so, pin the failure on the #70 CMC LT1!

[GlennCMC70]

durring the off season i pulled my 93 LT1 to put new gaskets on it to stop the masive oil leaks. other than the leaks, the motor ran like a top. had 80K on it when i put it in wheni built the car in '04, and i ran about 55 CMC races on it.
i thought i would be smart and pull the bearing caps just to see what the bearings looked like while i had it out. they looked good, but since i could see them i thought it would be smart to replace them. so all new standard rod and main bearings went in. i didnt plasti-gauge anything (stupid - in know). i just assumed since it was a 100% stock untouched motor, the crank and such had never seen the light of day.
i also put new lifters in it while the intake was off.
well once the motor was running again, i noticed my cold oil pressure was around 25psi w/ 15-50 M1 in it. normally it was around 50psi. i also noticed it never got higher that 25 when it reved. once warm the needle still sat on 25. it would move some, so the gauge was working. i went ahead and decided since time was short to the start of the season, i would leave it for now.
this past weekend i was seeing single digit PSI @ 5K. i think it barly made the weekend w/out blowing up.
on monday it took 15 seconds or so to start to build oil pressure. and then its only about 10 psi cold. not good. the lifters clatter like a mofo for a few seconds till it builds pressure.
i got pulled it yesterday. well the main and rod bearings look like new, just as they did when they came out of the box.
pulled each lifter, and all looks good.
took the oil pump apart, and it looks good.
no metal in the pan.
totally lost.
anyone wanna guess what is wrong? cam bearings? clogged oil galley? is there a oil gally that is common to the lifters and the oil pressure sender port on the top rear of the block?

[jeffburch]

If it wasn't for the reported puffs of black smoke I'd point to the guage/operator.
I wonder what the rings/lands look like.
Prolly didn't do a compression/leak down test huh?
Is the crank/rods at oem specs?
If they've been turned and you put in oem spec bearings?

Just throwing darts to spur thoughts.

jb

[AllZWay]

My first thoughts would be something caught in the oil pickup tube..... especially since you put on new gaskets and perhaps that gasket material partially plugged it.

My next would be a faulty gauge or sending unit.

[donovan]

If you are running an oil cooler, check to see if the check ball assembly is okay. I had one come apart and the check ball was plugging the hole on left turns and dropping pressure.

DD

[GlennCMC70]

i have no check valve in my oil cooler system.

[GlennCMC70]

took the crank to a friend @ a machine shop in Ft. Worth.
main's were .010" under and the rod's were STD.
he told me it was no uncommon to have the factory turn the cranks to remove a defect or flaw. so it could have very well been that way since new from the factory. so there is my problem. i removed the cam and the cam bearings are toast. so it will be going to the machine shop to get refreshed. possibly new pistons and a good balance.

[David Love AI27]

took the crank to a friend @ a machine shop in Ft. Worth.
main's were .010" under and the rod's were STD.
he told me it was no uncommon to have the factory turn the cranks to remove a defect or flaw. so it could have very well been that way since new from the factory. so there is my problem. i removed the cam and the cam bearings are toast. so it will be going to the machine shop to get refreshed. possibly new pistons and a good balance.

Did you look at the mains and see if they were marked .010 over?? Stupid question I know, but I'm doing the same to my motor and would like to know if there are any markings before I pull the caps...

[GlennCMC70]

i looked @ them, but ididnt notice anything.
i honestly just assumed they were STD. the motor was pulled from a factory stock car. 80K. factory gaskets. no reason to think it was a .010" under main.
go buy some plasti-gauge. use it and read it. only way to be sure.

[David Love AI27]

i looked @ them, but ididnt notice anything.
i honestly just assumed they were STD. the motor was pulled from a factory stock car. 80K. factory gaskets. no reason to think it was a .010" under main.
go buy some plasti-gauge. use it and read it. only way to be sure.

Got a 305 from a 85 Blazer w/85K... Already have the plasit-guage (3 colors.. LOL) only $300 complete... should get my through '07 then I'll decide if I'm going to move down to CMC or built up 350 to around 375hp

[j3ffbrooks]

Glenn,

this was my problem too last year and is why I missed Hallett. I did use the plastigauge, but my math skillz were lacking while I was calculating the measurements. I wasn't too excited about pulling the motor back out and tearing it down.

Check and double check.