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I APOLOGIZE FOR THE LENGTH OF THIS: Looking for some real world advice as I'm tearing down my relatively fresh motor - I know there are some who have experienced this as well as some real engine builders on here. I know what I am faced with, but need advice on parts to potentially salvage. I am absolutely sick after a knock under-load started in my 355, following a long and smokey burnout. I took my 1970 L46 out last Friday night, following a couple weeks of business travel, for a ride with my son - also a car enthusiast. It was well warmed up and probably 30 miles that evening, when on a country road I slowed down to a roll, pushed in the clutch, gave it a rev and dropped the clutch and stood on the gas to run through the gears. The car launched and drew a long and glorious smokey "11" for about 50-60 feet, then stuttered and nosed over as I grabbed for 2nd gear. No rev limiter, but I typically shift it by 6K as the cam is over by 5800. It's never nosed over like that, so I got out of the gas and slowed down. When I got back on, it was "rapping" on a cylinder. Obviously I broke or bent something... or worse. I was 4 miles from home, so limped to a nearby parking lot. At one point on the way there, it actually pulled itself down to an idle and killed. I coasted over, restarted and proceeded off the road. When I restarted it in the parking lot, it turned over hard, but restarted right away and seemed to idle fine. No knock, sounded pretty much normal. I slowly cruised the rest of the way home under part throttle, but if I pushed my foot into it at all and introduced a "load" it would knock. When I got home, I pulled the dipstick and oil looked normal, but was a QUART LOW. It's been using a little when driven hard - I think maybe drawing through the PCV - but that's another subject. So guessing the hard launch and high rpm starved it for oil, or possibly pump cavitated. I was hoping for a rocker arm...or imagining a lifter failure maybe...but pulled the covers, listened to the motor at idle, looked everything over and think the top end is okay. When cool the next morning, it will idle and moderately rev with no knocks, but once warm and attempting to back out of the garage, the knock was back. I decided it will need to come out for a tear-down. I drained the oil and the bottom of the pan showed the tell-tale glitter of likely bearing failure. I will also add that oil pressure on the motor has been excellent since I put it together, and I had healthy oil pressure when I checked right after this incident and on the drive home. I changed the oil and filter, and for the 2 seconds it takes to build oil pressure upon restarting, it sounded like a true rod-knock for a few revolutions and got quiet as soon as the engine had oil pressure. So, I am guessing spun bearing. At an idle it only appears when the engine is warm, and it is NOT a constant knock... it is more like a floating rattle, but I cannot pinpoint it with a stethoscope.
Original L46, bored to 355, stock forged crank, stock (reconditioned and sized) pink rods, 9.7 compression, sealed power hypereutectic flat tops, aluminum DART SHP heads with Howard's HD springs, and Howard's retro-roller hydraulic roller camshaft, Scorpion roller rockers, Howard's roller lifters and Howard's 1-pc pushrods. The motor was balanced, completely fresh, dynoed on crank (just shy of 400hp) and chassis dyno's, well broken in and has about 2K miles on it of mixed cruising, highway and some abuse. I am running a Muncie 4-speed with McCleod clutch setup and rebuilt 3.73 HD rearend. I ran a stock oil pump, and the pressure was likely really good due to tight bearing clearances. When I mocked it up originally and we mic'd the crank, rods and mains, the mains were 0.002 across the board and I think 0.0028 on the rear main, so I left those. The rods were loose at 0.003 on most, so I ordered a set of undersized bearings (0.001 thicker) and tightened them up. This left all the rods but 2 of them at 0.002, but one came in at 0.0018 and one was 0.0013 (tight, I know, but the old Motors manual listed minimum acceptable on the rods as low as 0.0007 -- really -- so I thought I could live with 0.0013. Now I'm kicking myself and probably should have run standard bearings on that and possibly the 0.0018 rod, but didn't ask an authority. Maybe the low level, high rpm and tight rod caused my problem. Won't know until I tear into it.
