Engine makes high pitched noise while running

Joined
Aug 17, 2006
Messages
20
Greetings,
I have a freshly rebuilt small block chevy (350) counter clockwise rotation motor, setup with crusader exhaust. I wanted to start the motor before installing back into the boat so I have it setup on a wooden platform in the garage. The motor has a closed cooling system (anti-freeeze) so I ran it for less than a minute without the raw water pump belt on. I spun the engine with a drill and the distributor tool before starting to make sure I had oil pressure. When the engine was running, I noticed it was making a loud, high pitched noise which seemed to be coming out of the carburetor. It sounded light some sort of vacuum leak. The engine has a Rochester quadrajet carburetor installed with the mechanical choke mechanism but does not have any vacuum ports or hoses. This is an 80?s setup. Additionally, the frame arrestor is not installed. The motor cranks over without making the noise. I tried cranking the engine with the coil wire disconnected. I hear the noise while the engine is running. The carburetor is the same one that came of the engine before it was rebuild, which seemed to be working fine, and was setting in the garage will the motor was being rebuilt. The engine ran before the rebuild but the performance wasn?t very good. In the off season, since the other motor was removed, I decided to take it to a machine shop for inspection. When it was disassembled, the machine shop informed me that the pistons were not installed backwards, which is required for counter rotating engines. A lesson for anyone buying counter rotating engines off the internet. Any idea what the origin of this noise could be? Thanks in advance for your help.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,306
with the motor running, your sucking in air. the sound of the air rushing plast the throttle blades is a high pitch whistle. install your flame arrestor and you wont hear the nois.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,306
Yes, normal. Put the spark arrestor on and you you won't hear it
 
Joined
Aug 17, 2006
Messages
20
Problem solved. I reinstalled the spacer plate which sits between the intake and carburetor after flipping it over. On the crusader engine this spacer plate is used to level the carburetor since the engine sets back about 10 degrees. Although Iit was no indication informing me it was backwards, this seemed to take care of the problem.
 
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