MonsterBilly

So I think I spun another rod bearing. I drive the hell out of my car. However, the engines I have had built were supposed to handle it. Currently I have a 331 that had a piston pin fail and it was bored an additional ten over and reassembled. But now another bearing.

What the hell am I doing wrong? I have the rev limiter set to 5800 rpms, I am running a little rich, I change the oil frequently... Im pissed. So im not sure whether to bite the bullet and but a ford racing 363 stroker or just get a dart 347 short block and keep my components. I am running good quality expensive stuff and I keep blowing bottom ends.

what is my problem? I have a rev limiter, I run good fuel. I just drive it on the street...... ****. what to do

bop11

Find another engine builder.

Starfury

Were the bearings plasti-gauged before final assembly to check for tolerances?

racer_dave

- plastiguage is horrible, it's fine for a rebuild on a stock block with a rebuild kit but it has NO place on any performance application.

If you're spinning bearings it is a clearance issue not a component issue. Either your caps are slightly too large reducing clamping force or there isn't enough clearance overall, or your bolts are not holding.

Get the block and rods machined correctly. When you get it back, measure it, don't take their word for it being right. Plastiguage is not enough. Get good measuring tools and use them. Check the machining on the crank and other components, not just the block. Clean everything when you get it back from the machine shop. Lots of times bits of metal get hung up in the galleys.

Use good rod bolts and make sure your torque wrench is reading right. If you really want to make sure its right, measure the bolt stretch.

Also, what kind of oil pressure are you getting? where are you measuring it? is the pan baffled? Use a magnetic oil drain plug and check it often so you'll see problems early.

Starfury

Hmm. How do you check bearing tolerances with a mic? It's easy enough to measure the bearing journals, but does bolting the rods and mains together sans crank really give you an accurate measurement of the inside bearing diameters?

racer_dave

Yes, pre-assemble with lube on all the bolts and measure everything. Use telescoping T gauges, measure each bearing in 3-4 places at different angles. Write down all the numbers. Measure the component and write down all those numbers. Calculate the clearances then you can move bearings from one position to another if you need to adjust clearances. You have to be good with your tools but that's how I've always done it. I twist my engines past 8400 routinely with no issues.

barnett468

yeah we need more info . . you have a big problem.

what rod bolts do you have?

did you have rods resized?

what are main and rod bearing clearances?

what oil pump are you using?

what oil are you using?

how hot does your engine run?

are you running narrow racing bearings?

there is a potential problem with the cranks having a big radius on them but running full width bearings . . the bearings can hit the radius which will kill them.

67mustang302

In addition to the above, what oil pan are you running and what heads?

Stock oil pans can run low in high performance applications if the heads have poor oil return passages.

Derf00

This sounds like a lot of money but, maybe try blu-printing your next build. If you keep spinning rod/main bearings you probably have an engine that's out of balance. What starts out with good clearances gets chewed up and spit out with vibration which causes clearances to change as the masses rotate.

At the very least weight out your piston assemblies to the gram and grind where needed. A few grams here or there will significantly reduce the vibration in the engine.

My guess is you have plenty of oil flowing but vibration will eventually cause you spin a rod or a main bearing.

That is of course in addition to the rest of the suggestions on this thread.

MonsterBilly

Unfortunately I am a pool guy not an engine builder. So I have had the work done for me.

To answer a few questions
I am running new trick flow track heat heads

I use Rotella t oil, I think it is a 40 weight

My oil pan is a stock type pan but does have a magnet oil plug


It's frustrating because I built the dam car to drive it hard and I can't seem to make an engine last.