S16/gti6 Dummy Build

[Mad Scientist 106]

Soooooo.........

 

I need to ensure I have enough piston to valve clearance on my engine.

 

Spec. as follow:

 

S16 block

GTi6 head

Catcams 4903110

87mm JE forged pistons

2.1 TDi crank

 

I had new valve seats cut and the followers were drained before reassembly by the machine shop (QEP).

 

The problem I have is, how do I check valve to piston clearance with hydraulic lifters?

 

I want to use the clay method, but don't know how the hydraulic lifters will effect the figure.

 

Nick (QEP) said its not easy to do................he said to just check, without spring etc. that there was 2mm extra clearance past the lift at TDC. i.e. The spec for the cam is lift at TDC is 2.95mm inlet and 2.45mm exhaust, therefore, if I put a dial gauge on the valve stem, there should be 4.95mm and 4.45mm respectively from the valve being seated to hitting the piston.

 

Obviously, this is not where the valve is closest to the piston.

 

What have others done?? Perhaps filling the lifters with oil like Peter T recomends will prevent the preload issue?

 

Help appreciated!

 

Thanks,

 

Pete

[Tom Fenton 1,542]

In the past I have had a dummy follower machined to take up the distance that the hyd would when pressurised. Then dry build and check with plasticine on the piston cutout as per usual.

[Mad Scientist 106]

Sounds like one solution, although quite time consuming as I really want to check each cylinder. Out of interest, can you point me in the direction of the dimensions of a "full" follower?

 

Just stripped the head down which I paid to be "ready to fit". Glad I did as its full of cack, has not had the valve stem seals replaced, has no cam shaft oil seals fitted and had no sealer under the cam caps. Unbelieveable. I feel robbed.

[stefan 4]

Why not just mock up the pistons without rings and gently turn the engine by hand?

Can fit the oil pump and crank it up before the test.

If you have any old valves at hand use that for extra safety, if you're worried to bend the new one.

I would find that you only need to try one cylinder as the others will be the same...but thats just me

Edited August 4, 2010 by stefan

[welshpug 1,661]

I think I have heard this technique somewhere;

 

Fit the valve+retainers with a light spring, then set up the dial gauge on the top of the stem, then manually push the valve down till it touches the piston.

 

Don't forget to work out true TDC as the piston dwells at the top for a few degrees either side of TDC+BDC.

[Mad Scientist 106]

Welshpug: I have done this, but without the retainers etc. I just set a dial gauge up and measured the distance between the piston and the valve in its seat.

 

The issue I have with this is that the valve is not at its closest to the piston at TDC. I really want to check all the cylinders for clearance, not just piston to valve but also valve to edge of cutout, throughout a full revolution.

 

I can't believe there is not a solution. All these engines being built and noone seems to know...............

 

Does anyone know what the difference in "height" of an empty lifter is to a "pumped up" lifter. Perhaps I could add the difference?

 

HELP!

 

[Mad Scientist 106]

Just found some info from one of Welshpugs old threads on another forum. At one point, PeterT suggests a "rough" guide is allowing 2.5mm on top of max lift at TDC for the inlet, and 3.0mm for the exhaust. I need to measure more accurately (magnets don't hold to alloy very well!) but think I have this. Can I trus this alone???

[petert 588]

This is how I do it:

 

Put the bare head on the block with a new gasket and one bare valve - no spring, retainer, collets etc. Tension down bolts to first stage only in order to squish the gasket. For the inlet, position crank/piston at 6 deg. ATDC ( 6 BTDC for exhaust). Set up a dial indicator on the end of the valve. Drop the valve onto the piston crown. This gives you the total clearance. Depending on the size of the cam you may need to check at 10 deg. ATDC as well, just be sure. The closet point varies depending on cam duration and con rod length.

 

At 6 ATDC you will be approx. 0.25mm closer than at TDC. Strange but true. I said 2.5mm for the inlet @ TDC as this will roughly equate to 2.0mm 6 ATDC. For hydraulic lifters 2.0mm is the absolute minimum for inlet, whilst 2.5mm is the absolute limit for exhaust.

[Mad Scientist 106]

Thanks Pete. Sent you a PM also.

 

Just to clear this up in my head:

 

When you say it will be 0.5mm closer 6 degree ATDC, I presume you mean when the cam is installed?

 

I have measured at TDC but want to check again tomorrow before I commit to figures.

 

If I aim for 2.5mm clearance on the inlet and 3.0mm clearance on the exhaust, will I be safe with durations of 282 inlet and 275 exhaust?

 

I can measure at 6 and 10 atdc (and btdc for the exahust) but I presume this will only be relevant when the cams are in?

 

I hope I am getting there................damn hydrulic lifters...........plasticine is so much easier!!!!!

 

Thanks,

 

Pete

[Mad Scientist 106]

One other thought:

 

If I were to assemble the valves on piston 1 with very light model springs, would they be light enough to not compress a full lifter? In this case, would the plasticine method work? Or would the plasticine compress the lifter a touch?

 

I'd rather check this 100 times than lunch ££££££££££££££££ in seconds.

 

Thanks.

 

[petert 588]

Whether you have hydraulic lifters or not, it makes no difference to the way you should be measuring the clearance. You're correct in saying the clearance will only be closer at 6 ATDC when the cams are installed. But you have to allow for this. If you have 2.5mm/3.0mm at TDC this will be ok for ANY hydraulic cam grind. It has nothing to do with duration, but rather the mass of the valve train, RPM and when they'll float. It would be unwise to take any hydraulic cam past 7500 with standard Mi16/S16 components. Forget plasticine, it's not accurate enough. Drop the bare valve onto the piston as instructed, then subtract the lift @ TDC.

 

For example, on a standard, unmolested Mi16 (D6C or DFZ), if you drop an inlet valve onto a piston at TDC you get approx. 0.185" (4.70mm) total clearance. If you fitted the 4903110 inlet, and set it at 2.95mm lift @ TDC, you would have 1.75mm of valve to piston clearance (4.70 - 2.95 = 1.75). This would be insufficient for a hydraulic lifter and you would most likely kiss the pistons.

[Mad Scientist 106]

Just to round off this thread I have got the following measurements:

 

3.0mm clearance on the inlet at TDC

3.5mm clearance on the exhaust at TDC.

 

Plenty there I think!

 

I also checked the clearance of the valve heads in the reliefs machined into the pistons and I have 2.5mm all round.

 

 

Parts have gone to be balanced now so assembly will be very soon.

 

Thanks all.

 

Pete

[James_m 0]

A few questions on this.... Would something like This be suitable for measuring? and how are we mounting this to the head?

 

Thanks James

[Mad Scientist 106]

That's right. A dial test indicator is what you need. I have a couple with magnetic mounts. If you look on eBay you can get the stands. However, you will have to adapt the stand to be bolted to the head as its alloy.

 

This worked perfectly by the way. The engine is now running like a sewing machine!

[James_m 0]

Another old thread resurrection! Any pictures of how the dial gauge has been mounted to the head?