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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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Spammer Hammer
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Could be rings installed wrong, pistons installed backwards...any number of things. Have you pulled the plugs to see what they look like? Compression check? Leak down check? All pretty simple and free things to do to help diagnose.
 

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Could be rings installed wrong, pistons installed backwards...any number of things. Have you pulled the plugs to see what they look like? Compression check? Leak down check? All pretty simple and free things to do to help diagnose.
When I changed the plugs a month ago 4 looked black and sooty and the other 4 looked white and chalk like.

I haven't done any other checks yet, I left it at the shop for now while I think over my options.
 

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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...
 

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Spammer Hammer
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Correct. And that means the problem exactly is?
Rings broken or installed incorrect. Definitely need a compression and leak down check. Easy to do yourself. Did my '66 GT a few weeks ago in under an hour. FWIW, it has 235K or 335K miles on it (don't know which) never rebuilt, doesn't smoke. All plugs looked like I had just taken them out of the box. However, all cylinders were weak at 105-110 lbs. Also, my engine has serious blow by and pours oil out the oil fill cap. Aggregates the hell out of me, but it's old.
 

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Quick Fuel 650 carb. Not sure the jets though.
Would be interesting see what size they are.

(I've also seen some freak instances of mixed sizes in the primary, and mixed sizes in secondary before).

Well, time to do the compression check. Anyone know what the proper compression should be? It's a 347 with JE 9.5:1 pistons.
I'm estimating ~180 (varies with elevation)
 

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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.
 

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Discussion Starter #13
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.
a. OK
b. OK

All I know is JE 9.5 to 1 pistons

Nope

And both sound like a rebuild that I can't afford.
 

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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.
 

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Spammer Hammer
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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.
 

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"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.
 

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We need to see the results of a compression test immediately. Do it dry, then wet. No point in discussing until we see that.
 
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