2tg - playing with cam adjustments - help!!

[o_man_ra23]

You can over-advance the intake and over-retard the exhaust, try advancing the intake and retarding exhaust one dowel notch, and see how that goes. If it gets worse, go back the other way. Doing one cam at a time is a better way, but takes longer. If you get it pretty close, then it will be a lot cheaper come dyno time.

Cheers, Owen

[sillycar chick]

This is gonna sound really dumb, but what happens with the chain? If you keep the marked link lined up with the dot on the gear, it will move everything else

[thechuckster]

the cam itself rotates to a new position, the chain stays as is. The dots will no longer line up.

You can either repaint the marks on the chain (not a good idea) or take careful note of these changes so at the next tuning you now how the engine has been modified.

[o_man_ra23]

the cam itself rotates to a new position, the chain stays as is. The dots will no longer line up.

first point is correct, second isnt so right. The dots from the cog to the chain will remain the same, and the camshaft rotates on the cog. That way you can advance or retard the cam with respect to the chain/cog position.

Just pull the pin out, move the cam in the appropriate direction(clockwise to advance, anti to retard) and put the pin in the new hole... do this one hole at a time... dont want to go too far in the wrong direction.

Cheers, Owen

EDIT: you dont even need to do this with the cams at TDC... just make not of which hole you took the pin out of, and put it in the next logical one.

[sillycar chick]

So then it can be done without even having to remove the timing chain tensioner or the having to play around with chain adjustment?

And then when the engine is at TDC, the notches in the cam will no longer line up "vertically" where they normally sit, is this correct?

Sorry for being a newb, Ive never played with twin cams before this engine, and keen to start playing around and getting a little more from it.

[o_man_ra23]

exactly correct, easy isnt it??

Cheers, Owen

[sillycar chick]

tried playing with the cams last night..... didnt really work too well.... engine was running very rough and making noises I didnt like, so I turned it off and didnt even try to re-time it. Probably becuase I couldnt just move the cams slightly each way, it was a big move to the next adjustment. I gave up because its a PITA to do with the bonnet on and I needed the car to get to work 2day.

So can anyone tell me if it is worth playing with/getting someone else to play with stock cams on these? Am I going to be able to gain any HP from doing so, or is it just going to run like a bucket?

And if anyone knows of good dyno-tuners in Brissy who play around with cams, please let me know. The dyno-tuner I used a few weeks back specialises in carbies and injection.

[thechuckster]

If you just rotate the pulleys you will get massive shift in cam timing.

changing cam timing is a combination of moving the cam a bit and using a different dowel hole.

Am not sure what the 2TG cams look like when you remove the pully, but there should be more than one hole in the face of the cam for the dowel to fit into. You rotate the cam in your preferred direction, then find closest combination of dowel hole and and pulley positions that suit.

Even my humble 18R had this setup on its camshaft (thoe for what purpose, i'm unsure).

suggestion: go back to your pile of 2TG spares first - and work out which dowel/pulley locations you want to shift to, then repeat on the working engine.

It will help if you put some timing makes on the camshaft next to a bearing cap:
-put some sort of degree wheel on the front of the cam
-set it up to TDC
-inscribe a mark on both cam and bearing cap
-rotate the cam in fixed increments (e.g. every 5 degrees) and re-mark the cam for each location
then attach the pulley and dowel to and work out which combinations of locations
produce the desired angle of rotation.

cheers,
Charles.

[Rodger]

My humble opinion Sillycar Chick.

Playing with the available cam timing through use of the OEM dowels is not going to gain you enough to be satisfied.

All you will really be doing is moving the peak bump on your dyno graph, up and down the rev range a bit.

It comes back to the stock profile. The stock cams just do not breath. Where the motor has the potential is, at the top end. To get that power curve to keep on climbing you need more top end breathing.

So I believe put the effort now, into setting up the motor with mild cams. I still do not know my specs but it was ground as a 3/4 race cam.

Ivan Tighe Cams in Brisbane can supply a list of cams he can do for the 2T-G. They are not listed on their web site but an e-mail will get a listing. I have just been through this with another contact.

Regards

Rodger

[barned01]

i don't know if it will help you. I just wrote it in the 18rg thread, and considering these 2 engines are quite close in their workings, would be highly similar.
http://www.toymods.net/forums/showth...985#post154985
you will need to know where tdc is for your engine (although the cam notches should at least roughly be pointing upwards with the timing on the crank at tdc, otherwise spin the crank another 360 degrees and see if that brings the cam notches pointing upwards)


Just set it to standard first. don't worry too much just yet about advancing or retarding the cams for that performance edge, just set them to the tdc setting.

