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Old 01-07-2018, 11:18 PM   #1
BonanzaK10
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Chevy 350 Smoking

Hi guys,

I figured it was time to ask for some advice from the pros so here I am.

I've got a 79' K10 Bonanza with a 350, TH350, and NP203 with about 80,000. It runs fantastic with the exception of it blowing smoke. It doesn't blow smoke on start up but after it warms up a bit it smokes pretty darn bad. Throttle doesn't seem to affect it except for when you let off and then it will puff a bit more for a second or two. Today I let it idle for awhile and noticed after about 30 minutes the smoke stopped and didn't recur while I was driving it. I lose a little coolant and a little oil but I believe them to be seperate issues (Pan gasket leak, and a leaky freeze plug behind the motor mount.) I replaced the intake gasket which didn't solve the problem. I had been thinking head gasket but I rented a block tester and according to the liquid I don't have any exhaust gasses in my coolant. No oil in my coolant or vice versa. The exhaust doesn't smell sweet to me but it'll make your eyes tear up, it is white in color, no apparent blue or black tinge to it. I had an issue similar to this but not as bad caused from overfueling. It has a new Edelbrock 1406 carb which I tuned not even 100 miles ago. I'm wondering if it's overfueling again but it gives no other signs of running rich, idles smooth, no trouble starting. I am in no way familar with carbs and am pulling at straws now. I'd appreciate any help you guys could give, thanks!
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Old 01-07-2018, 11:57 PM   #2
Matt Man
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Re: Chevy 350 Smoking

Quote:
Originally Posted by BonanzaK10 View Post
Hi guys,

I figured it was time to ask for some advice from the pros so here I am.

I've got a 79' K10 Bonanza with a 350, TH350, and NP203 with about 80,000. It runs fantastic with the exception of it blowing smoke. It doesn't blow smoke on start up but after it warms up a bit it smokes pretty darn bad. Throttle doesn't seem to affect it except for when you let off and then it will puff a bit more for a second or two. Today I let it idle for awhile and noticed after about 30 minutes the smoke stopped and didn't recur while I was driving it. I lose a little coolant and a little oil but I believe them to be seperate issues (Pan gasket leak, and a leaky freeze plug behind the motor mount.) I replaced the intake gasket which didn't solve the problem. I had been thinking head gasket but I rented a block tester and according to the liquid I don't have any exhaust gasses in my coolant. No oil in my coolant or vice versa. The exhaust doesn't smell sweet to me but it'll make your eyes tear up, it is white in color, no apparent blue or black tinge to it. I had an issue similar to this but not as bad caused from overfueling. It has a new Edelbrock 1406 carb which I tuned not even 100 miles ago. I'm wondering if it's overfueling again but it gives no other signs of running rich, idles smooth, no trouble starting. I am in no way familar with carbs and am pulling at straws now. I'd appreciate any help you guys could give, thanks!
Are you running a pcv valve? If so is it clogged? Does the motor have any blowby in it?
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1981 chevy K10 shorty 350/350C 12bolt, 10bolt, NP208
4" lift 33's
4.10's Detroit locker/Truetrac
Vintage Air
67 GMC Stepside Straight six/3 on the tree "The Peach"

K10 build http://67-72chevytrucks.com/vboard/s...d.php?t=671934

The Peach build http://67-72chevytrucks.com/vboard/s...d.php?t=733903



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Old 01-08-2018, 12:46 AM   #3
BonanzaK10
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Re: Chevy 350 Smoking

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Originally Posted by Matt Man View Post
Are you running a pcv valve? If so is it clogged? Does the motor have any blowby in it?
Doesn't appear to have any blowby or excessive crankcase pressure. I am running a PCV valve, it has vacuum at idle so that would indicate that it's not clogged correct?

Just took it for another drive. Fine for the first 5 to 10 minutes then it started smoking at idle. Doesn't smoke while driving, just at idle and getting back to speed. Parked it back at the house after around 15 minutes of driving and just sitting there idling it was putting out enough smoke that it was hard to see all around the truck. It appears this started out of nowhere a month or two ago so I discontinued driving it. Out of nowhere it began to smoke like that during a drive in town. Didn't overheat, puke coolant, nothing. I haven't driven it since then really so I can't tell if the gas mileage has suffered at all.
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Old 01-08-2018, 12:51 AM   #4
johnwaynejeep
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Re: Chevy 350 Smoking

oil and coolant consumption with smoke is a dead give away to a blown head gasket. But if your block test came back negative then I would think you're running rich. Run your finger on the inside of the exhaust pipe. If the pipe is covered in thick black soot, then you're running rich. Eventually you'll have dieseling and other issues.

