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Old 07-31-2013, 05:08 PM
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Smoking SB, Information Overload

So I've searched for threads about smoking SB's and read about a hundred postings about all kinds of things and learned a lot already. However now I'm confused about which advice actually applies to my situation. So here goes.

I have a mid 70's SB 327 in my 911. Unknown number of miles or years since its last rebuilt. Its got quite a high lift cam, edlelbrock manifold and carb, HEI distributor. The exhaust is completely seperate for each bank. On acceleration I get a big cloud of blue smoke only out the left tailpipe. There is no smoke on starting, even after sitting for a few days, there is also no smoke when I rev the engine up to about 4000rpm while in neutral. It only smokes when its loaded and driving. I did a compression test and got between 135psi and 155psi. Checked the plugs and #3 on the left side is oily and black, the rest are dry and brown. That cylinder #3 had 150psi compression.

Since it only smokes out one side, I've discounted oil getting sucked in from the PCV. And since it doesn't smoke on start-up, I think the valve seals are ok right? So I'm left with head gaskets or rings? Is there a way to confirm which it is? I'm optimistic its not rings because of the good compression test, am I right?

Cheers and thanks in advance.
Mike B
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  #2 (permalink)  
Old 07-31-2013, 05:28 PM
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You have a problem in no.3 cylinder. Possibly an oil ring rail or expander got twisted or out of place on rebuild. There is a reason for the black plug. No smoke on fire up is good. Smoke under power is usually a cylinder problem..
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Old 07-31-2013, 05:33 PM
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There were no 327's made in the mid 70's. 327 ran from 62 til, I think, the very beginning of 69.Your engine is either older by a few yrs,or,it's not a 327.As far as your question tho,are you sure that cylinder is firing? You could be sucking oil into the cylinder from a bad intake gasket,or,other sources.To accurately pinpoint the problem,you need to try a leakdown test.There are threads on here that desribe the procedure.
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Old 08-01-2013, 07:32 AM
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It could be a generically engineered 327.
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Old 08-01-2013, 10:08 AM
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Quote:
Originally Posted by smikeb View Post
So I've searched for threads about smoking SB's and read about a hundred postings about all kinds of things and learned a lot already. However now I'm confused about which advice actually applies to my situation. So here goes.

I have a mid 70's SB 327 in my 911. Unknown number of miles or years since its last rebuilt. Its got quite a high lift cam, edlelbrock manifold and carb, HEI distributor. The exhaust is completely seperate for each bank. On acceleration I get a big cloud of blue smoke only out the left tailpipe. There is no smoke on starting, even after sitting for a few days, there is also no smoke when I rev the engine up to about 4000rpm while in neutral. It only smokes when its loaded and driving. I did a compression test and got between 135psi and 155psi. Checked the plugs and #3 on the left side is oily and black, the rest are dry and brown. That cylinder #3 had 150psi compression.

Since it only smokes out one side, I've discounted oil getting sucked in from the PCV. And since it doesn't smoke on start-up, I think the valve seals are ok right? So I'm left with head gaskets or rings? Is there a way to confirm which it is? I'm optimistic its not rings because of the good compression test, am I right?

Cheers and thanks in advance.
Mike B
Given the condition of only smoking when getting on it, I rather suspect that the increased pressures are upsetting something. This does sound like a ring problem where blowby is being trapped between the first and second ring causing the second ring (which is really an oil control ring) to loose contact with the cylinder wall. Then when backing off the throttle the pressures between these rings have time to diminish and the ring returns to normal function.

Another place to consider is the loss of a cam lobe. This upsets normal function in the cylinder which will pull a lot of oil. Since you already have a suspect cylinder, pulling a valve cover and checking this action should be pretty quick.

Bogie
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Old 08-04-2013, 08:40 PM
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Its called ring flutter and that's exactly why most ring makers now use a bigger end gap on the 2nd ring
I highly doubt that's what's going on here but I have been wrong before. my bet is the valve seals and possibly even a worn valve guide.