[sillycar chick]

The car has been back to the dyno only to be told that its not my timing, its my cam timing!! GGGRRR!! Upon closer inspection it seems both the intake and exhaust cams are slightly advanced (looking at the notches against the arrows on the first cam caps).

I have tried playing around the cam timing but dont seem to be getting anywhere. My understanding is if you cant get it exactly on TDC, its better to have the intake slightly advanced and the exhaust slightly retarded. So therefore the intake would be acceptable where it is, but I have to try to move the exhaust cam so its slightly retarded. The closest I can get to this looks way too far though. It seems to be around 45 degrees or more from vertical (towards the spark plugs, not away).

So I am really stuck and dont know what to do to get it to get the cams where they should be. I have taken everyones suggestions into consideration but cant seem to get the holes in the gears to line up with where they need to be.

[o_man_ra23]

your exhaust cog may be a tooth out. Move it one tooth anticlockwise as your looking from the front of the car, and try lining up again. you can mix and match between the holes to get more adjustment. There should be 4 holes in your cog and 4 in the cam... pick the best combination.

If i were down there I woulda come round and shown you how to do it by now... takes about 20mins when youve done it before to set them up by eye.

Cheers, Owen

[sillycar chick]

your exhaust cog may be a tooth out. Move it one tooth anticlockwise as your looking from the front of the car, and try lining up again. you can mix and match between the holes to get more adjustment. There should be 4 holes in your cog and 4 in the cam... pick the best combination.

Hmm pretty sure I set the chain markings up as per the manual, but maybe it is wrong. But I did think of changing where the chain is just to make it all work, but havent tried it yet as I wanted to make sure this was ok to do. Because I have been moving the dowel around different combinations of the 4 holes and nothing seems to set it right, so I might have to move the chain a little.....

[o_man_ra23]

The chain position is irrelevant, as it changes every rotation due to the fact that there are more links on the chain than there are teeth on the cog. The beauty of adjustable cams is that you can move the cog around on the chain to find the best position... so long as the cam is correct with respect to the crank and dizzy, it matters about 3/5ths of F-all where the chain and cogs are. Forget about chain positioning, and shiny links, and marks on cogs, they mean nothing other than setting up for dummies that work in assembly shops. Anyone serious about setting up a car will look at cam position.

TDC is found where the piston is at maximum height. Put a screwdriver gently vertically down your plug hole and rotate the engine to find where the screwdriver is at max height. you should pick a point on the crank pulley about halfway between where the TDC mark is when the screwdriver is about 1mm down from its max height, as the factory markings are almost never correct.

Forget factory markings, and make your own, they will then be more accurate, you dont go to a dyno to get them to set your dizzy at 12 degrees advance do you?? you go there to get it set to optimum advance.

Get my point??

Cheers, Owen

[sillycar chick]

The chain position is irrelevant, as it changes every rotation due to the fact that there are more links on the chain than there are teeth on the cog. The beauty of adjustable cams is that you can move the cog around on the chain to find the best position... so long as the cam is correct with respect to the crank and dizzy, it matters about 3/5ths of F-all where the chain and cogs are. Forget about chain positioning, and shiny links, and marks on cogs, they mean nothing other than setting up for dummies that work in assembly shops. Anyone serious about setting up a car will look at cam position.

Ok, that is what I thought was the logical explanation, just nobody has actually said that in those words. you have just confirmed it for me, thanks!

TDC is found where the piston is at maximum height. Put a screwdriver gently vertically down your plug hole and rotate the engine to find where the screwdriver is at max height. you should pick a point on the crank pulley about halfway between where the TDC mark is when the screwdriver is about 1mm down from its max height, as the factory markings are almost never correct.

Hey, didnt you notice I have already been using a screwdriver? Have a look in the photo I posted earlier, post #45!
And I have noticed the harmonic balancer markings are wrong - it says 5deg when the piston is at TDC... just thought this was from using a 3T pulley and a 2T-G timing cover. I always ignored this anyway.

Forget factory markings, and make your own, they will then be more accurate, you dont go to a dyno to get them to set your dizzy at 12 degrees advance do you?? you go there to get it set to optimum advance.

Get my point??

Cheers, Owen

Thanks Owen, you are really helping me and encouraging my train of thought along, you are the only person who seems to be able to answer what I have been pondering. And sorry if Im being a PITA and sounding really dumb about it all, Im just learning on my own, no-one really to teach me I just try figure it out myself using a manual and some nous