Did this just start smoking all at once one day?

Check your choke plate. with the engine off, blip the throttle. The choke plate should be open 1/8 of an inch. Start the engine and the choke plate should open to about 1/4 of an inch. As the engine warms up, the choke plate should open slowly until it is completely open.
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Old 01-08-2018, 12:56 AM   #5
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Re: Chevy 350 Smoking

Never mind about the running rich. I just saw your last post. It sounds like you're burning coolant or transmission fluid.

Do the block test again because it is sounding like a head gasket problem. When you do the block test, don't just idle the engine. Run the engine up to temp and throttle up the engine to about 2000 rpm to simulate daily driving. Sometimes a leaky head gasket will not show until the rpm is raised.
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Old 01-08-2018, 07:05 AM   #6
Dead Parrot
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Re: Chevy 350 Smoking

Pull and inspect your spark plugs. Might get a clue as to what and where the problem is.

Check the fuel pump on cold startup. Have chased more then one 'exhaust leak' smell that turned out to be a fuel pump with a very slow leak. Once the motor is hot, you might not see any gas.

Is your exhaust riser valve working? (If it still has one) A stuck one can lead to some of your suspected problems.
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Old 01-08-2018, 10:18 AM   #7
cadillac_al
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Re: Chevy 350 Smoking

Eventually you should notice the coolant level going down or the trans fluid going down or the engine oil too. It's pretty rare for Chevy headgaskets to fail. Does that smoke have any smell to it that you could identify? If it still runs fine during the smoking then it must not be the carb. The earlier tip about the trans fluid should be verified. Remove the hose from the modulator (or at the manifold) and see if it is wet in there. If it isn't trans fluid then it must be burning oil. Valve seals are usually pretty consistent; worse at start up and not so bad when running. Does you valve cover have a baffle in the PCV hole?
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Old 01-08-2018, 03:33 PM   #8
BonanzaK10
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Re: Chevy 350 Smoking

Yanked the modulator line, clean no residue. Checked the spark plugs, couldn't tell much as they are almost brand new, no fouling or anything though. Warmed it up for 45 minutes to get it nice and warm and then I block tested it, this time the fluid came back yellow which indicates exhaust gas in my coolant. After the short 15 minute drive yesterday a check of my coolant level and its down about 5 inches lower than it was before I had ran it so I'm definitely using coolant. Strange thing being that I couldn't get it to smoke today while idling it in the driveway. So definitely something with the head gasket, heads, or block. Which is what I had planned on. Is there anything I should look for when I yank the heads? Any spots prone to cracking? They are the original iron heads that came on the motor in 79'. Any wear items I should do while I'm at it? It's a fairly low mileage motor. Also as far as I've read there isn't much you can do to pep the old heads up correct? Port and polish nets minimal gains?
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Old 01-08-2018, 03:38 PM   #9
Matt Man
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Re: Chevy 350 Smoking

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Originally Posted by BonanzaK10 View Post
Yanked the modulator line, clean no residue. Checked the spark plugs, couldn't tell much as they are almost brand new, no fouling or anything though. Warmed it up for 45 minutes to get it nice and warm and then I block tested it, this time the fluid came back yellow which indicates exhaust gas in my coolant. After the short 15 minute drive yesterday a check of my coolant level and its down about 5 inches lower than it was before I had ran it so I'm definitely using coolant. Strange thing being that I couldn't get it to smoke today while idling it in the driveway. So definitely something with the head gasket, heads, or block. Which is what I had planned on. Is there anything I should look for when I yank the heads? Any spots prone to cracking? They are the original iron heads that came on the motor in 79'. Any wear items I should do while I'm at it? It's a fairly low mileage motor. Also as far as I've read there isn't much you can do to pep the old heads up correct? Port and polish nets minimal gains?
Yea the stock heads aren't very good, fine for torque but are out of breath at about 4000rpm. If you have some money, putting a set of Vortec heads on will get you some decent gains. However, you will need to change the intake manifold, then you might as well add a cam (snowball effect). If the motor is in good shape and you are looking for more performance now is the time to upgrade.
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86 c30 crew cab dually 454/400 4/6 drop SOLD 1-8-11
1981 chevy K10 shorty 350/350C 12bolt, 10bolt, NP208
4" lift 33's
4.10's Detroit locker/Truetrac
Vintage Air
67 GMC Stepside Straight six/3 on the tree "The Peach"

