I grenaded my slant 6

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I've seen several that spun rod bearings, had one that threw #1 through the block, saw one in the junkyard a couple years ago that threw 5 and 6 through the block. Even though I like them, I don't think they are as durable as people like to believe. In contrast, I've never seen a 273 or 318 blow up.
All those are under performers. Low power/high reliability. The slant was the same. Not designed for max power (but did great with the hyper pack) but for how long?
 
All those are under performers. Low power/high reliability. The slant was the same. Not designed for max power (but did great with the hyper pack) but for how long?
I think it's an oil delivery issue. Others have talked about cross drilling the crank and or using full groove bearings and the problem is gone. I wonder if maybe what I did with Vixen's oil pump might do the same thing? I put the Hemi HP spring in it. She has 70 PSI idling hot. I've winged it to 6200 a couple of times, just to see if it would keep pulling and it never stopped. Pretty impressive for a stone stock head, only heavily milled. The two oil changes I've done on it since the mods have revealed zero evidence of any metallic particles. I even cut the last filter open. Nothing. When I pulled it to reseal the oil pan not long ago, the bottom end looked so clean you'd thought it had been assembled the week before. This is the engine I got from @RAT ROD AL. He said it had been rebuilt fairly recently when he and Theresa brought it up and all the evidence points strongly in that direction. When I finally make the swap to my new slant with the closed chamber head, if there's anything at all that ain't as good, this bad boy's goin right back in, cause it runs GOOD. lol
 
That's the 1st no.1 or 2 rod I've ever seen let go. THEY ALMOST ALWAYS let go through the block near the starter, no.5 I have seen let go in stock motors numerous times.

What sucks is this motor looks almost new.
New looking chunk of piston, nice painted block and new gasket at water pump... only 40 psi oil pressure turning at least 3000-3400 rpm ...sounds like it was doomed from the start.
The slant seems to do best in the .002's for bearing clearance,.001's are too tight...they could also use full groove mains or .. cross drilling the crankshaft like I did .. I would beat my slant to death taking on v8 cars and passing people on the hwy...routine high speed cruises at 3400-3800 rpm for 300 miles back n forth from Fresno/san diego.
Bearing were cherry when I checked one while changing the pan gasket... also baffled the pan and made a windage tray.
It didn't set the world on fire... but more importantly it also didn't set itself on fire..
If automatic, cross drill the crankshaft so the rods get full time oiling going end to end.
 
I broke 3 LA's (or they broke under me) but only 1 was pretty bad. 1 was a spun rod bearing. I did nothing to it but run it. It has oil, the oil light flickered on idle but I understand that was not out of the ordinary. Maybe it starved the #1 journal and it seized up and spun the bearing but the rod was done, the crank journal was done and to me the motor was done (original 273-4) so I took everything off that and put it onto a 318 short block. That one lost a rod bolt and once again, the crank was damaged as well as the rod, but I never even checked the bolts as it was supposed to be ready to go. Yeah, young and dumb. Third was a 340 that had a pin pull out the bottom of a piston. Strangest thing: It started knocking badly on the way home from Pomona car show and swap. I babied it but could not take the noise and finally succumbed to pulling it over and calling a tow truck. I got it home and pulled a head and found one piston was about 1/2 inch higher and had some valve scars on it. Pulled the rod and half the piston stayed in the bore. It literally pulled the pin right out the bottom of the piston, broken skirts and all. NO cylinder bore damage~! How the heck? I did window a Cleveland block once. Broke the rod and it literally blew out the side of the block above the oil pan and was still beating around the oil pan until it put a hole in that. I had to shut the motor down as it was still running. It happened 200 yards from my house so I just pushed it home!
 
Don't full grove main bearings do the same thing?
Unless they make a galley all the way through the crank. no they do not.
It's all mains feeding all rods, constant , instead of 2 feeding 4 and the end each Independent.

Where ever the leak is greatest...the combined volume fed will keep it oiled to kingdom come. No longer will one main be in charge of 2 rod journals.
 
Unless they make a galley all the way through the crank. no they do not.
It's all mains feeding all rods, constant , instead of 2 feeding 4 and the end each Independent.

Where ever the leak is greatest...the combined volume fed will keep it oiled to kingdom come. No longer will one main be in charge of 2 rod journals.
So then is it any different on the slant? in other words, I know on V8s you simply drill STRAIGHT through the mains. Is that the same procedure on the slant?
 
I tried the full groove mains on a cast crank engine. It lasted 100 miles before i had to replace the crank. And this was with the Dutra oil system mods.
 
