Just another 2056 build, Misc Questions Options

[sdoolin]

Have I mentioned that I hate the new spiral-in wrist pin retainers?

I saw a youtube vid where the person stretched the springs out so they looked more like a spring than a washer when sitting on the table.
Then they can go in with one finger.
You just start one end then compress the spring and they snap right in.

For getting them out, I took a tiny screwdriver and bent the tip to form a tiny hook to grab the end.

Like this one:
https://www.youtube.com/watch?v=vOYH_WICGYM

Thanks for the linky - I hope it helps me overcome my disdain for the things.

[Bulldog9]

This is exactly the way to do it. Stretched them about 3/4 to 1" then twist/rotate it in to place till it is tight and a long pic or thin screwdriver to slowly work it in. I wouldn't call it easy, but it wasn't bad.

Have I mentioned that I hate the new spiral-in wrist pin retainers?

I saw a youtube vid where the person stretched the springs out so they looked more like a spring than a washer when sitting on the table.
Then they can go in with one finger.
You just start one end then compress the spring and they snap right in.

For getting them out, I took a tiny screwdriver and bent the tip to form a tiny hook to grab the end.

Like this one:
https://www.youtube.com/watch?v=vOYH_WICGYM

[Bulldog9]

Steve Pratel - I have moved on from the CR thing, have removed .72mm from the tops of the jugs targeting a 9:1 CR.

So I imagine that your earlier measurements/assumptions were off? In an earlier post you said "Plugging bore (96mm), stroke (71mm), deck height (.039) and chamber volume (55.2) into the CB Perf. engine calculator it yields a CR of 9.3 - 1. Is that too much?"

If those number were correct, removing material from the jug will INCREASE your CR not reduce it. If you wanted to go from 9.3 to 9.1 you should have added to the cyl height with a spacer under the jug thus increasing cyl height not reducing. In other words when you reduce height you reduce the chamber size with same bore and stroke, this increases CR. Unless your initial measurements were off or you are doing new math. Either way its your engine man, do what you want.

[sdoolin]

Steve Pratel - I have moved on from the CR thing, have removed .72mm from the tops of the jugs targeting a 9:1 CR.

So I imagine that your earlier measurements/assumptions were off? In an earlier post you said "Plugging bore (96mm), stroke (71mm), deck height (.039) and chamber volume (55.2) into the CB Perf. engine calculator it yields a CR of 9.3 - 1. Is that too much?"

If those number were correct, removing material from the jug will INCREASE your CR not reduce it. If you wanted to go from 9.3 to 9.1 you should have added to the cyl height with a spacer under the jug thus increasing cyl height not reducing. In other words when you reduce height you reduce the chamber size with same bore and stroke, this increases CR. Unless your initial measurements were off or you are doing new math. Either way its your engine man, do what you want.

Nope, my earlier measurements/assumptions were spot on. There is a 1mm step in the head which essentially adds to the deck height, and I was not including that in my original measurement (my posts actually describe this in great detail - maybe you could read more carefully).

I have now removed .72mm from the top of each jug and have re-measured deck height. Deck height in the jug is .33mm. Add that to the 1mm in the head for a total deck height of 1.33mm. Plug the numbers into the calculator and it returns CR of 9.00:1

Exactly what I was looking for. Not new math and yes - it is my engine and I shall proceed as I see fit. Thanks for your help... (IMG:style_emoticons/default/screwy.gif)

[MarkV]

Just seems odd that the entire 914 world has to add shims to get their CR set and you are having to build a special jig to remove material from the tops of the cylinders. Did you ask Len about the step in the head? I looked at the photos and can't tell if the step is a recess or if it is proud of the combustion chamber. If it's proud of the head then I guess I can see why you are doing what you are doing. Why do the heads have a step are they some kind of ultra low compression bus heads or something? (IMG:style_emoticons/default/confused24.gif)

[stugray]

I got sage advice from HAM that there is 1mm of step (deck height) in my cylinder heads. This gives me a total deck height of 2mm.

I am targeting 9:1 Compression ratio. Plugging the numbers into CB's engine calculator and solving for deck height it yields 1.28mm for a CR of 9:1.

If the heads have a 1mm lip, did you account for that in your combustion chamber number?
Or did you measure the comb. chamber volume?

You comb chamber number seems smaller than a stock head.
I had to shave my heads down significantly to get below 55 cc.

Stock is almost exactly 60 cc.

I did account for the 1mm step in the heads in my combustion chamber number, or rather Len did at HAM. I did not CC the heads myself, that was done by Len at HAM. The spec sheet that came with the heads says the chambers are 55.2 CC. I am pretty sure Len's number is accurate. Much more so than mine.

I still find this conclusion suspicious.
I had my heads machined significantly and barely made it to 55 cc without the 1mm step.
If the step is designed to add to deck height, then it is not obvious if the 1mm contributes to combustion chamber volume OR deck height.

I fear that you might be double booking that value in your calculations.
The only way to be sure is to measure them yourself or call Len and ask.

