Road trip summary - and new issue

A little background before the technical questions:

This past weekend I took my Bronco on a trip from Birmingham down south of Jackson, MS. Not too far of a trip (260 miles each way) and knowing my tricky fuel gauge, I stopped every 100 miles for fuel. I got a fresh oil change (put in 5.5 qts) immediately before jumping on the interstate, and got going. The engine purrs about 2700 rpm at 70 MPH, and has a TON of torque to accelerate in 5th to pass and whatnot ;D When I hit the first 100 miles, I stopped and gassed up (13mpg) and checked the oil. I needed 2 quarts to get back up to full!! I put that in, bought some more for the road, and took off. 2nd stop, I pulled off, and the brakes hit the floor, nothing. Get off into a gas station and look underneath, brake fluid pouring down from above the rear diff. I guess the vibration rubbed a hole at where that brake line clip sits on top of the diff. Got the vice grips, krimped the line 6-7 times and pinched off flow to the back right wheel, added fluid, and then checked the oil. LOW AGAIN Added 2 more quarts, and took off. Made it to the farm and parked it for the night, needed about a quart when I got there. Repaired the brake line Saturday, drove it around the farm sat night, and then loaded the gear back up and came back on Sunday, using a quart of Marvel Mystery Oil, a bottle of Lucas Oil Stabilizer (Emergency kit stuff) and also used 3 quarts of oil. I had a blast driving it, but will need to look into some better seats and another gearset, that one is entirely too loud!

Now, what are all the possibilities for burning that much oil?
It dripped about 3 drops while parked overnight.
No oil sheen underneath the bronco.
No shortage of torque/horsepower
I know I am burning it, blue smoke at startup
blue smoke if I hammer the throttle
Coolant looks good and green
When idling, you can barely see puffs of smoke out of the pipe if the sun hits it right.
Oil pressure never dropped below 40, stayed just under 70
New PCV, but I do notice the line to the carb seems to "sweat"

Do all these symptoms point to bad valve guides/stem seals?

So you drove all of maybe 550 miles and burned 8 quarts (aka 2 gallons) of oil? That's a gusher if I've ever seen one, especially if it's all being consumed. Have you pulled your plugs? It's quite possible you have multiple issues, including guides and rings, but that's why I'd pull the plugs and take a looksee at each of the cylinders. Have you done a compression check lately?

I'm not sure I follow your math for how many quarts in 500 miles. If more than one I would want to poke around. Pull some plugs and see how they look. That can be an indicator.

If you have a basic compression gage you can give your rings a check. Take a reading. Then squirt some oil in the cylinder (10 cc or so) and re-test. If it goes up your rings are on the way out. If not your rings are good.

If rings are good then it is valve guides or a vacuum leak sucking it in. To check the guides take the valve covers off and try to rock some of the valve guides. If they rock then that is probably contributing to your oil use. It should move only the slightest amount.

My guess - just a guess. Your intake manifold gaskets are leaking. If the gaskets start to leak then vacuum pulls oil up from the lifter valley and it goes right into the combustion chamber. You may see this with one or two cylinders be REALLY oily and then the rest look ok.

The other option is your PCV is plumbed incorrectly. Is there a baffle in the valve cover (or lifter valley if EFI) where the PCV connects? Do you have it routed correctly? Carb versus EFI is completely different.

I was using almost one quart every 500 miles in the '67 Chev that has never been opened up. Had the valve stem seals replaced and now it uses no oil.

Thanks for the responses guys, this was the first trip I've taken it on since pulling the motor and installing new f/r main seals, head gaskets, and intake man gaskets. I know the math on consumption is odd, the only think I can attribute it to is how much skinny pedal I used, I tried to stay out of it as much as I could, but sometimes I couldn't help myself. I built this engine last year, and its ran great and never burned that much oil, just leaked some on the floor which is why I pulled it and dropped new gaskets a couple months ago.

When I pulled the heads there was a ridiculous amount of carbon buildup, which I believe came from trial/error learning how to adjust the timing and carb, since this has been my first one to learn on. I cleaned up the heads before reinstalling, and it never occurred to me at that time to check out the guides and stuff.

The valve covers are the script 351 power by ford, and on passenger bank there is a metal baffle/deflector inside the top of the port for the PCV. I have a rubber line going from there straight to the front/base of the carb. the drivers bank cover has a push on style black oil fill cap with a port and a line running to the base of the air cleaner.

For a compression test, Ive never done it but I guess you'd pull the coil wire and then do one cyl at a time leaving all the other plugs in or remove them all prior to testing? test while engine is cold, or let it warm up and do it? Id imagine do it warm, so everything has a change to expand before testing?

Thanks for the input so far, hopefully It will be a fairly easy fix!

Ryan

Compression check cold engine


Sent from my iPad using Tapatalk

What history do you have on this motor?

Last engine I had that smoked oil under load, rings were trashed. And that was still under a quart per 50 miles highway.

I know this might sound silly, but do you have the correct dipstick? Are you sure 5.5 quarts is correct? If you are overfilling it might blow it by (blue smoke). Mine takes 4.5 after I fill the filter to fill it to the correct mark on the dipstick (302). After I drive it a few hundred miles it MIGHT take another half quart. It might use a half a quart every 3000 miles and it is a very tired 1970s motor. Better a half quart down than to overfill it. If you have a custom oil pan you have to know exactly where on the dipstick you should be.

