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Just dropped the crank/FW/pressure plate to my machine shop for balancing. They will balance those to 1 oz-in., which seems to the industry standard. $280 for that and it doesn't even require bob weights...um not cheap. Somehow I suspect my stock crank is already balanced to that degree if not better.
I showed the machinist my piston/rod balancing numbers and he said they look great and are as good as they get.
These tools DO NOT WORK so DO NOT BUY this toolkit!
The delrin rod is 0.003" larger than the wrist pin so it won't fit into the piston nor the con rod! Totally useless.
The black steel pipe 2" end piece where the wrist pin clip is supposed to be mounted is also too large so it won't pass through the engine access hole!
I'm curious what CR the 3.8 has and Len told me my head chamber is 39.4cc. I cc'ed the piston top dome volume and got ~20cc. I estimated the head gasket is about 0.5mm compressed so that's about 3.8cc assuming 0 deck height.
So unswept volume = 39.4 + 20 + 3.8 = 63.2cc
Swept volume = 637.4cc (99mm bore x 82.8mm stroke)
So CR = 1 + 637.4/63.2 = 11.1 vs stock CR of 11.3
I wonder if I overlooked something or my head gasket estimate is way off. If the head gasket unswept volume is only 2cc, the CR would be 11.38 instead.
Since you have been so meticulous about everything else I might mention that the volume between the top ring and the top of the piston slightly affects the CR as well. You would have thought that with the larger bore and the heads have probably now been cut (?) that the CR would have gone up, not down.
Yeah, I did estimate that top ring volume but it was less than 0.2cc so that wouldn't change the CR much. Besides, the CR will go down if you add any more unswept volume.
Yeah, I would think the CR goes up too but the JE piston top is quite different than the stock piston so that could add more unswept volume to bring down the CR despite the enlarged bores and machined heads.
Originally Posted by rockhouse66
Since you have been so meticulous about everything else I might mention that the volume between the top ring and the top of the piston slightly affects the CR as well. You would have thought that with the larger bore and the heads have probably now been cut (?) that the CR would have gone up, not down.
When cutting the heads, unless specified, the minimum is removed from the surface. This is typically .001", unless the head is twisted. This will make almost no difference in CR thats measurable.
That said, the factory CR is also not whats advertised.
Thanks Jake. So are you saying my numbers are in the right ball park but the actual stock cr is lower than 11.3?
Originally Posted by Flat6 Innovations
When cutting the heads, unless specified, the minimum is removed from the surface. This is typically .001", unless the head is twisted. This will make almost no difference in CR thats measurable.
That said, the factory CR is also not whats advertised.
I'm curious what CR the 3.8 has and Len told me my head chamber is 39.4cc. I cc'ed the piston top dome volume and got ~20cc. I estimated the head gasket is about 0.5mm compressed so that's about 3.8cc assuming 0 deck height.
So unswept volume = 39.4 + 20 + 3.8 = 63.2cc
Swept volume = 637.4cc (99mm bore x 82.8mm stroke)
So CR = 1 + 637.4/63.2 = 11.1 vs stock CR of 11.3
I wonder if I overlooked something or my head gasket estimate is way off. If the head gasket unswept volume is only 2cc, the CR would be 11.38 instead.
I don't want to invest in a burette since it's just somethimg I'm curious about, not that I can change and tune that number.
I sealed up the side and top of the piston volume then put the piston on top of my digital scale. Then I weighed the water needed to fill the void. The scale reads 0.1g (0.1cc).
So I removed the fuel injectors and plan to send them out for cleaning. When I removed the cyl #1 injector, I found a small piece of chewed up plastic INSIDE the fuel rail. 1/4" x 1/"4, enough to block the injector inlet. I wonder how it got there. It wasn't introduced by me for sure as I capped off the fuel line connector as soon as I disconnected it. It's white soft plastic. Any one knows what it is and how it got there? Needless to say, I borescoped both fuel rails to make sure there is no more foreign matter.
I wonder if Cringely ever had any intermittent misfires on cyl #1
There are 6 piston sprayers that live inside the crank carrier housing. They are supposed to open and spray the bottom of the piston/bore whenever the oil pressure is greater than 1.5bar (~22 PSI). Below that pressure, they are closed.
I tested the old ones with oil and hand pump. All of them open up at the right pressure but one opened at 5PSI (between cyl #4 & 5) with a very poor spraying and half dribbling. Since oil pressure is above 1 bar at all times, this sprayer was spraying/leaking oil! It seems it didn't create any damage though maybe because the nozzles are really tiny.
Anyway, bought 6 new ones. Pressure tested them to make sure they work out of the box.
BTW, also got a great 6-pack coil deal from Warehouse33 (Thanks Jason!) Excellent communication, customer service, and fast shipping. Highly recommended.
06-13-2016, 04:31 PM
