Cam timing 172

[Dan@SJM]

Just dont the cambelt on the 172, and due to not being able to do it at work i didnt have a ramp, so everything has been a bit awkward.

I got the locking tool in on the crank, couldnt turn it either way. Then poped the caps out of the head and put in the locking tool, the cams were slightly out of alignment, so i realigned them and put n the tool. Did the belt etc. Started it up and it wont idle very well, when it does it sounds like its running wild cams, then misfires upto 2000rpm.

I havent had enough light to recheck the cam timing. but is there any other possibilities?

 

[edde]

Did you put the intake cam back on right as its VVT you might have got it out of allignment.

 

[Dan@SJM]

see this is whats worrying me! i didnt take the cams out or anything. But As it wasnt quite inline, i adjusted it back to allow the tool to fit. after 2000rpm it flies as normal. going to take it to pieces tomorrow and have another go.

 

[BenR]

You've either done it with the cams or crank out of position.

its quite easy to check if the rear of the cams are out of alignment when the crank tdc marker is at zero.

 

[Dan@SJM]

i suspect when i locked the crank i got one of the balence holes. where is the crank TDC marker?

 

[BenR]

i thought you knew these engines?

Look through the gearbox window for the slot on the flywheel and line it up with the zero marker on the gearbox.

 

[Dan@SJM]

the valver engines are what i specialise in! so its the same markings on the 172's

 

[BenR]

the same.

 

[Dan@SJM]

Thanks.

 

[Dan@SJM]

Yea, exhaust cam is out.

 

[Gweebs]

Yea, exhaust cam is out.

Is it working right now??

 

[Dan@SJM]

not yet, i cant get the belt back on with out the exhaust cam slipping. the belt is like half a tooth out!?

 

[tim124]

That crank pin is really hard to get in the right place, the only way i could be sure was to put a long 3/8 extension down one of the spark plug holes with a dial gauge on top. you should be able to feel it on the extension though by hand

 

[Dan@SJM]

ive got it tdc no probs. but the cams will not line up. i put the locking tool in the cams, put the belt on, it a bit loose between the two cams, tension the belt, turn it twice and the cam is half a tooth out.

 

[Mike@Rentech]

Loosen off the exhaust cam nut, the exhaust cam pulley will then move (make sure you leave the cam locking tool in place), corectly set up the belt timing.
Tighten the exhaust cam pulley bolt, make sure you torque it up to correct setting, job done.

 

[Dan@SJM]

ah... hadnt thought of that! ive given up on the damned thing now! its taken that much blood from me i feel weak!

 

[Dan@SJM]

well got the belt on, the timing is a little bit out me thinks, runs slightly lumpy, but doesnt misfire through the revrange. oh and it stalls alot lol.

 

[BenR]

The cams dont use locating dowels so you have to undo the pulleys if you want to tension the belt correctly and retain the correct cam timing.