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#195
by
andy2
on 05 May, 2007 13:04
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Well my newer setup involving copper headgasket and stainless steel "o-ring" is not holding much better than factory Headgasket and factory headbolts. I'll be pulling the head off to cryo treat it and possibly creamic coat the exhaust ports in an attempt to make the head more stiff also we will be lowering the compression a bit by upsizing precups from 6.2 NA to 6.5TD.We are having some issues with threads in the block as we got a little carried away with headbolt torque :oops: so we will need to put something bigger in place of the 12mm mabye 13,14 mm.Perhaps Bruce will post up some pics of his work done with the copper HG and head machining so it can be drooled over :lol: .I've got another car now so this car is not going to be daily driven all the time so we can take the time needed to sort out all of these endless issues to persue this engines max potential :twisted:.
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#196
by
jtanguay
on 05 May, 2007 15:06
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surprised that even with all those mods it is still leaking... i can only imagine the pressures going on in there :shock:
i hope the cryo & ceramic coating helps!!!
maybe going to bigger head studs will be the key??? there was also talk of a girdle that could go inside the head to beef it up, since the soft aluminum might be the problem.
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#197
by
malone
on 05 May, 2007 16:33
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Wow, how much boost were you pushing with the copper headgasket and o-rings? I'd like to see pics of the o-rings too. Hopefully the head stays put next time!
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#198
by
andy2
on 06 May, 2007 09:41
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I was only running 30 psi and have not yet setup the trubos But there is alot of fuel going into that engine with the 12mm head cranked up pretty good (105cc).On 30 psi the EGT's are out of control so I figure it will need 35-40 psi to lower temps and probably make a good bit more power in the process.
We were looking into making a head support (girdle) and possibly will be.
I was talking to an older vw mechanic and he said that the older 1.5 and early soild lifter 1.6 heads were much better quality,better material,better castings.He sugested using one of those castings to build up??
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#199
by
935racer
on 06 May, 2007 21:01
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Andy I have been working with fellow that has literally oringed and fire ringed hundreds of cummins heads, after my first couple of copper HG failures we talked about it and he said hes never had any luck with copper HG's, he told me for running O rings to use a fiber gasket and use an oring in the head and block. We are going to try and just make a fire ring on my new 1.6 daily driver in a couple weeks here, I will use a 1.9 MLS gasket because its already oversized ready for a firering! Shoot me a PM we can discuss some specs for the firering cuts/machining. Making a head girdle would be pretty badass :twisted: But I don't think its necessary. Those big cummins only run 12mm studs.
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#200
by
jtanguay
on 07 May, 2007 05:15
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i'm really surprised at the copper head gasket issue... copper is such a good soft sealer... but then again running at huge pressures and temperatures... :shock:
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#201
by
HarryMann
on 07 May, 2007 18:42
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Perhaps it's time to use Water Injection to control EGTs, lower Peak Pressure spikes and give you back some of that energy later in the power stroke - it's such a powerful tool... even 50% water to fuel might make all the difference?
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#202
by
QuickTD
on 07 May, 2007 21:22
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Perhaps Bruce will post up some pics of his work done with the copper HG and head machining so it can be drooled over :lol:
Ask and ye shall receive.
Milling the o-ring groove on the cnc, .040 diameter solid carbide endmill, careful is the word. Never used tools that small before to cut iron. Worked pretty well, if time consuming. 0.8inches per minute feedrate and ~0.015 depth of cut , 2 passes for each groove. The grooves go out around the (much larger) prechamber, sealing at the same location as the stock gasket.
Head gasket, cnc milled from 0.062" sheet copper. If anybody would like the math, I now have it.
O-ring receiving grooves, also cut on the cnc but with a larger 0.062 end mill, not as deep as the O-ring groove and in aluminum, so much less stressful.
The added head and block dowel pin holes are machined in the same setup, so the o-ring and receiver grooves register precisely.
Shame about the whole setup not working as well as expected. I can attest to the flatness and surface finish of the head a block surfaces, the only thing I can figure is that the head is flexing under load, or the studs are stretching. Larger head studs may help? Some sort of girdling for the head? I'm out of ideas...
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#203
by
935racer
on 07 May, 2007 22:01
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Nice work Bruce!
