Is there such a thing??
I had a quick look at it tonight & after reading the boards and watching that 2 minute clip on youtube i'm still none the wiser?
If any of you would be so kind to spell it out nice and simple for my dumb a$$ i'd be delighted?!
To start with you need a degree wheel , dti gauge and something to make a pointer out of, welding rod or coat hanger as you can see here.
You need to start by finding tdc, can be done two ways but I find the best way is to use the piston stop method, you can make one out of an old spark plug by knocking out the centre and tapping it to use a piece of threaded bar or you can buy one ready made just like this one
http://m.summitracing.com/parts/cca-4795/media
Or here is mine and you may borrow it if you ask nicely.
Now with your degree wheel fitted with all of the other plugs removed turn the engine to find the rough tdc, I find a straw comes in quite handy here. Now fit you piston stop, then turn the engine until the piston comes to a stop, look at you degree wheel and note the degrees
Next turn the engine the other way until it comes to a stop and again note the degrees
Take these two readings and devide the difference by two or work out the half way point in between in my case I had 7 degrees atdc (after top dead centre) and 7 degrees btdc before top dead centre, being a honda motor it's round the other way as the engine turns anti clockwise. Now when the degree wheel is at 0 degrees we have perfect tdc. Don't worry if you numbers don't look like mine as said above devide the difference and what ever that number is is your tdc, without moving the engine position you can adjust your pointer to point at 0 degrees to make things simple.
From here on will change weather you have a twin cam engine or a single cam but the principles are the same. You now need the spec(s) that cam with the cam(s) you brought.
Here are the specs from piper for the common bp270 and bp285 for th c1j and also for some odd the f series engines.
http://www.pipercams.co.uk/pipercams...anufacturer=19
You may need to make some sort of fixture kit to hold the dti gauge, some mild steel plate can be useful here as the mag mount base will stick better to steel than aluminium!!!!!! At this point you need to make sure that the shaft of the indicator is travelling in perfect parallel with the valve and be on the valve retainer and not on the rocker arm as this has a built in ratio which will mess things up, also worth setting the valve clearances at this point to nada, nothing edit bollocks just lost the lot I typed out!!!!!
Last edited by rs250nut; 05-01-2013 at 02:01.
Even Steve can't fook this one up!
What engine are you working on Steve twin cam or single cam c1j?
Steve, I'll pop past next weekend & time up the cam if you want?
Thanks for the infoOriginally Posted by rs250nut
It's just a lowly C1J I'm doing
Yeah I'm all up for that mate! Just want to make sure mine is done ASAP so the engine crane is free
Steve, I'll pop past next weekend & time up the cam if you want?
Thanks for the info Jon, but its still not 100% clear!couple of questions:
- I know the engines TDC as I marked a position on the crank sprocket & block. I'm a little lost about this whole piston stop though? If you put the piston stop in at TDC then surely I won't stop the engine from turning at its at TDC??
- The protractor wheel goes on the crank right?
- What am I measuring with the DTI?
Leave of as much stuff which will cause friction, ie leave out plugs, don't have the rocker assembly in place as it can be quite tricky to get accurate readings from the DTI as you're working to very small tolerances.Thanks for the info Jon, but its still not 100% clear!
- I know the engines TDC as I marked a position on the crank sprocket & block. I'm a little lost about this whole piston stop though? If you put the piston stop in at TDC then surely I won't stop the engine from turning at its at TDC??
Assuming that your TDC mark @ the crank is correct then don't worry about the piston stop.- The protractor wheel goes on the crank right?
When you're @ TDC (compression stroke!) off your marks, stick the protractor on the end of the crank, use your wire / welding wire etc and point it directly at 0degrees TDC.- What am I measuring with the DTI?
You are measuring lift of inlet valve number 1, 2nd valve in from the flywheel. It's really quite easy to understand once you've done it a few times.
Give us a shout when doing it if you're still stuck.
