How could this happen - Chevelle Tech
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post #1 of 24 (permalink) Old Nov 23rd, 19, 10:28 PM Thread Starter
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Rob
 
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How could this happen

About a year ago, I pulled my motor on my 68ss 396 Elco for a 4 speed conversion. It took some time, I posted a thread on it and the car ran great when completed. However, my main seal was leaking in the rear and I feared it had contaminated the clutch. So I decided to drive it until it was undrivable, pull the motor and fix it. The motor had about 6 k miles on it now coupled with a Jody M23w. Shortly after, during an easy cruise, I heard a BANG in the motor. It rattled for a moment then went away. I drove it home gingerly and when I got home, started it again... same BANG. So I shut it down and decided it was motor pulling time.

Got the engine to the original builder, Jim Larr. Jim Disassembled and found a part in the cylinder that we couldnít identify. I didnít have the air cleaner off for over 1 k miles, where did it come from? Turns out the mesh screen and base from the air cleaner had come loose, got sucked in thru the big quadrajet secondaries and into the intake. No idea how long it had been working itís way into the cylinder. Bad design Chevrolet!

A word of caution for those using this set up....it can happen.

By the way, Jim went thru the motor for me and fixed the damage, my auto tech forged pistons won the battle and were massaged and damage free. Replaced the bearings, rings, valve job to clean up the seats, rear seal fixed. Fired it up on a stand. No leaks and now I got to install it today.

For any So Cal people looking for a seasoned builder . Jim knows his stuff and after recovering from his illness, he operates a full shop in a building built on his property. He knows all engines but is really good at Chevy iron: rats, mouse and LS motors. Heís a good dude looking to rebuild his business . Jim Laar aka Engine Jim 760 561-2226

Check your screens on your quadrajeet motors.
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post #2 of 24 (permalink) Old Nov 23rd, 19, 11:38 PM
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Re: How could this happen

Thanks for the info and recommendation. Good stuff!


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post #3 of 24 (permalink) Old Nov 23rd, 19, 11:50 PM
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Re: How could this happen

Hmmmm, I'll have to make sure mine is tight.

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post #4 of 24 (permalink) Old Nov 25th, 19, 2:44 PM
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Was that the original air cleaner and screen or part of an air filter? I'm on my phone and can't blow the pic up


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post #5 of 24 (permalink) Old Nov 25th, 19, 4:30 PM
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Re: How could this happen

That could have been a lot worse like a stuck open throttle or a scored cylinder. Good catch on knowing when to shut it off and tear down to find the noise.
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post #6 of 24 (permalink) Old Nov 26th, 19, 10:47 AM Thread Starter
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Re: How could this happen

Yes. Original air cleaner. This is the spark arrestor that is pressed on over the opening. Never in my wildest thoughts would I ever have thought about this happening. Wanted to share as Iím sure itíll happen again somewhere out there. Iíll push a new one on but itíll be tack welding after!
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post #7 of 24 (permalink) Old Nov 26th, 19, 11:34 AM
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Re: How could this happen

I guess I can see how the screen got into the large secondaries of the carb, but I don't see how it would have ever gotten down an intake port or past an intake valve.

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post #8 of 24 (permalink) Old Nov 26th, 19, 11:41 AM
 
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Re: How could this happen

Thanks for posting this, it's always something, sometimes unimaginable things. I'm heading out to check my filter assembly.



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post #9 of 24 (permalink) Old Nov 26th, 19, 11:51 AM
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Re: How could this happen

When my first 69 Malibu 300hp 350 kept stalling out, the cause was a piece of the air cleaner paper in the float bowl.
I still don't see how it could have gotten in there, did someone have the top off of the quadrajet that I didn't know about?

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post #10 of 24 (permalink) Old Nov 26th, 19, 2:54 PM
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Re: How could this happen

Quote:
Originally Posted by RHinkel764 View Post
Yes. Original air cleaner. This is the spark arrestor that is pressed on over the opening. Never in my wildest thoughts would I ever have thought about this happening. Wanted to share as Iím sure itíll happen again somewhere out there. Iíll push a new one on but itíll be tack welding after!
I'm unfamiliar with the air cleaner. What opening, the PCV or ?

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post #11 of 24 (permalink) Old Nov 26th, 19, 3:58 PM
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Re: How could this happen

Quote:
Originally Posted by boyd66k20 View Post
I'm unfamiliar with the air cleaner. What opening, the PCV or ?
Look at the photo the OP posted. At the top left of the air cleaner base is a large tube opening. This opening should be capped by a metal mesh cap called the flame arrestor. The tube is part of the crankcase breather system.

Here's a picture of the flame arrestor cap. I still don't see how something that large could have ever fit down an intake port and gotten past an intake valve, no way no how:
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Last edited by Rich-L79; Nov 26th, 19 at 10:20 PM.
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post #12 of 24 (permalink) Old Nov 26th, 19, 9:16 PM
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Re: How could this happen

You must have big ports & valves and some serious hang time with valve openings to pass something like that.

It could have been a lot worse. So your Elky could go by an alias of "Dodge Bullet", as in you dodged one. Whew!
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post #13 of 24 (permalink) Old Nov 27th, 19, 11:18 AM Thread Starter
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Rob
 
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Re: How could this happen

I agree, I canít figure out how that could have gotten down there but it did. And it does fit down the secondaries. The end result is the motor was freshened up, new bearings, rings, all roller components checked and in great shape. Last, I fixed the rear main leak which was necessary anyways. Fingers crossed that everything is fixed. Again, Iíll replace it but tack welding it in.
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post #14 of 24 (permalink) Old Nov 27th, 19, 4:51 PM
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Re: How could this happen

Thanks Rich. That's what I thought. never realized there was a cap there.
For the valve cover ventilation to the carb. Cant see how it would arrest flames though. That should be the sheriffs job.

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post #15 of 24 (permalink) Old Nov 28th, 19, 4:19 PM
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Quote:
Originally Posted by RHinkel764 View Post
I agree, I can’t figure out how that could have gotten down there but it did. And it does fit down the secondaries. The end result is the motor was freshened up, new bearings, rings, all roller components checked and in great shape. Last, I fixed the rear main leak which was necessary anyways. Fingers crossed that everything is fixed. Again, I’ll replace it but tack welding it in.
RHinkel, thanks for sharing that information. I also have a 68 SS elky. I am also running the stock 350hp open element air cleaner, I will definitely be examining my screen assembly. I am getting ready to swap out my aftermarket intake and go back to the stock intake. It looks as if you are running a stock intake with that Qjet carb. I was wondering about your setup. Did you plug the two holes in the hotslot of the intake manifold just forward of the primaries? Also, are you using carb gasket and a stainless steel plate between the carb and intake? Or just a gasket? I do plan to use the exhaust crossover heat with the open restrictors on both sides and a divorced choke. Any advice from you or another member would be appreciated.

Steve
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