Excellent.
It takes a lot to do all this posting so thanks for all the effort.
Invaluable.

Graham

 

Thanks Graham.
I'm not finished yet!!!

Lots more to come

Daz

 

Plus the 'How To' book I hope!
Graham

 

Funnily enough I have seriously considered that!!!

 

Great work again Daz.

Another easy way to lap the valves in is do it from the other side of the head. find a bit of pipe that is a snug fit over the stem and pull the valve up into the seat as you lap. You dont suffer from yhe dolly sucker loosing grip on the valve face then. If you cant-contra rotate the head (i.e its just spinning the same direction) they dont lap in very well at all.

RE the collets. Get yourself a magnet on a stick the next time (of course i hope there is not a next time ) and just engage the collett with the magnet and then knock it off with a screwdriver. you will have a head done in 10-15 mins.

I will ask again........Please can you tell me where you get the engine paint from!

 

Erm am I missing something, you need to reshim the valves now!! and I havent seen any mention of that

PS Good to meet you.

David

 

Also - dont even bother wasting time trying to shim it up accurately with the heads on the bench. The only way is with it built up on the block.

The clearances move all over the place when you torque the heads down - quite amazing the squash/distortion in an ally head under torque!

 

Sorry mate keep eluding that question don't I? Not intentional!!

I have used two lots of paint. Both from Halfords as I got let down on the motorbike stuff. I have no idea what the results will be like once the car is running at 2bar lol. However I have used a matt black VHT paint from halfords. This tolerates upto 500 degrees c (direct) and then I have used a gloss black enamel. This takes upto 150 degrees c direct. I used a similar method on my MR2 Turbo and the paint remained intact. Only time will tell.

 

I was aware the valves will need to be shimed. I was also aware this was best done with the heads torqued up. That won't be done until I can afford some ARP head bolts.

Once the ARP's are in place then I'll get the feeler gauge out and start the shiming process.

Got a gearbox repair to pay for this month. So the ARP's may have to wait a while.

Daz

 

Thought I would be first to rate this thread

Keep up the good work

 

many thanks bob you're a gentleman

 

You don't need to torque he heads to shim them.

 

really, you sure, Im sure we used to torque heads, ahh no, doesnt make a noticeble difference, even on a race engine!!!!

 

phew.. for a minute I thought the guy who shimmed my heads who has been building race engines for 30odd years was wrong...

 

mmmm.. i shimmed up before installation of heads (in the hope they would not move and scoob heads were more stable than other engines i have worked on), then checked after installation and i had up to .05mm error

 

Are you sure your measurements were that accurate to begin with?

I checked mine after my studs were tightened and they were still within tollerance.

 

Yeah dead sure David. from building race bikes engines for years i have a set of 0.010 graduation feelers so its not far out. of course 50 microns is within the acceptable tolerance so as you point out it will not be easy to spot with normal 0.05 feelers

Interestingly at work we see the same thing. we have to produce an engine every 4 mins so this is all automated. we do a range of engines from 2 cyl (with a head similiarly stubby to a scoob) up to longer, less sturdy 3 and 4 cyliders.

the valves, spring seats, springs, retainers and collets are built up and then the head is placed on a plinth and slid into a CMM (cnc measuring machine if you like). Each respective bucket is placed upside down on that plinth, along with the respective cams.

The probe then dibs on each valve top, each bucket, and the BCD of each respective cam lobe and then shows the operator the shim required which he can drop in before the buckets.

In this program is a lot of 'fiddle factors' - offsets for each particular valve assembly at each point of each model engine. These are basically worked out by trial builds i.e pre model release builds whereby the prog runs, it gives the shim sizes and then after building the engine it is checked to see how far out they are and then the fiddle put into the program.

The variance is not consistent over a single head - it depends on the flexibility of the casting at that point and they tend to deviate more in the centre of a head than the outside. Cant remember the 'fiddle factors' exactly but i have heard up to .075 mm at certain places on the most flexible castings - which i assume is a 4 cylinder.