I tried the full groove mains on a cast crank engine. It lasted 100 miles before i had to replace the crank. And this was with the Dutra oil system mods.
What happened exactly?
 
I was heading down the freeway, breaking in some new 3.55 gears and the oil pressure went to 0 and there was a clunking noise. So I pulled over. When I tore the engine down the main bearings were all destroyed and the crank needed a .030 grind to make it usable again.

So what caused the failure? The machinest said lack of bearing surface area.
 
I was heading down the freeway, breaking in some new 3.55 gears and the oil pressure went to 0 and there was a clunking noise. So I pulled over. When I tore the engine down the main bearings were all destroyed and the crank needed a .030 grind to make it usable again.

So what caused the failure? The machinest said lack of bearing surface area.
Yeah I ain't buyin that. As many full groove bearings as are runnin around. Something else caused that. Hopefully it didn't tear it up too bad.
 
It's a reason, who knows if it's correct. But I ground that crank, installed new bearing and oil pump and ran that engine for an additional 30,000 miles without a problem, until the oil pump gear stripped. That includes hundreds of runs down the local strip.
 
It's a reason, who knows if it's correct. But I ground that crank, installed new bearing and oil pump and ran that engine for an additional 30,000 miles without a problem, until the oil pump gear stripped. That includes hundreds of runs down the local strip.
I trust you know there's a difference between the cast and forged bearings.
 
hahahaha, yeah I know the difference.
I was sure you did.....just askin. I really don't think a lack of surface area was it. MANY and I mean MANY newer vehicles take advantage of full grove main bearings. Toyota's been doing it for decades. I just don't see it. I'll put it this way. I'll be findin out. lol
 
I was heading down the freeway, breaking in some new 3.55 gears and the oil pressure went to 0 and there was a clunking noise. So I pulled over. When I tore the engine down the main bearings were all destroyed and the crank needed a .030 grind to make it usable again.

So what caused the failure? The machinest said lack of bearing surface area.
What was the oil pressure before it went to zero? That should NEVER happen. Is there a record of the clearances on those full-groove mains? What was the OA crush dim.?
 
The psi was 60. Plastigauge showed that the clearances were within spec on assembly. The full groves were made by buying 2 sets of main bearings and using the grooved half's on assembly. I am not sure what "OA crush dim" means.
 
So then is it any different on the slant? in other words, I know on V8s you simply drill STRAIGHT through the mains. Is that the same procedure on the slant?
Mostly. You make a v intersection to make a few connect. It was so long ago. If I had the crank still I could elaborate more.
Something about the passage sizing was also addressed.
 
The psi was 60. Plastigauge showed that the clearances were within spec on assembly. The full groves were made by buying 2 sets of main bearings and using the grooved half's on assembly. I am not sure what "OA crush dim" means.
Plain bearing ride on a hydrodynamic wedge of oil. The half groove bearing allow a volume of oil to enter that mass of oil is then squished out to provide a clearance gap when the groove diminishes.
With full groove main bearings you will need a lot more oil volume to accomplish the same thing.
Remember as pressure increases volume decreases.
 
The psi was 60. Plastigauge showed that the clearances were within spec on assembly. The full groves were made by buying 2 sets of main bearings and using the grooved half's on assembly. I am not sure what "OA crush dim" means.
Did you relocate the tab notches in the bearing caps, or file down the tabs on the lower bearing?
 
The psi is the same, full groove or not.
The leakage is the loss and that's bearing clearance related. ..so if the bearing clearance hasnt changed.. why would a tiny channel down the middle make a difference.

Most of these bearing feed holes are smaller than the ones in the block as well.
I bet you would alter psi opening that bearings feed hole given if the clearance is on the big side already.
The point where idk. I dont run them .003+
Balance in the system.
Are we opening up galley/feed sizes and not the bearings or are we doing both..then you need more oil psi/volume..which ever side you fall on.
 
I didn't file any tabs on the bearings and I was surprised with 60psi. I expected something around 35psi. I also did this 10 or so years ago. It was a "let's see if this works" experiment. It didn't and I moved on.
 
I didn't file any tabs on the bearings and I was surprised with 60psi. I expected something around 35psi. I also did this 10 or so years ago. It was a "let's see if this works" experiment. It didn't and I moved on.
That was the problem. The locating tabs on the bearing shell are in different locations, upper and lower. The bearings were either not lined up correctly, or the tab was deforming the bearing shell.
 
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