dan91

I'm assembling the bottom end of what will be a 300 whp range EFR build. I'm using ARP main studs and ACL main bearings. I used green plastigage (0.001-0.002") to measure the clearance in each cap. I torqued the nuts to 60 lb-ft. I did each one twice, once axially and once circumferentially. If I did it right, and am interpreting the results correctly, it shows that they are all very tight. I put pictures of everything in the attached PowerPoint (in the zip file). It's possible some assembly lube got under the caps for the axial measurement and made everything a little tighter, but I cleaned every bearing surface and the crank surface well with brake cleaner. Can someone with experience building engines please take a look and letting me know what you think? This is my first time building an engine. I think I need to get thinner bearings, maybe 0.001" oversize? I think most people run 0.0015-0.0025" for these types of builds, or possibly looser. It will be in a street car, not a dedicated race car.

Mudflap

I've been eyeball deep in this subject very recently. OEM spec is .0007-.0014" (service limit .004"). I believe the secret sauce number is 0.002" (ish).

Your are between .0008-.001. Which is quite tight. You can easily source a .001 smaller (diameter, I believe that is .0005" per half) and you'd be in good shape.

BTW I don't believe any good can come from that circumferential measurement.

Also, before you make any decisions, retake all of those measurements with the bore of the mains completely clean. Do not use any lube! Just carefully place the crank and don't spin it!

ryansmoneypit

iTrader: (6)

Or spend like 100 bucks and have a machine shop measure and tell you exactly what you need. Do you really want to be guessing about anything on this build?

Mudflap

No way would I just presume any ole' machine shop would give you the 'best' answer. I've been through 3 shops, each with various strengths and weaknesses. One flat out tells you whatever is needed to be said to get money, the other doesn't tell me anything because he doesn't really give a ****. The other is honest and helpful, but doesn't possess all the tooling and machinery to do the work.

Buy a decent dial bore gauge (NO snap gauges!) and learn how to use it. You'll need a micrometer of the same range as a reference. And if you can't repeat the measurement from scratch like 3 times in 3 different days, you aren't doing it right.

Machinists are just like any other business. They have good days and bad, good employees and bad, good equipment and not, schedules and priorities and bottom lines ($) they have to meet.

dan91

I don't plan on building many engines after this one, so I'm hoping to avoid spending money on measuring tools. Point taken though, it is better to be sure. I've emailed the shop that machined the block for his input, and Flyin Miata, where I bought the bearings. The main purpose of this post was to confirm I am using plastigage correctly, and reading it correctly, and you've confirmed my bearings are very tight. Probably great for oil pressure on an NA street engine, not what I am looking for for my purposes. To clarify, I cleaned everything, took the circumferential measurements, re-assembled with lube, found out the plastigage is supposed to be axial, took everything apart and cleaned the lube off, and remeasured. The only thing I didnt do was removed the bearings from the block and clean lube from underneath them, but I don't think assembly lube got under them anyway. I will re-measure again, cleaning more thoroughly.

matrussell122

iTrader: (1)

Im running .0025 on my main and rod bearings. I was always taught that looser motors make power. Then run amzoil 20w-50 and live happy

dan91

Update. An engine building I talked to said it is common with ARP studs to overload the bearing cap area with the higher clamp load, causing the hole to get out of round. The solution to that problem is line honing with the studs at full torque.

To confirm, I reassembled with the stock bolts at stock torque. The clearances were higher, above 0.001 always and close to 0.0015. I think a line hone is in order.

Does this match other people's experience with ARP main studs? The machinist I used claimed he checked and the block did not need a line hone when he was doing the over bore.

matrussell122

iTrader: (1)

It is necessary to line hone the block after installing arp studs

Mudflap

Good catch Matrussell! Yes ARP studs WILL distort the bore, I can tell you my numbers. I installed OEM studs at 50ft/lbs and measured the bore. Then I installed ARP studs and did three measurements. One at 40ft/lbs, one at 50ft/lbs and one at 60ft/lbs in order to monitor bore distortion. I found that at 50 ft/lbs I had a minor amount (~.0001") and at 60ft/lbs it smashed down by as much as .0004". If you were at the manufacturer recommended .0009-.0014" clearance, you'd be FUBAR.

So my solution will be to run the ARP studs at 50ft/lbs. They will be slightly weaker than if installed at 60ft/lbs. But I have had trouble with getting a line hone/bore in the past. The last time I got it done, they ended up opening up the width by .001" and then I got stuck in this how-the-hell-do-I-fix-that-situation.

