Weird engine noise...

[Silver_Bullet85]

So I've just got my truck up and running and noticed it's making this weird noise under load. The engine is a 383 crate with a quickfuel 750 carb. I haven't done a thing to it but instal it from when it was sent to me.

It's only when under load and doesn't make the noise at all when idling or reving up.

Any ideas? Maybe it's a fuel/carb/jetting problem?? I don't know much so any help or advice is appreciated. Thanks!

If the video doesn't work let me know...

https://vimeo.com/114719440


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[LTZ C20]

It sounds alot like lifter or rocker noise. Is the oil level at spec?  Does it have the proper oil recommended for that engine?


What are the specs and info about the engine? Brand, where bought, model?

If it's a crate engine say like from Summit or Jegs, copy and paste the info from the correct site for us to see.

[Silver_Bullet85]

Here's the build sheet, it's from tristar.

http://www.tristarengines.com/catalog/high-performance-crate-engines/gm/383/383-stroker-435-475-hp-460-480-torque-complete-dyno-d-hp-crate-engine-with-dart-shp-performance-aluminum-heads-3650.html

The cam is option 4.  Oil level is full, timing is set at 13 base and 34 total.


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[Silver_Bullet85]

I also pulled the valve covers and checked to see if anything was loose but it all felt tight. Barely any wiggle at all.


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[LTZ C20]

Nice Engine, has the same cylinder heads as mine. When you pulled the valve covers off, was it running or off?

[Silver_Bullet85]

It was off, didn't want to risk getting oil everywhere. Should I have let it run?


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[VileZambonie]

Recheck your firing order

[rich weyand]

Sounds like header slap from a set of Hooker headers to me.  Mine does the same thing.

[LTZ C20]

Probably wouldn't hurt just to make sure everything isn't moving excessively. 

As vile said, double check firing order.

Could be header slap too as Rich said but that's pretty loud. I could only hear slap on mine if I was lookin at the motor, that's loud and while driving. Possibly internal.

[bd]

Recheck your firing order

I agree.  It sounds more like an engine misfire.

[LTZ C20]

After you check your firing order, make sure all your plug boots are seated properly at distributor and plugs, look for any burnt thru wires that could short out.

[Silver_Bullet85]

First of all thanks for all the input and advice, this truck was largely put together based on the info I've found here, especially when it came to troubleshooting.

The firing order is right, all wires and plugs are new. It doesn't make the sound when the engine is at low load no matter the rpm. I just drove it around to get everything heated up and noticed with a temp gun aimed at the exhaust ports that they were all around 300 give or take 10 degrees except for cylinders 3 and 7. They were consistently 20-30 degrees lower than all the others.

When everything cools down I'll check the wires and plugs. Based on the build sheet what should my plugs be gapped at? I'll also be sure to take pics of what I find. Now just to hopefully ease my mind does any of this sound like a problem with the rods, valves, or cam? Those should've cause more noticeable problems I'm hoping...

LTZ, I checked the header clearance and there's no signs of anything making contact with anything else, and the sound is definitely coming from the drivers side.

I double checked the timing as well and everything's as it should be. Also, the engine was built and tested in Wisconsin and I'm in Corpus Christi so there's about a 1,200' elevation change, I've adjusted the idle mixture so she runs slightly rich but as lean as I can go without suffering any idle quality while in gear, maybe the jetting or something else should be adjusted also for the secondaries? Since the noise is only when it's under load maybe there's a fuel/air mixture problem when the vacuum increases??? I don't know I'm just throwing ideas out there, you guys are the experts...


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[LTZ C20]

Happy to help. Look at the paper work or call the place the engine came from for plug gap specs.

The header slap is not headers physically touching another part, header slap is the exhuast gases going thru the header tubes and bouncing around where there are elbows and bends.

Usually header slap isn't that loud tho, in your video, it's under loud, with the door open and I can hear your exhuast pipes too, that noise should drown out header slap. For it to be soo loud even with all the other noise makes me think a physical part is making noise or a miss fire as Vile and Rich said. You said the plugs and wires are new, are they all installed properly tho? Fully seated? No burn marks or kinks?

[rich weyand]

Plugs spec at .045 for HEI on most Chevy V8s, but anything between .030 and .045 is probably OK.

Under load, vacuum goes down, spark retards.  What is your base timing set at?  How much vac advance you running?

I still think it's header slap.  Those Dart heads have oversize valves and clean exits, with a quick-ramp cam, they're going to exhaust-pulse hard.  I run Flowmaster 40s and can still hear the header slap on mine.  I thought it was an exhaust leak or a bad lifter at first.

"Definitely coming from the driver's side" can be a false impression based on you sitting on that side.  Have you had someone else drive it and sat on the passenger's side to check what it sounds like from over there?

[Silver_Bullet85]

Here's the #7 plug. Doesn't smell like fuel and is at .052 inches gap (don't have a ring on me so I'm using my handy dandy electronic calipers lol)



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