PyroProblem

Im slowly putting together a build and had a couple questions for some EXPERIENCED builders and or MACHINISTS, or anyone else that can share useful information...

Factory connecting rod side clearance is .006" to .012" for both the b18c and b16a.

Im currently at .009" which is perfect for a factory build. However, Im using a Scat crank and Eagle rods and will be putting down a little more power than what the factory specs were designed for...

Ive spoken with a reputable builder and he said I will be fine at .009". I trust him and all my research supports his statements.
I feel pretty good about running it at .009" but I would like to get a few more opinions from a certain few people here...

Is .009" con rod side clearance OK for a performance build using aftermarket internals? Or should I open it up a bit more?

Im also at .005" crankshaft thrust clearance. Think I should open this up a bit also?

(This thread wasnt absolutely necessary, but I feel we need some more tech back in our forum)

92cxturbo

I'm no pro engine builder, but aslong as I can feel alittle side to side play on the rods I'm happy. The end play is alittle tight. maybe talk to a machinst to see if he can cut it to the wider end of spec which is .014 and see how much more to cut the rods while your at it.

Looks like you have a nice build going there. I always wanted to do a 95mm crank build.

DDTECH

95mm crank is huge..
Service limit is around 0.016, i tend to think in the middle seems to be fine.. you dont want it too tight, you should be able to move the rod atad..but not alot.

How much of a "wiggle" do you have on the rod??

rare92gsr

mine were set around 0.018-0.020, so far so good.

4g hatch

i hope you dont build motors for people with by making sure you can move the rod a tad!!!! and where do you see he is using a 95mm crank??? i see his sign says 92mm!!!


sounds like perfect #'s for a oem crank rod build but with a stroker app im not sure....i would like to hear more info myself from people that have done these builds...from my understanding to much clearance on either the crank or rods will cause the oil to run off the bearings..

DDTECH

i was talking about what cx said.. but whatever.. keep trolling dude.

4g hatch

PyroProblem

Yeah Id like to see a few more thousandths on the crank endplay also. I think .006"-.008" would be ideal. The rods I think will be OK from what Ive been reading.
Thank-you. Its actually a 92mm crank. The 95mm cranks are for the big boys!

PyroProblem

I have .009" connecting rod side clearance. So the rod is going to move a little.
No matter how I describe how much "wiggle" I have, thats not going to tell me if my clearance is too tight, or too loose.
Im really looking for actual hard numbers from other builders preferably with stroker crankshafts and aftermarket rotating assemblies.

PyroProblem

Thank you. This is what Im looking for! I am surprised at the large range of rod side clearance different builders like to use. Do you mind sharing what your crankshaft thrust is set to?

LOL

I agree. Im right where I wanna be if this were an oem build. I am just curious how increasing the stroke and throwing aftermarket parts into the mix may or may not want a little more clearance...
Part of me thinks .009" is fine, the other part wants a little more clearance. From my understanding, larger side clearance does not affect oil pressure or anything related to bearing clearances since its much larger than typical rod bearing clearances...

4g hatch

you may be right...a engine builder had told me that to much side clearance would cause the oil to run off the crank,but im thinking he was talking about excesive amounts of clearance....but im like you i would want a little more just because of the stroke but because the parts esepecially the crank is aftermarket!!! now if you was building say a true race car with a heavy duty clutch i assume you would want the clearances more??? since the clutch engaugment moves the crank slightly!!! i really wish there was a engine building forum!! it seems the few good builders left wont even come into the am forum anymore because its such a joke....i love to learn and pick peoples brains...its a shame

q16racer

if the side to side clearances is too tight, you will cause a whole bunch of heat problems and the oil wont "splash" out as easily possibly running into spun bearings. Just my thought process. May not be completely right but i typically i think i would want to ride on the higher side of OEM spec or just outside of OEM spec depending on the use of the motor.

I ran into this problem with my last h23vtec build. Ran both my rod and main bearing clearances, as well as side to side, to the middle of spec due to being a noob engine builder. It was too tight for what i was doing with the motor since it was a forged bottom end that saw 8500. The rod bearing could have survived longer if my main clearances (notably my middle main)

after talking with Don (i know, lol) all 3 of those guaranteed that motor not to last long but it survived 2 years and 30k miles, 150+ dyno runs and a lot of street fun.

and just fyi, you would get the same idiots in an engine building forum that you would here.

4g hatch

yea to tight i would think would cause heat problems also...but with forged stuff what is too tight??? and your right i guess the idiots would find there way into another forum also with the same dumb comments you read here

EG1834

You want to shoot for a number that is about 4 times your bearing clearance.

Think of it as an extension of your bearing clearances. If you have .002" bearing clearance and less than that on each side of each rod (.008" total), you will restrict oil flow out of the bearing area.

PyroProblem

Thanks for the input guys. My rod bearing clearances are right at .0017-.0019 for all 4 rods. So I guess my con rod side clearance of .009 should be just fine...

What do you guys think about my .005 crank thrust clearance? Should it be adjusted at all?

I have always used oem specs and clearances in previous builds, but this will be my first completely aftermarket rotating assembly and I know its the attention to details that will make or break my build.

unusual71

From what I have gathered, inline4s are not very sensitive to rod side clearance, hence the large tolerances. Also, I can't recall any cases of people modifying the clearance, if it was an issue it would probably come up more often. I have also heard the 4x rod bearing clearance as a target, and have even heard 3x from some people also, so .009" should be plenty.

PyroProblem

Alrighty thanks everyone. Im gonna stick with what I got.