I recently had a 69 Camaro convertible in the shop that was puffing out blue smoke over 4000 rpm, it was the valve seals.


easy way to check if that cylinder is firing right is with a water bottle on the manifold no hiss means cold/dead cylinder

Last edited by bigblocks; 08-04-2013 at 08:47 PM.
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Old 08-04-2013, 11:27 PM
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Bad seals/guides generally will smoke on start up. His isn't.

I agree w/those who suspect ring seal. There's a chance the bore is scored or a low tension ring was accidentally installed, or the second ring was installed upside down. Just because the bad hole showed relatively high compression doesn't necessarily mean all is well- a wet cylinder will seal relatively well even w/wear if it's wet w/oil.

You have quite a swing between high and low on the compression test- sounds like it may be time to freshen it up.
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Old 08-05-2013, 01:07 PM
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I had an engine that had the same problem as yours

turned out there was a 1/4 inch deep grove in my cylinder wall
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Old 08-06-2013, 12:48 PM
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.250" deep scratch?
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Old 08-06-2013, 12:52 PM
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Quote:
Originally Posted by AutoGear View Post
.250" deep scratch?
i might of exaggerated a bit there, i'd say a little less than an 1/8 of an inch scratch

the scratch was so deep that the whole cylinder needed to be sleeved

I just bought a new short block and tossed the old block in a corner
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Old 08-06-2013, 01:05 PM
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The only way to find the problem is to find the problem we can guess all day long.

I've heard if the 2nd compression ring is installed upside down it will consume extra oil. However the diagnosis of bore wear/damage makes total sense.
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Old 10-23-2013, 07:58 AM
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Pull the heads, install these:Pro Series SBC Small Block Chevy Aluminum Heads 210cc 64cc 350 | eBay

CAN'T beat that price, Combustion chamber should be the same as the 461-462 double humps, and check the cylinders while they're off. If there are deep scratches, drop the pan, pull that piston out, hone said bore, install new CAST ring set and re-install-torque to spec.

If the bores are nice and shiny like a mirror, (NO cross-hatch showing) just pull it and rebuild it. With those heads (double humps) Unless they're set up for NO-LEAD gas, they might have beat the seats in the head to death (or an 8th inch or more) has the 'lash' been adjusted often over the years? Solid cam?

Put a smaller cam in there maybe a 264deg or so and for better response and mileage.

You state that you really don't know the age/condition/mileage of your 327. If the block states in fact a '70, it's probably a 350 block with the 327 internals.

If you're in the Memphis area, I'd like to see it..!

E
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Old 10-23-2013, 03:20 PM
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I had a 327 in a new 68 Camaro back in the day. I found the valve guides (cut in the head) were shot on one cylinder. In fact, all of them on one head were too large. Pressed in guide cured the problem.
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Old 10-23-2013, 05:05 PM
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Quote:
Originally Posted by 77amc View Post
Pull the heads, install these:Pro Series SBC Small Block Chevy Aluminum Heads 210cc 64cc 350 | eBay

CAN'T beat that price, Combustion chamber should be the same as the 461-462 double humps, and check the cylinders while they're off. If there are deep scratches, drop the pan, pull that piston out, hone said bore, install new CAST ring set and re-install-torque to spec.

If the bores are nice and shiny like a mirror, (NO cross-hatch showing) just pull it and rebuild it. With those heads (double humps) Unless they're set up for NO-LEAD gas, they might have beat the seats in the head to death (or an 8th inch or more) has the 'lash' been adjusted often over the years? Solid cam?

Put a smaller cam in there maybe a 264deg or so and for better response and mileage.

You state that you really don't know the age/condition/mileage of your 327. If the block states in fact a '70, it's probably a 350 block with the 327 internals.

If you're in the Memphis area, I'd like to see it..!

E
Wth lol......awesome advise.
Small cube motor, 210 heads....and junk ones at that, and a cam picked by throwing a dart
At a catalogue.....sounds like a fun combo.
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Old 10-23-2013, 06:41 PM
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12 second recipe for sure !!! LOL.This is from July & OP hasn't ckd bak in since.
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