Few thoughts and questions, why go around the prechamber? I would have cut right into the pre chamber, and made sure I changed my feed rate before I hit the iconel :lol:
Reason being is that I think I'd want the o ring to be as close to the combustion area as possible, and in a perfect circle, with the oval like cut out for the pre cup its going to give that excessive PCP somewhere to squeeze between the copper HG and block/head deck surfaces a lot easier than if the O ring was consistant all the way around. Its kind of hard for me to type this and explain it :?
I am personally going to try and fire ring my new engine, I hear it holds a lot more boost than O ringing, makes sense.
Did you CAD that HG out yourself? If so that probably took a while, I need to do that soon :cry:
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#204
by
QuickTD
on 07 May, 2007 22:24
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The reason I went around the prechamber was to avoid leakage at the prechamber/head junction. The lower lip (counterbore) of the chamber is not a press fit in the head. If you drive out the chambers and measure them relative to the bore you'll find they only press into the upper bore, there is some clearance at the counterbore. This would port combustion gas over the o-ring to the coolant passages unless sealed at the perimeter. The stock gasket crimp ring goes outside of the prechamber for this reason, no attempt is made to seal it at the bore. This is even more obvious on the composition gaskets where there is a steel insert under the chamber, no sealing at the bore edge. The amount of added surface area is negligable, I didn't think it would make much difference. Then again, it didn't work, did it...
Perhaps using oversized prechambers and machining to insure that they are a nice press fit in the counterbore as well as the main bore and o-ringing it with round o-rings would be the answer. It would be impossible to end mill the groove through the inserts (much too hard for solid carbide, easpecially at that size) but since the groove is round it could be cut using a single point CBN or ceramic tool. Your turn to try it Dave...
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#205
by
QuickTD
on 07 May, 2007 22:30
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Did you CAD that HG out yourself? If so that probably took a while, I need to do that soon
Yes, I did, and yes, it did... Lots of plotter paper consumed for proofing... Like I said 2 posts up, if you or anybody wants the math I can send you DXF or IGES, no sense all of us having to suffer through it. Hell you can even have the NC code if you like, the more the merrier...
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#206
by
935racer
on 07 May, 2007 22:37
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Hmmm I see what your saying, that makes sense too, do you have any idea where it failed from? I kind of assumed that because you put larger precups in both bores would have been press fit. How tight of a press fit do you think you could do? I am still really new to machining, just got my first CNC mill, a Tree journeyman 330, 40 taper. Its pretty fun! I'd love the DXF file!
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#207
by
935racer
on 07 May, 2007 23:18
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I just looked at making some girdles for the heads, I don't think its gonna work, there are these supports that go from the edge of the head to the center of the head where the lifter bores are, I would assume these add quite a bit of strength in maintaining the bores roundness. The only decent way I see of making a head girdle would be milling these out than getting an end mill the same diameter as the recesses for the head bolts at the same depth than running it the length between the two outermost head bolt holes. So there would be 2 "girdles" , one for each side, basically they would be really beefy 1.6td valve cover hold down straps :lol:
But yeah, I don't like the idea of milling those lifter bore supports out...
FIRERING :twisted: (please work please work please work)
Guess I need to put my money where my mouth is and give it a try.
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#208
by
foxracer1
on 08 May, 2007 04:18
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So please explain the diff. between a firering and an o-ring. I thought i understood this but now i don't think i do.
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#209
by
QuickTD
on 08 May, 2007 07:27
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I'm also curious about the method of using CAD in the machining. Could you guys go into a bit more detail. I am currently an AutoCAD Architectural Drafter for employment and curious what software and methods you use.
Andrew
In order to generate a tool path for machining you need to start with a vector (line) drawing. I use bobcad/cam for drawing and generating the toolpath for most 2d stuff because it's cheap, simple to use and allows good control over the toolpath. (good product, just don't get yourself on their contact list or a salesman will call daily...) Once I've drawn the geometery or imported it from some other program (autocad) I use the machining tools within bobcad to offset the toolpath from the geometery (to account for cutter diameter or kerf). Then using the NC code generator, I select the entity or chain of entities to machine, select a direction (climb or conventional) and the software automatically generates the NC code to machine the particular detail I'm working on. I usually select each entity individually so I can control the order in which they are machined and avoid clamps etc.
There are more automated methods of generating the NC code from geometry, for 3D surfacing in particular, but I don't have the kind of money it takes to buy the software (10k+) nor do I do much 3D work that requires it.