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Negative experiences with the ZZ502?

44K views 56 replies 36 participants last post by  Stuart916 
#1 ·
Does anyone have any negative experiences first or secondhand, with the ZZ502? Excessive oil consumption, poor workmanship, etc? I am considering purchasing one and just want to do my homework. My plans are to add a Holley C950 EFI to it. Strictly street use. Thanks.
 
#3 ·
They're not torque plate honed from the factory and I've heard they use low tension rings. I've heard of a few 454's and 502's that had some blow-by/oil consumption issues that were taken care of by a torque plate hone and ring replacement.
 
#4 ·
I have owned two of the zz502's and have never had a problem one.The one now in my nova runs 9.68 in the 1/4 on a hit of nitrous.(175) The 1st one I had ran a 10.97 on the motor and the one now runs 10.68 on the motor. I bought the short block and added a bigger cam and eddy ovals.. I think they are a very strong motor..
 
#5 ·
Yep...it's SLOW out of the box!! Seriously, it's got a lot of great parts..but it needs a cam to get some power,,plus a little compression. A buddy put one in my old 68 SS/RS Camaro. I ran that car for years with a GM oval port 427, single plane and solid flat tappet cam and pump gas. When I drove the ZZ502 I was very surprised to find the 427 would have spanked it all day long and the 502 was completely out of steam before 5500 rpm!

If you get it, save some $$$ back for a cam and some head milling. Once you spiff it up a little it will run killer!


JIM
 
#7 ·
True, I ran the stock form for 4 years and it was always done pulling by the 1/8th mile. This motor has gave me no problems and with a new solid roller set up from Chris Straub and head work done it runs really good like a champ.
 
#9 ·
I have had mine in my monte for over 5 years...I get on it alot when driving it and take it to the track regularly. It runs 11.90's at 113+mph with the heavy monte and I have done nothing to it (the motor) and I mean nothing...not even carb tuning.

I will have to say it runs very strong and is dependable...and has much room to make it go faster...;)
 
#10 ·
I have installed 3 502's in cars, all of them have been awesome out of the box. The first thing we upgrade is the 850 vacuum secondary carb. We put a 850 HO from AED they wake up the engine big time. I wish GM would put a proper oil pan on them, most of the buyers are putting them in Chevelles, Camaro's, Nova;s etc.

Dave
 
#11 ·
I have been very happy with my 502. With a set of Performer RPM heads, Performer RPM manifold, Comp Cams 232/237 @ 050 (advertised duration 280/288), with .547 lift and a Holley 850, it has ran a best 1/8th mile at 7.54. Mine is a Gen V.. I have heard about them having low tension ring issues, but I have heard that the current 502's do not have the issue. I am in the process of upgrading mine with a Chris Straub cam and a set of the AFR 305's right now. I am looking to get about 650hp out of it. I am also going to have the heads milled to get a little more C/R out of it.
 
#12 ·
Outta the crate with factory timing specs and supplied 850 vs carb..it is a sheep in wolfs clothing.We have yet to swap out the weeny marine hydraulic roller and springs..but an 850 dp and 14* initial 36* total helped it for now.I think a baby big block 396 could swallow this cam all day long.I agree with the above.Strong rotating assy,decent heads(eddy rovals),but weak cam/spring combo.
 
#13 ·
Does anyone have any negative experiences first or secondhand, with the ZZ502? Excessive oil consumption, poor workmanship, etc? I am considering purchasing one and just want to do my homework. My plans are to add a Holley C950 EFI to it. Strictly street use. Thanks.
Yes, I have a negative for the ZZ502.
I bought one & although it runs extremely strong it uses excessive oil, real excessive like a quart every 200 miles! Another thing to consider is making sure whoever you buy it from will stand behind it. I bought mine from Scoggin Dickey in Lubbock Texas. That's "Scoggin Dickey" in Lubbock Texas & although it is still under warrantee I cannot get them interested in helping me with this oil problem. I called GM about it & they are more willing to help but act as the middle man which is basically no help if the seller is unwilling to assist. I see several comments from people with no issues but realize you can be un-lucky like I was. I won't buy another unless I pull the chrome moly rings out and replace with cast because that is where I think the problem is. The chrome are very hard to seat in properly.
 
#14 ·
Yes, I have a negative for the ZZ502.
I bought one & although it runs extremely strong it uses excessive oil, real excessive like a quart every 200 miles! Another thing to consider is making sure whoever you buy it from will stand behind it. I bought mine from Scoggin Dickey in Lubbock Texas. That's "Scoggin Dickey" in Lubbock Texas & although it is still under warrantee I cannot get them interested in helping me with this oil problem. I called GM about it & they are more willing to help but act as the middle man which is basically no help if the seller is unwilling to assist. I see several comments from people with no issues but realize you can be un-lucky like I was. I won't buy another unless I pull the chrome moly rings out and replace with cast because that is where I think the problem is. The chrome are very hard to seat in properly.
I think you would have even more reports of 502's buring oil, but alot of folks dont really put alot of miles on their cars per year, so they dont really know how much oil these things are burning.

The real issue IMO, is the bore distortion. The Gen6 454/ 502 tend to have pretty flimsy cylinders (at least compared to the bowties and even vintage blocks), and a plate hone is very necessary. The low-tension oil rings dont help. I had my 454 plate honed and re-rung after a couple of 1000 miles, as I was using about a qt. every 100 miles, and now I use about a qt every 1000miles, which I can deal with. Plugs still a little wet/sooty, but now where near as bad. My machinist only took .0005 out for the plate hone, which really is not enough to get it perfectly straight...needs more like .004, but I didnt want to buy pistons. Its a shame cause this thing really runs sweet.

