Best piston(type) boost and compression
Thread Starter
Melting Slicks
Joined: Apr 2018
Posts: 3,185
Likes: 779
Thanks for clearing that up man, definitely going to throw those two companies into the mix. Now that I have a specific compression ratio I want things are starting to clear up and I’m feeling more confident in my “general contractor” role. So with the potential engine builder using his contacts to source parts and me having one company I’ve been dealing with so far(paragonengines) I believe they are in Santa Clara. I’ll be adding RES and HPR tomorrow. Mordeth gave me a quick rundown and how to on calculating compression on my own and sent some links to compression calculators to use. If any of you have spare time or feel like double checking any calculations that would be much appreciated also. Again until I have heads in hand(arriving tomorrow) these a approximate figures but should be close. Using factory titanium rods heads CC at ~68cc, 4.00 stroke using 4.130 bore to allow for hone of .05(I believe) maybe I’m have the decimal in the wrong spot. Engine builder did some calculations and came to -12/-14 on the dish to get 11:1 while paragonengines came to -9 dish to achieve 11:1, both used 68cc on the heads. I’ll be playing with all the links Mordeth sent me and see what numbers I come up with. If you guys have any other specific parts/brands for this bottom end refresh I’d love to hear them, all bearing will be replaced of course ARP main studs are happening for sure any suggestions on the pins that connect the rods to the piston? Weight considerations? Rotating assembly will get balancing with the new parts just wondering if a certain weight is more of a problem or harder to balance, I don’t know what I don’t know and you fine gentleman who’ve been there done that are all I got, or at least all I have with no financial impact. Thanks again guys!!!!
Thread Starter
Melting Slicks
Joined: Apr 2018
Posts: 3,185
Likes: 779
Update on the rebuild, heads came in yesterday and I brought them to the machine shop today for inspection and inventory of what I ordered. Looked real nice! We measured for CC and I thought since I added a .010 mil I’d be around ~68cc I also had chamber softening done on the exhaust side, I’m guessing that kinda cancelled out the small mil because we measured 70.4cc. Because of that it ended up I didn’t need a custom dished piston to hit my compression number. Racetec flat top @4.1 ended up giving me 11.22:1 static comprehension and that’s in my 11:1-11.2:1 ideal window, saved me some money for sure and now I don’t have to wait on a custom piston!!!
