Visit The Dirt Forum for More Information

Author Topic:   all kinds of problems, oiling, carb, etc
posted August 07, 2003 02:54 PM
Ok, against my advice, we got an engine that I didn't care for a whole lot from a local engine builder. It is a flat top 355 with lower end components, ported 305 heads, and around a .550 lift cam with solid lifters. Motor is turning around 6000 rpms with a "worked" quadrajet carb, stock cast iron intake and exhaust. Now the problem. Two races in a row the car has fried main and rod bearings, and torn up the crankshaft. After the first night, the crank was replaced new bearings installed, and two rods replaced. The second time he had trouble getting oil pressure (20 at idle), but it climbed to 60 at about 2000 rpm. However, as the night went on, the oil pressure dropped and was only about 30 by the end of the A main. When he pulled into the pits and was idling, it was only about 15 psi. The engine builder seems to think it is the carburator running the engine lean and causing the oil to heat up, but the car runs at 180 degrees on the track water temperature, no higher than 190. We don't have an oil temperature gauge unfortunately. It seems to me that if the oil got hot enough to cook the bearings, the water temperature would be higher than that. Also, the oil doesn't seem to be burn't. If the oil gets hot enough to cook bearings, what will it be like? Does it "burn" like tranny fluid? I think these guys just didn't have bearing clearances set right. I had nothing to do with any of that though, so I don't know. I believe in both cases it was the rear bearings that had problems, but I am not 100% on that. Any insight? Thanks.


posted August 07, 2003 03:05 PM
If your water temp was only 180-190 then you werent running lean. And yes i would think that if the oil was that hot it would also show in your water temps.

rico 08
posted August 07, 2003 03:11 PM
What type of pan are you running?Sounds like you have alot of oil foaming going on,a windage tray,crank scraper,good pan will help,also what weight oil are you running?With a stock type pan i've always ran valvoline sraight 50wt oil,some say it's too thick but as long as you warm it up before standing on it you will be ok.Also make sure they are giving the crank racing clearances,anything under .0025 will cause problems,.003 is what i usually run.

posted August 07, 2003 03:14 PM
7 quart Midwest motorsports pan with trap doors, standard volume new oil pump, valvoline straight 50 weight oil.


posted August 07, 2003 04:34 PM
If the crank has been reground and it isnt indexed correctly it could cause the bearing problems by not being true to the world, also if the block was line bored and wasnt done correctly that would hurt the mains as well. Also if it is not a balanced rotating assemble that can be part of it.

posted August 07, 2003 07:21 PM
Also if the bearing clearences are too tight there wont be enough clearence when they reach operating temps causing them to fry and if the piston skirt clearence is too tight that can cause the bearings to fail as that puts strain on the bearings when the pistons start to seize in the block when warmed up.

posted August 07, 2003 10:10 PM
If you lost the mains , then it is definitely an oil starvation problem . Of course this could be caused by pretty much everything mentioned above , except for the lean carb . One extra thing to look for would be the trap door's welded in backwards in the pan . I've seen this on 2 separate Mid West pans that were brought to my shop by customers .


Hendren Racing Engines
Rutherfordton , NC

posted August 07, 2003 10:47 PM
Is there any pattern on the bearings? Meaning are say the front 3 all worn on the pass. side of the block and back 2 on the driver's side? Top of #1 and bottoms of all the others wasted? The former could be a bowed block/misaligned/wrong caps and the later could be overtightening the belt pulling up on the snout of the crank too hard (seen this at least twice when I worked in an engine shop couple years ago)

If you're worried about oil temps, use synthetic or semi-syn oil. I use either Valvoline Durablend or Amsoil 20w50 in mine with good results.

Back to the Archives