The Stovebolt Site Forums The Shop Area Engine Shop 292 smoking

I bought a 1937 chev pickup with a 1971 292 inline 6 about 8 years ago. It smoked a bit and I could smell oil when I first got it but the guy who sold it to me said he rebuilt the engine and lump and ported the head. I pulled off the head a few years ago to pin the rocker studs and the cylinders did not have a ridge at the top and the machineing marks could still be seen on the cylinder walls, so I beleive it was rebuilt. It has embossement type valve stem seals on the intake but none on the exhaust, so I added flat o-ring seals to the exhaust valve stems. I also added unbrella seals. Well it stopped the oil smell but it still smokes. It doesn't smoke at start up but when it get to temp (110-F) it starts to smoke. I heard that after market valve covers could be the problem so I tried a vented cap, a unvented cap, removed the cap, removed the PVC and it still smokes. Compression is good 160-180 pis (it has a cam), plugs are like new after a year. Before I tear it down and put new rings in I thought I would ask this forum to see if there could be another cause of the smoke.

You severely overdid it on the valve stem seals. "More" is definitely not "better" where valve stem oil control is concerned. Chances are you have badly worn valve guides now due to the valve stems being starved for lubrication. A small amount of oil down the guides is necessary to keep them from galling, particularly on exhausts. I'd suggest removing the head and finding a machinist who knows what he's doing- - - -and maybe pitch that "lump port" head as far as you can throw it. That's a racing modification that has no business whatsoever on a street driven vehicle. It's only useful at throttle positions and RPM ranges the average street machine never sees. Have you done a cylinder leakdown test to evaluate the sealing ability of the rings and valves? The slogan that used to be on every piece of diagnostic equipment Sun made back in the 1950s and 60s was "We Test- - - -Not Guess!"
Jerry

I wiggled the valves before installing the seals and they felt good, no slop. I will order a leak down gauge set and check that, it should be here by the end of the week.

I gather that you are not fond of the head work. What is the disadvantages of a lump and ported head?

Welcome to the forum FarmerJohn2. I imagine you will have an abundance of machine shops to choose from in your area. If you don't have any that you trust, I can give you the name and info for the shop I use in Ann Arbor.

"Lump ports" raise the bottom of the intake ports to change the angle of the gas flow as it approaches the tulip area of the back of the intake valve. It's a trick to improve the volumetric efficiency of the head, and it actually makes the port smaller. The velocity of the gases passing through the restricted port increase, which supposedly improves the "ram effect" of the intake charge as it fills the cylinder.

The problem is- - - -it only works with a very radical camshaft profile, and only at wide open throttle, high RPM operation- - - - -like a huge number of other race-type modifications people do, whose vehicles never get near a round track, or even a drag strip. They give up lots of low end torque and gas mileage to be able to brag about the cam that causes a lumpy idle and cylinder head modifications they'll never be able to make use of on the street without attracting Deputy Dawg and his speeding ticket book. I've proved those assertions to the students in the auto mechanics classes I taught over 30-somthing years, repeatedly, with more dyno runs than I can count.

Other than that, those modifications are great! (Where's that "sarcasm" emoji when we really need it?)
Jerry

Thanks for the offer. I will ask a few hot rodders around here first to see if they have any advise of a good head man. The last guy I took it to didn't do me much good.

Thanks for the input Jerry but I don't think I will pitch the head just yet. Once I confirm the rings are good I will once again take the head to a head guy but a different one this time. The engine runs good and sounds good but I hate the smoke.
Regards
John

I have no problem with people doing modifications like that- - - - -my kids had a roof over their heads and good food to eat for a lot of years- - - - - -thanks to folks who just had to have the latest fad- - - -regardless of whether or not it was beneficial. It's always more fun to go racing on the other guy's money, and I spent a lot of years doing that. The urge to "Go fast- - - -turn left" can be a lot more addictive than alcohol, nicotine, or drugs!
Jerry

