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Old 15-05-2015, 08:15 PM   #31
iain ambrose
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Now that I have the head cc details though I would check what compression has been lost due to the head work.


That's a fair drop from 10.5 : 1 but it's to be expected and should easily be offset by the port work flow increases.
If I wanted to regain the compression I could still get the heads flycut.
It's also possible to run without the 1mm compression rings although this would still required 1mm taken off the head in order to not squish the head gaskets and I would be concerned by leakage into the cooling system.

Major headaches with setting the correct geometry
I've managed to correctly shim the rocker shafts but I will cover that later.
With the engine mocked up once more I started by confirming the actual lift as being 497'.
This means the rockers are more like 1.3:1 rather than the advertised 1.25:1 but JC warned this may happen.
There are numerous 'guides' on the interweb about correctly setting geometry and many conflicting suggestions.
I won't go into details but I think one picture summed up the actual goal.



This makes perfect sense so it's my goal to get a 90 degree angle between the rocker pivot and valve stem at 50% lift.

After a quick play with shims under the rockers it was immediately obvious I was going the wrong way, so I removed them and recorded a straight fit.

Trying to get a consistent picture without a proper stand is tricky but I think it's giving a pretty good indication.
Clearly the angle is too acute
I have two sets (well nearly too sets having lost a couple of used ones) of lash caps that are different thicknesses.

Both sourced from JC but the right one is a new scat unit and thinner than the used left one.



As i need to either lower the rocker pivot or raise the valve height I ran the check again but using the old thicker cap.

Definitely an improvement, but not enough and in any case I don't have a complete set
Based on what I am seeing it looks like the rocker stands will need machining down to get things square with the new lash caps.
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Old 15-05-2015, 08:16 PM   #32
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I've just run through another check but this time focusing more on accurate camera positions.
There are no base shims and i'm using the new lash caps.

I might have to consult with the guru as my approach appears too inaccurate for repeatable results.

Ok, think I know how to sort the geometry.

First a hopefully more accurate picture at half life using the rocker pivot point as the center of the photo.


I got confirmation from JC that 90 degrees is the correct angle to achieve at half lift on both sides.
From the picture it's clear the pushrod is well short of 90 degrees and the valve side is just a little high.
The swipe pattern currently looks great on the tip.


I measured the thickness of the two types of lash caps I have:

1. Manley tight fit - 088' / 2.25mm - Fitted for this test.
2. Scat loose fit - 066' / 1.68mm

These seem to be the only thicknesses readily available for 8mm stem valves.

The solution appears to be machining the rocker stands and using the Scat caps.
Dropping the rockers should bring the pushrod closer to 90 degrees and lowering the valve height using the thinner caps should hopefully keep things close to 90 degrees that side.
As I have a selection of rocker stand shims it will allow me to fine tune things, which is something I cannot current do.
I'll see if JC will confirm my judgement and undertake the required machining.

On a related note I spent 5 1/2 hours getting the gearbox/drive train back into the bug this weekend so it's pretty much ready for an engine, should that be arriving anytime soon
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Old 15-05-2015, 08:17 PM   #33
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Update time:

Whilst I wait for my rocker stands to be machined I've moved onto dialing in the camshaft.
Having established an accurate TDC the goal is to confirm both inlet and exhaust open/close times match the cam card and subsequently the timing position is good.
An acceptable tolerance for a street engine is +- 1 degree off spec.
For fine tuning you can machine the cam wheel with slots so that it can be turned to adjust the timing position and there are also aftermarket wheels with eccentric bolts that achieve the same results.


My first issue is that the wbx engine has a different style of pulley wheel than a T1, so an off the shelf degree pulley wheel is not an option.
I located a printable degree template off the late and great Bob Hoover's blog page.

Not being sure of the required size I printed 3 options.
I also marked them up with the cam inlet/exhaust specs for checking.
Modified another cd so that I can fine tune the position once TDC has been established.


To establish TDC I fitted up number 1 piston and used a dial gauge through the spark plug hole.

For a precise position I measured 10' BTDC and marked on the pulley wheel and then 10' ATDC with another mark.


The center of the two marks is TDC which happily corresponds with the oem mark.
Accurate measuring is critical for this as the margins are less than 1 degree for a well dialed in cam, so I used one of my solid lifters on the cam and secured the gauge tightly on the case.

