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Discussion Starter · #1 ·
I rebuilt my GM Goodwrench 350 about a year ago in my '26 T coupe. It now has about 2500 miles on it and runs great. It is not visibly smoking. However I find myself adding oil all too often. (It's not leaking)
In the rebuild I threw everything away except the block, crank and carb. Bored and decked the block, polished and balanced the crank. KB hypers at 9.96:1 CR with Scat rods . .045 quench. Promaxx Maxx 183 64cc aluminum heads. Straub HR cam. Edelbrock RPM. QFT 600.
The only reasons I can think of for the oil consumption are rings or valve guides or valve stem seals
Compression test:
#1 180 PSI
#8 182
#4 185
#3 181
#6 190
#5 180
#7 180
#2 190

Leak down test:
#1 3%
#8 1.5
#4 1.5
#3 1.5
#6 1.5
#5 2
#7 2
#2 2

These results lead me to believe that rings are not the culprit.
The heads were new. I checked valve to guide clearance at .0018" on intake and exhaust when I built the heads. New valves and seals. Geometry is correct... set with the mid lift technique. Shouldn't be worn guides already.
I'm lost as to where the oil is going. The plugs are slightly oily. I do not get the puff of smoke at start up, like bad valve stem seals can show.
I'm pretty confident that I did not mess up ring installation... ring upside down or oil ring overlapped. Although in my dotage I suppose it is possible. :) Never happened before though.
I'm thinking it might be the valve seals even though I am not getting that startup puff of smoke.
I did a build thread on this engine, "Upgrading or Rebuilding a Tired 350 SBC?". In that thread I asked for advise on every part in the head, valves, spring retainers, locators, locks, and all the advise was spot on. I did not ask for advise on the valve stem oil seals. I probably should have. I installed VTOVS11530, small OD valve seals, 11/32"stem, .531" guide, .575" OD. from Competition Products. I'm wondering if I made a mistake there. I could only get calipers onto the guide to measure diameter. Couldn't get my mic in there square. My calipers said .531". I really don't trust calipers to .001". They could be .530". The seals did go on pretty snug. I can't find that information anywhere.
I get really confused when they insist on calling these parts out at 11/32" (.34375"). They are not. When the valve actually measures .3415. I know that is the closest common fraction, but we are working with clearances much closer than .00225". So if I have 11/32" ID seal and .3415" stems, I have .00225" clearance valve to seal. If that is the case, it is no wonder I'm losing oil. Do I have the wrong seal?
The other issue is, as I mentioned is the guide OD. Looking for seals it appears that .530" seals are more common. Perhaps I have installed .531's on .530" guides. Would that cause oil consumption?
Does anybody know the actual guide diameter for the ProMaxx heads? Could .530" seals be installed on a .531" guide?
I guess I could have boogered up a seal or two and not noticed it! But I'm pretty meticulous.
I have the car down for a trans rebuild anyway, so I thought I would address this issue while the car is down. I think I need to try seals first before going deeper, but am wondering what to order for sure now. There are several different materials to choose from, too. What material do you guys prefer?
Any advise you guys might have would be appreciated?
 

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You've got the right seal.
Valve stems are sized like pistons, the clearance is built into the valve stem and the guide ID is the nominal size....so the guide is 11/32" or commonly called .3437" and with the valve being .3415" you end up with .0022" for your stem-to-guide clearance.
The seals are made to fit the valve actual size. so you don't need to hunt for a specific .3415" seal, just " 11/32" valve seal".

Pistons being the same way, the clearance is built into the piston and not the bore.

.530" or .531" guide OD wouldn't matter either, not for the fit onto the guide. So that isn't a leak path.

Have you considered intake/valley leak at the intake gaskets?

What about your breather/PCV set-up? you can eat a lot of oll at a pretty steady pace with an improper baffled PCV valve.

The place people seem to mess up good valve seals is by pushing or pulling the valve through the seal without having the valve keeper grooves prepped for this. The sharp edge of the groove kills a seal.....so unless you hand prep the valves you have to consider the initial installation of the seal a one time use, using the pushover protector to install the seal over the valve stem.
Since you can't get the protector back in there at disassembly the seal gets junked if you take a valve back out again with the seal in place.......Unless the valves are deburr prepped for it ahead of initial assembly.

I like the flouroelastomer seal material. Absolutely hate old school PC Teflon seals.

Another thought,,,,what about high windage?? Wouldn't show up on a compression test or leak-down if windage amounts are overpowering what the oil rings can handle?? I know, it's a bit far down the rabbit hole....but a what-if?
 