I found this motor on craigslist out of a 96 bronco about 2 years ago, with approx 220k miles on it. It had never been opened up, still had some of the crosshatching in the cylinders, so I took it all apart, and sent it off to get bored .030 over, and had the block checked for cracks, hot tanked, etc. I wanted to go back carb'd, so I did lots of research on here, and learned how to build an engine following the info from this site and youtube. (Edelbrock vs Holley was a tough search, I shoulda gone Holley) I never did a compression check on it since it has ran really well, but I will do a cold compression check when I get a chance to tinker on it again.

The dipstick does bring up a questionable modification - It was the factory one that came with the motor, and since I was putting it in the bronco, I had clearance issues with it hitting the hood even with some extra bend in it. I needed to remove roughly 4" of dipstick tube, so I cut the tube, and then used the removed portion to measure how much I should shorten the dipstick, and then scribed the marks for full/low/add from the removed piece to the bottom of the new shorter dipstick. I think this shortening could have changed the trajectory of the dipstick into the pan, so when I was getting the oil changed, I had him stop at 5 quarts so I could see where it was on the dipstick, and it measured pretty close. I told him to go ahead and add another half for good measure, since I was hitting the highway and I knew it burned a little oil. I have only been driving it around town, so I never really noticed it burning that much until I took it on a trip with higher speeds and longer distances.

Hi, remove all the spark plugs before your compression test. Write all the numbers down. There are plenty of resources to learn about compression tests and adding oil to the cylinders to pin point rings and valve guides. If you installed an aluminum intake manifold you should know they are very susceptible to oil seepage from the valley into the intake runner. Good luck

Do the compression check and then we will be able to help more. Also since your pulling the plugs post a pic of them in order.

If you have a dipstick problem the net change is still the same.

Fresh engine with massive oil consumption. Rings installed upside down will cause that. Compression rings also control oil.

It's already been suggested, but a leaky intake manifold gasket can do just that.
If the gasket to a runner splits at the bottom, it will suck the oil out of the crankcase.
By chance, did you use an intake gasket without a steel support layer like the FelPro 1250? That type has been especially bad to do that with an aluminum intake.
Also, check to make sure you have a baffle in the valve cover under the PCV valve. The factory steel valve covers have the best ones. Aftermarket valve covers often use only a bent piece of metal that is sort of effective. Some have none at all. The oil can be sucked right out of the rocker area and into the intake.

I'd make sure the drain plug is tight. 5 quarts in 550 miles and the plugs still fire is amazing. are you sure you offset the ring ends when you installed each piston? I would also check the oil drain back holes in the heads so oil isnt pooling up in the heads. Could be something simple plugging the drain back and oil sucking down the guides or up the PVC. Check the fresh air in on the pvc system and make sure the hose is clear from the air cleaner through the valve cover cap. What did you use for valve stem seals?

Thank you for the input guys, I will post up the results once I get a chance to tinker on it, hopefully this weekend. With a 5 month old boy, our hands have been full around here! On the rings, I made sure I offset each ring 180* from each other on the install, for intake gaskets I used the felpro 1250 S3's which I believe are the good ones? For baffling the PCV, should I get a piece of foam to stuff in that metal deflector on the underside of the valve cover to act as a baffle if there is not one present? My heads are the aluminum Ford Racing GT40X, and came with valve stem seals installed already. I have noticed the PCV line has been very sweaty, which I don't really know how else to describe it. I've replaced the PCV twice, in hopes I would get a more quiet one that maybe didn't cause that sweat, but haven't had any luck yet. I believe the oil fill/breather cap has filter material between the hose bib (for line to air cleaner) and the inside of the cap where it pushes onto the VC, although I havent looked too closely at it.

Ok, I pulled off the oil fill cap, and saw oil residue at the top of the fill tube on the valve cover, and saw the filter material inside the cap has oil residue on it as well. Did not see any oil inside the air cleaner though. I noticed alot of oil around the PCV/grommet on top the valve cover, and the line to the carb was oily. I pulled all the plugs, which most of them looked tan/white, with two (#1 and #8) looking semi dark. Then did a compression test while engine was cold and carb was opened up:
1 - 185 PSI
2 - 185 PSI
3 - 185 PSI
4 - 180 PSI
5 - 177 PSI
6 - 180 PSI
7 - 177 PSI
8 - 185 PSI

I let the engine turn over between 5-7 times per cylinder, what do yall think?

Those numbers wouldn't scare me.

Put a little oil in each cylinder and run it again.
The change or lack of change in readings will indicate whether you have worn rings or valve seats.

Is a bad valve seal something I should be able to see from taking the valve cover off?

77RHINO said:

Is a bad valve seal something I should be able to see from taking the valve cover off?

Click to expand...

Yes.
Look through the valve springs. Sometimes the umbrella seals break up and won't shed the oil off like they are supposed to.

Hi, your compression looks good. Umbrella valve stem seal harden and crack with age, I thought yours were not that old. You may see them deteriorate through the valve spring. Sometimes small pieces are sitting on top of the head. I've heard the smaller viton seals are susceptible to damage during installation, but I'm not up to date on that. I don't know if valve cover baffles came up before but I would make sure the filler and PCV holes are baffled so oil is not hitting the holes in your valve covers. Shake the PCV valve to make sure it rattles. Good luck