My dial gauge was original purchased to set a diesel fuel pump timing and came with a handy extension to the reading tip.
This has proved invaluable for this test and simplified the whole process as you would normally be forced to read the lift off the rocker or even the valve retainer.
The results don't look good

I retested 3 or 4 times but came to the same results, so it appears I have an issue with the camshaft.
The exhaust is pretty close and could be down to measuring inaccuracies but the inlet is way off the closing spec.
Gonna need to consult with JC on this one.
And it was all going so well.....
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Old 15-05-2015, 08:18 PM   #34
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Just been researching about this cam and it appears the measurements should be taken at 50' of 'valve lift' rather than 'cam lift'.

Done some maths on my figures so far:

Inlet Open 23 BTDC
Inlet Close 53 ABDC

50' duration = 180 + 53 + 23 = 256 degrees.
Lobe centre = 256 / 2 - IO = 128 - 23 = 105 degrees.

Exhaust Open 56 BBDC
Exhaust Close 21 ATDC

50' duration = 180 + 56 + 21 = 257 degrees.
Lobe centre = 257 / 2 - EC = 128.5 - 21 = 107.5 degrees.

Lobe separation is (105 + 107.5) / 2 = 106.25 degrees.



Lobe center's are advertised as 108 degrees for both inlet and exhaust.
I fail to see how measuring lift from the valve rather than the lifter will change the lobe separations so IMO there is still an issue with the inlet lobe.
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Old 15-05-2015, 08:19 PM   #35
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Good news regarding the cam readings.
Spoke to JC and it appears I have a lobe offset camshaft with a 105/108 degree split.
This is an available option from Web but to be sure I need to dig out the original box/cam sheet to confirm.
Having some lobe separation should work nicely for me as it will extend the torque power band at the expense of maximum torque, but with so much torque to start with it's a trade off i'm very happy with
More specific details here --> http://www.compcams.com/technical/FAQ/LSAproperties.asp
Apparently my rocker shaft stands have been machined so I should be able to complete the geometry, order the pushrods and start the actual build.
Bloody hell, it's been over a year!

And that is everything up to date, but there is some exciting news coming early next week....
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Old 20-05-2015, 12:28 PM   #36
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Hi Iain,

I'll read this with interest later. I feel the inclining that I may be making some progress shortly on some elements Proper reply when I've read through!
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Old 21-05-2015, 10:39 AM   #37
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Good read Iain. What is your expected output with the build in its latest form. And the question that is the back of my head, and probably the answer is that you already have the carbs, but was FI a consideration?
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Old 22-05-2015, 12:07 AM   #38
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Quote:
Good read Iain. What is your expected output with the build in its latest form. And the question that is the back of my head, and probably the answer is that you already have the carbs, but was FI a consideration?
Thanks
Output is somewhat unknown but the latest addition to the project will certainly help!




Refurbished Dellorto 48's
I looked at FI but the cost is too high for a setup suitable for this build.
The stock system would never work and is way too simple by modern standards anyway.
Also the rocker stands are back so I hope to get the geometry finalised this weekend.
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Old 25-05-2015, 10:03 PM   #39
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Finally it's done

The machined stands brings the geometry spot on.
Interestingly the adjustable pushrod length is almost identical to the stock wbx one so I can use them.
All checks are now complete so I can start to actually build the engine
The case has been re-cleaned (had a quick bath) ready for assembly next week.
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Old 28-05-2015, 10:37 PM   #40
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Started on the case cleaning.
It's already had a chemical clean plus several 'baths', but there is plenty of stubborn grime in all the nooks and crannies.
After some research I ruled out using oven cleaner as it's not aluminum friendly.
Stuff like kerosene is out as this is being done inside, so nothing with fumes or anything that might damage the bath tub.
First I use a scouring pad with washing up liquid on the accessible areas.
Next up I used WD40 and left it soaking for a few hours.
It does work but you can't just wash it away with plain water and it required washing up liquid with more scrubbing.
Lastly I used some bath cleaner.

Actually to my surprise it is very effective and some work with a toothbrush has shifted the worst of the baked on crud.



This is a good start but I really want to get all that gunk out of there so I will get some more of this cleaner as it's working nicely
When this is all done I plan to use compressed air to flush out any particles that may have strayed into the oil galleries.

Just out of interest here is a wbx case along side a T1 case for comparison.



Red shows the head studs do not enter the case to prevent oil leaks and probably more strength.
Yellow shows two oil returns from the flywheel end to help prevent main rear seal leakage due to pressure.
Blue shows the gallery that returns circulated oil direct to the oil pump rather than to the sump.
Green shows the strengthening web removed to allow crank case pressure to flow between the piston banks.
You can clearly see that VW based the WBX on the T1 engine but made important changes required for a more performance application.
Also note the higher case roof to facilitate a 74mm crank and also the extra strengthening.

Unsurprisingly many performance T1 engine builders modify their cases in similar ways.
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