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Discussion Starter · #4 ·
You've got the right seal.
Valve stems are sized like pistons, the clearance is built into the valve stem and the guide ID is the nominal size....so the guide is 11/32" or commonly called .3437" and with the valve being .3415" you end up with .0022" for your stem-to-guide clearance.
The seals are made to fit the valve actual size. so you don't need to hunt for a specific .3415" seal, just " 11/32" valve seal".

Pistons being the same way, the clearance is built into the piston and not the bore.

.530" or .531" guide OD wouldn't matter either, not for the fit onto the guide. So that isn't a leak path.

Have you considered intake/valley leak at the intake gaskets?

What about your breather/PCV set-up? you can eat a lot of oll at a pretty steady pace with an improper baffled PCV valve.

The place people seem to mess up good valve seals is by pushing or pulling the valve through the seal without having the valve keeper grooves prepped for this. The sharp edge of the groove kills a seal.....so unless you hand prep the valves you have to consider the initial installation of the seal a one time use, using the pushover protector to install the seal over the valve stem.
Since you can't get the protector back in there at disassembly the seal gets junked if you take a valve back out again with the seal in place.......Unless the valves are deburr prepped for it ahead of initial assembly.

I like the flouroelastomer seal material. Absolutely hate old school PC Teflon seals.

Another thought,,,,what about high windage?? Wouldn't show up on a compression test or leak-down if windage amounts are overpowering what the oil rings can handle?? I know, it's a bit far down the rabbit hole....but a what-if?
Thanks for clearing up my confusion me on those measurements. I'm not much of a guy on rounding numbers. Measuring to 4 digits after the decimal point doesn't leave much room for rounding.
I had the intake off about a month ago while chasing a lifter tick. I looked for leaks then and didn't find any leak paths.
My PVC is in the left rear corner and has the metal box baffle that comes with the valve covers. The hose to the rear of the carb is not oily. I don't think it could be windage with the low operating rpm this engine sees. But who knows there?
I'm 'bout willing to bet that I have boogered up valve seals. Replacing valve seals is not too invasive. Easiest and cheapest thing to try first. It is easy to work on the top end of the motor in my Model T.
Thanks!
did you use a low tension oil ring?
No. They weren't low tension oil rings. That could do it though.
 

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what is the oil consumption in quarts per mile?

to make visible smoke is about 1 quart per 100 miles.
I built myself a 454 and used low tension rings and was using a quart per 200 miles and got no visible smoke until WOT.
GM still says a quart per 800 miles is OK.

A number of piston makers had trouble with insufficient oil return holes in the oil ring land resulting in oil use.
 

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Rod...from a Chrysler?
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My World Products heads came with cheap black rubber seals that crispied up and crumbled after not many miles.
The new Felpro blue guys did the trick. Consumption over.
 

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Race it, Don't rice it!
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Just a thought. I've seen, especially on intakes with 8 bolts and not 12, guys using those lift plates on the carb pads pull the intake under the weight of the assembled engine tear up the intake gaskets. Those plates are great, but a flimsy intake with 8 bolts or even 12, can't support the weight.
Run a Bore Scope down the carb and look for oil tracking at the rocker stud protrusion to the intake face to head interface and the backs of the valves.
 

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I was going to say same as BOOT, I just lived this and learned the hard way, rocker arm studs break into the intake runners, engine will pull oil thru the threads like you can’t believe.

Pull rockers and install some good Teflon pipe dope, reassemble and run it see what it does.

my car was pulling about 1.5 quarts in 800 miles
 

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Discussion Starter · #10 ·
Just a thought. I've seen, especially on intakes with 8 bolts and not 12, guys using those lift plates on the carb pads pull the intake under the weight of the assembled engine tear up the intake gaskets. Those plates are great, but a flimsy intake with 8 bolts or even 12, can't support the weight.
Run a Bore Scope down the carb and look for oil tracking at the rocker stud protrusion to the intake face to head interface and the backs of the valves.
Yeah, I don't use those plates. I have a leveler with 4 point hookups to the heads. Works better than the plate. I have one that I usually throw on when I take the carb off.
Did you seal the intake rocker studs? Permatex 59235 is fuel resistant.
Yes, I used Permatex Thread Sealant, but it was 80632. I wonder if that is the problem. I will get some 59235 and do it when i change the valve seals. Thanks for that.
 

