Help tracking down an engine sound
 

Hi,

My car is a 82 GS with 67k miles, mostly original.

I just installed a RB streetport exhaust but it is still making a very unusual/bad sound.

The sound is completely a function of the engine, not tranny related.

When the engine is idling I can't hear it but as the revs increase it grows louder and frequency increases.

The sound is best described as an ugly scraping noise. Almost like a bunch of small washers in a tin can being shaken around or something. When driving by cars or lane dividers etc it is even louder.

I was thinking it was the airpump (soon to be deleted once I get a proper belt). But it does not sound like it is coming from the air pump.


The engine has 67k miles and runs well. Good power, no issues hot starting etc.

The only unique thing with my car is an emissions delete and it is running a intake mani and Nikki carb from a 1974 RX-4 9I think). The OMP lines run to the float bowls.

No vacuum leaks are evident.
I had a coworker take apart my used oil filter and it was spotless.

Struggling to find out what it is! I will try and get a recording posted up soon.


Thanks

That would be an RX-2 or RX-3 71-73 Nikki. And there could be an issue with the intake gasket. Check it with a stethoscope (long hose held to your ear) for noise.

Or it could be the alt. Loosen it so the waterpump won't turn, then start the engine. It's ok to do this for a minute or less. Listen for the noise.

By the way, that intake manifold you have would be amazing with a hogged out Nikki. I have one that's been port matched to the engine unfortunately (not by me) but I'll still make it work. It just needs channels to be cut like a 79 manifold up under the carb spacer, so a modern hogged out boost prepped Nikki can be used. Then it's turbo time! Gotta trim the ACV area and see if it will fit with an S5 turbo.

Thanks Jeff!

Well I have a new intake gasket, O-rings, and a carb rebuild kit which includes the gaskets for the carb to intake.

I was going to pull the carb assy (including intake mani) but did not want to get involved in draining a bunch of coolant everywhere....How much coolant will I loose? I will need to look into bleeding the system then I would think.

I will try to pinpoint the noise better and get back to you. I am wondering if it has something to do with the passage that puts exhaust gas through the manifold. My intake mani is blocked off and sealed, but perhaps something at the gasket side?

Tonight I will post pictures so you can see what everything looks like!

BTW, as for alternator/waterpump I did not think that was it. Both the WP and alternator are pretty new (8k miles). It does not sound like an alternator bearing going bad, I've dealt with that on my dads FB.

Ok whatever you do, don't change the seats. Leave the OEM seats alone. Turns out all aftermarket seats that come in rebuild kits were machined incorrectly and they lead to constant flooding problems. Their ID is too big and thye have machining ridges inside that catch the edge of the needle preventing it from going up straight and sealiong correctly. It;'s bad enough for NA. What about if/when you go turbo? Leave the OEM seats alone.

If you must remove the seats to take out the pre strainer filters due to their being a restriction, then please be careful. I use a vice grip gently but firmly clamped and then a single smack with a hammer. The slot will strip if you try to remove facorty tight seats. But the slot is ok to use to reinstall the seats. If you must grind the tip of on one of your wide screwdrives a little narrower, go for it.

Get a set of 20mm freeze plugs and some RTV for the coolant ports. I always block mine off. You also nave to remember to fill the ACV port in with quicksteel so exhaust pulses won't carry any heat with them into the manifold with no coolant there to keep it cool.

Now that you mention it, maybe your ACV port is leaking. Like I said, fill it in, in the engine's ACV port. Then the manifold will be nice and cool for more power!