Hey everyone. I'm new to posting on Third Gen as well as posting in general. So here's my porblem...I have an 1986 Camaro Iroc with a 305. It was originally a stock TPI setup, but the costly upkeep made me switch to a carbureted setup. It now has an Edelbrock Performer intake manifold and an Edelbrock 1406 carb. I believe it is a 600cfm. Also, the distributor is a brand new MSD streetfire. Everything is pretty much barebone setup seeing as it is a daily driver. Right after the switch I started experiencing a very loud knock when when accelerating. I have relaced the dizzy to the new MSD, seafoamed the engine, unplugged one spark plug wire at a time to see if I could isolate the noise, tried premiuim gas and octane booster, the whole nine yards.....but no luck. Any ideas? I've used a stethescope, and the noise seems loudest near cylinder 4. HELP ME!

Also, I will be uploading video of the noise very soon..if i can..like said, I'm new to this
Ok. here's the video on youtube....Any ideas? Thanks in advance!
http://www.youtube.com/watch?v=YqRr6EOB03M

 

Given the audio quality of the video, it's not easy to determine. It's obviously more prevalent under load, but difficult to determine if it is a mechanical sound or detonation.

Are you absolutely certain the firing order is correct? Be sure to double-check #5 & $7.

Can you pull the rocker covers and observe the valve action while it's running? It might be revealing.

The noise almost sounds like a detonation or rod knock, but again the audio makes it difficult. The visual part of the scene is useless, so perhaps a WAV file uploaded to the site would be more helpful.

 

I just pulled the valve covers and did an inspection of the rocker arms and pushrods. All seems to be well as far as I know. Some seems to be seeping sufficiently more than the others, but I am not sure if that would cause such a radical noise, but again, i do not know. I will upload a video of the rocker arms with sufficient lighting. The first video was with a flashlight. Thats all I had at the time of making the video. Checked and rechecked the spark plug cables. They are in the correct firing oder. 18436572. Could the spark plugs themselves reveal any information, because I've yet to pull them. I will try to upload a better video tomorrow. Thanks

 

I've been told by a mechanic and a buddy of mine that he really doubts it is rod knock seeing as it was never there before and it can only be heard under load. He believes as do I, that it has to involve ignition or fuel. Any ideas that I haven't tried involving either of the two?

Also, before the tpi to carb swap, the tpi setup was equipped with an EGR. I currently do not ave an EGR on the carb setup. I do however have the option of putting one on because my performer initake has a egr port. Is it worth a try to go out and buy an EGR to see if it eliminates this knock/detonation or whatver it is.

 

Was adjusting rocker arms and found a bent pushrod on the fourth cylinder. Could this be the noise I was hearing??? Check out the video in my first post.

 

I'd worry about how that pushrod got bent.

 

When you swapped intakes, its possibly a small piece of carbon build up got in the cylinder. My neighbor had a jeep where we all thought it was a rod knock, and turned out to only be carbon loose in the cylinder.

With such little space between tdc and the valves, its a very possible cause for the bent pushrod, as well as the noise..

How long after the swap did you start noticing the sound?

 

It started almost right after the swap as far as I remember. The pushrod was only slightly bent. I replaced both on that cylinder today and it is still making the noise. Say it was a piece or carbon in the cylinder...how could I go about getting it out without tearing the head off.

BUT, i've discovered something new also. When I disconnect the vacuum advance, the noise virtually disappears....I've tried adjusting the vacuum advance with no luck there either.

 

How is your distributor curved?

 

You might have to do a little research, but I remember hearing that pouring some water down the intake at around WOT will clean it out. I could be very wrong though so make sure you look into it.

 

I have the same knocking noise on my camaro as well. My dad though I was missing my some trans liquid but I am not. I am thinking of swaping the engine out for a 350. I believe that my knocking noise is a result of old ago and lots of mileage

 

18camaroRS89..I've done the water down the carb. It's called steam cleaning. I've also done seafoam down the carb too.

And I made the decision today to do a 305 to 350 swap. I have built a 350 that should be pushing around 300hp. It'll be a perfect addition to my IROC. Not too big and not too small. Used to be in my 1971 chevelle, but I've since upgraded to a BBC. Gonna start the swap tomorrow.

 

i had a 1977 nova that had pretty much the same noise my flex plate bolts on the trans cam loose maybe yours are to just a thought