I am nearly ready to pull the motor now. It will be out this coming Saturday, then I will tear down for cleaning, inspection and rebuild again. MY QUESTIONS: For those of you who know, what am I likely faced with replacing? Can this expensive cam setup be salvaged if it appears to look healthy? Lifters? If pistons are good, would a person typically hone and re-ring? What else to check and consider, aside from a thorough flushing? I already spoke to my machine shop and will bring the block, crank and rods in for the entire ordeal. I plan to keep the car and motor for some years, and want a bullet proof roller motor. I've done about a 1/2 dozen SBC's in the past, and never made this mistake or experienced this. Oh well, pick up the pcs and rebuild. Any helpful advice appreciated.
BTW, here is what the oil drain pan looks like after you grind up bearings -- or some other part:
Last edited by JoeMinnesota; 09-18-2018 at 05:44 PM.
If the cam looks okay.... I would save it..I would take apart the lifers and clean them and then allow the machine shop to check the rest and wash it thoroughly.
jeezzz Joe....So sorry to hear the sad news about your 355......
Just Curious, what brand of oil and grade do you use? Sounds like you have a good sense of the potential issues. Please keep us up to date. Thanks
I ran Lunati break-in oil through the initial dyno and for about 500 miles on the car, then changed out to 5W-20 Mobil1 synthetic (hoping to keep my pressure within reason and good flow at start-up). No leaks - not a drip. WIX oil filter.
Ill let let you know what I find when the bottom end comes apart. I've actually been thinking about your Howard's roller and if I have to replace it may go to the .525 lift cam you are running, possibly their straight duration 225/225. Need to research more.
It it has been using oil when I hammer on it, but not smoking - only a short haze when you stand on the gas after engine breaking under part throttle for a stretch. Oil on the top and bottom rubbers on the oil cleaner when I pulled that off, so I'm suspecting it's drawing oil through the PCV and I may add a catch-can during this rebuild.
REMINDER - ALWAYS check your oil before you go for a cruise, even on a healthy newer motor. I really think I would have avoided this if it wasn't running a quart low. Really a tough lessen. There is a reason our new cars hold 6 and 7 quarts, even on 6 cylinders. Missing a quart on a 5qt system with one already in the filter is a pretty big deal.
Last edited by JoeMinnesota; 09-18-2018 at 08:37 PM.
Oil pickup is in the back of the pan. You gotta be really low to suck air under acceleration how far is crank cut at this point? A lot of people won't run a .020 under crank. Cam should be fine. Replace the 2 rods on that journal. Don't resize them.
Oil pickup is in the back of the pan. You gotta be really low to suck air under acceleration how far is crank cut at this point? A lot of people won't run a .020 under crank. Cam should be fine. Replace the 2 rods on that journal. Don't resize them.
True on the pickup. I don't have the short block out yet, but will soon. Will have to see what the crank scoring looks like, but it was standard going into the motor - just got a polish and balance, so could be ground. I assume you mean don't resize and reuse my current spun rod(s), but replace that pair with new? Will do. Thanks
Make sure cam bearings come out of it to clean behind them. All pipe plugs out etc. Pistons will need to be ck'd for scoring and cleaned well. Replace rings. Everything has to come apart for cleaning. Oil pump...really hard to clean screens on inside...best to change. Take lifters apart to clean and clean cam real well. Heads will need to come apart to get metal out from under valve springs. I've run .020 cranks just fine...but you have to be careful on heat treatment. Won't be any at that point. Might be able to get you a nice forged bottom end and make a 383! And maybe invest in a well designed oil pan.
The old saying about clearances is true. "A little loose and only you will know it. A little tight and everyone will know it".
I ran Lunati break-in oil through the initial dyno and for about 500 miles on the car, then changed out to 5W-20 Mobil1 synthetic (hoping to keep my pressure within reason and good flow at start-up). No leaks - not a drip. WIX oil filter.
