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Fixed timing and now smoke is filling the cabin

3K views 41 replies 12 participants last post by  22GT 
#1 ·
For those following my posts I bought a 68 with a 347 stroker that was supposed to have been rebuilt 6100 miles ago. I've been fixing a bunch of issues and finally had the money to have the sluggishly running engine addressed.

I replaced the exhaust manifold gaskets (leaking), plugs and wires but the car still ran sluggish and jerky. I knew the timing was out so I brought it to a local shop to check the msd system and timing. To my shock the timing was set 18 degrees out for what seems to be on purpose. Once the timing was set properly the motor "woke up" and is a beast, the additional power is fantastic.

Now the draw back, after 2500 rpm the engine starts smoking out of the breathers and dip stick. Cleaned the breathers and checked the pvc was not clogged up. After 4000 rpm or getting on it the smoking is bad and fillings the cabin pretty quickly via the steering column. This to me screams piston ring blow-by and that the piston rings are shot. Also, if the engine was rebuilt 6100 miles ago this shouldn't be possible.

Anyways, looking for more insight, advice and an estimate on what it will cost to fix both financially and time wise. Possibly even a run down of parts I would need.

There are still more issues with the car including the posi grinding but I'll save that for another post at a later date.

I was given an "off the cuff" estimate of $5000 to pull the motor, have it checked and reworked at a machine shop, rebuild it, reinstall it and fix the rear-end (whatever it turned out to be). At that cost is it even worth it? I also refuse to de-tune the car again to sell it to somebody else. I'm not that kind of person even though selling this car seems like the best option at this point. I'd need about $25000 to break even at this point as well which is never going to happen.
 
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#6 ·
This to me screams piston ring blow-by and that the piston rings are shot. Also, if the engine was rebuilt 6100 miles ago this shouldn't be possible.
I have to guess it was broken-in/run way too rich (if in fact rebuilt 6100 miles ago) or some scenario where there was a bad lean area of curve that caused damage. Like Patrick suggests a compression check would be a good idea!

If you can buy a lift (even one at harbor freight) and pull the engine yourself you should be able to shave $2k off the cost of pulling and installing the engine. Going further stripping the engine down to short-block and hauling it to a machine shop for work...
 
#12 ·
a. Compression test. Pay particular attention to pressure generated after FIRST pulse.

b. Cylinder leak-down test.

Do you know what pistons were used in the build? (placement of the piston pin relative to the oil ring?).

Know anybody with a high-resolution borescope?

I'm guessing broken ring or ring land, but that's just me.
 
#16 ·
Pull the engine and tear it apart. the problem may show itself on teardown; broken rings, etc.

If nothing screams then measure the bores to make sure the're in spec and if so hone them and install new rings on the slugs and put it back together.

But, before you do this do the compression tests. Dynamic and differential. The dynamic will tell you if there is low compression. The differential will tell you what is leaking.

My guess is the rings never seated or got overheated and lost their seal.
 
#17 ·
How would you go about what? Determining if it was actually rebuilt 6K miles ago? Tear it down is the only method to determine that. But don't sell yourself short. These cars are emensley easy to work on. At a minimum, you can pull the engine and tranny and reinstall.
 
#18 ·
"Now the draw back, after 2500 rpm the engine starts smoking out of the breathers and dip stick. Cleaned the breathers and checked the pvc was not clogged up. After 4000 rpm or getting on it the smoking is bad and fillings the cabin pretty quickly via the steering column. This to me screams piston ring blow-by and that the piston rings are shot. Also, if the engine was rebuilt 6100 miles ago this shouldn't be possible."

Wasn't this a common problem with the early 347? The oil rings on the 347 pistons pass through the piston pin cutouts. I've read lots of stories about 347 oil burners and it surely sounds as if you have one of them. Supposedly the problem has been fixed but I don't know what the solution was.
 
#21 ·
Thanks for all of the feedback guys. Sorry for the delayed response, we had a fundraiser for kids with cancer last night.

