14 mos, 4 motors

r lane · 08-23-2020, 03:46 PM

Gentlemens, I have broken 4 motors, 3.0 MFI track, in a little over a year. The first was due to low oil pressure that I think was caused by a restricted on board oil cooler. Still trying to get my head around that one. Repaired it and early into my third weekend, lost a rod bearing. 4 1/2 - 5 bar oil pressure, but noticed the oil temp rising and came in. Another motor that I ran prior to this current motor was refreshed and installed. Coming into the pits after my first session, a venturi bolt finds its way into the #1 cylinder. A couple of dings on the piston and head, bent a valve, no cylinder damage, checked rod for trueness and replaced its bearings. Back together and one session, oil pressure good, oil temp never came over 170 and suddenly rod knock. Have not taken it apart yet. Looking at my build notes, I have .0035-,0045'' clearance on mains and .0025'' on the rods. I have an odd oil system but other than changing the cooler setup, has stayed the same and was able to run my original motor 10 weekends before an upper end refresh. What was common to these 2 motors was a rebuilt MFI pump. I suppose a malfunctioning port could cause detonation enough to damage a bearing, but would think I would have a performance issue. I have seen comments that state not to reuse oil lines and coolers after a blow up though in years past I was able to make that work and I know of racers who have that same experience. 3.0 and turbo oil pumps. Input?

dannobee · 08-23-2020, 09:23 PM

Ugh. Rod knock but didn't hole the case? Which rods and bolts?

drgouk · 08-24-2020, 03:52 AM

Maybe cross drill the crank if its 2&5? Some pics would be good. Your main clearance's are on the large side.

reclino · reclino's Garage

What brand rod bearings are you using?

r lane · 08-24-2020, 05:33 AM

The first blowup which in hindsite I know had oil pressure issues, was June a year ago #s 2,4 &5, saved the case. The second one this June was on #4 with no case damage and this latest one is still in the car, so don't know the extent, but no hole in the case. The main bearings are Glyco, don't know if we have options there and the rod bearings are 2004 GT3. There are 2 versions of GT3. The second, maybe should be referred to as #2 had a cross drilled crank. On this latest motor, I have a serviceable filter on the scavenge side and a spin on for the pressure side. A 965 thermostat cap is in place of the thermostat. Pauter, Carrillo and standard SC and ARP bolts

r lane · 08-24-2020, 05:37 AM

I raced an E p roadster years ago in SCCA and we had to run the rods at .0035''. Totally different system but makes me wonder. Would like to know what the bearing clearance specs are for the guys who are not losing motors. Thanks, Bob

racing97 · 08-24-2020, 06:21 AM

The only time you see this repetition is when the oil cooler or oil coolers don't get Sonically cleaned .

Eagledriver · 08-24-2020, 06:25 PM

No reason for all these bottom end failures other than oil starvation. Maybe need a bigger oil sump or better baffling. If it’s a 3.0 you might need the better Venturi scavenge pickup, and the updated oil pressure relief springs.

-Andy

stownsen914 · 08-25-2020, 03:17 AM

I've heard of mysterious engine failures being caused by failed stainless braided oil lines that delaminated internally causing a blockage. It's not evident externally when this occurs. Might be worth checking.

r lane · 08-25-2020, 05:20 AM

Thanks for all of your insite and input. I think I am going to recooler and pop the plugs on the case. Can't keep doing what I have been doing, cause that ain't working. If the problem persists, then look elsewhere, but am running out of cranks. Will report back. Bob

mepstein · 08-25-2020, 05:30 AM

Take it to a race car engine builder. Peter Dawe, Henry Schmidt, etc.

blue911rsr · 08-25-2020, 03:42 PM

What size are your oil lines need to be 16 an if they are 12 that’s to small have seen a guy that had these problems till he went to 16

r lane · 08-26-2020, 05:53 AM

No, I have to build them, part of the fun, if you call this fun. To quote Doc Holiday to his poker opponent who was losing badly, ''maybe my good man, this just isn't your game, possibly checkers would be more your fare''. I am running -12 and will talk to the people at BAT on this issue. Prior to my first explosion which I am convinced was an oil pressure problem, I had put 10 weekends including some 3 day Mittys on my first engine which was more a street rod build. Ner a problem. Built a second engine with more compression and cam. Oil pressure readings were low, decided not to trust the OE stuff as a Bosch mech gauge said I was fine, and blew the engine good, 3 rods. Much investigation after repairing that motor, the final effort was changing the on board cooler and bingo, went from 35 to 75 PSI. 3 events later and popped that motor. Plugged in the refreshed street rod engine, 1 event and bang. This saga supports trash left in the system.
t

