Hi Guys,

I am in the middle of a TBI conversion on a 1976 corvette and at some point during the process it started making a really strange huffing/wheezing noise. It is very loud at idle and It happens even while cranking. I took all the spark plugs out and did a compression test and the results were OK, all of the cylinders were around 135-145 PSI.

To me it sounds like a leaking valve, but wouldn't that show up in the compression test?

Here is a video of it making the sound while I crank it over. All the spark plugs have been removed and a compression tester is in cylinder #1. Has anyone heard a sound like this before?




--Eddie

 

does it make the same sound whether the plugs are all in or not?

It sounds metallic, like a rocker not getting oiled. put a 1" heater hose to one ear and while its cranking, see if you can isolate the source to a certain pt on the engine.

 

Oh yeah, makes the sound while the car is running, it's even louder at idle.

I tried the heater hose trick and I could not really isolate which cylinder it is coming from. I opened up all the valve covers and oil is coming out of the lifters and all the valves are all moving. I even gave it a valve lash adjustment which did nothing to help.

 

i'd say its coming from somewhere

did you check the intake area, exhaust manifolds or even try under the car if its louder there? it does sound like its cyclical, like once every crank rev.

 

Hi Guys,

I thought I would report back that I figured this out. When I converted to TBI I left the old mechanical fuel pump in there, and it turns out that it was the source of the strange noise. I'm glad it was not something major!