I'm bringing the car home Monday after work and I'll start with the compression test then and report back after.

I've also reached out to the consignment shop because I can't believe the engine was rebuilt 6100 miles ago. Will see how far I get with them after Monday as well when I send all receipts and details of this newest issue.
 
#22 ·
Oh, separate issue, but smoke from the engine, even if it on fire, should not get inside the car.

There are about 1000 "my exhaust stinks" threads. If the car is assembled properly, you should never know that.
 
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#23 ·
Don't pull the engine and tear it down......what a silly recommendation. A few simple diagnostic checks could give you more information, and there are a few things that can cause your issue.

You can borrow a compression tester from any parts store to check the cranking pressures. Earlier you'd asked what the pressures should be, but nobody can tell since we don't know the static compression or cam specs. Just post the results of each cylinder. Remember the engine should be warm and the throttle should be wide open.

If that doesn't reveal much, do a leakdown. If you don't have that tester, or know someone who does, you'll have to buy one because parts stores don't typically have them to borrow. This will give a little better information on the engine. The tester can be bought for $75, but it's cheaper than just pulling the engine and doing a rebuild.


Each of the tests can be done under an hour, and could possibly save you a lot of pain.
 
#28 · (Edited)
Wow, that's an awful lot of blow by. 2 things that come to mind. Perhaps with the timing set at 18° and regarding the timing helped my thought is you had severe detonation and broke a piston. I don't think normally 18° would be a problem but either it is too much over all timing for your combination or your damper is off. The other is with a rich mixture you washed the cylinders down with gas and ruined the rings during break in. This is just an off the cuff thought.


I agree with Sportsroof69 on doing some trouble shooting before jumping in and removing the engine but some how I think it's going to have to get pulled.
 
#29 ·
I bought the compression and leak down testers at harbor freight on my way home from work today. Went to tread the line in and the friggin thing won't fit. The "body" of the fitting is too big for the gt40p heads. I'll need to buy an adapter that has a smaller body and more threads like the spark plugs have.


Second video from the passenger side. Had the wife work the throttle and she wasn't goosing it enough but you can still see the issue like before.

https://drive.google.com/open?id=0ByYUmoRqVSj0dlJwN1UzTjQ0ckE
 
#30 ·
I'm not so sure that's blow-by. To me, it looks like an oil leak from the front of the intake and/or valve covers that's burning off a hot surface and getting whipped around by the fan. That much blow-by should be pushing the dip stick up out of the tube.
 
#31 ·
The smoke is coming out of the tube and breather though. I just replayed the video in slo-mo and it's very apparent. The dip stick tube is blowing smoke from the hooded section and just above because it doesn't seem to be 100% sealed.
 
#33 · (Edited)
The motor is definitely sick but I think that the chark'd up plugs on the passenger side is what is making it run like that. The question is, where is all that coming from. I'm going to take a wild guess and say that its dumping massive quantities of fuel on that side assuming you have a dual plane intake.

It could be a sealing problem just on that side though too. Everybody already said do a compression and leak down test I think. Worn out valve guides/seals in the one head would do this so it isn't necessarily only the rings.

Normally, when an engine has too much blow by, you will see it at idle and it will get worse as the rpms go up. Yours doesn't appear to act like that. At some point in the rpms it just starts t blow like a locomotive. Looking at your videos, the smoke doesn't look like oil smoke because oil smoke will leave an oily residue behind. It looks like fuel smoke to me. That is why I leaned toward the carb. When the carb dumps massive amounts of fuel down in there, it washes the oil off the cylinders and the rings need that oil to lubricate and maintain the ring seal.

If you run an engine long enough with it dumping fuel the rings or/and the cylinder walls will eventually pay the price.
 
#34 ·
The odor of the smoke should indicate if it is oil vapor or not. Show us a video of the engine running with the breather cap removed from the RS rocker cover.
 
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