Neil Harvey · 08-26-2020, 08:13 AM

Quote:

Originally Posted by r lane

No, I have to build them, part of the fun, if you call this fun. To quote Doc Holiday to his poker opponent who was losing badly, ''maybe my good man, this just isn't your game, possibly checkers would be more your fare''. I am running -12 and will talk to the people at BAT on this issue. Prior to my first explosion which I am convinced was an oil pressure problem, I had put 10 weekends including some 3 day Mittys on my first engine which was more a street rod build. Ner a problem. Built a second engine with more compression and cam. Oil pressure readings were low, decided not to trust the OE stuff as a Bosch mech gauge said I was fine, and blew the engine good, 3 rods. Much investigation after repairing that motor, the final effort was changing the on board cooler and bingo, went from 35 to 75 PSI. 3 events later and popped that motor. Plugged in the refreshed street rod engine, 1 event and bang. This saga supports trash left in the system.
t

Time to stop. What's that say about stupidity, no offence meant.

It's time to take another approach here. There is no harm done when asking questions and having someone of experience lookover what you have. You still can build it, just remove any doubts.

Separate the engine into individual parts. The case, crank, rods, pistons, Cylinders, heads, service lines etc. Make sure you go through every part of each. For example, strip the case completely and go through the oil passages, relief valves , through bolt bores, everything. If you have any doubts, ask someone else to look over this. Once you are sure about the case, repeat the same for the other parts. Once you have gone through the engine, do the same for the parts in the car. Oil tank, service oil lines, Cooler.

Leave nothing to chance. Remove every part and inspect it in detail. Remember, these engines run and do not have tis sort of trouble. The issue is either in the parts you are not seeing or you are doing something in the assembly.

r lane · 08-26-2020, 03:07 PM

The filters off of my blowup. A system 1 in the scavenge position and a spin on in the pressure position. I bench tested this System 1 for what that was worth, and it seemed to have no trouble letting the oil through. Don't know what it's micron rating is nor do I know what it should be. I wanted it in that position so that I could check it after each session. May have been my undoing. A hint of golddust in the spin on. The flash is making the oil appear copperish. Drained 8 1/2 quarts out of the tank and case. No metal on the plug in the tank. Will report as I continue. Bob

stownsen914 · 08-26-2020, 05:14 PM

I wouldn't be comfortable with -12 lines on a race motor personally. That's a little smaller than stock, if I'm not mistaken.

r lane · 08-28-2020, 05:36 AM

1 undisclosed detail. When I built the car, a 78, I flipped the oil tank to in front of the rr wheel. Installed a 72 oil filter console with thermostat. A lot of cutting and reconfigureing on the tank. Mainly the verticle return pipe inside the tank was cut away from the existing oil filter flange at the top of the tank and that flange area sealed. Had to build a splash shield above the pipe as it was pointing directly at the oil cap and we had leakage. Obviously any number of snafus could have occurred in my constructing this tank, but is fairly simple in that oil is returned to the top and is sucked out at the bottom. My wonder is, is tank location a problem, also my scavenge goes straight to the primary oil filter and the later cars have it going to the coolers first and then to the filter. As stated, I had 10 successful events on this system until things started going south.
Is the later layout preferred over the earlier. At present, I have all of the coolers, plumbing, tank all lying on the floor and I am sitting on my work stool just staring at them. Thanks somemore, Bob

r lane · 09-16-2020, 05:40 AM

Am going back up with the motor, removed the main gallery plug post flush finding no metal. Replumbing the oil system with new coolers and -16 hose which is a bit of a pain to work with. Am relocating the tank from in front of the rr wheel to behind it in conventional position. The tank I am removing had been a converted SC tank, not from a 72. The thought occurred to me that under hard braking, all of the oil runs to the front of the tank and away from the suction port, leaving the port gasping for oil possibly. Don't think the factory ever ran a race car with a tank in the 72 position, but did that 1 year tank have special baffling to handle possible oil starvation.

stownsen914 · 09-16-2020, 01:17 PM

Does the 72 tank sit in a different/opposite orientation compared to the more rearward location?

r lane · 09-16-2020, 03:58 PM

It is somewhat similarly shaped, and flipped 180 looking the other way, rearward. It is a 8 quart tank which is why I used a later one for the extra 4 quarts. The outlet port on the 72 tank going to the suction side of the engine is on its aft lower corner and if it were flipped and installed behind the wheel, that port would then be on its forward side. Just wondering if that 72 tank was baffled to handle the oil shuffling away from the suction port under braking. I.E. did the factory see that as an issue. Would like to determine whether or not my tank location has played a part in my oil pressure/volume issues, causing me suddenly a rash of motor failures. Thanks, Bob