So I cant recommend a crate motor to anybody after my own experience...not a BB GM crate motor anyway...unless they change the program.

PS - I was at my machine shop, and couldnt believe how much thicker a vintage MKIV blocks deck was compared to my 454's...seemed like twice as thick!
 
#15 ·
I'm surprised by the limited number of comments re the oil burning issues. This has been a well-known problem with these engines.

the ring grooves in the pistons are cut shallow for the low tension rings and won't accept normal rings.

Vince was that you that posted the pics of the cylinder walls and puddles of oil in the cylinders?
 
#16 ·
You mean this Tom....rings not even touching the cylinder by the bolts:

PS - this is what you get for 5000.00 from GM!



 
#29 ·
I have installed 5 of them now for friends..4 of them run great, the 5th had a cylinder that to my knowledge was never honed..the engine went to sh!t right after start up and WE HAD TO SUE for our monies back!! Good thing that dealer is now out of buisness....I read these post in shock..I thought I was the only one who had an issue with the 502..
 
#17 ·
I had the same thing with my 454HO.
About 15qts in the first 2500mi
rebuilt at 2600mi. (rings in up-side down--valley cover kept intake from sealing)

Plate hone, new rings, heads machined for better seals.
Has not used a drop of oil in the next 2500mi.
 
#19 ·
so it's essentially a crapshoot, you either get a good one or a bad one. Despite there being a warranty which is used as a selling point we have guys rebuilding the engines at their own expense. No?
 
#21 ·
Had my engine over a year before it was even started----warrantee gone.
Bought from Summit---came from Pace Chevrolet.
Neither Summit nor Pace had ANY interest in even trying to back this.
People at GM were weenies as well.
Claimed no one was having oil issues:sad:.

Tried discussing this with a local Chev dealer----and it became my contention that most GM employees and GM dealer employees are absolutely clueless twits.
 
#23 ·
i think you need to check with gm on mfg. date, most of the problems have been taken care of,i'm talking about a zz502, ring tension,valve seals,rocker studs,all taped holes in heads heil coiled, had mine for about 2 1/2 years, only about 2000 mi but they are hard ones,changed cam&carb only all stock valve train,3900# 67 chevelle th-400 3;42,2800 conv best et 11;64 116;50
L Evans
 
#24 ·
My machinist said that the bores were so flimsy (my new 502/509 project) that you can hear the honing stones were chattering when plate honing till it was rounded out.

GM warranty is waste...pretty much get referred back to who sold it to you, and who sold it to you says go to GM. Maybe I'm not vocal enough, but I thought a warranty means I dont have to be vocal???
 
#25 ·
Vince on offence because we didnt know about Mark Jones prior to you buying your GM 454 crate motor but with the problems you & Bryan had if i were in the market for a $5k bbc motor it would be s Mark Jones/Vortec pro on Ebay 475cid BBC 571hp/588lbs trq pump gas friendly BBC with a good idle vacuum for power brakes for $48.50.

It's pre tested on dyno to get perf #'s and also to breakin motor/cam /rings etc and check to eunsure all is ok and no leaks etc prior to customess getting it which is great,just install and your ready to go knowing there no issues with the motor.

Scott
 
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#26 ·
All this is why if i were in the market for a $5k bbc motor it would be s Mark Jones/Vortec
pro 571hp/588lbs trq pump gas friendly BBC with a good idle vacuum for power brakes for $48.50.


Scott

$48.50-----I'll take 10:D----got $500.00 burning a hole in my wallet right now:D
 
#27 ·
I hear ya Scott, but I bought this years before Mark showed up. I also purchased this with the understanding that if there was an issue, the local GM dealership would help.

Hindsight is 20/20. When you buy a motor that is "new", you expect to avoid this issues. I stick local now, easier to show up and talk to the builder rather than email/phone calls.
 
#28 ·
This what I have found with the zz502 engines. I have done 6 of them in the last 2 years. 4 were new out of the crate (don't ask me why a customer would buy a new engine and then take it apart!) and 2 were used.

The last engine I did was for R2B2 motors in Duluth Ga. It was a new engine that was never driven, but cranked up in the car for a short time, then it developed a knock. The #7 and 8 rods were never torqued down. Lucky for them the engine was not driven and the crank still looked new. The rods were even easily repaired as the bearing bearly spun.

The engines as a whole I am not impressed with the "fit and finish" The bearing clearances are usually all over the place. I checked 1 engine that had around .0015 on the first 4 mains and .004 on #5. The rods had around .0017. I personally like the low tension rings, but the cylinder finish leaves a lot to be desired. Not only is the bore finish wrong, but the cylinders are usually not round and true.

My recipe when I get these engines in the shop is to hone the cylinders for extra clearance in including plateau honing, deck the block, resize rods, balance assy, change cam, Crower roller rockers, 1 piece pushrods, cylinder head work including multi angle valve job and cut the heads (sometimes up to .080 depending on final compression ratio choice), and set spring pressure.

I have gotten over 600hp out of them with 10.6 compression. IMO they can be made into a great engine, but not worth the money out of the crate.
 
#30 ·
I've got one and nary an issue. It's been torn down and redone a bit with heads, cam, etc. so we'll see what happens after the re-fire.
 
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