I grenaded my slant 6

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jos51700 said:
First, that sucks. I set a rod knocking in a slant 5, but never windowed one. Sucks double on a fresh build too!!

Second, pistons made in.....?

The time mine popped, a guy said there was a oil passage in the crank that was undersized on some slants that caused the rods on that journal to go south. Anyone else hear that?
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I've never heard that one, BUT I have seen and heard that the #5 is notorious for being the one that lets go.
 
225 in our 1st 67 b'cuda stuck #5 rod through side of block also. A seasoned Chrysler tech that I worked with said this was common failure/death of a slant.
 
I wonder if anyone has any theories on the #5 failures? It's common enough there must be something to it.
 
RustyRatRod said:
I wonder if anyone has any theories on the #5 failures? It's common enough there must be something to it.
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Could be oil supply, could be harmonics, could be shaft torsion, could be block flex....what else...?
 
RustyRatRod said:
Crapped if I know.
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I don't know either, but in looking at how the lube oil flows in a slant, I can determine that:
rod ends 2 & 3 are oiled through #2 main
rod ends 4 & 5 are oiled through # 3 main
rod end 1 is oiled through #1 main
rod end 6 is oiled through #4 main
so rod ends: 2,3,4,5 are split oil flows
and rod end:1,6 are dedicated oil flows.
the rear main oil galley also feeds the oil line up through the block and head to the rocker arm shaft.
so there is definitely more oil flow demand towards the rear half of the crank.
Perhaps #6 is not a known bearing spinner, because of the dedicated oil supply.
So why is #5 and not #4 reported most often with a failed rod bearing, they may be both so close to failure that when the furthest one from the oil pump
(#5 vs #4) goes, the other is not far from failing also. Or it may be that #5 is actually the furthest rod bearing away from the pump (on a line that is shared and is also supplying a secondary lube to the rocker arms) so it fails catastrophically first.

Saying all of this without any empirical data. It would take a computerized 3D model to know with confidence, but for an on line argument I think this has some substance.
It is also important to note that the OP had a failure on #1 cylinder, and to me that rod failure appears to have initiated at the piston pin end, not the rod end. But that is from looking at one photograph of parts picked up from the road side. So there is a large opportunity for error on that failure analysis.

Meaning, the reasoning on why #5 rod bearings fails is a WAG, Wild *** Guess
and the reasoning on why the OP #1 rod failed is a SWAG, Super Wild *** Guess
 
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my68barracuda said:
I don't know either, but in looking at how the lube oil flows in a slant, I can determine that:
rod ends 2 & 3 are oiled through #2 main
rod ends 4 & 5 are oiled through # 3 main
rod end 1 is oiled through #1 main
rod end 6 is oiled through #4 main
so rod ends: 2,3,4,5 are split oil flows
and rod end:1,6 are dedicated oil flows.
the rear main oil galley also feeds the oil line up through the block and head to the rocker arm shaft.
so there is definitely more oil flow demand towards the rear half of the crank.
Perhaps #6 is not a known bearing spinner, because of the dedicated oil supply.
So why is #5 and not #4 reported most often with a failed rod bearing, they may be both so close to failure that when the furthest one from the oil pump
(#5 vs #4) goes, the other is not far from failing also. Or it may be that #5 is actually the furthest rod bearing away from the pump (on a line that is shared and is also supplying a secondary lube to the rocker arms) so it fails catastrophically first.

Saying all of this without any empirical data. It would take a computerized 3D model to know with confidence, but for an on line argument I think this has some substance.
It is also important to note that the OP had a failure on #1 cylinder, and to me that rod failure appears to have initiated at the piston pin end, not the rod end. But that is from looking at one photograph of parts picked up from the road side. So there is a large opportunity for error on that failure analysis.
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@RustyRatRod ...is. there a slant 6 schematic I can access?. My younger brother was a mechanical engineer for Ford. He may have some insight.
 
WV64Signet said:
@RustyRatRod ...is. there a slant 6 schematic I can access?. My younger brother was a mechanical engineer for Ford. He may have some insight.
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WV64Signet,, a couple of options:
1) google ‘slant six oil flow’ you will get at least a page of FSM views of the slant motor oil flow. Over the course of the slant six production, the only time the flow path changed was when the hydraulic lifters were introduced. These views are typically looking through the motor from the #1 end.
2) get a vintage Factory Service Manual. On eBay most days. There in the engine section you will find the diagrams mention above.
3) get an engine roll over and a slant block and head. Disassemble, peruse, contemplate and sketch out the oil flow as you see it. Hopefully you will be somewhat close to what is shown in #1 or #2 listed above.
 
my68barracuda said:
WV64Signet,, a couple of options:
1) google ‘slant six oil flow’ you will get at least a page of FSM views of the slant motor oil flow. Over the course of the slant six production, the only time the flow path changed was when the hydraulic lifters were introduced. These views are typically looking through the motor from the #1 end.
2) get a vintage Factory Service Manual. On eBay most days. There in the engine section you will find the diagrams mention above.
3) get an engine roll over and a slant block and head. Disassemble, peruse, contemplate and sketch out the oil flow as you see it. Hopefully you will be somewhat close to what is shown in #1 or #2 listed above.
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Copy All. Thanks

Service manual is right here. I'll pull the other web sources you mention. He likes puzzles and car builds.
 
