[project] Project 205 Xu13j4

[Andy 105 1 Cars]

Valve spring tester would be great, but expensive to buy and for a one off, definitely not worth it. Ideally, you need a weight, say 3/4 kg from an old fashioned set of scales . Then , place spring on a flat hard and level surface and measure the free height,. Add known load and measure height again . Plan ‘b’ involves a G clamp , set of bathroom scales and a couple of bits of flat wood. Put the G clamp around the scales , using wood top and bottom to protect scales and give an even surface. Then wind the clamp until you have a few kg of preload on the scales , then reset the zero. Then wind the clamp an accurately measured number of turns and read the load applied . You now know that the g clamp applies x kg per full turn . Use your ‘ calibrated ‘ clamp to measure your spring . Plan ‘c’ Give Catcams a ring and ask them to clarify the discrepancy between the published data for those PAC springs and the ones you have in front of you . Thinking about it , plan ‘c’ goes first 

[Andy 105 1 Cars]

Post script. If you look at the data table, the spring appears not to be entirely linear. I think that there is some rounding in the load column which is causing the discrepancy . There is another way to look at this. The springs are well made and consistent . So, if you install them all at the same height, you will be running all 16 valves with the same preload . I have used 37.00mm now on four engines . I am pretty sure that Peter Taylor has used the same installed height when he has used these springs (?, Peter May confirm ) , so perhaps the thing to do to move your build on is the measure said installed height and sort out spring seat shims to get said height . I ended up buying some one off shims from ‘Precision Shims ‘ in Australia . Great company to deal with and quick dispatch 

[petert 587]

A valve spring tester. Best visit your local head reconditioning place. Ask for a load at 37, 38, 39 and fully open, say 26mm?

Edited October 1, 2019 by petert

[B1ack_Mi16 67]

Yes I will try to get it measured somehow. Maybe the bathroom scales in the hydraulic press will work as I'm not so tempted on paying someone to do it.

 

Finished revision 12 on the headgasket and got it converted to a DXF file finally last night, so now I just need to re-calculate the compression ratio before I select gasket thickness and place the order.

 

[petert 587]

For some stuff, you just have to pay. Spring heights & loads is one of those things, if you want piece of mind. I can't understand why you wouldn't after investing so much money.

[B1ack_Mi16 67]

It is mostly down to my new personal situation. Having a house one ideally should be minimum 2 to pay on.. so I just try to do everything quite on the cheap side these days.

I know the setup worked fine to 8000rpm as it was before so I'm not afraid of just putting it back together as it was in worst case, but for sure I will get it measured somehow.

[B1ack_Mi16 67]

Did some calculations on the spring design (as close as I could get it without spending too much time on it). Will be interesting to see if it matches reality or not.

 

 

 

Force vs. length, strangely enough, L = 37mm seem to give more or less exactly 40kg of force.

 

Edited October 2, 2019 by B1ack_Mi16

[Andy 105 1 Cars]

Yep.That's exactly what PAC claim for this spring . Set the installed height at 37.00mm . It will be correct .

[B1ack_Mi16 67]

Yes. Although this is my 48mm long and 3.9mm diameter spring.

Catcams confirmed on email that the spring they sell today certainly is 46.2mm and 4.1mm diameter. 

[B1ack_Mi16 67]

Measured the head chambers today to 45cc

Also used clay and put into the valve cut-outs of the pistons which in total was about 3.5cc complete.

Volume between piston and bore from top of piston down to first  compression ring is about 0.5cc according to my CAD model.

 

Luckily the piston cutouts was a bit less than I had estimated, but it seem like the engine have been running with 11:1 compression in the current configuration with 1.3mm thick headgasket, and not 11.6:1 as was the aim back in the days when my enginebuilder did most of the work anyway.

 

To get the compression up to 11.6:1 I will need a 0.8mm thick headgasket.

 

Do anyone know whether 0.8mm is enough clearance between the top of the piston and the surface of the head itself, or can the rod stretch more than this during high revs?

Is there a rule of thumb or do I need to calculate this too...?

