Technical 305 making knocking noise

305 sold as a 350.
Too much oil pressure at idle.
Carb is a little big for a 305.
"Air gap" intake sounds like a single plane, not good on a small motor.
That makes EVERYTHING about this motor suspect.

 

Manifold is edelbrock performer air gap, dual plane, idle to 5000 rpm. I agree carb is a little big, but it was what I had in the garage. A 500 would be ideal. The seller was supposed to provide me more info about the engine, but the texts go unanswered. It was running good after installation though.

 

have ya pulled the valve covers yet?

 

35lb is too much at idle?

 

Yes. The rough rule of thumb on a SBC is 10lbs per 1000 rpm.

If you install a high volume pump(BBC) when you don't need it,
you end up with too much oil pressure, and most of the oil
gets byp***ed around the filter.

 

Valvetrain

 

35 psi at idle is perfict
Never less than 20psi
Stop running the engine and find the problem

 

Haven't made it home from work yet today. Took a glance a couple days ago and didn't notice anything drastic.

 

That info is in Smokey Yunick's first book, Power Secrets.
http://shop.carbonpressonline.com/product.sc?productId=60&categoryId=2

 

Very interesting, never heard that before.

 

That's for a race motor...Should be higher than 10 per thousand with stock bearing clearances.
10 per thou is minimum for a race motor or an old bomb on borrowed time.

 

Hate to say this but it sounds like a cracked piston skirt.
Cast pistons ?

 

Sounds like tin to me. I second the suggestion to take a super good look at all the tin work around the flex plate and I'd grab the flex plate [shut the engine off first] and yank it around, back and forth, forward and back while listening for creaking and popping noises. Put a pair of leather gloves on so you don't tear up your hands on the ring gear.

 

X2

 

Why does a stock motor need more pressure than a race motor ?

 

Maybe because stockers don't see 8000rpm, much less sustain 5000+rpm for 100 laps?

If a stocker pumps 30-40lbs at idle what the hell would be the pressure at 8000rpm?

How much splash on the rotating internals would happen when pushing oil out of the bearing p***ages at 100lbs, might not get enough return to the pan if the top of each head is a bucket?

 

Has any one ever made a seafoam/oil mixture and poured it down pushrods and let it sit overnight to help free up stuck lifters? ATF/oil mixture? Kerosene/oil?

 

I saw some guy on yahoo spray a ton of carb cleaner at the lifters, but that is not something I am interested in doing. At this time, I am not really interested in the kerosene/oil but I read about old timers using it.

 

I tried this before work today and did not hear any cracking or popping. I couldn't find my leather gloves, so I had to use my rubber gardening gloves.

 

It doesn't. It has to do with bearing clearances.
A stock motor has to last 100,000 miles.
Also , modern drag race engines use very, very light oils to make more power.
Not practical for day to day, all climate usage.

 

Broken exhaust valve spring. Rocker and push rod are jumping around, slapping stuff.

 

sure could be. if he keeps running it and drops the valve we'll hear more noises.

 

sounds like valve train to me , loose or cracked flywheel has a ringing "tinny" tone to it also you should see the rust powder tracks from the flexing if its on the crank mount portion . find out if the valve train is stuck first before putting any elixers in the motor to try to loosen things up / and as for oil pressures , the newer vehicles use a higher pressure pump . at warm idle my 96 BBc has 60 psi @800rpm and thats from GM , my 02 firebird has 40 all stock .

 

I'm not so sure why its confusing.
But stock bearing clearances and stock oil p***ages need a stock pump.

Loose bearing clearances, (be it built that way or if its worn out,) or opened up oil restrictions need a high volume pump.

Tight bearing clearances and restricted oil p***ages need a high pressure pump.

Also, there's no way you can blow any gaskets or seals because of high oil pressure. Overly high crankcase vapor pressure can overcome the seals and gaskets.

There's also no way to fill the valve covers because of a oil pump choice. It doesn't run out of oil in the pan because it pumped it all out. The pressure inside the pump causes cavitation, and then it quits pumping oil.



http://www.enginebuildermag.com/2009/06/oil-pump-technology/

Eventually the point is reached where the suction created by the spinning gears causes the oil to vaporize and form tiny bubbles in the wake of each tooth. This causes a loss of flow and pressure because the pump is now churning vapor rather than pumping liquid. What’s more, when the bubbles implode, the shock waves erode the metal surfaces inside the pump. Over time, this can increase pump clearances and cause a permanent loss in oil pressure.

In a stock Chevy small block oil pump, cavitation typically occurs around 5,500 rpm, causing the pump’s output to flatline regardless of how much faster the engine revs. This can cause a potentially dangerous drop in oil pressure just when the engine is needing more oil, not less.

 

Sooo your saying a stock SBC that idles at 800 rpm. Should not have any more than 8psi ?

 

Is there any noticeable skip to it, or does it still run smooth?
If still smooth, I doubt theres any bent push rod, pulled rocker stud, or perforated rocker arm.

My old *** ears says it's the flex plate, due to the odd rhythm and the metallic ring to all that racket!

 

Noises can and will fool you!
Had a 5.7 hemi powered ram truck here.
A Bit noisy at start up then quieted down and idled pretty nice. @ 1500 rpms it was rattling pretty good and at 2500 sounded like it was going to come apart.

Here's what we found:
Remember this is all on the same truck!
Cracked exhaust manifold
Many Loose exhaust manifold bolts
1 bent pushrod
Sheared cam pin
1 spun and pounded bearing @#7
One small piece of #8 bearing in the pan and none in the journal, can't find any of it. If I didn't find that one piece I'd swear they didn't put one in.
It was way too quiet at idle to have no bearing and that kinda slop on the rod journal.
Today I realized there's more to noises that meet the ear
And the rest of the bearing is with the socks that don't come back from the dryer

 

I'd lay money on this, more than once I've pulled pans to put in rear main seals in mid 80s pickup 305s n seen monster chunks of piston skirts laying in the bottom of the pan. Very common problem , the one that hurt the worst was in my not very old at the time "cream puff" 85 4x4 305 it was missing almost up to the ring lands. But it did paved the way for a 383! Flux

 

Still waiting here too.
I'm gonna hold my cards on this one.
After checking under the valve covers,...pull one plug wire at a time.
If the noise goes away, or diminishes it, with no ignition, you found the bad one. Might be too late for this test.
Don't worry about running it a bit more. You're gonna have to sleeve that one anyway.