High Compression 3.2L Engine Build

[TANTO]

MM93 - not a rebuttal, but can you expand please?
"Carrillo a while back ...when running forged pistons since you end up with so much oil flinging out from around the rod bearing anyways"- Can you explain the theory here about why more oil on pins w/forged slugs? the sightly increased clearance makes a path for oil to come in from the ends of the pin hole?
Personal momentary thoughts : I'm skeptical about the need or want of ARP bolts for anything on an NA/stroker build as well as any aftermarket bearing coatings that just add a potentially negative variable that hasn't gone thru extensive testing in our application. Also don't have confidence of better oil/bearing materials. I would more likely expect a slight degredation over the years. Airplane engines have long ago perfected bearings materials/technology "i think" - where car mfgr's paying attention(?) I suspect the only reason to not open up a C engines bottom end under 250k is the real fear of getting sub-par bearings or sub par wrench turners. Measuring bearing clearance is an extremely difficult thing to - rely on measurements or Plasigage or both? My generation used plastigage almost exclusively, but i did recently by a full set of Mitutoyo ten thousands gages myself. My thoughts (again as of today only) is measure first and then verify with the plastic. The sleeves are the big issue as they require a line hone or line bore and a line hone(even a vertical) with alum on bottom/stl top is just not going to cut evenly. I suspect MM had an align "bore" done which i understand is what the big race folks use. A pretty scary step that requires an ultra precise top level machine setup that will cut both the top and bottom evenly. Please correct my assumptions - here to learn. Great thread and thanks to MM93 for sharing/teaching.

 

[MotorMouth93]

The guy said that forged pistons can operate at higher sustained temps than cast so can get away with less direct oil spray. All of the aftermarket rods I've seen do away with the oil hole, on the C30 and various other 90s Honda engines, and I've never heard of any issues coming from it both in reading various forums and talking to people in the industry.

I don't think it's safe to say that any technology has been perfected, material sciences have advanced significantly over the last 30 years, aviation is just extremely slow to adopt anything new or different since safety and reliability are the absolute highest priority and if something works there's no reason to touch it. There is far less motivation to push the limits of an internal combustion engine in aviation, since that just decreases reliability, and if you want to build a fast plane you just use a jet.

In the case of coatings, automotive OEMs have started using coated bearings to help prevent premature wear from constant start/stop, and coated bearings are quite popular among racers and engine builders to buy themselves a few critical moments to save the engine in the event of an oiling failure. ACL sells race bearings using the same Calico Coatings dry film lubricant product I had applied to my bearings. Oil is another thing, the fully synthetic oils we have today are far better lubricants than the 10w30 dinosaur oil these cars used in 1991. (Honda actually updated the Japanese owners manuals in the early 2000s and added 5w40 as an approved fill, which wasn't really available in the late 80s and early 90s.)

All that said, OEM uncoated bearings work just fine. There's a lot of 30 year old 150k+ mile NSX engines out there to prove it. 99.99% of the time the crank isn't touching the bearings, and all these coatings are really doing is trying to help with that 0.01%. With the amount of time and money that goes into putting an NSX engine together, I just see it as a little bit more insurance. If I can't get the clearances I want (0.0020" minimum, preferable closer to 0.0025") with the coated bearings I'll probably just use uncoated, since I think having more clearance without coatings is probably safer than running tight with the coatings.

Yeah I had my block vertically line bored, for billet mains line boring is the only option as a few 0.01" material has to be removed from the new steel caps which wouldn't be possible just with honing, then had the block checked out by another guy to make sure it was all done well. Aluminum blocks with steel caps can be line honed as well, but it takes a skilled machinist to do it without causing more problems than solved, as we learned the hard way with block #2.

I agree on the ARP bolts, they have caused me a lot of trouble for probably no benefit. I don't think I would use them again in the mains. On the rods, if you've got a set that check out good as far as bore geometry goes then just leave them alone too, but a few of mine were further out than I wanted to run there so I had them resized with the new bolts.

As far as plastigauge goes, no reputable engine builder uses it but I think it's great as a sanity check before assembly (or if you're just doing a bearing slap job on a BMW S motor that eats bearings). You have to be careful measuring main clearances with it though, as any benign runout in the crankshaft or misalignment in the main housings can throw it off. Measuring clearance with a bore gauge isn't really difficult, but it does take a little practice to get a feel for it, especially zeroing it with a micrometer can be a little finicky. You also have to be careful that you aren't dragging grooves into the bearings, a mitutoyo bore gauge will put grooves ~0.0001" deep into the soft Honda bearings. If you haven't done it before, I recommend practicing on the housings without the bearings installed so you can do it over and over without damaging anything.