I'm at .0017-.0021" on all main bore clearances with ARP studs at 50ft/lbs. I'm going to push 25psi into this motor and try to hit 400hp. Wish me luck!

matrussell122

iTrader: (1)

Just look around for a better shop. is it really worth neglecting a few hundred on a motor that youre going to have thousands into. When i did my machine work i gave the shop the block, rods, pistons, crank, studs and bearings. The bored the cylinders, balanced the crank, line bored the crank with arp studs installed, and set my oil clearances on each individual bearing to be what i wanted .0025. they also gave me spec sheets on everything they did.

Pay some freight and ill drop it at my shop here for you if you cant find a good shop there.

AlwaysBroken

You need to line/align hone (dunno spelling) whenever you do ARP main studs. That's what my machinist told me and I got good plastigage numbers on the first assembly.

Your guy should know what to do, basically they torque down the mains with the ARP studs and redo the crank hole to make it round again. You can't skip this for reasons that this thread makes obvious. If a machinist told me it wouldn't need a hone, I would be immediately suspicious of his expertise.

dan91

I had the block line honed. When I previously checked the clearances, I managed to fatally damage one of the bearing shells, so I bought a new set and gave them to the shop. I picked everything up yesterday, and today I rechecked the clearances. They were once again less than 1 thousandth according to the plastigage. The machinist gave me measurements for each cap, all between 0.0018 and 0.002. Now I'm stymied. I'm starting to wonder if my torque wrench is inaccurate. Anyone know of a good way to check? I don't have a second one to compare it to.

Mudflap

I don't believe you can over-torque it to achieve 1mil less clearance. You'd really have to crank on it. Go buy a torque wrench from whomever, use it to check against yours and then return it. Or buy one from Harbor Freight, I checked my cheap-o wrench against a calibrated, $2000 unit, from work and it was perfectly fine. You don't store your wrench with it tightened down do you?

I took my block back to the shop when I didn't believe their numbers and had them re-check it with plastigauge, they then showed me the results. You could go that route, but I found it to be kind of a useless exercise.

dan91

Well, I learned something through this debacle, so I will share. It turns out I was using plastigage wrong. Since a crankshaft is an over-supported shaft, the caps force the crank into alignment to some small degree. While this is happening there is load going through the bearing cap and into the crankshaft, which will smush the plastigage and give a false reading. Basically its showing how much the bearing was deformed during installation, as opposed to the static clearance after installation. The machinist told me you can only measure one cap at at time. I'm not sure if that means tighten 4 down and then plastigage the remaining one, or just torque one cap down with plastigage and leave the other 4 journals free. I plan on experimenting to see what gives accurate results. My small concern is the 10 bolts are supposed to be torqued in a sequence in stages, which can't be followed if not doing all 5 at once.

The bearings I got back from the shop also had scratches on them axially, as though the crank was checked for end play with the bearings dry. This irritated me, since they were brand new bearings and the machine shop scratched them. Turns out, the scratches were from the measuring tools for determining clearances. The bearings have a anti-corrosion/break in/sacrificial coating on them that scratches easily and reveals the shiny metal underneath but causes no performance issues.

Madjak

With all bearings installed and with a coating of engine lube, torque all main caps down in sequence. I tap the main caps with a hammer between each torque loading to make sure the cap settles cleanly and square. Once at full torque remove one cap, install plastigauge (I do two short strips: one near the top, one near the side). Torque down that cap, remove the same cap and check gauge reading. Clean off the bearing, add some engine lube then reinstall cap and the repeat.

Make sure you don't spin the crank whilst the plastigauge is in there. This is more important for rod bearings as the crank can move easily when torquing the bolts.

dan91

I'm starting to think I'm special. I torqued all the caps down dry, removed the center one, added plastigage, and put the cap back on. Removed the cap and looked at the plastigage, it showed almost exactly 0.001. Then I removed every cap and just torqued one on with plastigage, the #1 cap, and it again showed 0.001. Then I tried checking the clearance on a connecting rod with the crank not in the block. That also showed 0.001, but I don't trust that at all since the rod was wiggling all over the place. I think I have to do that in the block.

I'm going to call the shop again tomorrow and ask them to use small words and talk slowly. I don't understand how I can screw this up so consistently.