Hey.. everyone loves an engine failure mystery - Brand X

Sooo this one has me a bit puzzled... Foxbody 302 build, has maybe 5-7k miles on it. Re-ring frankenstein build, block I got out of the junkyard and rotating assembly I got from another fox motor. Everything was cleaned properly, crank polished by hand and on lathe, block dingle ball honed, all clearances checked (bout 1.5-2 thou on mains and rods).

Had a vibration develop at 4k plus RPM recently so stopped driving it and took it out. #5 main is toast, all the rods are fine though, none of the bearings look great but #5 is definitely the culprit. Usually with oil starvation a rod dies first so not sure what to think about this one, it clearly is a 50z crank and I had 50 oz weights on the flywheel and balancer... (SB fords have a 28oz and 50 oz external balance depending on year etc)

2 things that stick in my head:

1 - The starter bendix sticks for a couple seconds after starting then retracts... This actually started with the last motor (which blew up) I actually had drilled the starter holes out when I first put this motor together to get the bendix to return properly, just firing the bendix manually with a "lone wolf 3000" it would pop back immediately but when the motors rolling it takes a couple seconds... But perhaaaps it has been shoving the crank into the main during cranking...

2 - I had raced some audi looking mercedes a couple nights before the vibration developed... it was a deep freeway pull soooo it's possible the pan was sucked dry... that said it was full on oil, and I'm only spinning it to 6k on with a stock oil pump and pan... surely stock SBFs can handle 6k with a stock pan/pump right? It's always been my experience though that rod bearings die before mains sooo *shrug*

I know nothing about Fords...but did you check the bearing clearance on EACH journal? Crank is straight, yes? So runout was checked and in-spec?

Beyond this, perhaps looking at restrictions in the oil feed is the next place to go? What does that routing look like on the 302? Where in that feed sequence is #5: start or end?

Last, visually it just looks to me like #5 was simply too tight, or there was a pile of dirt that got dumped into that somehow??? (maybe stuff was trapped in the oil feed passage and when things came up to pressure it all went straight out)

The .0015-.002” on the mains would concern me, I run more than that on my rods. Remember what Monte Smith always said, “build a loose engine, only you’ll know, build it tight and everyone will know”.

Did you take the new oil pump apart and clean it out prior to the build?

[u][/u]

I like that !
Not sure who coined it but there’s also “ Loose is Fast “

that looks like crank to bearing rubbing, not enough clearances or not enough oil flow on start up

Yes all clearances checked, crank straight? dunno but the motor it came out of had bearings that were like new.

#5 is at the end... so ya oil starvation is a possibility.

Block was cleaned pretty thoroughly so kinda doubt the dirt theory



I mean it was that after polishing to b00t *shrug*



Well clearly it rubbed at some point, 0.00175 shouldn't be toooo tight tho, was primed before start-up and also had plenty assembly lube.

I think there are 2 or 3 different external balance specs on the SBF, aren't there ?
Never had my stock '89 5.0 to 6,000 - ran out of pull long before that.
.0015 sounds too tight to me, regardless of make & size.

I agree with topside, they were done well before 6k, more like nose over just under 5500 and go figure ford replaced my 86 5.0 Capri motor twice for bearing related issues and 3 T5 transmissions as well. Fun cars but the stock parts pushed always seemed to catch up sooner then later. A cat delete, 3.70 rear gear and comp ta tires and things would start to break soon after.

You need .003 minimum on mains! Also, possible you drained the pan which doesnt help. I think factory is 5 quarts. If you have aftermarket heads the drainback can be less than OEM.

I agree with the clearances being too tight, my first engine had .0025 on the rods and
spun a bearing on #7, rebuild now .003 and no problem....yet.

Joe

There is, 28 and 50, this is a 50 and it had the right ones

You guys are crazy, .003" crank bearing clearance? This isn't the titanic

How big is the O.D. on those mains?
The standard race clearance standard is .0010 per one inch of journal diameter, rods, mains or cam journals
There are way to many internet and forum racing experts that have only raced on their keyboards, most of their "knowledge" is based on reading or hearsay, no real world at the track or dyno testing and racing
I was told years ago by a Ford SS drag racer, Ted Wells(he race 1967 a 410 HP 427 C.I. side oiler motor that he shifted at or above 8800 RPM ), to run a little more clearances than the recommended minimum if i wanted my NHRA Street 426 Hemi stock class race motor to live, he was correct .
I've used 0033+ on the mains and .0030+ clearance on the rods long before you bought that Daeco race drum from me with no bad results on hundreds of street and strip and drag race only motors,Hemi, RB.B and lots of SB Mopars
Yuu will never spin a bearing with those oil clearances, you may with less than .0010+ per 1 inch of bearing I.D. diameter on the clearances

Says the guy with an engine that ate a bearing.

True, still say it wasn't the clearances tho... :P

the saying goes : "no one will know if the clearance is too loose, but they will surely know if it's too tight". or something like that.

Well that's not quite true, it has a ton of clearance now and you definitely know it

How do you know? If it has enough pump volume the pressure shouldn't suffer much. And then its usually at idle. That factory Ford crank probably looks like spaghetti noodle under heavy power. It been proven many times. Clearance is clearance. If there's lack of lube or flex, parts touch. Then the bad stuff starts. Open the clearance until they don't touch. Provide enough clean oil to keep them separated. That's the bottom line.
Doug

Looks pretty clear to me it was an oiling issue....No way no how I would run the clearances that tight for sure. Not 100% familiar with windsor oiling but if you really think it wasnt a bearing clearance isseu(which is hard to believe)then I woudl start looking there as to where oil travels in the engine. Hard to tell from pics but looks like it had plenty of "stuff" going through it too, but could just be the pics and lighting.

Heh there's a limit... I didn't bother checking that main clearance but it's gotta be huge... it vibrates horribly at 4k+... enough to warrant pulling the motor

I wouldn't think your extra clearance on your #5 would cause a vibration. Your oil pressure should cushion that. Did your oil pressure change when the vibration start? All your bearings (even your rod bearings) looked scrubbed to some degree. I just took apart a 1976 440 that had original bearings in it. The 440 bearings looked better than any bearing in your pictures. Maybe a vibration damper failure? Lack of oil pressure? I agree with the larger clearances as well, unless your running 0W20 oil, in your non-performance engine. Just my

It's definitely the source of the vibration, and yes oil pressure dropped

You added extra clearance. How did you do that? It's "huge" but you don't know what clearance it has? But you are sure it's your issue. You took the time to take it all apart. Then made a change and didn't measure anything? Crack check anything? Put it all back in the car. Uhmm.
Doug

I mean come on, you find a massive wiped number 5 main and you're not going to attribute it to a high RPM vibration?...

And actually yes I did mag the block and the crank, I found a good deal on a 331 stroker though so none of that is going back in the motor

Are you going to measure the clearances on this one? BTW, what bearing clearance does ford recommend?

Yes just like I did the last one.

Is this car m/t or a/t? iapco103

manwell

These engines have several variations of flywheel , I suspect that the one you have is incompatible with your crankshaft and this is the source of the vibration and bearing wear.

Finding the correct one can trying at the very best. You will need a very patient FoMoCo parts man to help you.

Best of luck , iapco103