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Discussion Starter · #11 ·
Run a Bore Scope down the carb and look for oil tracking at the rocker stud protrusion to the intake face to head interface and the backs of the valves.
OH! I missed this first time through. I hadn't thought of that. I have one that my son gave me. Hooks to my phone. Forgot about it. Now all I gotta do is find it. And maybe get him to show me how to work it again. o_O
 

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Discussion Starter · #12 ·
Have you considered intake/valley leak at the intake gaskets?
I was just thinking about that possibility of a vacuum leak at the bottom of the intake gasket. Would it be possible to test for this by running a small hose from the oil drain back hole in the head out the oil fill hole in the valve cover and hook it to a propane bottle?
The place people seem to mess up good valve seals is by pushing or pulling the valve through the seal without having the valve keeper grooves prepped for this. The sharp edge of the groove kills a seal.....so unless you hand prep the valves you have to consider the initial installation of the seal a one time use, using the pushover protector to install the seal over the valve stem.
Since you can't get the protector back in there at disassembly the seal gets junked if you take a valve back out again with the seal in place.......Unless the valves are deburr prepped for it ahead of initial assembly.
I'm betting this is where my problem is. I never used a protector. Always installed the seal on the guide, oil it up good, carefully work the valve up through the guide and seal, and install the spring. Didn't know there was such a thing as a seal protector. I probably boogered up every one I ever put on.
How are you hand prepping the grooves? Using a stone or file? Where do you get seal protectors? Are they like a piece of a straw? What about taking a wrap or two around the groove with scotch tape?
I've looked for a valve seal installation tutorial but can't find anything relevant.

what is the oil consumption in quarts per mile?

to make visible smoke is about 1 quart per 100 miles.
I built myself a 454 and used low tension rings and was using a quart per 200 miles and got no visible smoke until WOT.
GM still says a quart per 800 miles is OK.

A number of piston makers had trouble with insufficient oil return holes in the oil ring land resulting in oil use.
The rings I used were UEM-4000AM8-030 for the KB9901HC-030 pistons. I don't think they are low tension.
I didn't keep close track of oil I added. If it got a little low I added. I'd guess it is in the 2-2.5 quarts per 800 miles range.
 

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I struggled with an oil consumption problem similar to yours for a while , test results like yours , tops of pistons had oil wash( mine were actually shiny where these are light brown . Second ring in upside down ( per grants phone help guy ) dammit , lite hone , new mahle ring set , engine now uses a quart in 27-2800 miles . look for washing / light color around perimeter of piston crown . another sign , the tips of my turnouts would show soot ( excessive) inside , a slight tan coloration on the outside . compression / leakdown will not show the problem .
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Rod...from a Chrysler?
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Scotch tape works for installing the seals.
 

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Discussion Starter · #15 ·
Yeah I know that it is a possibility there is a ring problem. I'm trying to ignore that for now! :)
 

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Discussion Starter · #17 ·
That's what I did for more years than I care to admit ..
That's what I did for more years than I care to admit ..
Well, I won't let it go on for years. If the seals don't fix it, I'll pull it this winter and fix it while there is snow on the ground.
I should have the seals changed about the time my trans comes back. I'll know then.
 

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Yeah, seal protector is like a piece of a plastic straw, just shrunk nearly closed on one end...like a condom for the valve tip. Soft clear plastic.
All of them I have came in with the sets of valve seals....but not all sets come with the protector and I don't have a clue why, so I save them in my toolbox so I always have one.
Valve gets installed in the head, seal protector over the tip after that, then the seal pushed on.

Prepping the valve stem/keeper groove sherp edges I do with a small hone stone....600 grit wrapped around a popsicle stick or piece of keystock woulsd also work.

Pushing the valve through a new seal in theory wouldn't hurt the seal since you need the upper edges of the seal surface to remain as manufactured....the main damage is pullng an unprepped valve out through the seal, that can knick the upper square edge of the seal lip and turn it into a tiny funnel at the seal-to-valve interface

No idea if the propane through the oil return hole would be a valid test.
 

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for years guys built engines with no valve seals, and never on the exhaust side, as the factory seals were just those orings which could not do much.
 

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Compression rings and oil rings are two different functions. The most likely time you see both fail is in high wear engines where the cylinder walls are gone in taper and ovalness.

One thing not considered is wiped cam lobes. Which arrives at the question of one cylinder or many showing oil pull over?

Lots of problems with guide fit on aluminum head’s. Final fit should be with a reamer not an abrasive brush.

Bogie
 
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