More Air Flow for a Model 425 on a 327 SBC

[Marc]

An idea is to connect one breather to the air filter and replace the PCV by a breather?

An other idea is to install such a sytem

http://mewagner.com/?p=444
http://www.engineprofessional.com/artic ... _34-44.pdf

Very expensive!

[Marc]

I am thinking just an orifice restriction plugged in the hose, inserted above the PCV

[Marc]

or/and add an oil catch can on the hose return to the mixer.

[storm]

or/and add an oil catch can on the hose return to the mixer.

This is a very good option combined with a working pcv.

[Tom68]

I have a bad PCV valve. I already noticed oil being sucked too much by this valves, and oil on the throttle blades when dismantling engine....

More likely you've got a pressurised crankcase from poor piston ring seal.

[Marc]

Please Tom can you explain your though behind your wording?

FYI I see oil deposits everywhere on the intake parts of the engine, getting more and more thick deposits until the valves bowls. Yesterday I spent 2 hours cleaning 1 head with tar solvent and a light brass brush, all the cleaning job is about the intake bowls. I see oil in the intake manifold as well.

Marc

[Tom68]

Please Tom can you explain your though behind your wording?

FYI I see oil deposits everywhere on the intake parts of the engine, getting more and more thick deposits until the valves bowls. Yesterday I spent 2 hours cleaning 1 head with tar solvent and a light brass brush, all the cleaning job is about the intake bowls. I see oil in the intake manifold as well.

Marc

Carbon in intake bowls comes from valve timing overlap on petrol engines amongst other things, oil in the inlet tract before the heads comes from the crankcase ventilation system, often pushed there by blowby (cylinder pressure passing the rings into the crankcase etc).

Normally you'd establish that you have good ring seal with at least a leakdown test before upgrading the airflow side of the engine. Still, knowing the engine well from past experience you may know it's sealed up pretty good.

[storm]

I have a bad PCV valve. I already noticed oil being sucked too much by this valves, and oil on the throttle blades when dismantling engine....

More likely you've got a pressurised crankcase from poor piston ring seal.

Good thinking there @Tom68, I hadn't considered the short block not have been rebuilt and actually be quite worn and loose.
@Marc has the short block been rebuilt or are you just doing a "top swap"?
Just incase you don't know a "top swap" is simply changing the heads and intake.

[Marc]

Dears,
Thanks for your comments,
My camaro is a 6 cyl original, V8 327 was built end of the eighties (all papers available) with a cam etc and I have the car for 20 years... Maybe i ran 15 k miles since then... I doubt this engine never saw a lot of miles on it...Just took out the timing cover out and check slack on timing chain, I measure it is 5/16" taken from a straight line at the widest gap between the cam and crank. My Chilton's manual indicates a value of 1/2" for worn out chains, so I am still far from worn out.
I am rather confident about the engine bottom end. Cylinders are white.
Marc

PS it is a misery to post pictures as image are not resized automatically.
If you want to see some particular parts just ask me!

[Tom68]

Dears,
Thanks for your comments,
My camaro is a 6 cyl original, V8 327 was built end of the eighties (all papers available) with a cam etc and I have the car for 20 years... Maybe i ran 15 k miles since then... I doubt this engine never saw a lot of miles on it...Just took out the timing cover out and check slack on timing chain, I measure it is 5/16" taken from a straight line at the widest gap between the cam and crank. My Chilton's manual indicates a value of 1/2" for worn out chains, so I am still far from worn out.
I am rather confident about the engine bottom end. Cylinders are white.
Marc

PS it is a misery to post pictures as image are not resized automatically.
If you want to see some particular parts just ask me!

Timing chain wear is measured pin to pin over several pins, easy check is pick the chain up in the middle of the sprocket, a good chain won't lift far. You also have the opportunity to grab a multi keyed set to get whatever cam advance you chose.

[Tom68]

P.S. ring seal takes several forms, you can have blowby without having cylinder wall oil overcoming yhe rings.

Is it a small journal with valley breathers ?

[storm]

Timing chain wear is measured pin to pin over several pins, easy check is pick the chain up in the middle of the sprocket, a good chain won't lift far. You also have the opportunity to grab a multi keyed set to get whatever cam advance you chose.

Timing chain wear can be measure on the engine exactly how Marc explained.

P.S. ring seal takes several forms, you can have blowby without having cylinder wall oil overcoming yhe rings.

A compression and subsequent blow by test(s) would reveal if the compressions rings are a problem.

[Marc]

Maybe I should have started by making a compression test before dismentling.... now the heads are out. I think I just have now to rely on previous engine built, as was my positive consciousness when I started with these top end mods.
I also guess that a worn piston seal makes the engine exhaust blue smoke. For some reasons I never saw blue smoke neither oil smell at the exhaust. Looking at the cylinder heads intake bowls it is like oil agglomerated there making deposits inside valve seats, and FYI I found oil also below as far up as the carb trottle blades. Maybe I am wrong but I cannot conceive that amoult of oil to travel behind intake valves from the cylinder chambers even which a pressurized engine. Spark plugs are also white and clean.

While running, engine was making good vacuumn, like 17 @ idle and > 25 inHg when you release gas pedal.

I am thinking to buy this
https://www.amazon.de/-/en/gp/product/B ... X78W&psc=1

+ add some kind of orifice downstream PCV valve, don't know what hole size though.

Yesterday I started to grind the first of the heads exhaust ports, mostly blending job between insert and bowl. The burr are effective and I think I shall quickly switch to rotating grits on a dremel.

Regards,

Marc

[storm]

From your description of the vacuum readings I would say your compression rings are ok. Also if your car sits for so long you may actually find the residue you have seen is old petrol that has "gone off". It thickens, discolours, and looks like oil, I never let it sit in small engines (lawn mowers, chain saws, fire fighting pumps) because it makes it very difficult to start them when spring comes.

I am thinking to buy this
https://www.amazon.de/-/en/gp/product/B ... X78W&psc=1

Over the last few years catch cans have become very popular (in Australia at least) and a few different companies are now making and selling them, the first designs worked but since then there have been testing and technical advances made. They have found that catch cans need to be sized to the capacity and potential power output of the engine. A small catch can can possibly be a restriction to proper ventilation. Also if you are environmentally minded please do not ventilate a catch can to atmosphere, there are 2 reasons for this. First if the catch can is vented to atmosphere it is possible for unburned hydrocarbons to escape, second the catch can needs engine vacuum for it to work efficiently ventung to atmosphere creates a vacuum leak and limits the systems ability to extract oil vapours efficiently.

[Marc]

Hi Storm
This oil catch can is working with or without the breather. It is clear to me to use it without. What I like is the baffle. I think to add stain steel turnips in the baffle.

Besides, I have another question.
As said I measured wear on timing chain, and from what I hear it is still some wear... what would you do if you were me? replace it or not replace it? I checked in my old car papers and the mains were line bore (align hone), so I need a 0.005 or 0.010 reduced centerline timing chain but impossible to know exactly with my tools. So I even don't know which timing chain I 'd need?
With this question, we can go further and ask about the status of the cylinder bores, main and rod journals...

I am questioning myself, also I am thinking my engine is still more than ok for the intended use... but it is good to see what other think/ would do in my position.

Thanks,

Marc