DarrenW
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| posted on 20/1/06 at 07:48 PM |
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DIY TDC point
What i sthe best way to fairly accurately determine true TDC point with engine in situ and not removing any bits off engine? (ie heads etc, plugs and
easy 2 minute jobs are ok).
I heard of someone who made a probe that screwed into spark plug hole ........ dont know how to make or use though.
Cheers,
darren.
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SeaBass
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| posted on 20/1/06 at 08:02 PM |
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Dowel through the spark plug hole?? With pencil lines marked on...
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NS Dev
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| posted on 20/1/06 at 08:05 PM |
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You need a dial gauge, with some sort of extension glued onto the plunger on it, and some dort of rig (magnetic stand usually) to hold it in place
down the plug hole.
Obviously on the pinto it's all at an angle so is a tad fiddly but it will still work.
You get approx TDC, then put the gauge in with a few mm of "droop" travel left on it, then wind the engine one way until the gauge peaks
and then starts to drop again. Make a mental not of where on the dial gauge it starts to drop, then wind it back t'other way and do the same.
Once you have a rough idea, make it precise and set the pointer ring on the gauge at the point where it starts to drop on one side, and and make a pen
mark at the "drop point" the other side.
(you need to do all this because the crank moves quite a oong way for very little gauge movement near to tdc)
Once you have two marks on the dial gauge, wind the crank one way until the marks and pointer ojn the gauge line up, then make a timing mark on the
front pulley, then wind the crank the other way to line the other gauge marks up and make another mark on the pulley.
Set the engine exactly 1/2 way between the marks and hey presto, bang on TDC.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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britishtrident
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| posted on 20/1/06 at 08:06 PM |
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bit of 1.2mm welding wire --- don't use wood in case it breaks and a thicker rod could cause damage.
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SeaBass
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| posted on 20/1/06 at 08:08 PM |
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There you go... the long answers...
Ah a bit of timber in the combustion process never harmed anything... After all look at a woodburning stove!
I had fun looking at those autograss machines at Autosport International. Of all the things in the cheesy demo arena my father said he'd like a
blast in one of those the most...
[Edited on 20/1/06 by SeaBass]
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NS Dev
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| posted on 20/1/06 at 08:09 PM |
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.....................all depends on how accurate you need to be!!!
The visual methods can leave you a fair few degrees out. If it's a stdish engine that's no probs, but running very tight piston to valve
clearances and ignition very close to its limits means you need to be accurate to a degree.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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NS Dev
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| posted on 20/1/06 at 08:12 PM |
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quote:
Originally posted by SeaBass
There you go... the long answer.
I had fun looking at those autograss machines at Autosport International. Of all the things in the cheesy demo arena my father said he'd like a
blast in one of those the most...
Cool!!!
was a tad cheesy but the grassers kicked ass as usual!!!!
did you see the 600hp Wildcat V8 mid engined mini in the nasa area? I am supposed to be buiding a car to enter that class in 2007 but I am not so sure
now!!!!
I thought a 350hp supercharged 5cyl volvo engine would be enough in a Mini but maybe not then!!!!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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MikeR
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| posted on 20/1/06 at 09:04 PM |
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Wuuuuuuuusssssssssss
you already compete against people with 60hp more than you (youre 190ish vs the 2l lexus 260ish) and that doesn't bother you (ok, so
you've never actually beaten them)
now once you get to the difference between 350 and 600 hp in similar light weight cars the traction has to be the biggest issue (and driver) .......
you'll be fine....... just add in my mods. Now get on with it.
don't forget how much that lardy iron blocked v8 will weigh.
This is a public service announcement on behalf of the "i want to see nat race a real car" brigade.
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JB
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| posted on 20/1/06 at 09:48 PM |
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Finding TDC
I did read somewhere to use an spark plug with a tube down the middle with a soap bubble on the end, the bubble changes in size as the piston gets to
the top. Never tried it and not sure if it works.
When finding TDC there is a lot of crank movement for not a lot of piston movement around TDC. So you find a point before TDC where the piston is 2mm
down the bore and then a position after TDC where the piston is 2mm down the bore. TDC lies mid way between these two points. This is more accurate
than just trying to find TDC.
John
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rusty nuts
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| posted on 20/1/06 at 10:03 PM |
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Cut the center electrode from a spark plug, weld in a bolt so thatit sticks through into cylinder. Screw into no one cylinder after making sure piston
is at bottom of stroke. if possible attach timing disc to crank pulley bolt ,ensure timing marks are visible or fit stiff wire to align with pulley or
disc. Rotate engine backwards using spanner on crankpulley bolt or gently push car backwards in top gear until piston touches bolt . Mark pulley or
zero disc. Turn engine forward gently until piston touches bolt again, mark pulley or note reading on disc. Divide reading on disc or measure marks on
pulley, divide by 2 . remark pulley in center of 2 original marks . Turn engine to final mark or center reading on timing disc that is T.D.C. Long
winded explanation but simple in practice.
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Chippy
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| posted on 21/1/06 at 12:18 AM |
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If you require your TDC caculation to be near correct it's quite a complicated procedure. There is about ten degrees at TDC, were the piston
appears not to move. Burton Power do a nice TDC finder that screws into the plug hole, part No. DRA31491M, plus LMA079/M thread adaptor, only £7.50
and £3.70 + VAT, but you would need to have/borrow a dial gauge.
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Surrey Dave
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| posted on 21/1/06 at 10:37 AM |
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Measure with a dial gauge to say 5 or 10mm down the stroke each way then note movement on degrees wheel and tdc should be the halfway point.
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