Brutalac
Mini Owner
Joined: 21 May 2007
Age: 46
Mini: Ljubo Custom 12'75, GT/XE
Posts: 2172
Location: Novi Zagreb
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 Posted: Mon Oct 13, 2008 5:29 pm Post subject: Bregasta Timing (na Engleskom) |
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By Tom Fenton,13th May, 2005
Well today I have spent a few hours in the garage timing my cam in. I thought I'd write a quick guide on how to do it for those of you that are not familiar.
First off I made some supports to hold my engine clear of the bench to allow the crank to turn. I don't have an engine stand and I have not put the engine onto the gearbox yet hence the need to do this. I knocked these up out of a bit of timber I had in the garage.
Sorry for the poor quality, think I have buggered the pictures up when I resized them.
Next job I did was to check the piston to deck height while I had the clock out. This is worth doing to make sure that there is nothing drastically wrong with your build.
Firstly I set the clock up and zeroed it on the block deck surface.
Then I moved it to above the piston raised area, and then turned the crank till TDC was achieved on the clock. I was then able to read off the distance the pistons were down the bore.
As standard, I believe the pistons come to 40thou down the bores. My engine had the top of the block flashed to clean it, the deck height ended up at between 26 and 27.5 thou down the bores. I was happy enough that these were all close enough together.
I also checked the crank endfloat using the clock on the end of the crank nose, and lifting the crank against the thrust washers with a lever in the webs. I got 3 thou which is mid limit.
Next job was to check the cam endfloat. I did this again with the clock by placing it on the end of the cam with the nut tightened, and then lifted the cam carefully with a lever. I got 3 thou endfloat after I adjusted it, which is bottom limit.
After that, I also checked the timing gears for alignment, by setting the clock up on the cam gear tooth edge, and then carefully re-positioning the plunger over the crank gear. I found them to be 30 thou out of line and so I was able to correct them to within 2 thou using selective assembly with shims.
Next up was to fit my timing disc pointer. I made this some years ago by welding a piece of rod to the end of a 5/16 UNF bolt. I then filed a point on the end. The bolt is then screwed into one of the timing gear holes in the block, and a locknut used to secure it at the right length to meet the timing protractor.
I then fitted the timing protractor. I also made this a few years ago, by drilling a 5mm hole in the end of an old crank pulley bolt, and then tapping it M6. This allows the timing protractor to be bolted onto the large bolt. Simple enough but works well, as it allows the disc to easily be adjusted.
The next step is to find TDC using the clock in a similar manner as I did when checking the deck height. This allows you to set the protractor up correctly so as it reads TDC when the engine is at TDC.
Once I had done this, I put the clock in place to measure full cam lift. This allows you to then read off the protractor the point at which full lift occurs, and hence adjust your timing wheels to get full lift where you want it. On the cam I am using full lift was recommended to be at 110 degrees. You will notice I am using a length of stainless rod down into the follwer, usually I would use a pushrod but the ones I had with this engine were fubar'd so I binned them long ago. I have yet to get any more hence had none to use to do this with! If anyones got a set of GOOD pushrods (e.g. no 'pip' on the end due to wear) they want to sell PM me!
There is a little variation to be done on most cams, as most reach full lift and then dwell for a short period, maybe 10 or 15 "crankshaft" degrees. My cam was no exception. Therefore it is needed to take a reading of when the cam first reaches max lift, turning the engine in both directions. For example, if a cam was theoretically supposed to be at max lift at 110 degrees, but had 10 degrees dwell, then you would set it so that it reached max lift at 105 degrees, and stayed there till 115 degrees, hence 110 being the mid point of the full lift period.
I have read a few other methods of timing cams in, but that is the one I use and it seems to have worked fine when I have done it in the past.
Cheers! Tom.
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gregor.tm
Mini Owner
Joined: 08 Jun 2007
Age: 53
Mini: MK1 traveller 66, mini turbo, ženin mini ;-), Elf, Spity,...
Posts: 998
Location: Maribor SLO
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| Posted: Tue Oct 14, 2008 7:14 am Post subject: |
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he, he, tom fenton autor èlanka ima jednog najeèih turbo minija i dobar prijatelj carl austina ta se i vidi po njegovom autu.
bravo Brutalac, kako si se samo sjetio njegovog èlanka.
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