I have a 351m completly rebuilt it has about 300 miles on it and I think it is shot!!! The oil pressure runs about 3/4 scale when cool and when it heats up goes down. At around 2500 rpms the guage reads 1/4 (eng warm) At idle the guage goes to zero and I hear a knock. Also at 2500 it sounds like a diesel. I spent about 3k on the eng. Here is what was done. Any Ideas?

Aussie Heads
Stock Pistons
Bored 30 over
Crank 10 under,polished
Rings,bearings etc
Crane 272 Cam
Edelbrock 650 (1406)
Edelbrock performer 400
MSD 6a
MSD dist
Roller timing chain
High vol oil pump
Headers
New damper

 

I don't think your in bad trouble yet! Just don't run the engine anymore. I would take it back out and look all the bearings over real good. Did you plastigage the bearings when putting back together? Maybe check seat on thrust bearing. Possible bad oil pump. Maybe some junk fell into oil pan and clogged oil pump. Just throwing out a few ideas! Need to go back in and have a look see before all your worked is wasted. Good Luck!

 

I agree with mudcobra , "don't" run it anymore than needed, till you can get it back out.

Not being able to see it, sounds like too much clearance on the rod or main bearings.

Get the engine back out and check the bottom end out again.

 

Sounds to me like you have the wrong bearing in there .. Cranks .010 under, are sure you put .010 over bearings in it ..
Differently pull it out and go back through the bottom end .. Something's not right .......

Remember To check everything twice and then recheck when ever you have doubt's about anything .. Spending and extra 20 min's recheck it before you install it is better then not and wasting 3K of your hard earned money.

 

What happens is the oil runs to the bearing oil galleries and then its not really getting resistance it should because the bearing isnt tight enough on the crank and therefore your oil pressure will just pour out of the journals. Like the one guy said up there, you need to check to bottom end out, check it before you blow a rod.

 

shazam
Remember me I am the guy who put the head gasket on backwards, the pass side did get a little hot. I am wondering if this caused the problem. I took a compression check yesterday got 160 on drivers side, on the pass side got 135. This is not right! The eng has only 800 miles on it. Yes I am convinced that I have to pull it out. The oil pressure problem was from the beginning. When I first started it it was about 3/4 scale after it warmed up it went down to 1/4. Now it starts out at 3/4 and after it gets warm it drops to 1/4 at 2500 rpms. Then at idle it goes to zero and I hear a knock (a deep one). I hope I did not hurt the crank. I Guess 351m's are easy to come by. I will repost in a couple of weeks and let ya know. Thanks Art

 

Squiggy
I have a High vol oil pump in the there. With the wrong bearings it must be really flowing!!!! Thanks Art

 

Like mentioned above, take your time going back over this, check and re-check and you will find the problem. Good luck!

 

I agree with the others about the bearings. I'd bet the crank is still OK if you've been careful to avoid running it. That compression is worrisome, though. The hope would be that the rings wore some, and not the cyl walls. If they look good, maybe there is a head gasket problem.
Sorry you've had this trouble!

 

The crank is the first to go on any 4 stroke, so in term you may have a ratched crank, but not too bad, like if you still get the 1/4 oil pressure its still enough to lubve everything, but the knocking indicates a bottom rod mount tapping back and forth on the crank... Kind of like making an O with your thumb and first finger and pretending a pen is the crank and bounce it around in there, but not as bad if you still got 1/4 oil pressure. So tear the oil pan off and replace those bearings with the right ones. Good luck

 

My plans are to pull her out, pull the pan and keep fingers crossed. I am also concerned that the compression was low on the pass side.(130) 160 on drivers. I am the idiot that put the head gasket on wrong and it ran a little hot on the pass side. temp guage was normal. I am concerned that I may have cooked somthing here. When I removed the head the piston,cyl walls and head seemed ok. It looks here that I messed this up. I guess the best thing to do is remove heads and check them, remove pan check all bearings, remove pistons on pass side check rings etc. Its labor and a gasket set.

 

How is oil pressure when you first started after the rebuilt?
If it was good then but has been getting worse, maybe you got a lot of dirt in the oiling system and it just wore it out.
Why did you take this apart in the first place, any problems?
If you had a bad rod before, and didn't do anything, you might still have a bad rod.

It takes 3 things to have the proper clearence:

Crankshaft size
Good bearings
and the most forgotten, Rod and main housing bore size.

I just got done with a customers race engine, could not get oil pump to prime, after pressure feeding the system and dynoing it ran fine and had oil pressure. But when it sat no oil again.

Found the oil pump had the pressure relief valve in backwards.

Volumn and clearence = pressure (I think that's some sort of science law)

 

Tim/Everybody.

I am sure that I will find a bearing problem here. What really concerns me is the compression. 160 on drivers side and 130 pass. I realize that the eng only has 800 miles on it. With my configuration listed in the beginning of this thread really has me sweating here. I have Aussie heads/stock pistons. I am thinking that my compression should be higher. As I mentioned I might of cooked the Pass side(130). After I put a new head gaskit on right checked head for warpage with a straight edge, put it all back to gether and it started right up, no miss etc. No miss now just knock! A couple of other things are not right either. Per this forum I was told to do initial timing at 8 degrees befor tdc (272 Cam). When I set it to 8 degrees the eng would run ok,but could not restart it due to starter drag. I decreased it towards tdc and started to ping. I still could not get it to start without a little starter drag. The closer I got to tdc the better it got. Temp was fine 1/4 to mid range.

I also removed the spark plugs and all spark plugs were nice light brown. I do notice a fuel smell when I removed the right side Valve Cover. I checked oil and its clean and correct level.

I really must of messed this up. Please look at my configuration in my gallery or listed in the inital post. I am going to pull the 351m,C6 as one unit next week. Ant thoughts anyone. Thanks Art