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ZZ502 knock

7K views 29 replies 16 participants last post by  GoFast Beaumont 
#1 ·
I have just installed a new ZZ502 full dress engine in my 72 elco.

The only thing I have change from the original crate engine is I put a Edelbrok High flow Long water pump in replace of the short pump supplied from GM.

The care runs great and maintains 70 lbs of oil pressure and idles at around 30 lbs.

The issue I have is that when a start the car up I have a knocking (noticeable but not extreme) noise on the passengers side of the engine. It sounds to be coming from the upper part of the engine. There is no smoke or usage of oil. I have change the oil at 500 miles and it was "clean". I am running a 5/30 Castro non synthetic oil for break in.

Once the car is warm (runs at a consistent 185 degrees) the noise goes away. All of the valve noise is normal for a big block.

The shop that installed the engine, (has a very strong reputation for it's work in the area) said that it is a minor case of piston slap and to not worry about it.

I have also heard the stamped steel rocker arms can be noisy.

I have not had the valve covers off to see if the valves need an adjustment.

Am I making something out of nothing?
 
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#2 ·
Well rocker arm noises under the valve covers usually sound different than piston noises, and also have a different speed or tempo to the sound. If I were you, the first thing I'd want to find out is if those engines have forged pistons, ( I think they do, but I'm not positive) and if they do, are they 2618 alloy forgings or 4032 alloy forgings. The 2618 don't have as much of a tendency to knock during cold operation as the 4032 alloy does. The 2618 pistons don't expand and contract as much from temperature change, so they are usually installed with a .004" piston to cylinder wall clearence, and the 4032 alloy slugs call out for a .007" piston to wall clearence since they expand considerally more when they warm up. So the 4032 alloy pistons will often knock when the engine is cold, until it warms up which is when they tighten up i the cylinder bores due to their expansion.

If you have 4032 alloy pistons in the engine, then there's a very good chance that the knocking is coming from the pistons, and that is normal for that alloy to do that. So you should try to find out the small details of the ZZ502 build to see if it lists what alloy those pistons are, (if they're forged pistons). I'd want to rule that out first before you move forward in looking at any other possibilty for the knock. If the pistons are not forged and they're hypereutectic pistons, then the knocking is not coming from the pistons unless the bore or hone job on the cylinders was done completely wrong, or perhaps if the wrist pins are installed wrong or defective. But I would not jump to any conclusion like that.
 
#3 ·
the pistons you have in that engine are GM part # 12533507 and they are forged, but I cannot find information on the internet as to which alloy they are. You sould go to the dealer parts dept with this part number and ask them to look up the specs and find out if it's the 2618 alloy or the 4032 alloy used. Because it doesn't even list which it is in the GM catalog. What you can also do if they cannot give you an answer on that, if ask them what the installation directions say such as what the piston to cylinder wall clearence is. if it's .004" or .006 or .007" because if it's the latter, then there's a good chance that it's your pistons you're hearing and that isn't a problem as long as it goes away when the engine begins to warm up.
 
#4 ·
I think people have advised you about using GM crate engines instead of engines built by members here like VortecPro. GM crate engines are junk. I have said it on here many times. I have seen many of these engines torn down for various reasons. Oil consumption, knocking, you name it. I have seen cylinders with less than 1500 miles on them that were all different sizes and closer to being square than they were to being round. I have always been a GM fan but they build crap crate engines. You need to talk to the dealer that sold you the engine and start a paper trail. Start asking now what they are going to do to help you.
 
#17 ·
Being a guy that likes to build my own engines, I just wish GM and some of the others would offer their engine packages in kit form un-assembled at a discounted price. I very much like the idea of starting out with all new parts, but I want to verify the specs and do the assembly myself. Truthfully, I'd rather have my own engine even if a pro builder could give my 100 more horsepower with the same parts.
 
#7 ·
Most of the time piston to wall clearance is way to tight in those GM crate engines. If the noise goes away after a little warm up I say you are fine. If it knocks under a load then you have a problem. Have a friend with a 502 in his Nova and after spraying it a little the engine went south. When they pulled it apart all the cylinder bores were scored up from being too tight. His machinist said bore time .030 with a .005 to .006 clearance minimum.
 
