Glex25

iTrader: (11)

Lets see how many engine builders are here. I have been reading a few articles and spoken with a few shops that have said for high horsepower builds to run the bearings on the loose side for crank deflection. I have also seen a few people on this site speak about running looser tolerances than factory for big builds but no one ever give numbers or say what tolerances they actually speak off. So I'm reading the service manual and looked at the factory specs for con rod bearings and main bearings and their tolerance.

Factory Manual Specs
(Bearing oil clearance) = (Connecting rod bearing inner diameter) –
(Crankshaft pin journal diameter)

Standard : 0.034 - 0.059 mm (0.0013 - 0.0023 in)
(actual clearance)
Limit : 0.070 mm (0.0028 in)


(Bearing oil clearance) = (Main bearing inner diameter) – (Crankshaft
main journal diameter)


Standard : 0.035 - 0.045 mm (0.0014 - 0.0018 in)
(actual clearance)
Limit : 0.065 mm (0.0026 in)

Now I'm reading these articles and there is some very good info in here.
They all state for big power to add .0005 to the max value with in the acceptable spec range.


http://www.precisionenginetech.com/t...g-tech-part-1/

http://www.clevite.com/techbulletins/CL77-1-205R.pdf


Now it seems like our factory specs gives us a pretty wide range as far as the tolerance for the Con Rod oil clearance but to add .0005 to that value would add wear on start up in that area or a need to use heavy oils.

If you add .0005 to the oil clearance for the main bearings then you will be just under the outer most limit that the factory recommends. The main bearing tolerances are a little tighter than the Con Rod.

So for those that say they run their motor with looser tolerance are you just speaking of running .0023 for con rod oil clearance? .0018 for mains? or are you adding .0005 to those values?

If you use STD size bearings which are the smallest that I know we can order. What modifications have you done to achieve those oil clearances? machining the crank?


I'm putting this out here for the DIY people and tired of just seeing build threads with no discernible knowledge.

bjmax

These are available from ACL..

Sizes available:
H-STD: Standard factory size, for most applications
H-.025: Oversized by .025mm or .001"
H-.25: Oversized by .25mm or .010"
HX-STD: .001" additional oil clearance

I used the ACL STD. This because i'm using the 10w40 Redline thats slightly thicker then 5W30.. running now for 5k mls and no problem. at 10k iám going to take a look for the condition.

+/- i 'm around the 0.063 mm (0.0025 in)

I hope this helps.

jerryd87

iTrader: (4)

those clearances provided are the specs recommended for 10w30 and 5w30 oil they are not the end all be all, most build will be fine with them however. a perfect example the recommended specs for a small block chevy 350 which has a smaller main then us(2 inch vs 2.38 inch, the larger the diameter the larger the clearance needed) by spec should run a .0015-.002 main clearance, i have ran .0031 using 10w30 oil before with gm zddp additive with no problems.

now some people will claim you need to run tighter clearances because the block is aluminum and expands more, i personally call BS because none of the pros do this with aluminum small blocks/ls series motors only the backyard mechanics do. i also call bs because while aluminum does expand more, the actual section the crank is riding in is steel surrounded by aluminum. on top of that the metal does not just expand outwards, it is going to expand inwards as well towards the crank and bearings so the whole more expansion is moot, if anything it would make the clearances tighter. just one of those bs "i read it on the internet so it must be true" things.

for referance i personally have HX-STD bearings and while it will vary depending on what i measure i intend to run .003-.0032 con rod clearance and .0032-.0034 main clearance with 25w50 race oil. if they are smaller then that ill have the crank polished some to open the clearances. that is actual clearance as measured with micrometers and a dial bore guage though, i dont trust plastiguage on a high power vehicle.

bjmax

Same here.. I don't use that...

konrad

iTrader: (15)

So what clearance would you guys recommend for the VQ for 650-700whp? I recently spun 2 mains, don't know what clearance I had tho. My rod bearings were untouched. This was with 7k milles on a shitty tune

bjmax

Who done you build? can He or She tell you the clearance you had? and what oil? I think when you stay in the high standard clearance range it should be oke with a good tune and good 5W30 - 10W40 oil.. and most important before you use that power be sure the oil temperture and pressure is OK..

jerryd87

iTrader: (4)

its also going to depend on your driving style, personally ive never had a issue running larger clearances BUT it has downsides. such as you have to let your car reach operating temp while idling before driving it, start the car and dont touch it. it also tends to burn a bit more oil. i like the additive package the 25w50 race oils have and with the changes they have made to diseal oils in the past couple years(what i used to run and still FAR better then gasoline oils) im just going with what hasnt changed. if your going to run it hard i also recommend the thicker oil, and HIGHLY recommend no more then 3k oil changes, recommended probably in the 2k-2500 range again depending how you drive it.

