Big Block rebuilding
Thread Starter
Intermediate
Joined: Aug 2007
Posts: 38
Likes: 0
From: Toronto Ontario
Big Block rebuilding
I have recently bought a 74 big block and when I changed the oil from 12w50 to 10w30 I heard lots of pinging from inside the valve covers. I also found that the new pcv valve and breather I installed is now throwing oil out the breather. Iwas told the other owner put the heavy oil to hide the engine noise and that I would need to rebuild it. Any thoughts and if I do rebuild, any suggestions to ick up the horse power without doing any major modifications?
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
Check valve adjustment first, that could be the clatter under the valve covers.
Do a compression and leakdown test, that'll tell you what kind of ring seal you have. That will most likely be the determining factor.
Do a compression and leakdown test, that'll tell you what kind of ring seal you have. That will most likely be the determining factor.
Team Owner
Joined: Jan 2003
Posts: 21,234
Likes: 19
From: Freestate Corvette Club! Elkridge, MD
St. Jude Donor '17
You should be running 10w40 in that motor.
Give it a compression test, they should read in or around 150ish
What is the oil pressure at idle?
FWIW I am facing the EXACT same issue on my 1971. My motor does have great compression though.
Give it a compression test, they should read in or around 150ish
What is the oil pressure at idle?
FWIW I am facing the EXACT same issue on my 1971. My motor does have great compression though.
Last edited by Ragtop_Rob; Nov 28, 2007 at 08:32 AM. Reason: second thought
Thread Starter
Intermediate
Joined: Aug 2007
Posts: 38
Likes: 0
From: Toronto Ontario
oil pressure gauge reading at idle
Hey there, The oil pressure reads around 40 at idle.
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
The compression LS4 cam pitiful must go, bigger valveswould be more icing on the cake. looks like from the hood you have
you would have room for a good high rise intake.
Last edited by Little Mouse; Nov 29, 2007 at 12:20 AM.
Team Owner
Joined: Jan 2003
Posts: 21,234
Likes: 19
From: Freestate Corvette Club! Elkridge, MD
St. Jude Donor '17
oh your oil pressure is fine.... Does the knock go away fairly quickly after start up? For the most part mine does, but there is also an exhaust valve knock that you clearly hear through the right side pipe that never goes away.
Can you do a compression test - this will give a good picture of the overall health of the lower end.
If you are fairly sure the last owner used heavy oil (and it sounds like he did) you could just drain the block and pop the valve covers and intake manifold off and replace the lifters. BUT if it is just a tiered motor you are only postponing the inevitable.....
I have pretty much decided that even if I want to just turn around and sell mine I still have to fix the motor. If you stay with stock parts, it is fairly cheap to do depending on how your motor mics out. So my only decision is crate motor and 5 speed or not.
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Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
You can either pick up a cheap engine stethoscope from Harbor Freight or get an 18" hardwood dowel, about 1/2" diameter from a hobby store. Put the dowel against your ear, then against different parts of the engine. Sounds screwey but it works. If you're lucky enough to find one of the cheap engine stethoscopes, it works even better. Find the source of the problem before you start tearing it down, IMHO.
There's nothing wrong with running 50wt oil on an engine with wear. There should also be no reason to replace the lifters, they don't know or care what weight oil is in the engine. If you do have rattling/sticking lifters, add a can of Marvel Mystery Oil. It's the only one of the so-called Snake Oils that really works.
Good luck, hope it's something simple. By the way, a big source of "tic tic tic" is loose header bolts, and many times what sounds like a lower end knock turns out to be loose torque converter bolts - make sure you check both of those.
There's nothing wrong with running 50wt oil on an engine with wear. There should also be no reason to replace the lifters, they don't know or care what weight oil is in the engine. If you do have rattling/sticking lifters, add a can of Marvel Mystery Oil. It's the only one of the so-called Snake Oils that really works.
Good luck, hope it's something simple. By the way, a big source of "tic tic tic" is loose header bolts, and many times what sounds like a lower end knock turns out to be loose torque converter bolts - make sure you check both of those.