#10 ·
Bullet,
I have the 454ho crate engine. I had a similar knocking sound that started as a light but noticeable knock that what I thought was near the back distributor area (resonating sound in hindsight up firewall tunnel) . However it had that certain beat and knock that at 1st gave me that "this ain't right feeling" Fast forward it got a little worse over time. One night I was in the mood for adrenaline rush and I took it out and spun it up right out of the driveway and BOOM! knocking got a whole lot worse, oil pressure crashed. Brought it right back and sure enough I could now hear it coming from bottom end.
Pulled the engine and was amazed at what I had found, the middle 3 main cap bolts were all basically falling out and finger tight. Turned the bearing for sure as the crank must have been walking and flexing a 1/2 mile in there. Even nicked a valve and bent that valve, also nicked the combustion area with edge of valve. I was lucky enough not to damage the crank beyond a good polishing.
I had more issues with this engine from day one 16 yrs ago, bad rings, lifter noises (non adjustable set up heads). I agree with many of the other posters that say GMPP crate engines are crap. I ended up replacing much of the rotating assembly and its been good so far.
I will say this, if you can get them to stay together and/or have the luck to have purchased a good one, they are very nice and very powerful and are fun to drive once dialed in on pump gas.
After I thought back over the years running it before it came apart, this engine always had a slight vibration. Well it must have always had that loose walking crank from day one. Now after a new rebuild it just feels right and tight like a good engine should.

Good luck with it and hope its something more simple.
 
#11 ·
Bullet,
Read the GM tech bulletin about the oil bypass set up. Most of these GMPP crate engines come with the pre installed bypass that is set up for the factory GM oil cooler and if you are not using that you need to remove the one. What happens is your oil does not return quickly enough under high loads/rpm
I tried to copy and paste but don't know how to work this site that well however its been posted and the below member has it up.



engines Feb 10th, 09, 7:20 PM Thread Starter
70_chevelle
Tech Team

Join Date: Mar 2001
Location: SLC, UT USA
Posts: 585
Re: how to bypass oil cooler on 98 454?
 
#12 ·
I don’t think you should be hearing any kind of audible knock regardless of piston type. I’d get GM on notice asap at least to document the issue.

I also had a 454HO - no noise except for valvetrain but the 454HO’s have different pistons. ZZ502 pistons are made by JE.
 
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#13 ·
Does it sound kinda like this?



The current 454 in my car (soon to be replaced by a VortecPro 467) has a noise on startup, that pretty much goes away once at full temperature. It took me forever to find someone else with a similar noise online, because many online videos/recordings mute or distort the sound somewhat. Mine sounds exactly like this video - not exactly a deep knock, but a squealy/chirpy type knock that dissipates as it warms up.
 
#18 ·
I bought my 489 rotating assb. & Brodix heads from Wolfplace, I think Vortecpro also sells the parts needed if you want to assemble the engine yourself, heck I think there's a bunch of pro builders that will do the same here edit: I doubt GM would do that but you never know, check the GMPP cat. ?
 
#28 ·
A kit is only the start ! Literally every part has to be machined, massaged, filed. Then it takes several thousand $ worth of tools just to assemble.

Not to mention knowhow !

I'm pretty darn sure GM isn't hand massaging these crate engines. My guess is they are little if ANY different than any other assembly line engine they build. Pull parts off the rack and slap them together. I can do that good or better and and my engine building tools are probably worth $100.00 total at a swap meet. Besides, I just want to do it myself, even if it ISN'T better.
 
#27 ·
The OP didn't ask for a lecture on crate engines versus buying one from a builder.

The sound going away as the engine warms up is inconsistent with a rod knocking due to a bearing problem. As the oil heats and gets thinner the noise would INCREASE, not go away. If water temp and oil pressure are normal, there is no metal in the oil when drained, the filter looks normal, and the noise goes away after warm up, I'd be content to drive and enjoy.
 
#30 ·
most likely the lifters. the cast valve covers can really pronounce the noise more than it should be. as well a cowl hood will really elevate the noise more than it really is.

Given you finding when the oil warms up, id just double check the filter, keep a eye on the oil gauge and run it. if nothing happens in the following 250miles, most likely your head plays games with you.
 
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