Engine smoke, need some advice

[Tomahawk30]

Hi guys and gals,

My 71 Longhorn has a mid-90's era Gen 1 crate engine that appears to be very clean internally. When I first bought it a few months ago, it would puff a bit of smoke on startup, but clear up pretty quickly. I assumed it was valve guides or seals and planned to just get to them down the road sometime. Since then it has gotten to the point that it smokes out both pipes fairly heavily at higher RPMs as well. It has true dual exhaust with no crossover, smokes from both sides, and both sides appeared to get worse at the same time. I did a compression test with the engine cold (would be tough to do warm with the headers making plug access difficult), and all cylinders were between 120-122 psi.

I first noticed the smoke getting worse not long after having the oil changed, and when I had it done I opted for the high mileage synthetic assuming it probably had quite a bit of mileage on it. After pulling a valve cover and the intake manifold, I'm not sure that is the case and I'll probably go back to a Castrol GTX 10w-30 or 10w-40 when I get it all back together. The valve area and the lifter valley were both pretty pristine with no sludge to speak of when I opened them up.

I currently still have the intake manifold pulled (stock quadrajet intake and carb), and plan on trying to get it all back together tomorrow with new gaskets. I replaced the spark plugs this week, and the ones I checked again today all appear to be oily already. Given that it is smoking almost equally from both sides of the engine, would the consensus be that it was likely an intake manifold leak? I would have thought valve guides or seals, but I wouldn't have expected them all to get that much worse at the same time. I also wouldn't expect both head gaskets to go simultaneously.

Am I on the right track with the intake? Thoughts? Sage advice? Horror stories?

Video of the smoke as RPMs increase:
https://youtu.be/q6joCtXns6w

[/url]

[/url]

[swamp rat]

The answer would have been in the gaskets that you scraped away.. Ether that or bad oil scrapers on the pistons..

EDIT: The intake theory would also mean an air leak so if ya put it back together and have to readjust the cab a great deal may help to confirm the theory along with no smoke.

[Tomahawk30]

Ya, I have the gaskets still. I'll look them over again and see if I can spot something. They came off pretty easily, just leaving a bit behind around the coolant openings.

[Tomahawk30]

So I just went back and checked the gaskets, and there is oil on the surface of both gaskets around the heat riser port, while the rest of the gasket surface looked nice and clean. If it wasn't properly sealed around those ports, I assume that could draw oil into the exhaust, but not into the ignition chambers, correct?

[hugger6933]

I have changed oil types before and had a vehicle start to using oil i changed to a different brand and it stopped. Now years ago oil was broken into two type the paraffin based and petrol based. the later came from the south and the former from the northeast[Penzoil and Quaker state to name a few]. Now I have had many times [now this has been years ago]on an engine type you have change from one base to another and start or stop the oil usage. Now that was on good running truck that saw no problems until the oil change.
Of course you run into the strangest stuff in use car/truck business.

[garyd1961]

Originally Posted by hugger6933

I have changed oil types before and had a vehicle start to using oil i changed to a different brand and it stopped. Now years ago oil was broken into two type the paraffin based and petrol based. the later came from the south and the former from the northeast[Penzoil and Quaker state to name a few]. Now I have had many times [now this has been years ago]on an engine type you have change from one base to another and start or stop the oil usage. Now that was on good running truck that saw no problems until the oil change.
Of course you run into the strangest stuff in use car/truck business.

Years ago this was true but I don't think it applies today. The old Quaker State made from Pennsylvania crude would gum a motor up. I remember taking valve covers off and them being completely covered with a thick sludge. If you were using QS oil you couldn't switch or all this sludge would go through the motor clogging everything up.
Today QS will run as clean as most other oils.

[Tquillen]

Another thing you might check:

A leak down test will confirm if you have a piston ring issue. Run the leak down on every hole, and see where you hear it leaking by. Also see how each hole stacks up against the others.

It's really odd for it to be so equal between holes. What does it do under full throttle?

[Tomahawk30]

At full throttle it does about the same as what was in the video (I think). I don't know that I ever opened it up all the way, but I definitely never noticed it letting up any at higher RPMs. I went ahead and ordered me a new edelbrock intake that will be here Tuesday or Wednesday. I sheared one bolt head on the water neck just trying to remove it and the second one won't budge. Seemed like as good an excuse as any for a new intake! Once the new one is in and everything is back together I'll see if it improves. I'm hoping it was oil pulling around those heat riser ports on the intake gaskets. If not, I'll move on to a leak down test. Hoping it doesn't come to that...

[slikside]

"I first noticed the smoke getting worse not long after having the oil changed, and when I had it done I opted for the high mileage synthetic assuming it probably had quite a bit of mileage on it. After pulling a valve cover and the intake manifold, I'm not sure that is the case and I'll probably go back to a Castrol GTX 10w-30 or 10w-40 when I get it all back together."

It could be as simple as that. One of the advantages of sythetic oil is that it will penetrate in places that a coventional oil won't...providing better lubrication. But if your engine is a bit worn, you can find yourself with more leaks than with a conventional oil for the the same reason.

I say do as you're thinking, and go back to a conventional oil after you get it all back together, and see if your "smoke profile" returns to it's previous pattern.

EDIT: Is that the Castrol High Milage sythetic you put in? If so, I now recall I considered that myself a few years ago, and call the 800 number on the container and asked about it going into an older flat tappet cam motor....they did NOT recommend the oil for that application! Might want to call them yourself if you have that setup. Since that time I have remained with conventional oil, and a zinc addetive. (sorry to open THAT can of worms)

[midniteblues]

I don't recall the part# for the gasket but edelbrock recommends a certain gasket too help with sealing the intake.
I never worried about it and just use the cheaper fel pro.