If you measured the comb chamber volume with the clear acrylic disk sitting on top of the 1mm lip vs sitting down flush with the comb chamber, you would get a difference of 2.3 CC

There has to be a simple answer to: "WHY is there a 1mm step in the heads?"
I have never seen or heard of that as that is an automatic deck height of .039 assuming that the pistons are flush with the top of the cylinders.
Maybe that step is for pistons with a non standard wrist pin height?

[sdoolin]

Just seems odd that the entire 914 world has to add shims to get their CR set and you are having to build a special jig to remove material from the tops of the cylinders. Did you ask Len about the step in the head? I looked at the photos and can't tell if the step is a recess or if it is proud of the combustion chamber. If it's proud of the head then I guess I can see why you are doing what you are doing. Why do the heads have a step are they some kind of ultra low compression bus heads or something? (IMG:style_emoticons/default/confused24.gif)

I agree it seems odd that I am seemingly the only guy on the planet (in the "world") to go down this road. (IMG:style_emoticons/default/blink.gif)

Len is the individual that informed me of the 1mm "step" in the heads. It is proud of the roof of the combustion chamber proper. I don't know if the heads are anything other than "standard" RS spec heads from HAM.

Len has weighed in on my build a few times by PM, which leads me to believe he is reading this thread occasionally. The fact that he has not weighed in negatively with respect to the removal of material from the jugs leads me to believe I am OK.

I test fit everything yesterday (a few times) and I measured .33mm (1/3 of a turn) of deck height in the jug with my calibrated screw/plate measuring device. The measurement is very repeatable, and is very (very) nearly identical across all cylinders.

The heads bolt up, with a small gap between bottom of head and top fin of the jug (no gasket at base of jug, or in the head). I did not measure this gap (yet) but since there is space there with everything torqued to spec, I believe I am OK.

[sdoolin]

I got sage advice from HAM that there is 1mm of step (deck height) in my cylinder heads. This gives me a total deck height of 2mm.

I am targeting 9:1 Compression ratio. Plugging the numbers into CB's engine calculator and solving for deck height it yields 1.28mm for a CR of 9:1.

If the heads have a 1mm lip, did you account for that in your combustion chamber number?
Or did you measure the comb. chamber volume?

You comb chamber number seems smaller than a stock head.
I had to shave my heads down significantly to get below 55 cc.

Stock is almost exactly 60 cc.

I did account for the 1mm step in the heads in my combustion chamber number, or rather Len did at HAM. I did not CC the heads myself, that was done by Len at HAM. The spec sheet that came with the heads says the chambers are 55.2 CC. I am pretty sure Len's number is accurate. Much more so than mine.

I still find this conclusion suspicious.
I had my heads machined significantly and barely made it to 55 cc without the 1mm step.
If the step is designed to add to deck height, then it is not obvious if the 1mm contributes to combustion chamber volume OR deck height.

I fear that you might be double booking that value in your calculations.
The only way to be sure is to measure them yourself or call Len and ask.

If you measured the comb chamber volume with the clear acrylic disk sitting on top of the 1mm lip vs sitting down flush with the comb chamber, you would get a difference of 2.3 CC

There has to be a simple answer to: "WHY is there a 1mm step in the heads?"
I have never seen or heard of that as that is an automatic deck height of .039 assuming that the pistons are flush with the top of the cylinders.
Maybe that step is for pistons with a non standard wrist pin height?

The heads are brand new from HAM and the spec sheet that came with them (hand written - probably by Len) indicates that specific combustion chamber volume. I have not CC'd them myself as I (still) trust Len's number much more than I would mine. Len has communicated this 1mm step to my via PM, and he indicated I needed to add it to my overall deck height. I believe his words to me were "you'll have plenty of room". I choose to believe the guy.

I guess we'd need Len to weigh in on the reason for the 1MM step. It is there, I can see it and I even measured it (it is 1mm). I'll try to snap a picture of it today.

Thanks for the thoughts Stugray.

[sdoolin]

The mysterious 1mm "step" really does exist folks, pic below...

[sdoolin]

[sdoolin]

Combustion chamber volume as measured by HAM...

[MarkV]

You would think that if Len saw this thread he would chime in. There must be some kind of explanation. Hopefully you aren't subtracting for a step that has already been subtracted.

I would probably mock up a pair of lifters, push rods and rockers and do the clay test to verify that you aren't going to have valves getting too close to pistons.

[sdoolin]

You would think that if Len saw this thread he would chime in. There must be some kind of explanation. Hopefully you aren't subtracting for a step that has already been subtracted.

I would probably mock up a pair of lifters, push rods and rockers and do the clay test to verify that you aren't going to have valves getting too close to pistons.

I have reached out to Len, and yes - I do intend to clay the heads. I will manufacture an adjustable pushrod this week such that I can use the exact ball ends that came with my pushrods.

[HAM Inc]

The initial reasons we started putting a step in the new heads over 15 years ago was for head strength, and to simulate the thickness of the factory head gasket, which is ~.75mm.

Of course back in the '70's VW issued a bulletin calling for the removal of the head gasket, and restoring the lost deck ht by putting a spacer under the jugs. The 1mm step eliminates the spacer compensation requirement.