oh yah one other thing is with the thicker oil you will make a little less power, very unnoticable but this is because of the increased windage and weight of the thicker oil on parts. and it also slightly reduces fuel economy, personally i find it negligable though, ill trade 3 or 4 whp for what i know will not fail me. those clearances i listed konrad are what i intend to use for 700-800 whp range for you to referance, but i intend to drive her hard.

oh yah a little edit side note, take a look at the facilitys they build your engine in, its not always the clearances, most of the good shops have a seperate "clean room" they build engines in, thats the way to go. dirt will spin a bearing as sure as too small clearances, small clearance with heavy oil, or large clearances with thin oil. take a look at the pics hal had up in his build your engine thread in the classifieds. the room he had all the engines in was spotless, probably coulda eaten off the floor, thats the right way to do things.(ok mayby eating off the floor is a bit of a stretch but you get the idea lol)

konrad

iTrader: (15)

I build the engine, but I had someone measure it for me, told me to order standard bearings. I than found out he never measured ****. I was using castrol syntec 5w30. I had a bad tube for 7k miles , my wideband would show a/f 18+ every time it went over 6psi and I would redline it a few times. I know that was dumb therefore I'm not kicking my self for it. Just want to make sure I do it properly this time around, with proper build, proper clearances, proper brake in, proper tune, and proper oil.

I drive the car normally with a lil racing, few fish tails, drifts,burn outs here and there.

Glex25

iTrader: (11)

My focus is to get a clearance of no more than .0020.
The thickest oil I want to use is 10W40 Synth.

The change of seasons make it hard for me to run much looser.
I have issues as is during the winter finding 10W40 synth oil locally.

The original clearance measurements were done with a Micrometer and Bore Gauge
but I'm double checking them with Plastigage just to be safe. I took apart the mains and the bearings looked fresh but I was getting some noise when I let go off the gas at anything above 3k RPM everything was pointing towards the mains.

konrad

iTrader: (15)

Wow #1 cause for build engine failure and only 9 posts. No wonder some people are on their 5th build...

midz350

iTrader: (4)

Goodbye thread.

See you in five years.

bjmax

.... This is bad. Builders could put some useful info here.

Boosted Performance

iTrader: (14)

If a shop has figured out the "magic" number for bearing clearances through trial/error/r&d/investing a lot of money...why would they just share the numbers?

There aren’t many shops here that have a 90%+ success rate with these engines, and those that do will never share the secrets. Understandably so…

jerryd87

iTrader: (4)

ill have my build up soon enough if people are patient, although god damn weather keeps delaying me from going home >.< got the spare engine now so ill end up sending it to the machine shop within the first week of me being home.

ace32x

iTrader: (10)

went pretty loose on my bearings ill check the specs when i get home (at my office atm) but no bearing issues so far have 4k miles on it. (just headgasket or sleeve issues haha )

edit: i run 5 40 motul for oil aswell

konrad

iTrader: (15)

with all the failed engines I seen here it seams the shops are doing R&D/trial/error with the customers money on customers cars
I dropped off my block, crank at the machine shop Monday, should be back next week, I'm having the shop measure everything for me, and than I'll check it myself again. I will be shooting for the max clearance of oem spec for both rod and main bearings.


my block made 7K milles with no signes of bearing material, and than it failed on the dyno. I must mention thats 7k miles with a bad tune (A/F 18-25) lots of redline runs, no measurements taken for bearings at all, just bought standard ACL bearings and torqued with harbour freight torque wrench.
With all that in mind I'm surprised it lasted that long.

Resmarted

iTrader: (2)

Well there's more to it than just what size bearings and oil...

If the shop that put your sh*t together didn't even tell you what clearances were in the thing, you were kinda f*ckd from the beginning imho. They probably didn't even line hone the damn thing.

I had lots of problems with my local shops, and d*cked around for a while waiting for no progress. Finally said f*ck it, and sent my stuff to dynosty. I'd reccomend you do the same.
My old machine shop that was working on my build (didn't get anything done), is really good (built a few top fuel v-8's, plenty of big blower v-8's, 308's, 4g63's etc) but just couldn't get the vq right.
I'd say save yourself the headache, the risk, the money, and most importantly the time and send it to a proper Z shop, and let them do what they do best.

jerryd87

iTrader: (4)

line honing isnt always required, if the bores are still straight then your paying a machine shop $200 bucks(well in hawaii anyway) essentially to do nothing. same with decking the heads and block, if you take a machinists rule across the tops of them after they are cleaned, use feeler guages, and they are straight theres no sense in doing it.

theres a reason i bought the tools to check everything myself, 300-500 bucks in tools can save you that on a build on just one engine build.

Resmarted

iTrader: (2)

That's true, but I'm fairly positive if you upgrade to arp studs 9/10 you'll have to have them line honed when you increase the torque specs on the main caps.

The problem I have with buying tools to check specs etc is they aren't proven. Yeah expensive/high quality tools are less likely to be off, but I trust a machinist's tool that's been used many times so the machinist knows how/where it's off.

Cass007

iTrader: (34)