Ok, I got the leakdown gauges. I have one question, how critical is it to have the piston at TDC? I removed the push rods so all valves are closed but the pistons are at different locations. When I set the left gauge (98pis) so the right gauge is at zero See photo #1. Then hook it up to the cylinder the left gauge goes down to 88psi and the right gauge goes to all most to 20% see photo #2. Then if I increase the left gauge to get it back to 98-100 the right gauge goes into the yellow range, photo #3. Is the piston location critical or is it more important to have constant pressure going into the cylinder? It appears to me very little leakage.
Any thoughts?

John

All the pistons should be at, or very near TDC. Wear in a cylinder happens mostly in the first inch of piston travel down the cylinder, so the tension on the rings will be at a minimum near the top of the stroke. DO NOT tinker with the pressure regulator while testing- - - -you're defeating the purpose of the test if you do that. Line pressure needs to be adjusted to exactly 100 PSI with no air flowing. Once the air line is connected to the cylinder, the pressure on the second gauge indicates the percentage of leakage. For instance- - - -100 PSI line pressure with no flow, and a cylinder pressure of 88 PSI=12% leakdown. There is no need to disable the valves- - - -just point the distributor rotor to the plug wire of the cylinder you're testing, which will assure both valves are closed. A leak rate of 10% or less is acceptable. Any more is an indication of leakage somewhere- - - - -air from the carburetor is a leaky intake valve- - - -listen at the tailpipe for exhaust valve leaks- - - -air from the oil filler indicates leaky rings. Bubbles in the radiator indicate a cracked head or head gasket problems. "All of the above" is why I rarely, if ever waste time on a compression test. Cylinder leakdown tells me where, and how much leakage there is.
Jerry

The only thing you need to worry about with the piston not at TDC would be the tendency for it to be pushed to the bottom of the stroke when you apply the air pressure. If the piston is halfway thru the stroke, it's going to have the most leverage to turn the crank. If it doesn't move, then I don't suppose it would really be an issue.
As far as photo #3, I have trouble understanding why there's a yellow range on gauge #2. Less leakage is better, but it can't possibly be zero unless the piston is glued into the cylinder (maybe by rust), but I think you'd know that.
[on edit] Jerry's right about the rings being looser at or near TDC. I hadn't thought about cylinder taper.

I always lock the engine with two pairs of vise grips on the flywheel- - - -one at each side of the opening in the bottom of the bell housing. It's also possible to clamp the fan belt in such a way to immobilize the crankshaft.
Jerry

Got the pistons up to TDC (thanks for the tip to use distributor as a pointer) and the pressure gauge set to 100PSI. Leakage is 5 -10% on five cylinders, one is at 18% which I can smell gas as if air is coming out the carb so most likely a intake valve leak.
Gauges are a bit fussy, they creep up if left hook up to the supply air. Also I get a 5% difference if I set leakage to zero see photo as compared to setting pressure gauge to 100psi. Anyway it is an interesting test, I think I will test my 1962 Ford 600 tractor. I've been debating about rebuilding that engine.
So unless you guys have a different opinion, I would say the rings are good and just have the head redone.
Thanks for the help
If someone knows of a good head guy in the northern Detroit area (Warren,Utica or Sterling Hgts) please send my way.

The spark plugs look like they are all burning pretty clean, hopefully the head can be rebuilt and take care of the oil burning. I don't know anyone in that area as far as machine shops, one of our members is in that area, I think he is 1954 MI.

I have a friend in Dearborn with a large car collection. I'll see if she has anyone to recommend.