Ill let let you know what I find when the bottom end comes apart. I've actually been thinking about your Howard's roller and if I have to replace it may go to the .525 lift cam you are running, possibly their straight duration 225/225. Need to research more.
It it has been using oil when I hammer on it, but not smoking - only a short haze when you stand on the gas after engine breaking under part throttle for a stretch. Oil on the top and bottom rubbers on the oil cleaner when I pulled that off, so I'm suspecting it's drawing oil through the PCV and I may add a catch-can during this rebuild.
REMINDER - ALWAYS check your oil before you go for a cruise, even on a healthy newer motor. I really think I would have avoided this if it wasn't running a quart low. Really a tough lessen. There is a reason our new cars hold 6 and 7 quarts, even on 6 cylinders. Missing a quart on a 5qt system with one already in the filter is a pretty big deal.
Thanks for the response Joe!
On My build, I ran Driven 15W-50 break in oil for the 20-30 minute break in @ 1,800-2,000 RPM with an occasional engine rev to 2,500 RPM. My builder of the bottom end of the engine did the break in my garage and was present doing it. I then took it out on the road for about (6) 2,000-4,000 RPM full throttle accelerations, to complete the ring seating. Went home and changed the Breakin oil and mobil 1 filter to conventional Driven 15W-50 and a new Mobil 1 filter. Drove the car moderately for the first 500 miles. Changed the oil again @ 500 miles to Mobil 1 0W-40 European Formula (which is what i have used ever since) and another new Mobil 1 filter. All has been good for 5 driving seasons. Don't know if any of this matters with your situation but just sharing for the future.
BTW-I have been using the GM 1 qt truck filter on my C3 for 30 years. An oil change is 5.5 qts with the bigger filter.
One other question joe-What was your oil pressure when oil was hot? Seems to me that Mobil 1 5W-20 would be too thin. I have an 81-82 oil temp gauge in my clock dashboard pod for 30 years now and when my oil temp is about 160-175 Degrees, my oil pressure is 40 PSI at idle and 60-70 PSI at higher RPMs as a reference.
I would never spend all that money and time with a polished crank. That’s most likely why the 2 tighter clearances were there.
Why do you say that? On a 80K mile forged crank that is in great shape, checks out well and is standard dimensions, why would I grind it and not use it? Not sure I understand. Could be the case on the clearances, but I should have kept std bearings on those two - that's on me. That's why you mic them out. Anyhow.
One other question joe-What was your oil pressure when oil was hot? Seems to me that Mobil 1 5W-20 would be too thin. I have an 81-82 oil temp gauge in my clock dashboard pod for 30 years now and when my oil temp is about 160-175 Degrees, my oil pressure is 40 PSI at idle and 60-70 PSI at higher RPMs as a reference.[/QUOTE]
With the thin oil, I still had very similar pressure to you at idle and at higher rpm always around 70 PSI. Thanks for idea on the oil filter - I'll need to consider that.
Think that when a cam lobe is wiped, then it's a hassle getting the grit removed from the block, making it necessary to remove cam bearing, oil gallery plugs etc, don't think that it's as much of an issue when its a rod bearing. If it was mine, would of course disassemble short block, take apart the oil pump to inspect for damage unless you just plan on replacing it. Would ask the machine shop to glass bead a couple of the pistons, (mask off the ring lands before glass beading), (probably would pick the ones that spun the rod bearing) If any metal from the spun bearing is embedded in a piston skirt, it will come out during glass beading. When glass beading, it is possible to actually see the metal get removed from the piston skirt. Of course if there is embedded metal in one piston, all of them need to get glass beaded. As mentioned, wiping a cam lobe is when the metal gets everywhere, so chances are there should not be any bearing metal on the piston skirts, but just to play it safe that is one thing to have done.
