SBC 350 diagnosis

[bikersmurf]

$1600 crate motor from summit, done! Have never had issues with these 290 hp engines.

From Summit
Estimated Total CAD $4,024.41 (3g for the motor + 1g shipping = 4g and a lateral step for power)


Hopefully it's a lifter... even though they all seem to be working right. That's why the intake is coming off next. It'll be a shame to have to remove the Ram horn off the drivers side head for the first time in 48 years. Passenger side had to come off about 10 years ago.

 

[whitey45]

Likely not a lifter,30 years of wrenching, having my own shop, seen a lot! A lower end knock can sound like an upper end noise all day long. I would pull the pan, and start removing rod journals,you will find the culprit!

 

[pjohnson]

I would think pulling pan and inspecting to be easier than pulling the manifold, at least by a little bit.

 

[waiting for time]

Have you tried adding some atf fluid to the engine. This helps to clean up the hydraulic valve adjusters.
Had a sharp nock with a VW boxer with hydraulic valve adjusters, added some atf to the engine oil and it never came back.

 

[bikersmurf]

Likely is a bearing... if it is, the motor will be coming all apart. So either way the manifold will need to come out. The mechanic who has listened to it said it doesn't sound like a bearing. I could be wrong but it doesn't sound remotely like the two other spun rod bearings I've had.

I'd much rather work on the top of the motor than under the truck with oil dripping on me while lying on the ground. If it's not something up top, the motor will have to come out. The bores don't look too bad, it'll likely need a to be pulled for a quick rebuild. If they're too beat up, I'll be finding a runner and pulling this one. I'd like to rebuild this one, but when I can get a lower mileage running 350 Vortec for $500-700 with a complete truck for parts there's a limit.

The current $300 runner has lasted 21 years (so far), so I'm not opposed to picking another good runner and building this one over the next few years.

 

[waiting for time]

What is the sound like, sharp or dull?

 

[bikersmurf]

Have you tried adding some atf fluid to the engine. This helps to clean up the hydraulic valve adjusters.
Had a sharp nock with a VW boxer with hydraulic valve adjusters, added some atf to the engine oil and it never came back.

That's a good thought Michael... but it's beyond wanting to cross my fingers and hope for the best. Everything needs to be inspected... unless an obvious cause is found. I'm 1/2 expecting something to come out through the side of the block... the noise is bad.

 

[bikersmurf]

What is the sound like, sharp or dull?

Sharp

 

[bikersmurf]

Hopefully this link will work...

 

[bikersmurf]

This was at first, and it has gotten louder since this clip.

 

[nogo]

Is that smoke and or steam I can see in your clip?...If so, where's it coming from?
After reading the thread I was expecting to hear a tick or low knock, that's quite a racket you've got going on there!.....Don't think I'd bother removing pan, heads, etc, thinking it's time for a repower.

 

[pb4ugo]

First, I'd remove all the belts, so you are listening to just the engine, and remove all possibilities of the noise being something external. It seems to be running smooth, is there any vibration, slight shake, or miss? In the video, the noise clicks for a while, then seems to go away for a moment, is that correct? What's the oil pressure like?

 

[bikersmurf]

All belts are off for first (really the second video).

Oil pressure is steady and the same as always. I've only got stock Toyota gauge though.

No vibration, runs smooth... so long as at least 4 of 8 cylinders are connected. I was shocked that it ran smoothly on 4 cylinders... on only 2 it sounded like a thumper (single motorcycle).

It may well be time for a repower... but being both broke and curious, I'm going to find the cause before I throw in the towel. Also this motor still seems soooo strong and has been faithful to me, I feel I owe it to figure out why it's sick. After 21 years and bringing me through the worst snow storm in 50+ years, I'm at least going to pull the intake, heads, and oil pan. Most of that'll need to come off for a repower anyway.

 

[reddingcruiser]

Did any one suggest wrist pin issues? Won't affect oil pressure and can sound like upper or lower end noise.

 

[bikersmurf]

Yes... mechanic who listened said it didn't sound right for wrist pins... but also didn't recognize noise. Knowing my luck it'll be the rarest and most improbable thing possible... and I'll have what I need to fix it handy.

Did any one suggest wrist pin issues? Won't affect oil pressure and can sound like upper or lower end noise.

 

[waiting for time]

The sound is similar to empty hydraulic valve adjuster but maybe louder.
You might want to try with a stethoscope if you can pinpoint the location as precise as possible, might save time and frustration.
Hope you find it.

 

[pjohnson]

Hearing the actual sound, I'll toss my .02 cents in and say its a lifter problem.

 

[POTATO LAUNCHER]

Hearing the actual sound, I'll toss my .02 cents in and say its a lifter problem.

Agreed, sould like a lifter to me also.

 

[bikersmurf]

That's why I'm planning to pull the intake.

A steel rod in the intake sounds like it's being hit... in time with valve movement.

 

[whitey45]

Just pull the valve covers! Curiosity is killing me! Might just be a bent pushrod and flopping rocker arm!