Sealer on the threads of the intake bolts really helps keep them tite and leak free. It should be used on all but the four outer corners since they are blind holes.

One of the most important steps it too retorq the intake bolts
After a few runs/warm ups. I like to redo them when it's warm.
Most people forget and that's where a lot of the internal leaks happen once they loosen up.

Are you sure the bottom of your intake isn't cracked anywhere they can be hard too spot.

I'm not a auto trans guy but I've heard you can suck and burn trans fluid too.

[Tomahawk30]

slikside: That's interesting on the high mileage oil not being compatible. I'll definitely look into it. Judging from the condition of the lifter valley and the rockers there aren't many miles on it. Can't really see any wear to speak of.

midniteblues: I'll definitely use thread sealer on the intake bolts when it goes back together. As to whether the intake has any cracks, not that I've found. The underside between the bottom and the splash shield is completely clogged with hardened crud from years of use though. Guessing it was just swapped onto the newer crate engine by some previous owner. I did look into the auto transmission fluid, but I could find any signs of fluid being pulled into the vacuum line.

[Gromit]

I would suggest replacing the valve seals while you have the manifold and carburetor off.. not that they need to be off but because there is more room and also just in case your smoke problem turns out not to be from the manifold.

I believe the crate motors just use the cheaper (rubber?) valve seals and you can get the Fel-Pro Viton ones for $20

There is a clamp type (no-hands) spring compressor tool that helps make the job easier but I would have to search for the exact one again - there was a youtube about it - I think the tool was about $80 to $100 but well worth it. There are several versions of those spring compressors but this one was designed specifically for swapping the seals with both hands free. Of course you still needed the air compressor to hold the valves closed.

[ElKotze]

I hate to say this, but the engine in my Longhorn did the same thing. I started restoring the Truck so I pulled the motor and took it apart just to see. Turned out Valve guides are worn out, couple of valves burned and the cylinder walls completely washed down. Complete rebuild!

[Tomahawk30]

Gromit: I probably should do that while I have it apart. I hate to buy another $100 tool that I might use twice, but it wouldn't be the first time! I might see if I can borrow one. It'd definitely be worth the cost of the new seals just in case.

ElKotze: that's been my fear as well. I'll get it together and see where it stands before putting much more money into it. I have a line on a freshly built 355 that I wouldn't mind picking up. The guy is willing to do part trade for my engine if I go that route, but that's my backup plan.

[Gromit]

I remembered the tool - it was a Proform and is $45 or so from Jegs

Powerbuilt also makes a version but I've only seen a photo

Here is the youtube (not mine) where you can see the tool in use on an old small block

https://www.youtube.com/watch?v=OsGqmOQus6Y

If you don't like clicking links you can navigate to youtube and search for this title:

"Replacing valve stem seals in 305 H.O. small block chevy from 1986 Monte Carlo SS"

It is the one with over 268,000 views (wow, who knew valve seals were so popular)..

In the old days (2009) those Viton umbrella seals didn't always fit without sometimes needing to modify the valve guides; so I would be cautious when ordering to make sure the ones you choose will fit; though luckily it is a common item and not like the big box auto stores will be able to gouge you on a $20 set.

I think the newer Fel-Pro Viton versions might fit the OEM style without modifying the guides but I don't know this - maybe someone will chime in or you can try the Summit Tech support if you order from them. Worst case you replace with the OEM rubber style.

[Metaldoc]

replace the pcv valve it could be bad.

[Ken B]

Originally Posted by ElKotze

I hate to say this, but the engine in my Longhorn did the same thing. I started restoring the Truck so I pulled the motor and took it apart just to see. Turned out Valve guides are worn out, couple of valves burned and the cylinder walls completely washed down. Complete rebuild!

Add me to the list. My Longhorn did exactly the same thing, smoked some when I first got it and then slowly began to smoke like a freight train! It had only 86,000 documented miles on it at the time but it sat in the original owners garage for almost 16 yrs without being turned over... I think rust may have built up in the cylinders and when he went to start it from its long nap it did some damage. I pulled the intake off, it had never been taken off previously and it was spotless inside. This is what my motor looked like when I pulled the intake, literally. I only cleaned the surface on the heads where the new gaskets went. The original owner claimed to have changed the oil every 2500 miles and I do believe him. New gaskets and valve seals didn't cure the problem... I put in a new GM crate motor, I kept the original motor to rebuild when funds allow...

[Tomahawk30]

A little tardy on the update, but the weekend before last I got everything put back together. Ended up buying an Edelbrock intake since I had it apart anyway. New distributor hold down, new water neck, etc, just to clean it up a bit. After getting it all back together, I'm back to getting a puff of oil smoke at startup (as expected since I haven't done anything with the valves yet), but there's no smoke at all while it is running. I suspect I was leaking some coolant at the intake and burning that, especially at higher RPMs. One of these weekends I'll go ahead and do the valves too and see if I can clean that up, but for now all seems to be well!

As always, thanks for everyone's input! I love this site!!!

Side note, I went and looked at a 71 Jimmy K5 yesterday... Quite a bit of rust, but man I'm tempted!!!

[im4darush]

Valve guide seals should be fixed. The tool shown above works great if you have an air compressor. I recently did this and most of my seals were dry and fell apart as soon as I touched them. The longer you drive around this way, the more dried up/burned oil accumulates on your valves. This will degrade performance and fuel economy.

[Metaldoc]

I pull the spark plug out, lower the piston and push in 1/4" rope in the plug hole. Put in as much as possible then raise the piston to compress the rope against the valves. Change the seals, lower the piston and pull the rope out.