Timing In Cams

[jonb_5 6]

Hi,

 

I am going to be timing in my new 16 valve head at some point so will need to time in both cams. I have done a few single cams but just wondered if anyone had a good guide to how to do it??

 

Many thanks

 

Jon

[welshpug 1,627]

its the same process, just done twice!

[Tom Fenton 1,526]

Only thing to be careful of is that the valves don't clip each other.

[toolie72 67 1 Cars]

TURN HER OVER BY HAND IF NOT SURE

bent two valves years ago with my dad "helping me" didn't turn it by hand-oh how I laughed-no wait a minute that's not right-I thought I was gonna be sick-had those bent valves on my workbench for years to remind me to check and check again lol

[dobboy 231 2 Cars]

I created a tapper/bent a valve too with my first timing belt change.....i don't think it matters if you turn it over by hand or not, the valves are really fragile and easily bent.

 

If it's a GTI6, are you aware that you need to swap the bottom pulley for a 1.9 8v one to get the pin in the correct position?......which i believe is the piston MDC position.

 

If you have the head off, i'd pin the bottom end, and very carefully pin the cams, then put it together, then fit your belt.

 

I'm sure someone else can explain it better, but be careful as it's easy to bend a valve doing the timing. I think the engine is known as an "interference engine", which i believe means the inlet and outlet valves cannot pass by each other without hitting each other if not timed correctly.

[woodymi16 24 2 Cars]

Hi,

I am going to be timing in my new 16 valve head at some point so will need to time in both cams. I have done a few single cams but just wondered if anyone had a good guide to how to do it??

Many thanks

Jon

http://forum.205gtidrivers.com/index.php?showtopic=164807&hl=

[jonb_5 6]

Thank you for the the guide. Makes perfect sense now.

 

What I do have a question about is it says if I turn the cam so the valve is at the desired lift the cam will stay in position, but if I let go of the spanner the cam will spring back to position, because of the valve spring force.

 

How can I lock the cam in position to then put the timing belt on??

 

Many Thanks

 

Jon

[allanallen 528 2 Cars]

The timing belt needs to be on and correctly tensioned before you start to alter the timing.

[pip470 61]

The pin goes in the hole on the pulley which is keyed on the cam. So as long as you haven't loosened the bolt holding the cam gear too much. Once the pin is in the cam will not turn but the pulley will. When you attempt it you should see what I mean. Hope that makes sense.

[jonb_5 6]

Thank you for the advise.

 

Following the advise in the guide, I have started by following the "New cam fitting, timing lift at TDC" section. It states to install the cams which I have done and turn to desired lift amount and the cam should stay in position, this is where mine then springs back, It states it should "happily sit where you have left it", is this the case and I am doing something wrong?

 

Obviously I don't want to fit the belt until I have got this first part right as the lift on the valves could be wrong so I don't want to move to TDC.

 

Just to check I am taking my valve lift positions from number 1 cylinder as a quick look at the bolt holes on the pulley end suggest the hole is miles out from lining up to be able to pin it in place.

 

Many Thanks

 

Jon

[allanallen 528 2 Cars]

YOU MUST FIT AND TENSION THE BELT BEFORE YOU ATTEMPT TO SET THE CAM TIMING!

If this isn't obvious I highly recommend getting someone else to do it for you.

[jonb_5 6]

Completely understand what you are saying, but your statement seems to contradict the guide I am reading which is the main reason I am getting confused.

 

It specifically states to fit the belt after setting the initial timing, and then go back and re-check, now I really am confused.

[allanallen 528 2 Cars]

What are you trying to do exactly? Fit and tension a belt or adjust the cam timing with vernier/adjustable pulleys?

[welshpug 1,627]

"initial timing" means just that, that the camshaft and pulley is in the right place to fit the belt and turn the engine over.

 

i.e if using an original pulley, it would be as close as possible to its pinned position, so you can rotate the pulley a few degrees and fit the timing pin, this is one point where people can get it horribly wrong, by just plonking the cam in willy nilly and turning it after tightening down the cam ladder.

 

that will result in bent valves.

Edited April 22, 2016 by welshpug

[allanallen 528 2 Cars]

Nice explanation Mei, I see what the problem is now!

 

When I fit verniers without pin homes I mark them with a standard pulley, this is a good way of double checking you're doing it correctly.

 

As I said previously, the belt needs to be on and tensioned correctly before you attempt to set your cams properly.

[jonb_5 6]

Thank you the advice.

 

All I am trying to do at the minute is time the standard cams with pulleys in. I will fit aftermarket cams and pulleys eventually but for now because I am learning I would sooner damage the second hand parts which havnt cost me very much money than the nice new shiney parts. I.e. before having head rebuilt etc.

 

Because the head came to me with the cam lobes on number one cyclinder facing away from each other as in Sandy's guide I left them at this. Following your advice above I have this evening fitted the cam pulleys and rotated forwards until the pulley holes and holes in the head lined up and inserted some bolts. Probably rotated about 20 degrees or so.

 

Please see below for the position of the pulleys and the position of the lobes on the cam.

 

At this point I think I am ready to turn the crank to TDC which I have established and marked off and then slide the belt on.

 

I can the use my DTI to accurately position the timing etc.

 

Would you agree this is correct.

 

Once again thanks for the advice.

 

 

 

[welshpug 1,627]

the head does not get fitted with the bottom end at tdc, fit the bottom pulley and pin it, pistons will be mid stroke.

 

if they are standard camd then the pinned position is correct, no need to alter the timing from there.

 

 

use plain pins not bolts, bolts will damage the alloy castings and allow slop.

Edited April 22, 2016 by welshpug

[jonb_5 6]

Just to check, when you pin the crank with pistons at mid stroke should it be with piston of rising??

 

I only ask as it will spin twice for each cam rotation??

 

I think that is correct?

 

Thanks

 

Jon

[petert 555]

Pinned is 90 deg BTC for #1 and #4.

 

That happens twice in an engine cycle.

[jonb_5 6]

So i have set TDC on number one and turned back 90 degrees, (turning back is clockwise looking at the flywheel) roughly and I am probably half a turn out at the timing end from the smaller holes in the crank pulley.

 

It does however line up perfectly with one of the larger holes.

 

Should I be particulaly concerned with this? Maybe it is a different pulley? Is there an angle from keyway to hole i could check out. Not forgetting its a XU7 crank.

 

Many Thanks

 

Jon

[welshpug 1,627]

keyway on the cranks are all the same, when pinned the keyway should be pointing backwards, the pin hole is 8mm and 70 degrees up from the keyway.

[welshpug 1,627]

which pulley are you using? the xu7 and xu10j are harmonic balancer type and are known to slip placing the timing hole away from the 70 degree distance from the keyway

[jonb_5 6]

I am pretty sure its off of the xu5 i stripped. Ill check the 70 degrees measurement.

 

[jonb_5 6]

So just had a quick check.

 

One of the large holes in the pulley aligns with the bottom left hole as you look at the timing end. 120 degrees round clockwise from this is the smaller hole in the pulley so potentially something is out of alignment.

 

Any ideas?

 

Thanks

 

Jon

[welshpug 1,627]

8mm hole, should locate in slot behind pulley circled