Think that when a cam lobe is wiped, then it's a hassle getting the grit removed from the block, making it necessary to remove cam bearing, oil gallery plugs etc, don't think that it's as much of an issue when its a rod bearing. If it was mine, would of course disassemble short block, take apart the oil pump to inspect for damage unless you just plan on replacing it. Would ask the machine shop to glass bead a couple of the pistons, (mask off the ring lands before glass beading), (probably would pick the ones that spun the rod bearing) If any metal from the spun bearing is embedded in a piston skirt, it will come out during glass beading. When glass beading, it is possible to actually see the metal get removed from the piston skirt. Of course if there is embedded metal in one piston, all of them need to get glass beaded. As mentioned, wiping a cam lobe is when the metal gets everywhere, so chances are there should not be any bearing metal on the piston skirts, but just to play it safe that is one thing to have done.
Metal flakes are metal flakes. It doesn't matter where they came from. If they're in the oil, they're going to be everywhere.
Metal flakes are metal flakes. It doesn't matter where they came from. If they're in the oil, they're going to be everywhere.
BOY AIN"T THAT THE TRUTH, It makes no difference due to ANY small flake of anything can cause havoc to some parts that require oil. Starve any part for oil...you will have a problem...which is just logical.
I will say that I AM NOT the worlds best high performance engine builder.. Not by a long shot....but I have been around some guys who fit that classification and I know from them that often times when the engines they use for racing that are at thigh rpms a lot of the time...they would use push rods that were restrictive thus not allowing all of the oil that could not normally be pumped through them.
They stated that the top end does not need to be fire hosed with oil and by using the restricted push rods that it allowed more oil to stay in the pan when the engine was at max rpm. I have personally seen this when these engines were on their dyno being run due to the custom valve covers they had made had a Plexiglas top on then and I could watch the oil from the push rod when the engine as cycled. It seems to not effect any top end parts due to a lack of oil due to they never told me or showed me any part as that had failed. AND I saw many parts that had failed in the other engines they had used and why they failed. So not knowing if this means jack squat or not.. Thought I would mention it because they sell these pushrods for a reason and not knowing if it was oil starvation or a problem in the bearings....I feel it is hard to point to what the issue is at his time.
Joel,
I would tear it down and decide the best course of action. Pay attention to the break away force on the fasteners to give you a clue where to look closer. Disassemble, clean and inspect everything as you would for any other tear down. Pull all the core plugs first. I usually drop the parts in a big Rubbermaid tub and run brushes thru and pressure washer on it. Fill the garden pump sprayer with ATF /Kerosene mix to spray it down after a rinse as it comes out of the soapy water tub. If it was a rod bearing, You will want to grind the crank for insurance. Consider resizing the rod if it did not get too hot - Look for color. Fresh bores so it might only need a slight hone. Reuse the good pieces. Replace the rings and bearings.
Joel,
I would tear it down and decide the best course of action. Pay attention to the break away force on the fasteners to give you a clue where to look closer. Disassemble, clean and inspect everything as you would for any other tear down. Pull all the core plugs first. I usually drop the parts in a big Rubbermaid tub and run brushes thru and pressure washer on it. Fill the garden pump sprayer with ATF /Kerosene mix to spray it down after a rinse as it comes out of the soapy water tub. If it was a rod bearing, You will want to grind the crank for insurance. Consider resizing the rod if it did not get too hot - Look for color. Fresh bores so it might only need a slight hone. Reuse the good pieces. Replace the rings and bearings.
That's what I would do.
-Mark.
good plan - thanks. Yes, the entire engine will be torn down and anything in question after cleaning and inspection will be fixed or replaced. Too large an investment in the first place to band aid it together. Thanks for everyone's input!
Now's the time to fix oil consumption issue also. Cylinder bore prep and proper piston/ring combo is key.
JIM
not sure on the consumption. I have a reputable shop I've used for 4 motors. Last one leaked down at 1% on nearly all cylinders after a couple thousand miles. Used torque plate, etc. we will see what it needs.
09-18-2018, 05:40 PM
Advice - Spun Bearing (more than likely) Rebuild