K10 build http://67-72chevytrucks.com/vboard/s...d.php?t=671934

The Peach build http://67-72chevytrucks.com/vboard/s...d.php?t=733903



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Old 01-08-2018, 03:55 PM   #10
BonanzaK10
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Re: Chevy 350 Smoking

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Yea the stock heads aren't very good, fine for torque but are out of breath at about 4000rpm. If you have some money, putting a set of Vortec heads on will get you some decent gains. However, you will need to change the intake manifold, then you might as well add a cam (snowball effect). If the motor is in good shape and you are looking for more performance now is the time to upgrade.
I'm looking for more torque if anything. Don't need huge horsepower gains but not slowing down up hill would be nice. I was trying to stay away from the Vortec's since I'm already running an Edelbrock intake. Starting to sound like I may as well yank the engine to do the heads and then toss a cam in it. I was looking at the Comp Cams 12-300-4 which seems good for torque. I have access to a 5.3 Suburban for $900 and now I'm strongly starting to contemplate that as being the more economical option. I'd be lying if I said I wasn't worried about that swap though.
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Old 01-08-2018, 04:02 PM   #11
Matt Man
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Re: Chevy 350 Smoking

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Originally Posted by BonanzaK10 View Post
I'm looking for more torque if anything. Don't need huge horsepower gains but not slowing down up hill would be nice. I was trying to stay away from the Vortec's since I'm already running an Edelbrock intake. Starting to sound like I may as well yank the engine to do the heads and then toss a cam in it. I was looking at the Comp Cams 12-300-4 which seems good for torque. I have access to a 5.3 Suburban for $900 and now I'm strongly starting to contemplate that as being the more economical option. I'd be lying if I said I wasn't worried about that swap though.
I guess it depends on what you want a 5.3 swap WILL snowball on you, but they have way more power and efficiency obviously. I have a stock GM Goodwrench 350 in my truck with a edelbrock performer intake, 4 barrel quadrajet and Ram Horn manifolds with all the emissions hooked up also has 4.10 gears and my truck has plenty of power for me. My motor cost 1550$ shipped to my garage from Summit. But like you said, your motor is pretty fresh so I would just fix what you have and motor on
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86 c30 crew cab dually 454/400 4/6 drop SOLD 1-8-11
1981 chevy K10 shorty 350/350C 12bolt, 10bolt, NP208
4" lift 33's
4.10's Detroit locker/Truetrac
Vintage Air
67 GMC Stepside Straight six/3 on the tree "The Peach"

K10 build http://67-72chevytrucks.com/vboard/s...d.php?t=671934

The Peach build http://67-72chevytrucks.com/vboard/s...d.php?t=733903



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Old 01-08-2018, 07:27 PM   #12
johnwaynejeep
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Re: Chevy 350 Smoking

Talk to a local machine shop. They can tell you what your options are as far as power gains. Don't skip the machine shop, they will need to verify that your head and block deck are straight and true.
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Old 01-09-2018, 10:43 AM   #13
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Re: Chevy 350 Smoking

If you pull the heads and reuse after inspection, replace the valve seals.

There are several good threads on the forum about cams for the stock 350.
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Old 01-10-2018, 11:21 AM   #14
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Re: Chevy 350 Smoking

Sounds like rusted head gaskets then. My truck used to have a hot engine but I wasn't using the extra power so I put the stock heads back on it. If I towed more often in mountain country then I may have appreciated the extra power. My stock engine will haul cars easy enough for me. You could be back on the road for the price of some gaskets. I do like mild rv cams in a stock chevy 350 for a few extra ponies. The stock cams are just too mild for me. I say go ahead and upgrade the cam and throw some new head gaskets on it.
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