Cost to get heads flycut8/7/2023 I'd stay away from thick copper cyl shims. Deeper exhaust valve pockets, if needed, will also lower cr. One upside of this mod is that the flame does not have to climb over the mountain, as Ron is want to say. Often, material is removed directly under the crown of the piston for balancing, so I don't worry too much if I stay away from there, and take some off the top. It's possible to remove some material from the piston crowns to lower compression, but piston manufacturers don't recommend it, yet I have done many over the years without issues. Will this result in a car that is fun to drive and last? Yes, but top rings may take a beating if detonation occurs in the ring lands.Īre there any alternatives? Yes. 8.8 static compression might be a start, but you may have to shim even more to achieve it, further increasing deck and quench. Should I be looking for a different set of heads?Īll good points made by Ron, who has spent a good part of his career understanding deck height/quench/dome/cr relationships.ĭoug, you asked if shimming could be a solution? The short answer is yes. I guess what I am getting at is ,I have time to get it right.Īm I to understand that with the current heads that I have I really will not be able to recreate a good To the Metal guy.So If I have a Body that is ready to have the power plant put back in her by Sept 2017Įverything has this Hugh learning curve! I really just want to hear her sing the way it was designed. Hell it won't be till November till it takes its trip The things we do!!!! The car is a complete shell right now. I was able to get it to goįrom point A To point B but any RPM over 4200-4500 it was really just making noise.Īfter a year or so of is type of driving I made the decision to Tear it Down!, When I bought my 912 it was barley running. Have heard of stories from people on this board and my other Porsche friends ,that the 1600 motor will I understand that this 912 will never have the type of torque of an SC, however from what I Rev limiter kicks in ! I get great joy not going fast but hearing and feeling the Porsche Power train at 4500-5800 it feels great in in any Except I really likeĭriving in Second gearI, My SC will do right at 62 MPH at 5900 rpm and it will pull all the way up till the I have 1978SC ,it it not the fastest car I have ever owned however when I drive it I always think of the line (I can't get my car out of second gear) of the old I can't drive 55 Sammy Hagar song. I want this motor to preform as It did when it was new. I have spent a lot of time and energy,getting this motor as close to stock as I can. If you simply shim the head up, you have increased the clearance, which requires more ignition advance which means you must design for a very low CR not how these engines left the factory.īy edit, much shorter: The chamber geometry is VERY important regarding how an engine functions, more so than simply CR values. Regardless, it is now a given that a tight quench means less ignition lead required, meaning you can run a higher CR. It is important in that it affects the ignition lead required by the chamber tight enough (.04" or less) and the flame travel sees the chamber as smaller than it is for more reasons than I want to type tonight. The area of the bore with that clearance, assuming it is tight enough, is considered the "quench area" 1mm is on the edge of being a "quench" clearance. You are aiming at the way the engine ran out of the factory, so to find that, you really need to find the factory chamber shape, which is ~1mm piston clearance at ~9.25:1 and the resultant ~34* ignition lead. That is largely a result of the combustion chamber shape, which influences the required ignition lead less is better, since part of the burning isn't first used to push the piston the wrong way prior to TDC. Click to expand.IC engines run better or worse primarily on their ability to burn the mixture in the chamber at the right time to deliver force from the piston to the crank.
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