So I built my 5.3 last winter with new bearings/rings and immediately had the "sewing machine sound" at idle. Figured it was "normal" due to the upgraded trunnions, pushrods, LS7 lifters (so entire valve train) & Sloppy second cam. Stock bore '04 lm7. Figured on about a 360-320 HP build N/A. nothing too rowdy. Drove it most of the summer then was chasing an unrelated braking issue. Finally fixed it and drove to town & back. Pulled up to the driveway and it shut down on me. Limped into the garage to figure it out. (Didn't like the odd noise at all)

Ended up being a broken valve spring, bent push rod and damaged piston. Pulled the engine over the winter and replaced the damaged piston, re-rebuilt the heads with new keepers and a new spring, gaskets and so on.

Now reading the posts on this issue I believe that the noise is in fact "normal" due to all of the changes I did on the valve train/cam swap. I just pulled the pass side valves cover and verified that the rockers are not loose but have slight side to side movement. Coils don't appear to be binding.

Here is the build: Sloppy 2nd cam, new 7.40" pushrods, new valve springs, new valve keepers, reused the valve retainers, stock bottom end, 706 heads, truck intake, LS1 converter, 4L60e trans. Car is a 1969 Buick GS California, 3640 lbs, 12 bolt Chevelle SS454 rear end - 3.31 gears.

So is this noise considered normal for a mildly built 5.3? I've run the rockers and everything is torqued to 22 ft lbs, pushrods are centered in the hole/no rubbing, springs don't appear to be binding. With the engine dropping a valve like that, I'm nervous that the pushrod length could be off.

Thoughts?

Yes I did read the other posts here on the subject! Still confused

Jimmy

 

And the part # is ... ???

You have GOT TO BE kidding. I hope.

And the actual measured lifter preload is ... ???

Normal, mostly, for ones that aren't opening their valves at the exact point that the engine is sitting at, at the moment of observation.

OK, so now the next most stressed (or wore out or poorly set up or whatever) spring will break next time you start it up.

To some extent. If not built PROPERLY, it's largely unavoidable. Built right though, it should be at a minimum. That's not a particularly "aggressive" cam, in terms of ramp rates and such; won't really run "the best"; but for its given level of "big cam" issues in general (noise, lope, low vacuum, high fuel consumption, stress on other valve train parts, etc.) it's not too horrible. Being an old generic kinda conservative profile, it's usually not too hard on its neighbors.

Could be. Probably is. How did you measure for it? Which adjustable push rod did you use, and how did you decide what its length was, in relation to what you ordered? What experience building motors do you have? (what kind; not so much, how many, or for how long)
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If you have double valve springs they tend to make a bit more noise than single springs.

 

Push rods, went with manufacturer spec. at 7.4" same with the new lifters. Springs are new (not used), retainers were inspected and were ok. Keepers are new, rockers are new, so everything was replaced when the cam was installed. Springs are single and good to .660" lift. BUT that does not explain why I had a spring failure. It is possible that the pushrod failed first (bent). And no nothing else failed when I restarted the engine after fixing everything.

Wannafbody - just running single springs for simplicity, new seals, springs & keepers. Sound seems to be trunnion bearings. Its up high under the valve covers, both sides.

 

Were the heads milled when the engine was rebuilt? What thickness head gaskets were installed? Any time you pull the heads on these engines and change parts, you should check to see if you need to adjust pushrod length.

 

Milling was not needed, LS9 head gaskets were used.

Jim

 

I have Never, Ever used a set of 7.4 Pushrods with any aftermarket cam on any LS that I have ever worked on. But then Again, I actually verify the preload.

I think I have 4 new set of them just laying around because people just trust a salesman....

You need to check the actual preload. Too much can cause the issue your describing.

 

What valve springs? Did you buy them off Amazon by chance?

 

I see nothing wrong with reusing valve spring retainers, depending on whether or not they're high mileage, and a few other factors. Ti retainers can sometimes wear a bit, and I'd replace them in that situation. However, IMHO, new parts can, and have, contained defects of one sort or another. Retainers that have seen 40,000 miles or so with no issues have pretty much proven themselves as defect free. If not obviously worn from a spring wearing into them, I say set the installed height of the new springs, and send it........

 

Most ls engines have a sewing machine noise. Even stock engines. I have a stock 5.3 dod engine that makes all sorts of valvetrain noises. Rockers should have side to side play on base circle but no lash. Should be preloaded. Stock lifters have lots of room for error but changing gaskets and cam would likely technically require a longer p-rod, probably a 7.425 - 7.450. you could measure if you wanted. 7.4s are likely still in spec. But for measurements just get the 0 lash length at base circle and add desired lifter preload. Tool is like 25 bucks. But if it isn't ticking like a bad lifter and is just noisy, that's pretty normal.

 

Pushrod checker is "out for delivery" right now. I'll get it checked after work and let you know what I find. Never had this problem with Buick 455's of SBC. Buick is shaft design, and SBC/4.3 V6 are traditional rocker design. My son uses the shaft set up on his 6.0.

 

Modded LS engine owners are the only ones who can hear the sewing machine. Because the Ford or Mopar will be too far behind to hear it!!