The issue is the oil timing is wrong on these engines. You should have full oil pressure to the rods at 70* ATDC and that is IIRC but it is close to that. That's why a Chevy doesn't need full groove mains. The Chryslers get full oil pressure way before they need it so the full groove mains helps that. Seems to be worse on the SB but it is wrong on both. The higher the engine speed, the worse it gets.

There are only two fixes for the high rpm stuff (unless you get a block that has the oil passage in the correct location).


One is have a crank drilled with the oil hole turned counterclockwise. The other is more complicated. That is the only way I know to correct it.

I still haven't given up on the SB yet. I was offered a good 360 block from a member here. Just pay freight. There are a lot of good guys on this forum. I'm interested. I will need a set of rods and 2 pistons a rebalance and a cam. That's doable. I might even have the crank ground for more stroke. Will see. Thanks again guys

Dave you're making me rethink using 1/2 groove mains on my 434. I had to order a set of .001" unders so I have the other grooved half. My rods are 2.00" and the clearances are .0023-.0025" using King aluminum rod bearings and King mains.

well, i'm not certain what caused this yet. I will get it apart and examined sunday and go from there. I may change this build up alittle with possible added stroke and more cam.

I wouldn't be so quick blame the mains, or crank needs cross drilled, or anything else. My first thought is it was too tight

Dont forget to look into this.

Would not be surprised if your problems are related to this, rods dont try to pul a pin out of the piston without reason.

Obviously it's important to have adequate oil delivery to bearings, and to have proper clearance which will vary depending on the engine and type of usage.

One thing that is often overlooked is the bore of the rod must be round, straight, and sized properly. It's about as important as round and true crank journals and round and straight cylinders. When the bearings are encapsulated in the assembled rod, if the bearing shells are not evenly and tightly contacting the rod bore they can walk around, and they also heat up significantly more because the poor contact between the bearings and rod doesn't transfer heat away from the bearing very well. The bearing shell is then prone to distort from excess heat and lack of support, which usually reduces the oil clearance, which is the beginning of the end.

That may not be what caused your problem, but it's very possible it was. If bearing to journal clearances are on the tight side that's 2 strikes. A lot of rods are honed with methods that are "iffy" and when not done correctly make the bearing bore bell-mouthed. I always inspect and measure the rod bores. On engines that have some run time on them you can look at the contact surfaces on the back of the bearing shells and the bores and see how well they fit.

Real sorry to see this Dave, i've put street stuff together but would rather have a motor done by a professional when it's going to see a lot of rpm and has high cost parts.
Mick

Believe me that thought entered my mind when I seen oil gushing from the bottom of the pan. I'll see how I feel about that when its ready for assembly.

I will never use another set of used rods.

Looking at the broken parts that fell out I think your right. Too tight and not enough oil.

There was killer rotating assy on here a few weeks ago. Killer rods, and Killer stroker crank, don't know your cash flow, but it was reasonable.

Here's another thing to think about. The last two builds(408) had .002 on rods and mains and never had a failure but had full groove mains.

You said rods were used and new bolts installed. Were big ends checked for size and roundness

On big blocks there's a wide groove bearing and a narrow groove bearing. Both are full groove. I use the narrow groove.

yes they were checked at a machine shop. i checked bearing clearance again before assembly.

if i remember right i believe these calico bearings were a narrow bearing. i used a federal mogul main bearing.

i'm also second guessing the oil mods as a cause. i have heard the guy that posted those his engine also came apart. not saying thats the cause, but not sure i want to perform those mods on next block.

I doubt that clearance was too tight, but I don't remember what oil you used. I am about ready to fire mine off and it has .0021 on the rods and .0024 on the mains. I'm going to use a 5w30 oil. If yours was too tight I'll be screwed just like you.

I think a lighter grade oil and FGM's and you will be ok.

joe gibbs xp4 15/50 non synthetic(breakin). like i said last 2 builds had .002 on rods and mains with full groove and using 20/50 amsoil, no issues. i had 100# oil pressure when first fired up, 75 when it got warm and 55 when it let go.