Pts Gr. A Cam

[jimmi 0 1 Cars]

Here are engravings on top of my cylinder head: GrpA 4078 RALLY CAM / FL @ 106'/ Clearance 0.25 / 0.010 in.ex.

 

I assume the 0.010'' refers to cam bucket to base of cam lobe clearance ( thousands of an inch) when cold ?

I assume FL = Full lift ( valve opening) ?

What does the 0.25 clearance refer to ? - and is that millimetres or thousands of an inch ?

 

Finally - I have marked true TDC on flywheel - Am I right in thinking that I should be getting FL @ 106 crank degrees after TDC ?

[petert 550]

FL will be the lobe centre line (LCL) at 106 deg., after TDC.

0.25mm = 0.010"

0.010" is too tight for the exhaust however, you'll end up riding a valve when the engine gets hot. Factory minimum is 0.013". I'd use that.

Be careful when setting up the cam by LCL method. You need to allow for the dwell on the top of the lobe. Confirm by taking a lift measurement 20 deg. either side. There's plenty of videos on the net if you're unsure.

[jimmi 0 1 Cars]

Thanks for that Peter.

I measured the clearances between cam buckets and base of cam lobes.

 

The current clearances are as follows:

 

Cylinder 4 EXHAUST: .008'' INLET: .006''

Cylinder 3 EXHAUST: .010'' INLET: .008''

Cylinder 2 EXHAUST: .012'' INLET: .008''

Cylinder 1 EXHAUST: .010'' INLET: .008''

 

Haynes manual lists tolerances as: EXHAUST .014'' - .018'' and INLET .006'' - .010''

 

Hence, all INLET valves are within tolerance but all EXHAUST valve clearances are too 'tight' - Could that be reason I'm getting a 'pinging' noise when revving / loading the engine ?

 

When I had the head off I found that the previous engine builder had fitted the pistons 'back to front' ( I have already corrected that problem ) and I could see that there had been valve / piston contact as the top of the piston crowns/rims were 'marked' ( crescent shaped )

 

Obviously, I'm gonna have to re-shim all exhaust valves

[petert 550]

I'd leave #2, 0.012" is fine but absolute minimum. I thought the range was 0.013"-0.018". Any wider than 14-15 thou they get too noisy. If too tight, you'll burn out an exhaust valve and loose compression. Valve-piston contact is from other issues.

[jimmi 0 1 Cars]

Peter, I do not know how many times this head has been skimmed and I have fitted a 1,50mm headgasket. I removed amd had the head 'surfaced' as it was pressuring the water system when I purchased the car.That issue is now sorted. I measured the volume of the head chambers -which are now only 24.2cc, ( IIRC the head depth is now 87mm.) Peugeot do not sell a thicker gasket in the UK (or elsewhere AFAIK ). Any thoughts to solve the piston / valve contact given that when refitting the head I used the normal dowel positions / standard crank/cam pulleys.?

-As per my earlier post I now have a vernier/adjustable cam pulley waiting to be fitted

[petert 550]

The only way is to measure the engine. ie drop a valve onto a piston at TDC, without a valve spring, and subtract the lift at TDC. Only then will you know the answer. It's actually more correct to repeat the procedure 6 deg before (for exhaust) and 6 deg after (for inlet) to get an accurate measurement.

[jimmi 0 1 Cars]

I spent today checking the cam timing. Fristly, I found true crank TDC using a dial-gauge down no.1 plug hole (center line of the 'dwell' angle - 50 thou. either side of TDC). I zero-ed in the degree wheel/disc which I had fitted to the front crank pulley. Next I moved the dial gauge to read off the top of no.1 inlet valve bucket to establish true full- valve lift /opening (center line of 50 thou. either side of max lift ). To my surprise I found that, as fitted, the engine was set up with full valve- lift @ 88' after TDC - and not @ 106' after TDC as per the camshaft spec. ! - Therefore the camshaft was set-up @ full lift 18 crank degrees / 9 cam degrees too early. ( This I think is the reason the inlet valves were 'kissing' the piston crowns ? )

 

This got me thinking how I messed-up the cam-timing previously. When I last changed the head gasket / fitted new cambelt, I did as per the Haynes manual instructions - used bolts through the crank and cam pulley timing holes ( thus pistons were 90' before TDC /halfway down bore ) and fitted the new cambelt. I never considered that the cam pulley may have been re-dowelled - I removed the pulley today to find that is the case.

To solve the issue I removed the belt from the cam pulley, rotated the camshaft to ensure that the cam lobe on no.1 inlet was at full-lift then rotated the crank until I got 106' After TDC and re-fitted the cambelt.

Upon spinning over the engine by hand I noticed immediately how much easier it was to rotate ( no more valve contact I think ). I have re-checked all marking and all is well. So I did'nt bother fitting the adjustable cam pulley.

Fingers crossed - gonna fire it up tomorrow - time for a beer now !

Edited October 24, 2015 by jimmi

[jimmi 0 1 Cars]

Started the engine today - it fired-up on first turn of key - all now good - no more 'pinging' / inlet- valve kissing pistons gremlins Must get rolling road session booked to get ecu map maxxed.