Cam timing without head/rockers fitted on a 1500

[sparky_spit]

Just checking I've got this right before ploughing ahead....  I've got the camshaft (Mk3 grind) fitted to the block, along with the crankshaft and front plate/keeper etc.  I'm not ready to put the head and valve gear on yet but want to fit the cam chain and timing cover.

I want to use the equal overlap method but obviously have no valves/rockers to set, measure or watch, and can't set 40thou and measure equal gaps, etc.  I've identified and marked TDC for the crank on No1 cyl. I've also put a cam follower in place for both inlet and exhaust for No 4 cyl.

Using a dial gauge on a magnetic stand I can check the cam lift via the followers for No 4 cyl. When both of these are on the rock and are of equal height I'm assuming this is the correct point at which to time the cam into the crank at No 1 cyl TDC. I've tried it and the dots/scribed lines on the sprockets and front plate do line up, although I wasn't going to rely on these as it's a reground cam.

I think this is correct, and I'm doing exactly the same thing as using the rockers (but in a slightly different way) and just wanted to check it's correct before going any further. 

[Gt6s]

Yup sounds about right. Overlap at TDC. Go for it.

Laurence

[sparky_spit]

Well, that didn't go too well.

Initial cam setting using the equal overlap method is okay. However, there's a practical problem with testing it afterwards without the rockers and valves in place.  The dial gauge is almost too sensitive. It moves as soon as there is any lift and this seems to be somewhat in advance of the correct timing (for example No1 inlet opening at 34deg BTDC instead of 25deg BTDC). Likewise, the closing point is somewhat retarded from what it should be (65deg ABDC). Max lift is correct at 110deg ATDC. Doing it like this, you cannot tell where you are on the lobe's ramp and when the valve itself would actually start to open once all the slack in the valve gear is taken up.

The amount it is out by is approximately 8 to 10 degrees or so. It is centred okay about max lift so I'm sure the timing is basically correct.  This 8 to 10 degree error equates to about 10thou lift/fall at the pushrod where the dial gauge is located.  And obviously, is probably equates to the slack in the rockers/shaft/tappet clearance. So, I'll need to check again once the head and rockers are back on. The head is away at Towler Engineering having the valve seats recut after I put new guides in and bought some new valves.

I'm betting that once put together, if I put the dial gauge on the top surface of the valve caps and test again it will give me the correct 25/65 degree readings, or as near as dammit.

Fingers crossed.

[sparky_spit]

The head is now back and looking very nice.

I've also timed in the cam, with some kind assistance via email from Markus (GT6M) who is a top bloke.  Max lift is now spot on at 105deg ATDC, 5deg advanced from the book figure of 110. This is 3degs to account for initial chain wear and 2degs to give slightly more lower down torque at the slight expense of top end power.  My choice, as this 1500 engine is not likely to used above 5000rpm very much and most of its use is normally around 2500 to 4500 in truth.

I'll see how this goes in practice.  If it does not work out how I wanted it's not too difficult to put it back to 110.