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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Silver_Bullet85 on December 16, 2014, 05:10:42 pm
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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 (https://vimeo.com/114719440)
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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.
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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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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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Nice Engine, has the same cylinder heads as mine. When you pulled the valve covers off, was it running or off?
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It was off, didn't want to risk getting oil everywhere. Should I have let it run?
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Recheck your firing order
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Sounds like header slap from a set of Hooker headers to me. Mine does the same thing.
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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.
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Recheck your firing order
I agree. It sounds more like an engine misfire.
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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.
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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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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?
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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?
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(http://tapatalk.imageshack.com/v2/14/12/17/d6d306c6e14bc28cacc78d84ae7257b5.jpg)
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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Been a busy couple days but thanks for the responses! I wasn't able to get much work done but I was able to check the wires and one of them has a cut on the boot thats causing it to arc onto the headers and theres some kinks on the others, I plan on checking them all tomorrow morning and replacing a few.
Rich, I had my brother drive while I sat on the passenger side and the noise was barely noticeable (window up, down, door open, closed). Base timing is at 13 deg. the vacuum advance port was plugged by tristar and its running on 35 deg. total advance. It runs smooth and has gobs of power but it feels like the power isn't as strong as it should be for 475hp.
I'll check all the plugs and wires I can tomorrow and see what I find, if theres still a problem I guess I should remove the valve covers and look for something odd while its running?
I did remember something significant that happened back when I was installing the engine. The first time I manually turned the crank in order to line things up I heard a pretty noticeable crunch from the drivers side, there wasn't any resistance at all before or after and I never felt a crunch I just heard it and figured it was just everything settling in. Never noticed anything odd about how the engine ran at all and it sounds very healthy at idle, just when under load it makes that noise.
Thanks again for the help guys.
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That cut and arcing plug wire will really cause a problem. When it arcs to the header it stops the electricity from going to the plug because the path of least resistance is thru the cut to the header instead of thru the plug to the block as it should be. That short causes a heavy or dead miss fire. Which Rich, Vile and I all suggested. That could be causing the noise. What cylinder was the cut wire on, drivers side cylinder bank, cylinders 1,3,5,7? Would explain why it's louder on drivers side too.
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LTZ, it was on the drivers side, #3. I changed all the wires and pulled the valve covers to check while it was running. Noticed there might be a slight knock somewhere but all the rockers seemed to function well, I'll put some vids up at the end.
So after replacing all the plug wires and checking all the plugs and making sure they were gapped correctly (they all were all .040-.045) I took it out for a spin. For about the first 1/4 mile of normal driving around there was no sound at all. I went out in the country and opened it up a little and I could barely notice the sound, sounded more like the exhaust than anything else, but as I drove it I noticed the sound started to come back. This time it was when I passed a concrete barrier on the pass side that I heard it, but it was nowhere near the level it was at. After about 15-20 min of driving it had grown louder still but not loud enough to catch on video.
Some of the plug wires were just barely long enough to reach the dist and I checked them after driving and I guess they had relaxed as they heated up. I might try and get some longer ones to ensure they're not vibrating out of good contact.
New wires with covers off:
https://vimeo.com/115028391 (https://vimeo.com/115028391)
New wires with covers back on:
https://vimeo.com/115028439 (https://vimeo.com/115028439)
Driving with the new wires:
https://vimeo.com/115028533 (https://vimeo.com/115028533)
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One more thing, I think the question was asked earlier but I forgot to answer, I'm running castrol GTX 10w-30 with some zinc added I believe.
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What wires are you using?
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These guys:
(http://tapatalk.imageshack.com/v2/14/12/19/428140d748c87f0f2672e0ab28f777bc.jpg)
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Aftermarket OEM equivalent.
Get rid of the resistor-core wires. If you are running resistor plugs, you don't need resistor-core wires as well. They're just trouble waiting to happen.
When I researched spark plug wires, I found a dozen inquiries on the net that were "If you were going to get new plug wires, and you weren't going to spring for a set of Taylors, what would you get?" So I got the Taylor helical wound solid core wires. Next auto club meet, a guy who wrenched a bunch of the dirt trackers around here for years took a look under the hood and said "Oh you put the Taylors on. That's all we ever used on the race cars."
OK, so they're $55 a set. Is that real money, given that they work?
http://www.summitracing.com/parts/TAY-74206
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Good point Rich, I haven't had time to research some good wires but it was on my list as these feel cheap, thanks for doing the homework for me lol. It probably wouldn't hurt to get better plugs either, I'm a fan of delco but since everything else is a step above stock I'd be cheating myself in not getting the best fire I can. Any advice on good plugs?
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Going to change the oil tonight, engine has probably 100+ miles or so on it and I'm not sure what oil is in there (came full from tristar). Probably doesn't need it but might as well so I can cross it off my list and be certain of what I'm running.