07508471903
I know the engines TDC as I marked a position on the crank sprocket & block. I'm a little lost about this whole piston stop though? If you put the piston stop in at TDC then surely I won't stop the engine from turning at its at TDC??
-Assuming that your TDC mark @ the crank is correct then don't worry about the piston stop.
The protractor wheel goes on the crank right?
-When you're @ TDC (compression stroke!) off your marks, stick the protractor on the end of the crank, use your wire / welding wire etc and point it directly at 0degrees TDC.
What am I measuring with the DTI?
-You are measuring lift of inlet valve number 1, 2nd valve in from the flywheel. It's really quite easy to understand once you've done it a few times.
Leave of as much stuff which will cause friction, ie leave out plugs, don't have the rocker assembly in place as it can be quite tricky to get accurate readings from the DTI as you're working to very small tolerances.
Give us a shout when doing it if you're still stuck.
07508471903
I would never trust some marks on the pulley, do it right with a degree wheel, with the piston stop in the engine it will never reach tdc as you are stoping it just short, and the same happens when you turn it the other way, you end up just shy of tdc. Mid way between these two points is bang on tdc, for example if you turn it clock wise and end up at say 17 degrees btdc record this, next turn the engine until it stops in the other direction say you have 11 degrees atdc, what's the midway point between these two reading on your degree wheel? 28 devided by two is 14 now with the piston stop removed you can reach tdc. The degree wheel will not be reading 0 degrees it will be at 3 degrees now, without moving the crank either move your pointer to 0 or adjust the degree wheel. This is the most important part of degreeing in a cam,if you don't get this right everything will be off.
The next part can be done a number of ways, this is the easiest way, set your dti up on number one bucket, an extension on the dti may be useful here or use a push rod centred in the bucket, find the base circle of the cam shaft, the round bit without the lumpy bit on, next turn your degree wheel to what the cam manufactures says peak lift should be at, as in my link in a previous post this should be 112 degrees atdc, now loosen your cam gear bolts and turn the cam shaft without moving anything else until you see the highest reading on the dti gauge. This is now bang on full lift where it should be. You could go one step further and find the centreline of the inlet profile yourself, but this maybe one step to far at this point.
All this said and done now its best advised to book some dyno time to properly dial in the cam to find out where your engine likes it best, don't go to far without measuring p2v clearances in the case of a c1j or both v2v clearances and p2v clearances on a twin cam engine.
Last edited by rs250nut; 05-01-2013 at 17:13.
I'm missing something here - if you're timing in on bucket number 1, your timing an exhaust lobe are you not?
I'm no expert but when I timed mine in I did it on bucket number 2 which is piston 1 inlet valve.
I'm sure its just a typing mistake as earlier in the post he mentions doing it with number 1 inlet that's second bucket from the flywheel.
I would personally find true tdc with a dti gauge on top of the piston steve if the head is still off. The original markings could be a fair whack off. If the head is on use a piston stop like rs250nut suggested.
I use this method http://www.burtonpower.com/tuning-gu...ng-timing.html
Last edited by Brigsy; 05-01-2013 at 19:36.
Sorry ment to say the first inlet valve have not messed about with a c1j for a few years now.
By jove I think i've done it?!
For some reason I couldn't get it into my head until I started doing it
The Cylinder head is already on the engine so I used a socket extension as a piston stop to find absolute TDC (Thanks for the top tip RS250NUT!)
Then wound it round to 112 ATDC and adjusted the vernier pulley to reach maximum lift on the camshaft.
You're all right that it's blummin easy when you know how to do it isn't it?!
I think if i did it again I would have preferred to have done it with the head off as i've still got a little nagging doubt about finding the TDC with an extension bar...?
Maybe I should get myself a Piston Lock? Do you think it's worth me using one of those?
100% worth doing it with a proper piston stop as you have a certain amount of dwell to take into consideration, if it were my car now I would have it on the dyno and finish off the fine tuning. I always wanted to make a timing cover for a c1j with a removable cover so timing adjustments could be done on the fly, when my workshop is fully setup I will look into making a few.