"I love it when a plan comes together!" Some of my former high school students are running their own shops these days, and two of them have a racing team together. I "retired" from the public education system in 2011. I hope they make truckloads of money- - - -their taxes are paying for my retirement!
LOL!
Jerry

FarmerJohn,

Unfortunately my friend's favorite long time machine shop has closed. Coincidentally her suggestion is to contact Tom Langdon in Utica, who is well known here on the Stovebolt Forum. He might have a recommendation for you.

www.langdonsstovebolt.com 586-739-9601

For 292 parts you might contact 12 Bolt Tom Lowe at 319-310-6920

www.12bolt.com

Here is another reply from my friend which might help you:

Contact Roseville High School and ask them for suggestions. They have an amazing auto tech program which restores / modifies a couple cars each year which are always at Detroit Autorama.

Also could try Dynamic Machine Shop but they are on the west side . We've used them in the past. 734-722-4050 https://www.facebook.com/p/Dynamic-Machine-Shop-100089727400374

Does the 1971 292 have valve quides?

I mean ones that can be removed and replaced.

Other members can probably tell you what the best repair would be. Years ago I had a shop rebuild a set of small block heads for me, they installed bronze guides that were supposed to be "The cat's meow". I don't know the specs on the head job but the engine was just a daily driver, it ate oil badly. I had another set of heads rebuilt by a different shop and they used steel guides and apparently knew the ropes on the correct tolerances, it took care of the oil problem. In all of the Chevy cast iron V8 heads, the factory guides are machined directly into the casting with no additional type of insert and those will normally run 100,000 miles or more with little trouble. A machine shop can bore the original guide and press in a thin wall sleeve and then hone the sleeve to the correct diameter. I assume that your head can be machined and new guides can be pressed in, I have very little experience with the inline engines.

Thanks for the comments. I will be speaking to a couple if cyclinder heads guys next week. I am hoping that they can ream and press in a sleeve, I don't see why they cann't. I guess it all depends on the persons expertise and the equipement to do the job.

When I was building a lot of cylinder heads, we bought thin wall bronze valve guide sleeves and reamed the guides .030" oversize, pressed the sleeves in, and reamed the ID to fit the valve stems. The reamer had a reduced diameter pilot that centered it in the ID of the original guide. It was quicker, and somewhat more accurate than replacing the entire guide. When boring guides out completely and pressing in replacements, there's always a danger of cracking a head, and/or getting a guide severely misaligned with the valve seat. K-Line, Goodson, and a few other machine shop supply vendors have the sleeves, and installation kits for them. I can usually find sleeves at bargain prices on Ebay. The 292 will need 0.343" diameter sleeves. (11/32" valve stems)
Jerry

Thanks, I spoke with Tom Langdon today ( I got his name from Tim Godbout). His first recommendation is also closed but will look into others and call me back. We must be talking to some of the same people. I will give the high school a call tomorrow.

Got the head back today. He told me the valve guides are good and the main reason for the smoke is because it was missing the valve spring metal cups (see photo), so he added. He replaced the positive seals and the o-ring seals and resurfaced because of it being warped. He also said that it is at its max allowable surfacing (see photo)and I should use a head saver gasket because it may have too much compression with the cam. I checked local auto store, they heard of that but can not find in their catalogs.
Where can I find a thicker head gasket?
Any thoughts if it really being needed?
Any thoughts concerning the cups?
I spoke to the guy who replaced the seals a few years ago and he said to let him know if it resolves the problem. He has taken them off in the past and hasn't heard of it causing a problem.

Use positive seals- - - - -OR- - - -O rings- - - -not both. The engineers who designed the head factored in a little bit of leakage down the guide to keep the valve stem lubricated. Your valve stems will run bone dry now, and wear out quickly. The only engines I've worked on that ever needed the "head saver" gasket were GM diesels. Those gaskets come in four different thicknesses. The 292 doesn't have enough compression to worry about head gasket thickness.
Jerry

OK thanks, I will just use a standard head gasket, that makes sense to me.

The guy who redid the head did not put the "lumps" back in. It appears to me that I have to remove the intake valves to install the lumps. Which I can do but not sure if I want too.
If I don't install will there be a problem?
If I do install should I use JB weld on the back side?
It appears there was some type of epoxy on the underside of the lump (see photo).