(http://tapatalk.imageshack.com/v2/14/12/19/de495b98d3c8cf420e6cf1c6105267a5.jpg)
Also noticed the main belt needed a little tightening, maybe that could be contributing to the noise... didn't sound like it but again, process of elimination...
Stay tuned, we'll see what I find in the oil pan next...
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Autolite 24. Same wrencher told me that's all they ran in the race cars. The Autolites are more immune to fouling than the ACDelco's.
If you want to stick with ACD, run R45TS. That's what I'm running, and have had no problems, so didn't switch to the Autolites yet.
Resist the urge to buy hoity-toity expensive plugs. Waste of money.
(You might want to check the engine recommendations, too. They should tell you what plugs they recommend.)
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The FRAM oil filters are supposed to have been improved from dismal reviews a few years back, but that is their bottom-end filter. The Tough Guard is the better one. Most people speak highly of the NAPA Gold and the Wix filters.
Probably doesn't make any difference on a new engine, because it's only gonna be on there for 500 miles or so, right?
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Good info, thanks a lot. I try to stay away from the waste of money stuff which is a big reason I keep coming back here honestly, but yes, I'll be changing it at least once a year. The weather stays pretty consistent in south Texas so I don't have to worry about that and it's not a daily driver either, heck my daily driver isn't even a daily driver lol. The company truck sees more miles than anything else, almost 30k this year alone...
If I'm still experiencing problems I'll probably upgrade the plugs next, I'll try for the autolites and see how they work.
Well the oil is clean and not burned, ran a magnet through it and got nothing either so that's reassuring. It seemed a little thinner than the 20w-50 but it was a little warm still so hard to tell.
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just a tip, but if you go napa (which i have been slowly go to since i get a discount with them) ask for the filters in the back. its still the napa gold but without the box, and its srink rapped and is something like 2 dollars cheaper
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Sounds alot better. The small noise now sounds like it could be header slap. Sounds alot better tho. I'm using MSD wires, they have been great so far. Also, check your specs sheet for the head to make sure you get the right dimensions for the plugs.
The AC delco oil filter is also good. I'm using a delco filter, and it's also working great, IMO the factory filter does the best job of filtering the smallest pieces.
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i use duralast brand wires on my truck but in my impala i use ac delco cause autozone sells them.
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On a new engine, you should change oil at 100, 500, and 3,000 miles, then 3,000 thereafter.
So don't forget that 500 mile oil change.
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What Rich said.
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Sounds like header slap from a set of Hooker headers to me. Mine does the same thing.
What's 'header slap?'
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Sounds like header slap from a set of Hooker headers to me. Mine does the same thing.
What's 'header slap?'
(http://image.wikifoundry.com/image/2/C8PoJQwIbGjFUpUwrVrHUQ458647/GW300H169)
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Sounds like header slap from a set of Hooker headers to me. Mine does the same thing.
What's 'header slap?'
(http://image.wikifoundry.com/image/2/C8PoJQwIbGjFUpUwrVrHUQ458647/GW300H169)
(http://i.imgur.com/F7HjV7o.jpg)
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Exhaust pulses from the engine hit the thin walls of the header tubes where they bend, and make a metallic ticking sound. Sounds like a bad lifter or an exhaust leak. You can tell if that's what it is by pushing on each header tube at the corner and seeing if that changes the sound, although sometimes you only get the sound when you have your foot in it. The Hooker 2453 headers (for the K trucks) in particular, slap on #3 and #4, which bend sharply back coming out of the engine. Those bends are 90s, where the down bends of the other tubes on a V8 are 45s.
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Exhaust pulses from the engine hit the thin walls of the header tubes where they bend, and make a metallic ticking sound. Sounds like a bad lifter or an exhaust leak. You can tell if that's what it is by pushing on each header tube at the corner and seeing if that changes the sound, although sometimes you only get the sound when you have your foot in it. The Hooker 2453 headers (for the K trucks) in particular, slap on #3 and #4, which bend sharply back coming out of the engine. Those bends are 90s, where the down bends of the other tubes on a V8 are 45s.
I liked your previous explanation better. I giggled for a long time at it!
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Haha you guys are ridiculous. That made me lol.
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It's crazy how time flies by sometimes, just figured I'd check back in and update y'all as to what I learned. I remembered when installing the engine that the indicator for TDC was a little bent and so I started playing with it and learned (by trial and error) that I was a few degrees off of where I should be. So now I'm at (according to the bent indicator) 18 degrees initial and 39 total mechanical advance. This has pretty much eliminated the noise and the engine runs a lot better too, now I just need to dial in my mixture screws and idle speed a little more to get everything back to how I like it. Thanks for the help everyone!
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Good to hear.
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What about detonation what's your cranking compression turn the timing back and try it
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He shouldn't start to see detonation on 87 octane and 8.5:1 until 20* BTDC, unless the plugs are fouling.