![]() ![]() The real point in all this madness Van, was an exercise to see if it was even remotely possible to build a motor that was completely non interference WITHOUT having to flycut the pistons at all. if I find a combination that I like, I might use it in my upcoming 2.6 build. With a build using SBC, many options are out there and I am still exploring. My math shows machining factory pistons that additional ~.135" would drop the compression to 7.88 approximately. I am a soon to be graduated mechanical engineer, so this is more an experiment just to see if I can come up with something that works, and also purely because crunching the numbers on this stuff is the most entertaining thing I have to do on a saturday night and I though I'd share what I measured/learned Why not just maintain your timing belt? Or, worst case scenario, keep a spare head on hand?Van, it may very well be that. This concept seems like the answer to a question nobody's asked. How much would your compression ratio suffer? The problem with this, is that this piston will need a +6cc dome just to bring compression back to 8:1 on a 4.060" bore. 170" below the deck and would need a dish only. 300" deep valve relief.Īt stock deck height, a 1.425" pin height piston would sit. 045" down in the hole, assuming it had a monster. That would mean that a SBC chevy piston with a 1.550" compression height would be non interference if ran. 210" at the valve contact area) to be non interference with a. Meaning the turbo pistons only need to be machined an additional. It's twice as deep as the NA recesses or nearly so. 250", the part of the piston where mine has an obvious valve strike is a slightly more shallow part of the bowl, maybe. I'm about to measure how deep the dish is, stand by. The crown is thicker on the turbo pistons and the dish is deeper than the. I just thought I'd post this up for those considering doing this mod like I am. Essentially we need a combined clearance of ~.385" between the HG, the deck clearance, and the depth of the valve relief to have a completely non interference motor with. 080" piston to valve clearance in a worst case belt break scenario with intake valve wide open near redline and leave no chance of valves getting bent. What this means is that on a stock NA motor, the valve recesses need to be machined ~. Piston rock at TDC is ~.005" on a 100mm bore, so that needs to be accounted for as well. 185" past the valve pocket, so of course, it bends. ![]() So in the event the belt breaks with an intake valve wide open, the deepest tip of the valve will be. 340" closer to the piston at full lift vs when the valve is on it's seat. ![]() The valves in the head are at a 45 degree angle so with the stock cam lift of 12.2mm, the deepest reaching part of the intake valve extends. This gives an approximate piston to valve clearance of. The factory head gasket is ~.040" when compressed, and the intake valve pocket on an NA piston is ~.115" deep. Additionally, the vertical clearance between the exhaust side leading edge of the intake valve and the deck surface is ~.0025" on a stock valve and seat. The volume of the dish on a 951 piston is ~26cc. Factory pistons sit proud of the deck by ~.003". The compression distance of the factory piston is ~1.599. I took some measurements today, and wanted to post some commentary on the prospect of building a non interference 2.6 liter with SBC pistons.įirst, some data concerning the factory motor. ![]()
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