The lump port modification involves permanent alterations to the head. Now they must be reused. The epoxy was probably there just to temporarily hold the lump in place while the short head bolt was installed. The bolt actually secures the lump once it's installed- - - -no adhesive needed. What part of the lump is hitting the valve, and how much trimming would be required to get it to slip by the valve stem? You have a race-type modification to what is probably going to be a street engine, so you're pretty much a victim of the other guy's mistakes now.
Jerry

That's what I thought, that the head bolt holds the lump in place. Now that I have the lumps out of the head I am not so sure. For one thing they are aluminun, not good for maintaining clamp loads with uneven surfaces. I don't remember seeing a shoulder on the lump where the head bolt should sit. I will take a better look at it today and let you know.

If you don't want to reinstall the lumps, put a SAE Grade 8 hardened steel washer under the Allen bolt to spread out the clamping load of the short bolt, and maybe shorten the bolt head to about half its normal height. Just leave enough of the socket head to get a good torque on the bolt. You'll end up with a more free-flowing port than the original with the big pillar in the middle. Then use the lumps for sinkers the next time you're bottom fishing for catfish!

www.ebay.com/itm/155745766417?

LOL!
Jerry

Ok that's what I will do. The lumps were only held in by a small screw up from the bottom and some type of epoxy.

Don't forget to plug that screw hole- - - - -major vacuum leak otherwise!
Jerry

Just playing devils advocate here. If the head was ported out to add the lumps and the head bolt jacket removed, wouldn't it be to large a chamber without the addition of the lumps? I have prepped a head for the lump port install and you must remove a vast amount of material to complete it..

I agree with Craig's thoughts on this.

My thoughts:

Because the head has been modified to accept the lumps, you will loose the gains they provide in performance, or possibly worse because of the big changes in port volume if you leave them out.

Each small bolt used to hold the lumps in are typically drilled by hand. So you might need to discover which lump goes into the correct port. I remember reading somewhere that you need to have one valve removed to get them in. When you remove a valve, number everything to make sure the valve and it's parts go back into the same hole. A valve spring compressor can be rented from a local auto parts store.

If you find you need to re-bed the lumps in epoxy when you re-install them, try to use an epoxy that is rated for high temperature. If you do use epoxy, dry fit everything before you glue them back in. McMaster Carr will have a nice selection of high temp epoxies to choose from.

I found this link that might help. It goes into detail the steps need to install the lumps. You can skip most of it because all you need to do is re-assemble: Lump Installation

I hope this helps!

If the engine isn't going to be used in a racing application, why would the port volume be an issue? People who insist on doing race engine stuff on a street driver probably have no idea what they're really doing, or how to go about it properly. They're just throwing money away for no reason other than the brag factor.
Jerry

Well, I tried leaving the lumps out but couldn't due to the screw that holds the lumps is place goes through the water jacket (see sketch). I didn't realize this until I put antifreeze in and the carburetor started to fill up with antifreeze, just my luck. Pulled off the intake and saw the antifreeze coming up through the screw hole. Per the video from DavidBraley the screw hole should have been drilled at the out side of the head bolt not the inside (see photo). Now i got a problem, some of the smoke could have been more white than blue meaning I was burning water. I was loosing a little antifreez but thought nothing of it, it wasn't that much, will have to pay more attention. So I remove the head, pulled the valves installed the lumps used permatex #2 on the bottom of the lump and will use permatex thread sealant on the thread and hope for the best.

The simple solution would have been to plug those holes before you installed the head. An Allen setscrew with a little LocTite on the threads would have been a permanent fix.
Jerry

Agree. One good thing is I found a bad o-ring seal on a intake valve. I guess the guy that did the head wasn't as good as I thought he was. Of coarse unless I damaged the o-ring pulling the retainer off but I don't think so. I will now check them all.