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| Dynamic compression opinions? https://slantsix.org/forum/viewtopic.php?t=47244 |
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| Author: | SLANTEDRAM [ Fri Dec 09, 2011 8:40 am ] |
| Post subject: | Dynamic compression opinions? |
My slant build up for my 84 ram consists of a hydraulic cam motor with stock deck and cylinder head mating surfaces. I am using a set of kb 268 pistons on k1 technology 7" rods. I have not measured exact deck height clearance or combustion chamber volume yet so I am assuming measurements based on information found here: http://www.slantsix.org/articles/stroking/worksheet.jpg this setup yields about 7.4.-7.5 dynamic compression and static compression of about 8.5. the camshaft that will be used has a centerline of 110 degrees, has 40 degrees of overlap and I am considering installing it @ 102 centerline with the intake valve closing @ 52abdc to help boost the DCR and give more low end torque. the questions I have for everyone are: should I mill the head some to increase static and dynamic compression? Will this motor be a dog with only 7.5DCR? Should I leave it @ a lower compression due to a future turbo install? The motor will be starting life naturally aspirated for break in but soon to follow will be efi and a turbo. this is the main reason I have kept compression low to start with. any and all opinions are much appreciated cheers |
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| Author: | Doc [ Fri Dec 09, 2011 11:09 am ] |
| Post subject: | |
Lots of assumptions and "guess-work" in this question... but it's good to see that you are looking at this engine build in terms of DCR. I took my "WAG" at the numbers and came-up with 7.25 DCR, (58 cc head, .045 gasket, 52 degrees I.C. & -.02 deck) This would work OK for a low boost turbo set-up but is low for an NA engine. You need to get some exact measurements and decide if you want a strong NA engine or a great Turbo engine... you will not have both with the same build. Just my opinion... DD |
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| Author: | CNC-Dude [ Fri Dec 09, 2011 9:01 pm ] |
| Post subject: | |
Its hard to try to build an engine that has two different intended uses, or will have double duty. If you dropped off 2 different engines at the machine shop, both of them being the same slant basically, but one was going to be prepped for forced induction and the other a N/A engine. You would find that they would take different paths thru the machining processes based on how they will be used, and that one of them might not be suited for use in the other application that it wasn't prepped for. You might find you need to prep your engine based on the future forced induction application moreso than the N/A one. |
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| Author: | SLANTEDRAM [ Sun Dec 11, 2011 6:03 am ] |
| Post subject: | |
thanks for the input guys. I think I will focus on the naturally aspirated motor combo for now and we will see about building another slant for the turbo  . I guess I need to to get some assembly and measurements done so I can take the head back to the machine shop for some trimming! I think that a 50cc chamber will get me in the ball park of a better DCR of around 8:1 |
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| Author: | DadTruck [ Mon Dec 12, 2011 6:05 am ] |
| Post subject: | |
For your N/A motor,, you may want to think about doing all of the milling for compression increase on the head and unless the block is really out of plane, don't cut it at all. then when you want to do the turbo build, you will just be looking for a second head to work with.. to do a lower compression that will be turbo compatable. this saves you the crankcase,, depending upon how hard you plan to hit it,, to optimize either a N/A or a turbo,, you would select different cams, ring end gaps,, |
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