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Excessive crankcase blowby

Madgyver

Bronco Madman
Joined
Jul 30, 2001
Messages
14,238
Valve seals or piston rings?

I will have to pull motor to investigate.

Before I do, what other options do I have or what else can I check?
compression checks tops out at 150-160 all 8 cylinders.
oil on sparkplug threads.
sparkplugs changed and burns good.
oil all over transmission and under carriage, source of it looks to be the valve cover breathers or am I missing something?

loss of power on highway inclines.
Ran well after break-in.
once over heated. Motor is a year old so low miles.
intermittent white smoke out of exhaust through RPMs

I was going to get an oil catch can but that's just a band-aid fix.

smog heads on a 74 351W. smog ports plugged.
 

bulletpruf

Contributor
Full Member
Joined
Mar 31, 2019
Messages
361
You don't need to pull the motor to investigate. Try a leakdown tester. That should help you diagnose.

White smoke with no smell is usually water; that could be a blown head gasket.

Do you have water in the oil? Oil in the water?
 
OP
OP
Madgyver

Madgyver

Bronco Madman
Joined
Jul 30, 2001
Messages
14,238
You don't need to pull the motor to investigate. Try a leakdown tester. That should help you diagnose.

White smoke with no smell is usually water; that could be a blown head gasket.

Do you have water in the oil? Oil in the water?
Recently changed oil, month ago and already black and very low so oil is going somewhere.
 

Hazegray

Contributor
Sr. Member
Joined
Aug 10, 2004
Messages
795
Could possibly be an intake gasket problem, sucking oil up from lifter valley and/or leaking out mating surface. Did you have the heads milled by chance when the rebuild happened? Rare, but sometimes you have to have the intake milled to match the amount removed from heads...
 

B RON CO

Bronco Guru
Joined
Jun 29, 2016
Messages
2,339
Hi, I agree with Hazegray, especially if you use an aluminum intake. I would pull the intake and take a close look at the gaskets between the lower intake port line and the valley.
Also you say your intake breathers seem to have blowby. Don't you have a PCV system? Do your valve covers have baffles?
The compression seems to be too good to have a ring or valve guide problem.
Good luck
 

ared77

Bronco Guru
Joined
Apr 21, 2013
Messages
2,518
And wouldn't valve seals be unlikely as they were new a year ago? Or could the "once over heated" situation have damaged the seals??
 

nvrstuk

Contributor
Just a Bronco driver for over 50 yrs!
Joined
Jul 31, 2001
Messages
6,865
Like already mentioned several times... leakdown first then intake gasket check... Overheated once can cause some major issues... how HOT is hot?

Simple easy check on your breathers being the exit point or not for some or more of your oil loss on your low mileage engine is to clean the area around both breather and PVC and them thoroughly so in a 5-10 min 3,000 rpm run you can then see if the valve covers are freshly covered with oil or not. Heads warping from too much heat sounds like what you might be thinking already?

That and the leakdown will give you some more clues to use...
 
Last edited:

phred

Bronco Guru
Joined
Aug 25, 2006
Messages
3,305
Loc.
Earth
Hey Mad. Could be bad intake gasket. Mine did that after about 4 hours in a new engine. Aftermarket intake and iron heads. Pulled the heads and they check out fine. New head gaskets and intake gasket and the problem never reoccurred.


Sent from my iPhone using Tapatalk
 

WheelHorse

Bronco Guru
Joined
Nov 22, 2004
Messages
2,490
Valve seals or piston rings?

I will have to pull motor to investigate.

Before I do, what other options do I have or what else can I check?
compression checks tops out at 150-160 all 8 cylinders.
oil on sparkplug threads.
sparkplugs changed and burns good.
oil all over transmission and under carriage, source of it looks to be the valve cover breathers or am I missing something?

loss of power on highway inclines.
Ran well after break-in.
once over heated. Motor is a year old so low miles.
intermittent white smoke out of exhaust through RPMs

I was going to get an oil catch can but that's just a band-aid fix.

smog heads on a 74 351W. smog ports plugged.

Overheated...how bad? May have glazed the cylinders or stuck a few rings.

Buy a vac/pressure gauge. I had one from Craftsman where you could unplug the breather...place the conical adapter into the hole and push it tight (would have to hold it in place) and rev the engine...you'd watch the crankcase pressurize. Engine was shot.

Only way I know, to figure out the why, is a true leak down test. Listen where the air is leaking out of it and the percentage leak down.

Quick cheats if it's rings...Engine Restore in a bottle. Only stuff I have heard from old mechanics that works. Honey stuff is crap yada yada, but Restore will bandaid it until the funds allow for a teardown, break the glaze, thorough hot soapy water wash and a new set properly gapped rings if everything else is in spec.
 

Readhead

Full Member
Joined
Feb 7, 2018
Messages
155
I’m running a 302 so I’m not sure if this applies to a 351 .
There is an early and late model intake gasket on a 302 maybe a 351 guru could chime in and answer that question
 
OP
OP
Madgyver

Madgyver

Bronco Madman
Joined
Jul 30, 2001
Messages
14,238
I got Taz to pull the intake again and this time he found this.... see pics.

Intake and exhaust rockers for #1 cylinder were out of place. I could see how it bounded up. Exhaust rocker retaining locknut came off and was sitting on the head. Other nut was still on stud but loose.
We will get this fixed first and then go from there.

Taz did mention to me a slight drop in oil pressure.
 

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Rustytruck

Bronco Guru
Joined
Feb 24, 2002
Messages
10,879
the only time I've seen push rods like that was bad valve adjustment on start up and a friend who bought a set of used rebuilt heads and slapped them on the engine and tried to start it, all the push rods bent on one side of the engine. there was no lubricant on the valve stems and minor surface rust stuck the valves tight. A full disassemble was an expensive lesson, push down on those 2 valves and make sure they are free.
 

73azbronco

Bronco Guru
Joined
Nov 11, 2007
Messages
7,154
Interesting how you got the newly designed curved push rod to work on the older motor:)
 
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