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#15
by
zukgod1
on 02 Sep, 2008 10:30
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Hmm, never thought of that..
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#16
by
Mark(The Miser)UK
on 02 Sep, 2008 11:52
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Exactly... nice attempt at a pic, but couldnt you have made it slightly 3 dimensional with a semi translucent rear area depicting the first lobe on the cam rather than the blue crocodile eating a swivvle chair. :shock: :mrgreen:[Andrew restate that hammer tap procedure. It just struck me that if the bolt is tapped then theory makes me wonder that if the bolt was a tight fit then it is moving the cam away from sprocket...Nah I'll leave that thought in, but the ability to tighten bolts with fingers straight away disproves my idea.]
When a bolt is tightened, the threads of the bolt are not a perfect fit to the threads of the hole. Once the bolt head comes into contact with something, in this case the cam, that something pushes the bolt away from the hole it is threading into. The slight difference in thread sizes, between the bolt and hole, means that there will be a sight space between each of the threads, in the direction of the hole:
Tapping the bolt will apply force to move the sprocket further onto the shaft. It works for me.
Andrew
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#17
by
belchfire
on 03 Sep, 2008 18:08
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My perception of bolt torque was that it was the tightest that a fastener could be tweaked before it reached the yield point. In theory, if you torque the cam bolt past 33 ft/lb then it would stretch and actually be weaker. The only way to increase the torque is to use a larger bolt or a higher grade. Still, the cam does have a keyway...
Turns out that I did bend one of the intake valves and doncha know, It's apparently a rare gold plated titanium 3 groove type that had to be ordered.
Cost $31 bucks! Glad it's only one. Hope to have it running next weekend.
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#18
by
Turbinepowered
on 04 Sep, 2008 01:20
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My perception of bolt torque was that it was the tightest that a fastener could be tweaked before it reached the yield point. In theory, if you torque the cam bolt past 33 ft/lb then it would stretch and actually be weaker. The only way to increase the torque is to use a larger bolt or a higher grade. Still, the cam does have a keyway...
Sure... except that the same grade bolts can be used for a variety of torques.
My donor-Rabbit's oil pan had grade 12 bolts all the way around, but I can guarantee that they weren't anywhere close to their yield strength even if overtorqued.
Fastener torque specs simply indicate the amount of turning force necessary to put the desired preload on the bolt, to give a desired amount of clamping force.
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#19
by
belchfire
on 07 Sep, 2008 20:40
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It's true that you could tighten a high grade bolt to a lesser value and thus achieve a certain clamping force but why spend the extra money for a better bolt than you need? While engineers will err on the side of a higher safety margin, the bean counters will cut wherever they can. I've gone round and round on the subaru forum as to why my impreza takes 4 1/2 quarts of oil leaving me with a 1/2 quart on the shelf instead of making a slightly bigger oil filter that it so desperately needs. Bean counters figured that saving 1/2 quart per car would add up to millions in their pockets.
I would surmise that the choice of fastener is dependent upon space considerations, number required, and clamping force needed. If a grade 3 is sufficient for an oil pan, then 12's are a waste of money. I wonder if someone replaced your bolts either because they were available or the originals snapped when someone was trying to get a leak stopped.
:arrow: Back to the subject:
The engine is back together and I took it for a run. Seems to be OK other than the old lifters rattling until warm like they did before.
Replaced the injectors and it starts a little harder. I think pump timing will be next.
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#20
by
belchfire
on 05 Oct, 2008 19:05
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I am going to post this reply on the other topic "new cylinder head" as well. libbybapa was right. After checking that the IP wasn't 180 deg out I pulled the head. I could see where bad IP timing would cause it to run poorly but it has nothing to do with compression. Both heads appear identical so I installed an injector and glow plug in the old one and CC'd the pre-chambers. Original german head = 11cc. New head = 13.5cc. Hammered out the inserts. Maybe not the best idea, but I was pissed.
The new insert is about .020" larger in dia. and .007 longer than OEM.
I cc'd them both and amazingly, they were 3cc's each. I then cc'd the spherical chamber up to the edge of the insert boss and that's where the difference was.
How to fix this: I could calculate the volume of the head gasket and get a thinner one. Problem is that I'm already using a 1 notch gasket.
(B) Can't mill the head as the valves are flat on the surface and the chamber's opening would be altered.
(C) Mill the block (also known as a complete tear down) to raise the piston height, however, the amount milled might make the pistons hit the head/valves.
So my real choices are to (A) spend another $500 on a non Chinese head after dumping a grand and a month's worth of work on it or (B)-
Sell the whole thing as-is and get something else non VW. :cry: :cry: :cry:
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#21
by
gigaz2
on 06 Oct, 2008 02:18
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you got 265psi consistently across cylinders?
can you measure piston protrusion?
that is very weird, guys that make the 1.6/1.9 franken should have the same problems because of the low compression, but they don't. why?
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#22
by
belchfire
on 06 Oct, 2008 11:15
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I don't know about the 1.6/1.9 franken engines, but if it's a 1.9 block then the larger displacement would take care of a larger chamber volume.
Come to think of it, maybe that's what's going on. If I got a 1.9 short block then maybe this head would work.
As for starting. I can get it started but I have to put the pedal down and let it smoke to high heaven then go. It runs rough & dirty until I get into a good boost then it clears out. It's clearly a compression thing.
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#23
by
burn_your_money
on 06 Oct, 2008 15:52
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My car has 250 psi and starts up great everytime, even now that it is getting close to freezing. I doubt it will last me the winter, but I'm too broke to buy a new motor right now so I have to keep milking this one.
I think you have a different problem then compression
My starter is not very healthy, battery is fair. Pump is freshly rebuilt and so are the injectors.