How is cam timing set on standard cams?

[rossocorsa]

Getting a bit confused on this, story goes that on my volumex engine I have a standard exhaust cam but an OE fiat lancia inlet cam supposedly off a strada/ritmo 130tc. To keep it simple (or so I thought) I have initially built the engine up using standard fixed cam wheels with the intention to substitute adjustables later. That's fine but the more I look the more I find the set up confusing, does anybody know if the dowels in the camshafts are always in precisely the same position (they look to be in line with the number 4 lobe peak but could be a few degrees +/- ) or if fiat achieved precise timing by slightly varying this position, secondly what variation did they use on the cam wheels with regard to the timing holes that mark the tdc timing position? Unfortunately I only have vx wheels (and maybe one ie example) the 130tc cam came without. Until I understand this properly I am struggling slightly, I will fit the adjustables to achieve same current timing at first but need to know what this actually is; on the inlet from my observations it seems that full lift position is a bit out from standard 130 TC (with the fixed cam wheel that is currently in place ) but I need to find a crafty way to identify the full lift position with the engine assembled ( mental note: next time do it with the head off first!)

[HFStuart]

With the cam heding towards full lift there is room to get a dial gauge point onto the top of the shim.

I'd them mark a point 1mm or so below full lift either side of the full lift and midway between those is full lift. If you have  cheapo magnetic stand for the gauge the main part often has an M8 thread where it screws into the magnet. That allows you to remove one of the cambox bolts and fix the stand.

[rossocorsa]

With the cam heding towards full lift there is room to get a dial gauge point onto the top of the shim.

I'd them mark a point 1mm or so below full lift either side of the full lift and midway between those is full lift. If you have  cheapo magnetic stand for the gauge the main part often has an M8 thread where it screws into the magnet. That allows you to remove one of the cambox bolts and fix the stand.

Thought about that but couldn't see how to mount the dial, will have a look at that idea it sounds feasible thanks!

[rossocorsa]

Managed with block attached to rear coolant gallery cover


Finding it difficult to measure precisely as engine is stiff to turn with belt on, not really safe to do with belt off but has at least given me a good idea of how cams are set at the moment.

[WestonE]

Alan

OK deep breath you need to time the cams into the boxes using degrees away from full lift either ATDC inlet or BTDC exhaust (after top dead centre before top dead centre). This is done with them off the head using a tappet bucket in Number 1, a DTI a protractor/ cam timing wheel and a pointer. You first mark FL (full lift) red to red is conventional then swing the cam to the correct position and mark this. BTW full lift is in the middle of the degree swing with the protractor as there is cam dwell at full lift. The GC books will be your bible for how to do this so read twice and copy step by step. Your Strada 130 TC cam is a 7/52 item timed FL @ 112 degrees ATDC this is where the cam should be with the engine at TDC and precision matters. You will need sharp triangle needle files for the marks and different colour paint.

You will get in a mess with standard cam wheels unless you are incredibly careful and you cannot achieve the accuracy to make the engine give its best. 

Enjoy.

Eric

[rossocorsa]

Thanks Eric I think I have got my head around it now my biggest confusion was which variables fiat used to set the fixed positions on the standard engines. My feeling is that the standard setting on a 130 TC cam allows far too much overlap on a vx engine so am aiming to bring the full lift position back a bit and start from there.

[WestonE]

Alan

Sorry for the late reply. My experience has been the Strada timing is near ideal as it is actually minimal overlap which is what the 7 of the 7/52 indicates.

Good luck.

Eric