How do I set my cam timing?

[tight fart]

My 2l Zetec has had the top end rebuilt and I'd like to double check the cam timing.
Normally I believe the cams have slots in the end where you would lock when doing the cam belt etc, mine dosen't.

[Garybee]

Are they aftermarket cams then? If so you'll need to be able to measure valve lift at TDC to time them.

[tight fart]

Yes aftermarket and unknown.

[Evoluzione]

Try Google with 'How to set camshafts with adjustable vernier pulleys' or something similar. Catcams had a good guide I seem to remember.

[Blaxlinde]

It's a matter of finding true TDC ideally using a dial guage on the piston top (make sure you check it in both directions and split the difference),

Mark "true" TDC & use a good crankshaft degree wheel

Then again with a dial indicator & degree wheel compare the cam manufacturers specifications for valve lift at a given Crank angle and adjust Vernier gears, pulleys or stepped keys to make the numbers right,

PS, beware of hydraulic lifters/adjusters, they muck you around if you're not expecting them.

[Blaxlinde]

I just re-read that your cams are custom and "unknown" in which case you'll need to measure lift, duration and overlap etc then compare such data to find the closest cam set in a catalogue somewhere, then set up to those specs, otherwise find a reliable performance engine builder and go from there.

This is one of those things that could be impossible to get right as an amateur, as a Pro builder though, it's all in a days work.

[tapkaJohnD]

Blaxlinde clearly knows whereof he speaks, and on finding TDC of "checking both ways and splitting the difference" (or like that.)

Probaly all in a days work for a pro, as he also says, but I'd suggest that a piston stop is a better way for an amateur. They are availbale ato screw into the sparkplug hole; note the poistion where the piston stops, turn it the other way, note that stop position. TDC is EXACTLY halfway between those.

John

[Blaxlinde]

Agree on the piston stop for beginners,

[PaulKemp]

If you don’t know the cam timing information from the cam manufacturer then equal valve lift at TDC is safe and very close to optimal

http://sideways-technologies.co.uk/forums/index.ph...

[tapkaJohnD]

Gosh, Paul, although I've often advocated the ELoO method (That article is mine) I've just not known if it can be applied to twin cams.
Is it usable in that case?
I do know that it cannot if the cams are assymmetric.

John

[99hjhm]

PaulKemp said:

If you don’t know the cam timing information from the cam manufacturer then equal valve lift at TDC is safe and very close to optimal

http://sideways-technologies.co.uk/forums/index.ph...

That works on a single cam with fixed LSA. Not on a twin cam engine.

[tapkaJohnD]

99hjhm said:

That works on a single cam with fixed LSA. Not on a twin cam engine.

Please explain why not?
Yes, a singkle cam wil automatically set both intake and exhausr at ELoO.
But if you set the Equal lift seperately on each camshaft, won't that be the same?

John

[99hjhm]

A single cam timed evenly and based on symmetrical profile will be timed well enough to work, probably even to manufacturers specs. This will give (for example) 106 MOP inlet 106 MOP exhaust for example, the cam will be ground to 106 centres between the lobes which is why you get your even figures.

On a twin cam you can time the cams where ever, how would you know where 106 degrees is? the cams are infinitely adjustable and fully independent. Easy way to bend valves if only running .050-.060” clearance at CPA.

[tapkaJohnD]

Of course! Doh! You could achieve ELoO anywhere, at any height, from the base circle to full lift!
Thnak you (although I really should have thought of that myself!)
John

[PaulKemp]

Good point, I was definitely thinking of single cam.
However the equal lift at TDC would still be safe as both cams would be in phase.

I assume the engine is built up and the thread poster does not want to pull it apart and put placticine on the pistons.

Just found an article that say you can... needs 3 dial gauges.

I confess to not having absorbed the full details as I’ve just got back from an afternoon in the pub

http://www.alcester-racing-sevens.com/cam_timing.h...

[DVandrews]

The link above outlines my method for setting cam timing using the lift at TDC which is the most accurate and repeatable method. Wth the right kit it is the easiest method as you only have to establish one point on the cranks rotation.. TDC. There is an article on my website which outlines the method.

Dave

[tight fart]

Thanks for all the above info, I've now got the timing info and will pass it to someone with more knowledge than me to sort.
(160thou at tdc.)

[99hjhm]

Did you get the information on what MOP that gives? 160 thou at TDC is a lot on a 4v engine.

[Boosted LS1]

Keep the valve caps loose initally.

[227bhp]

99hjhm said:

Did you get the information on what MOP that gives? 160 thou at TDC is a lot on a 4v engine.

Suspect he means 60 (1.52mm), but it depends on the spec of the engine and that has never been mentioned.