside to the next size, make a centre main strap and have a go at milling a dish in the pistons. Not sure what size yet though as i haven't calculated the CR.

998 turbo in progress.... DONE..........KNACKERED LOL

Alright, i got the measurements done on the CMM to 4 decimal places!! Centre of the bore is the datum and the offset is to the centre of the pocket. this one is for bore no4+2 just invert the measurements for No3+1.

http://www.turbominis.co.uk/index.php?p=20&id=3301

Edited by chappers on 21st Feb, 2007.

998 turbo in progress.... DONE..........KNACKERED LOL

"The Des Hamill book states that you should use a 35mm dia flycutter and cut between 5 and 6mm into the bore wall, depending on valve size.

Depth of cut depends on valve lift."


Referring to this topic I did the pocket milling yesterday:

http://www.minifreunde.at

How much did You cut into the bore? It looks something like 3-4mm.

1,8mm deep, 5mm wide.



The deepness is measured to my cam/cylinderhead, so i think it`s variable to any other engine...

http://www.minifreunde.at

**Depth.. lol
Machined them into a built engine?? ..Nutter.

Hey guys sorry for reopening an old thread and all.. but i have a question.

If the block is pocketed for a 1275 head is it then still possible to use a 998 head? Or do i HAVE to use a 1275 setup from then on?

nope you can use a 998 head, just your compresion ratio will be a bit lower and chamber shape will be less than optimal. but it will run.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.