gemellocattivo.com

No...I just checked the math and the right number is closer to .050 per surface (.100 total) for a 3" bore, .043 for a 2" bore to remove .001 per side or .002 of the ID and have it clean up completely. If you just take the .002 total off the surfaces (.001 each) and the bore was ,.002 over to start then the hone will JUST touch the top and bottom so its right in that direction but you basically removed no material from the sides so there is nothing to hone....its still oversize. Its simple math, x^2+y^2=Z^2, where z is the radius of the bore, and x the cut depth, z^2-x^2=y^2 and y= sqrt(y^2) then let excel do its thing....and you need to cut a lot of the x direction to get a small gain in the y direction.

I guess out of round is not so bad though....I THINK the normal failure is pinching.....nothing to really back that up other than I've been told it a couple times and it seemed to make sense. If its true, as the bottom pushes down the sides pull in and grab the crank so clearance on the sides is much more important than clearance top to bottom and out of round wide on the side could be considered the ideal shape for the bearing bores. But for sure if you cut .002 off the surface the bore will shrink .002 in one direction and basically nothing (like .000002) in the other direction.

So your math is getting the dimension at the parting surface reduced by .002. I get it, that makes sense. It was early and I wasn't following well enough.

_________________
Wade Williams
Master Ferrari Tech
Restoration Tech
Engine Machinist
Fabricator
Racecar Driver

Plus you get numbers that do seem stupid big in one direction to make a small change in the other direction...I guess .010 which seemed big but was way to small. Circles are hard to fix once they are oversize. Coat the bearings, plate the crank, skim cut the caps.....all options have pluses and minus I guess.

Here's the thread: https://www.speed-talk.com/forum/viewto ... 15&t=61699

Apparently, being perfectly round is not really a big deal. I've read several topics on SpeedTalk discussing various cheats for round bearing bores and bearings. One builder even said he'd put a C-Clamp across the parting line of a connecting rod and squeeze the big end bore down a couple thou across the parting line, then hone round. When he released the C-clamp, the bore would be oval. He said this showed less bearing wear around the parting line for highly stressed engines.

As long as the clearance is correct for forming/preserving the hydrodynamic wedge at the top and bottom of the bearings, what happens around the parting lines is apparently not nearly as important. Being in a straight line and having the right top to bottom clearance are the two big points.

I've even read an article in Engine Builder that flatly stated that bearing clearance is defined using the TWO POINT measurement of the bearing perpendicular to the parting line. Obviously this definition isn't very worried about what happens at the parting line.

There are a few things to unpack there....but at the end it comes down to being careful of the source. There is no auto manufacture that I'm aware of that allows out of round bearing bores, that's true for lots or reasons but oil flow the light load friction numbers are about film thickness everywhere no just the lightest load points. Race engines are about surviving extreme conditions so a different set of concerns in some ways which leads to different specs. A "street engine" is a mixture....it still lives most of its life at low load but there is an understanding and expectation it can be pushed a bit. then there is the justify the choice to yourself of your customer that we all get trapped by.....its still good because stuff...I'm terrible for doing that to myself.

I think the bearing will be ok as is with extra clearance, when in doubt run it loose generally applies. I think they will be ok with the skirt cut and will hold oil pressure a bit better so probably better overall. I'm honestly not sure which will be better at high load but suspect they will be similar as pinching clearance at the parting line is the same......but this is beyond my actual knowledge base so just guesses really and I'm in no way saying I think you've made a poor choice

Carry on

My goal RPM for this engine is 8500. The way I drive, it'll see that EVERY DAY.
But it will also still sit at stoplights and in Beltway traffic.

Neighbors will LOVE you

but for how long is the question? bigger gaps allow thicker oil film which allows an increase safety factor. You're going pretty tight so thinner oil should give plenty of pressure but extended high rpm running will heat the oil and then its too thin unless you start thicker which means very high pressure in normal driving. You'll get an idea of pressure during break-in I guess and better know where to go weight wise.

Back to RPM....when I 1st got the 308 I rev'd it to redline all the time, normal shifts at 5k, rapid accel at 7700. Didn't really think about it, that's just what felt right. I noticed the BMW that was about the same hp and weight and redline was doing about the same thing. on the 308 after the 1st blower I noticed was generally shifting at 3500 or 4k and rarely went past 6500. Then after the bigger blower shifted it lower yet, general driving shift at 2500-3000, almost never over 5k as there was just no point other than making noise. The only change to the engine was the boost, the curves were about the same just higher hp and it totally changed the way I drove the car....that last blower it reminded me of driving a big block vette, let the clutch out at near idle and it would just shake go...still spun to redline pulling like a bear, but in lower gear that just made the tired spin or has way less then WOT so no reason not to shift, accel was the same but less noise. I expect the V12 will like about the same rpm..3500ish for normal driving shift point, maybe 6k for spirited use.....I'd be surprised if you don't find the same as you increase hp.

I didn't say it would see 8500 every day in the driveway...

I have a fairly gigantic oil cooler that I'm integrating into the system. It's a tube and shell heat exchanger with a core 3" diameter and 18" long. I had it built for this app with 1 1/4 water connection on one end for the pipe and the body and 1 1/2 at the other end for the pipe at the engine. Of course when I ordered it I didn't know what the final mounting angle would be, so the drain plug isn't even close to a useful location, but there it is.

https://www.realfierotech.com/posting.p ... 3&p=157586

[quote="The Dark Side of Will" post_id=157586 time=1552965293 user_id=129]
Here's the oil cooler and all the lines installed. After these pics, I filled the cooling system and actually started the MoFo for the first time in over a year.
However, I did not start it with the oil side of the oil cooler connected. I capped the oil lines on the cooler and used a non-oil-cooler filter adapter. I'm still organizing the oil filter adapter and I need to lap the seats on the cheap Summit fittings because they were showing some bubbles during the pressure test.








[/quote]

Oh yeah, here's the unpacking pic:

[quote="The Dark Side of Will" post_id=156800 time=1510168914 user_id=129]
Oil chiller has arrived:



3" diameter by 18" long shell and tube core, with 1 1/4" water connection on one end for the Fiero coolant pipe and 1 1/2" water connection on the other end for the Caddy thermostat connection. Oil connections are 3/4" NPT. It weighs too much.
Also includes a ground lug and sacrificial anode drainplug since it's built to my specs, but intended for marine use.
[/quote]

Did you put it on the water hot or cold side?

I had one (aeromotive I think it was)on the blower engines on the hot side figuring it helps warm the cold oil but then hold the temp to no more than say 250F....went round and round, looked at oil t'stats setup then just did the hot pipe figuring the water t'stat at least added some control....it seemed ok but I never did any track stuff. Haven't done anything similar for the v12, at least not yet.

What are you thinking oil wise then? the big side clearances will want thicker, the tighter top/bottom thinner.....40 and see?