That's all I know of it's what's available in the FSM and online. I wonder what effect if any full grove mains and an HV oil pump would have? ....and let's not get into the "don't put an HV pump on a slant 6"......let's leave that discussion for elsewhere. I'm just curious of the HV pump and full groove bearings would have any effect on the possible bearing issues. I would think so.

But without data, it's probably just another SWAG. LOL
 
I would try improving oil flow on the inlet side of the pump. Maybe enlarging the p/up, radiusing sharp corners etc. Similar to the BB mods.
 
RustyRatRod said:
That's all I know of it's what's available in the FSM and online. I wonder what effect if any full grove mains and an HV oil pump would have? ....and let's not get into the "don't put an HV pump on a slant 6"......let's leave that discussion for elsewhere. I'm just curious of the HV pump and full groove bearings would have any effect on the possible bearing issues. I would think so.

But without data, it's probably just another SWAG. LOL
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When I ran my 170 slant in "stock eliminator" I had no problems. After I milled the head, bigger cam and 500 holley 2 bbl, I started having issues with #5 bearing (always caught it before additional damage). After using full groove mains, no more problems.
PS: stock aftermarket replacement oil pump (not the HV pump), which is HV compared to the OEM pump.
 
70bigblockdodge said:
Seems like the front rods always break the block. The back ones just hang on banging away till they seize.
That sucks.
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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. 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..
 
jos51700 said:
Could be oil supply, could be harmonics, could be shaft torsion, could be block flex....what else...?
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Poor lube, assy., or components, on a stock/mild Slanty..period...none of those "tech mysteries". Otherwise the failure rate would be well over 50% for an engineering oversight that "deadly"....go to any dealer and look at what's in the scrap pile, or re-boxed/crated waiting to get sent back, .....from 229 V-6 Chebby disasters as shortened 305's in the late '70's-early '80's, said 305's eating exhaust lobes(4100 Caddys too), to modern Hy Theta engines that now have a lifetime warr extension, pattern failures due to mfr processes/materials or design/engineering show up quickly & often. The latter of this simply is not the case,....
 
I had a rod bolt nut back out on me and do that. The engine was rebuilt be National Cylinder Head Exchange and it was nocking really bad when I bought the car. It ran for about 30 seconds in my custody and bang. I found one rod bolt bent and still connected, the other was intact separated from its nut and in the oil pan.
 
Charrlie_S said:
When I ran my 170 slant in "stock eliminator" I had no problems. After I milled the head, bigger cam and 500 holley 2 bbl, I started having issues with #5 bearing (always caught it before additional damage). After using full groove mains, no more problems.
PS: stock aftermarket replacement oil pump (not the HV pump), which is HV compared to the OEM pump.
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Cool, thanks, Charlie! Yeah, the stock pump (aftermarket replacement) gives over 70 PSI idling cold with the high pressure spring in it. That's what I'm running now.
 
MOPAROFFICIAL said:
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. 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..
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No, they'll never set the world on fire, but they sure are a LOT of fun!
 
I do not have any experience with the 225. The failure of #5 rod brg though is intriguing. Must be a reason. Any more ideas?
 
Chinze57 must be busy with college since RustyRatRod's offer is great and he is very knowledgeable with many parts on his shelf, and would be an interesting guy to meet in person. "3.5 hr down to Georgia Southern" suggests that Chinze57 lives in the Atlanta Metro area and I recall Rusty is near Macon, so just down the road. I'd jump on it.
 
Dartswinger70 said:
They used to say in the 80s that the slants "run forever' I guess not ...:)
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Heck, mine had over 300k on the odometer without a rebuild, all it needed was a replacement exhaust manifold and paint. The original owner took very good care of it.
 
Ottmundr said:
Heck, mine had over 300k on the odometer without a rebuild, all it needed was a replacement exhaust manifold and paint. The original owner took very good care of it.
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yeah there was an aura about the slant, cab companies ran em etc. they used to say they would run forever back in the 80s, if any are still around now running unrebuilt, thats pretty good...
 
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.
 
RustyRatRod said:
I wonder if anyone has any theories on the #5 failures? It's common enough there must be something to it.
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I think I saw a v video from uncle Tony s garage he was saying something about it .thats why it needs a windage tray . I welded one in my slant and the strainer needs to be touching bottom of pan . check him put on you tube
 
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