Over time we grew the step from .75mm to 1mm for a couple of reasons: it's a safe deck ht spec, and since most (every one I've ever seen, and I've decked over a hundred of them) cases need the spigots decked to correct sagging and warpage the increased step ht allows the cases to be decked to either allow zero deck in the jugs, or to at least compensate for the lost deck ht from a minimal spigot decking, which is generally in the ball park of .005", though bus cases can be quite bad and I've had to deck some of them as much .5mm to correct the sag/warpage.

I have no idea why Steve had so much deck in his jugs, but having decked as many cases as I have I know that these things do vary quite a bit, and I have seen some that were way off from typical factory specs. It happens.

[MarkV]

The initial reasons we started putting a step in the new heads over 15 years ago was for head strength, and to simulate the thickness of the factory head gasket, which is ~.75mm.

Of course back in the '70's VW issued a bulletin calling for the removal of the head gasket, and restoring the lost deck ht by putting a spacer under the jugs. The 1mm step eliminates the spacer compensation requirement.

Over time we grew the step from .75mm to 1mm for a couple of reasons: it's a safe deck ht spec, and since most (every one I've ever seen, and I've decked over a hundred of them) cases need the spigots decked to correct sagging and warpage the increased step ht allows the cases to be decked to either allow zero deck in the jugs, or to at least compensate for the lost deck ht from a minimal spigot decking, which is generally in the ball park of .005", though bus cases can be quite bad and I've had to deck some of them as much .5mm to correct the sag/warpage.

I have no idea why Steve had so much deck in his jugs, but having decked as many cases as I have I know that these things do vary quite a bit, and I have seen some that were way off from typical factory specs. It happens.

The question is whether he should have used the 62.2 cc figure that you provided or whether he should have subtracted for the step and used 55.2 as his combustion chamber size. I vaguely remember that when you did my heads 9 years ago they came back with a step but I used the cc number that you calculated. It seems like if he subtracts for the step the compression ratio is going to be calculated wrong.

[DaveO90s4]

Assume the 62.2 chamber volume is inclusive of the 1.01 mm step (not an unreasonable assumption). Assume also flat top pistons.

Swept volume is 514.12 cc

Chamber vol is 62.2 cc minus 0.72x48x48x pi equals minus 5.2 cc yield chamber vol 57.0 cc

Add stated 0.039" (1 mm) deck height equals 7.2 cc

Total volume at bdc equals 514.12+ 57.0 + 7.2 = 578.32 cc

vol at tdc equals 57.0 + 7.2 = 64.2

Static cr = 578.32 / 64.2 = 9.008.

That's my maths anyway.

Looks spot on. Subject to the initial two assumptions

Dave

[HAM Inc]

If you read the yellow spec sheet, which we prepare with every pair of our new heads, you'll see the following:
Chamber volume = 55.2cc's
1mm Step volume = 7.0cc's.
Total head related volume = 62.2cc's
Add 62.2cc's to the volume in the jugs @ TDC and you have total unswept volume.

Seems pretty straight forward to me, but if you guys have a suggestion of how to make this any clearer, I'm all ears.

[stugray]

Dave090s4's calcs are correct.

They match mine:
96mm X 71mm swept volume:
48X48X3.14159 X 71 = 513,914 / 1000 = 513.914cc

Head comb chamber (including 1mm step) = 62.2cc
Volume of step = 48X48X3.14159 X1 = 7.2cc
Comb chamber (minus step) = 62.2 – 7.2 = 55cc
Measured deck height before trim = 1mm
Cyl. Deck height after trimming of .72mm = 1.0 - .72 = .28mm
Deck height = 1mm (in head) + .28mm (in cyl) = 1.28 mm
Deck height volume = 48X48X3.14159 X 1.28 = 9.26 cc

Total volume = Swept volume + deck height volume + comb chamber volume
TV = 513.914 + 9.26 + 55 = 578.174
Compressed volume = deck height volume + comb chamber volume
CV = 64.26
CR = Total Volume / Compressed volume
CR = 578.174 / 64.26 = 8.997


So I think the answer is: this works just fine.
However if the OP had ordered the heads without the 1mm step, he could have shimmed the cyls UP to reach target CR instead of machining the cyls DOWN.

That is exactly how mine is setup, but I had heads with 56cc comb vol (no step), cyls shimmed for a total deck of .89mm for a final CR of 9.2.
My spigots HAD been decked so my cyl only deck was less than 1mm to start with.
If I had wanted to adjust down to CR = 9.0, I would only have had to add more shims.

[sdoolin]

Y'all are killing me. I think we are in violent agreement that my CR is very nearly 9.0:1?

(IMG:style_emoticons/default/hissyfit.gif)

[DaveO90s4]

Seems that way!!

Maybe revised spec wording along the lines "Total combustion chamber volume per chamber is 62.2 cc. This volume is measured from the cylinder head compression mating surface so includes the volume created by the 1.00 mm lip."

Just a suggestion.

DaveO