Little engineering project for someone?

[M3GTR]

Hi all

I need some help from someone who has access to engineering tools like lathes etc and also likes an engineering challenge!

I need to build some kind of measuring device that can be used to measure the bdc (bottom dead centre) length of stroke in an M20 engine so that I can compare (and identify) a 2.7 engine over a 2.5 engine without taking the head or sump off!

Current thoughts are around using a spark plug or similar metal body that would screw into the spark plug hole. Mounted into this would be a tube that will allow a flexible metal cord e.g. plastic coated net curtain wire, to be threaded inside. Once inside the chamber, the guide tube would be shaped to guide the flexible wire directly onto the top of the piston in the middle.

To measure, the assembly would be calibrated first (flexi wire marked up at the point where the wire enters the tube) against a known 2.7 engine and known 2.5 in the hope that there will be enough difference between the two marks on the wire to positively identify a 2.7. In use, the body and guide tube would screw into the spark plug hole (so the guide tube inside the chamber must be able to both pass down the spark plug hole and also rotate once inside) and the wire passed down the tube. The engine would be manually rotated whilst holding the wire against the top of the piston until you find bdc and check the calibration marks.

If you haven't already guessed, this tool is required to police the use of 2.7 engines in racing where they are not allowed. If there's anyone out there with engineering know-how who would be willing to take on the project, your help would be much appreciated and may even be rewarded if I can drag some cash out of the club!

[karlp]

These are my thoughts to help you.

No need to calibrate first as you will find it difficults to get any two engines to line up to the mark on the wire.
Use a flat flexible 'rod' within the 'spark plug'. On this rod have markings at every mm interval.
Place tool in engine and place at TDC (off flywheel). Note marking on rod (eg. 10.6).
Turn engine to BDC (mark on flywheel). Insert rod further and take reading. (e.g. 80.6).
Stroke measured.
This setup will compensate for skimmed heads, different piston crown heights and also different spark plug thread lengths.
The stroke lengths for 2.7 and 2.5 are known.

Another idea would be to set the engine at BDC insert tool then turn engine by hand at least past the TDC mark and the markings on the rod would automatically give you stroke.
Obviously would need to put some protective object on the bottom of the rod to prevent complaints of scratching piston crowns of these engines.

Just some thoughts.

Karl

[Ant]

I'm with Karl on this, there is no way to hide the extra stroke length on these engines, the net curtain wire seems the obvious choice here for material. It would be easy enough to remove the ceramic sections from an old spark plug and insert a guide tube for the wire.

Its a good idea, I know lasy year there were grumblings about a few competitors sneaking an extra 200 cc under the wire:lol:

did the dyno not provide the data as intended Paul ?

[M3GTR]

Thanks for the pointers guys... I think you're right on measuring overall stropke instead but I guess the principle of the tool itself is pretty sound.

There's always rumblings of there being 2.7 engines being used, so this is just a long overdue way of policing them withouth having to go to the expense of stripping an engine to measure it. The dyno gave figures for the start of the year, but this is a tiool that can be used ad-hoc to check. Dyno results can be artificially reduced lots of ways (but of course nobody does that

Still need somone to make the tool though....any takers??

[racecar]

pm sent - gotta m8 who reckons can help - he cannot get on zone at work for some reason - have sent contact details
ross

[billgatese30]

what angle does the spark plug enter the head in realtion with the vertical line of the cylinder?

[M3GTR]

pm sent - gotta m8 who reckons can help - he cannot get on zone at work for some reason - have sent contact details
ross

Nothing in my PM box mate. Might be best to email me.
Cheers
Paul

[M3GTR]

what angle does the spark plug enter the head in realtion with the vertical line of the cylinder?

Not sure mate.. I haven't got access to the tech specs of the head cross section and no time to do a mock up. I'm guessing it isn't too sharp an angle though by looking at it.

[billgatese30]

so long as it isn't too sharp an angle other wise your rod will have to be flexible to avoid hitting the cylinder wall and not getting to the cylinder face

if made too flexible then it may give varying results.

too stiff, and it won't flex down the side of the cylinder and it will therefore not measure the bore accuratly

should work actually, had a quick look to try and see some head photos and it looks like you could get away with it quite easily.

[Simon13]

will have a word with my old man, right up his street.

If only i had my 2.7 built. Then i could do it all for u as have 2 325's at them moment. But one will be 2.7 in the next few months/years!

[racecar]

guys email address is dc@cham.co.uk - name david cottrell

[Project_E30]

I can do it if you want.

Could you do a draft drawing, even a scanned scribble so I know exactly what you want.

Cheers