Would the ability to adjust the timing on the fly actually give you that much benefit Jon?
Surely if you're trying to adjust the cam timing on the rollers you'd be guessing where it is as you wouldn't have the DTI's & Protractor?
I would use a piston stop to determine true tdc steve, just incase its out. Take you ten mins to make one out of an old sparkplug
Then dial it straight up & leave it be, you geeza
I can't dial the piston as i've got the head on now.Then dial it straight up & leave it be, you geeza
I meant with regards to the cam.
is the sump still off? or have you put that on? you could do it upside down.
Yeah the sump is still off, and I had that idea but I couldn't see how to find the TDC using the bottom of the rod?
if the engine is on a stand you could spin it upside down then with a pushrod/long extension or something you should be able to measure it.
The piston stop method is easiest, surely? Even just using a bolt will suffice mate.
I think you're right as there is so little vertical movement of the piston around TDC that there is scope for error, especially going through the spark plug hole (with the head off it would be ok as you are unlikely to get any deflexion from any extension used), as I found out trying to setup my trigger wheel for EFI (see my Project Yellow Peril thread).
Using the piston stop method ensures that you stop the piston where vertical movement is more pronounced and therefore a bit more accurate.
You would not need the dti and protractor on the dyno Steve as you would only be making small adjustments just to see where you engine likes it.
Send me your address and you can borrow my piston stop.
robw thanked for this post
Following this guide and the one here: https://www.rtoc.org/boards/showthread.php?t=4744 I had a go at timing my Piper 285 last night. I think I got it right but not sure!
I got a bit confused as to which cylinder you are supposed to time it on. Scoffs bit says Pot No. 4 (which I believe is the one nearest to the water pump?) but this guide refers to no 1 (nearest the flywheel?)
any ways what I did:
Found TDC on Pot No. 4 (nearest water pump) using the piston stop method, then timed the cam to 112deg by resting a DTI gauge on the inlet valve of Pot No 4 watching it till it stopped rising, noting the degree then seeing when it dropped and picking the half way point between the two. The numbers all seemed to line up on the protractor with a bit of tweaking on the vernier, will this be right or should I have done all this on pot number 1?
I'm not running a dizzy so not worried about that.
but here is the bit that had me puzzled for a long time, when I put the vernier on the cam to start I lined it up with the timing mark on the crank sprocket by copying where the timing mark on the OE cam pulley is by lining up the little notch that the pulleys have to lock it on the cam, then marking the OE mark onto the vernier in the same place.
So when I put the chain on and lined up the two timing marks, found TDC on pot no 4 the inlet valve angle on that pot was miles off and couldnt be corrected on the vernier, so I had to take it all off and move the cam/pulley around a bit on the chain and try it all again did this a few times till it all seemed to look right on the protractor.
So any advice please, have I messed it up or does it sound right?
we did it on no1 cylinder the clutch end but tbh it dont make any difference, what we make the difference is the dizzy drive it had a offset that has to be right otherwise it will be 180 degrees out but again in the past ive just swapped the leads around jeff
not too worried about the dizzy as i have the Nodiz system to put on, but the drive gear could be taken out and moved around to the required position by the looks of it?
If I want to advance the timing on the cam by say 2 degrees on a 112 deg cam, should peak lift be at 110 deg or 114 deg?
To advance the cam, the highest lift would be seen earlier in the cycle - so a lower BTDC number is what your aiming for.
I dialed in my bp285 to 109deg.........time will tell (once I have it dyno'd) if it has made much difference
ok got it, I went for 2 deg advance but have gone the wrong way! good job I checked.
so i have found tdc using a piston stop but is it possible to put the cam in 180 deg out. as when looking for the maximum lift on the inlet for pot 1 (flywheel end) as the inlet dose not open until after a full turn then at around 110deg its open.
I don't think the came will go in 180 degress out mate. As long as the engine is at correct TDC you'll be o.k.
cheers alex.
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