 

No problem, you know where I coming from with feeler gauges then

I got 'told' about cheap feeler gauges, my Dad being an engineer threw my old ones in the bin!

 

Blimey now I'm really confused can someone talk me through the process of measuring these valve clearances. Mark did your thread have any details on his when you polished your heads??

Any help with this greatly appreciated.

Daz

 

Lets put it this way, it wont do any harm to shim them whilst they are torqued down.

 

There is details on there yes Daz.

Or........Shim them on the bench, then check them when heads are on the block. With a bit of luck they will all be fine, but if they are not its no great shakes to change the odd 1 that might need it.

sorry for the confusion

 

That sounds sensible!
I wonder what API do?
Graham

 

get yourself abit of paper, put 4 circles on representing the inlet side, and 4 representing the exhaust side.

measure each shim with a metric mic, write this size in the appropriate circle, then put the shim in the relavent retainer and put the relevant bucket over it obviously oiled (or preferably molyslip/assembly greased) up.

install your cams and caps, torque them down carefully.

measure each gap as accurately as you can with feelers (between the bucket and the BCD of the cam - obviously you have to turn the cam for this so if you are doing it on the bench watch out for valve collision between in/ex)

Write this gap down on your bit of paper uderneath the relavent circle.

clearances you are after are 0.2mm(0.008") inlet, and 0.25mm(0.010"). Im not actually sure what the tolerance is as i like to get things absolutely spot on but most engines are +-0.05mm. hopefully someone can confirm.

if you have a clearance of say 0.27mm on an inlet valve, and you know that you have a 2.05mm shim in there, a bit of maths will tell you that a 2.12 shim is required in that location.

with it all written down you will be able to move shims around to different places, and you may get away with only buying/grinding a few down. If you know anyone local who builds engines and has a load, they may just let you exchange with them.

 

Brilliant Mark. Can't thankyou enough. This is whats scooby net is all about fantastic!!

Daz

 

Disagree. SN for me is about threads like these in this forum. full of guys having a good bash themselves and refreshingly devoid of muppets!

 

Yes I would concur about the lack of muppets in projects atleast!

 

It's work noting that you only have to nip up the cam caps on the subaru, as they only have 2 cylinders per cam, which means that that you don't need to have any valves open to measure the clearances, so no valve collision issues regardless of piston postion (and no valve-valve collision as it's seperate cams).

0.05mm is a huge margin of error when shimming the heads, I would usually settle for +0.01 -0.0mm or if it can be easily acheived, absolutely spot on.

If the heads were 4 cylinder jobs, then I would do down the route of shimming after torqueing the heads. I prefer not to on a subaru as you have to start spinning the engine round on the stand (but it's purely personal preference. In my experience of shimming subaru heads, they are within 0.005 (5 microns) of the untorque clearances when torqued up.

Of course if you were to try that on heads or a block that wasn't actually flat, then you would get different results!

Also worth noting that I find it easier to work in thou as the numbers are just more friendly.

Paul

 

Just noticed something that I missed being the total novice I am.

Just about to put some pics on and I noticed that the locators on the block for the cylinder heads or gaskets were missing. I dont know how essential these are. Can I get away without them or do I need them. The reason I am asking is that I have already put the heads on and torqued them up. Here's a pic with rings where I think they should be when compared to Steven's similar pic.

Mine http://www.scoob.co.uk/rebuild/cylin...tharpbolts.jpg

Steven's
http://www.scoob.co.uk/rebuild/stevens.jpg

If I do have to get some put in will I be able to reuse the head gaskets considering they havent been used or would the fact that they've been torqued up mean they need replacing?

Thanks Guys

Daz

 

From an engineering point of view the spacers are essential!
They 'square' the heads to the block, to the cam drive belt and anything else related to the block/head alignment!

As to reusing the gaskets.....not sure i would take the gamble myself.

Sorry to be negative.

Graham

 

the dowels are essential, you can probably reuse the gaskets, but without the dowels there is no guarantee they will have crushed in the same way. If block and head are both properly flat is shouldn't be a problem, max clamping load is only acheived when hot.

Glad to see the studs arrived okay.