 

[Andy 105 1 Cars]

Others on here are more qualified than me to give definitive advice ..However, when I went through exactly this process for my 2.3 litre engine , I specified the piston dish volume based on a 1.00mm gasket , with the piston flush with the deck at tdc . Reason for 1.00mm.? Main one is squish volume . 0.8mm May be o.k, but I think it is a bit marginal . Other clearances will be fine or not depending just on your measurements and calculations . Valve lift at tdc and just after, piston pocket depth , gasket thickness etc . Check all this as these considerations as this factor may determine what gasket thickness you can have , unless after checking you are able to machine the valve pockets if needed. 

I am absolutely sure you know all this better than I . 

Best of luck.

 Andy

[petert 587]

I've run 0.7mm, which about the limit for a steel rod. You'll obviously need to recheck your valve-piston clearance.

[B1ack_Mi16 67]

Ok, the rods are Crower cromoly H-beams and pistons are quite light, but maybe a 1mm gasket and 11.4:1 still will be a nice compromise.

 

The valve to piston clearance I think was quite good, it was more scary with the valve to valve clearance I seem to recall, but indeed it should be checked out.

A bit boring though to set all the timing etc. and then dismantle the lot again. I suppose that is how to do it with a piece of clay or something like that on the valve?

 

[petert 587]

No, I do it dry, no spring or retainer, and drop the valve onto the piston, measuring how far it travels with a dial indicator. Then subtract lift @ TDC. Don't forget you need to do the inlet at 10º ATDC and the exhaust 10º BTDC.

[B1ack_Mi16 67]

Ok, I can do it with the old gasket then as a start.

[welshpug 1,657]

thought you would be running more than 11, arent the cams quite wild?

[B1ack_Mi16 67]

That's why I hope to at least get it a bit up using a thinner gasket... first time I measure the volumes myself so engine ain't exactly as it was supposed to.

[Andy 105 1 Cars]

50 minutes ago, B1ack_Mi16 said:

That's why I hope to at least get it a bit up using a thinner gasket... first time I measure the volumes myself so engine ain't exactly as it was supposed to.

Yep. It happens . When I did mine I specced the pistons on the assumption that the CC volume was 40cc. It was more like 43.5cc which , as they say, buggered things up a bit . The lesson is  to prep the head, measure the CC volume, then spec the pistons with a known HG thickness , lift at tdc etc . You do not have that luxury as your pistons are already in place . Out of curiously, are your pistons flush with the deck at tdc ? 

Andy

[B1ack_Mi16 67]

Indeed that is the way around when doing it properly.

 

I could have put a different head on it of course, but the big valve job etc. did cost some cash so I prefer just to keep it now.

 

The pistons are exactly flush with the deck it seem.

 

 

[B1ack_Mi16 67]

Dialled in TDC this evening and measured valve clearances.

 

 

 

 

 

[B1ack_Mi16 67]

The center plate of the old Cometic gasket turned out to be exactly 0.8mm thick, so I put that between the head and block and bolted the head down.

 

The clearances I found is as follows:

 

 

And this is the camdata

 

[B1ack_Mi16 67]

Not sure what to use the +-10 deg values for at this time unless I somehow measure valvelift too based on cam-position?

[petert 587]

The piston is usually closer to the inlet valve after TDC. Every rod and stroke combination is different however. You'll need to do it again at +5 (inlet) and -5 (exhaust) to be sure.

 

Considering your TDC figure for inlet, that only leaves 1.23mm (0.048"). It's going to be worse for two reasons:

 

1. The inlet will get closer after TDC

2. You wouldn't install that inlet at 108. It should be more like 106, which will further decrease the valve-piston clearance.

[B1ack_Mi16 67]

I think I'll have to test-mount it anyway then.

Time up the cams with dummy springs installed in one cylinder and try to do some logging of the camlift around TDC.

[Andy 105 1 Cars]

Yep. Or , if you have it, the lift vs degree curve from the cam manufacturer , because that would tell you what the lift was designed to be at those angles . Catcams seem to publish that data with their cams, but not sure about other suppliers .

When I did mine, I asked the piston manufacturer to give me a VP depth ( which I specified ) that gave me 3.mm clearance at tdc  Just to be sure though, I did as Peter suggested and bolted the head down with one weak spring in one valve and checked at and around tdc . At least I then knew that I could swing the timing around my 106 degrees LCA  with at least  some margin