GM ENGINES KNOCK

[Motorbike]

The LS1 and LS6 uses Nodular Iron cranks . A bit more stout than cast cranks .

No resizing the rods during a rebuild on these either , they are throw-away little units like the 4.6 .

The aftermarket has recently jumped in on the cracked rod technology

 

[MB289]

Hi all, new member here. I've been reading the board for about a year, but have not posted.

I have a 99 LS1 Camaro with about 52K miles. I'm currently running RL 10w-30. I just got a sample from the last change to send for UOA. The oil has a little better than 5K miles. The sample is my first use of RL. Before RL I used M1 10w-30 and M1 0w-40. I did an ARX treatment at the end of 0w-40 with a rinse of Penzoil 10w-30. I'll post the results when they come back.

My LS1 also has the "piston slap". However, when the vehicle is cold, in the winter below 40F, I believe I hear two different startup noises. The first is the diesel noise noted above. But, I also hear a deeper "slap" on acceleration that I believe is the piston slap. I don't hear the slap above 40F. Both noises go away totally when the vehicle reaches op temp. At op temp the motor is wisper quiet. BTW, the diesel clatter on cold start is audible during the summer for about 2-3 minutes. So I guess my LS1 can be added to the list.

The car only has a lid as far as mods go. The car is my daily driver and won't be modded until it is a "fun" car only. BTW, the car uses about 3/4 quart of oil over 5k miles, which I find acceptable. However, I should point out the car is not raced and is driven like any other street car.

Sorry this is getting long, but as far as the piston slap issue, I don't feel this is a durability problem. As someone who used to build/machine engines for a living I've seen a number of engines with piston slap, ie hi-po engines with forged pistons, that slap and on tear down looked fine. However, I do believe GM has a few design flaws in the LS1 that should be fixed. Like some said if I paid 50k for a new vette I would be very disappointed to hear piston slap like mine has. It's also interesting that most 98 LS1s don't have the piston slap or oil consumption issues. I've read that in 99 GM went to low tension rings and opened the clearances up, slightly, on the LS1s to gain a little more HP. This, in my opinion would account for the startup noises heard on 99 and later F-bodies. However, I have not been able to verify the above.

PS to Patman, why did you get rid of your 98 LS1?

 

[Patman]

I was dumb to get rid of my 98 Formula, it was a moment of weakness, due to a few factors. Part of the problem was that my wife got her licence so she took over my daily driver (a 2000 Civic) so I was faced with the need to drive my Formula in the winter, something I did not want to do (I didn't even drive the car in the rain more than about 200 miles worth of the 27,000 miles I drove the car), and had nowhere to store it, and no money for a winter car anyways. Plus I was also getting sick of the 6 speed, as I was tired of misshifts at the dragstrip, one of which cost me $2200 when I busted up my rear end.

Another factor was that I was working midnight shift, in a section of downtown Toronto that I didn't feel comfortable leaving my car. And my wife was pregnant and couldn't drive standard, so I needed to have a car with an automatic at home for her (just in case) while I was at work.

So I ended up trading it for a 97 Grand Prix GTP. Then less than a year later I traded that for my 95 Formula. I drive this car in the winter, so in hindsight I should've just kept my 98, drove it in the winter and converted it to automatic. I could've done that for labor costs only too, because at the time there was a guy in my car club with a 98SS who wanted to convert it from auto to 6 speed. So we could've swapped parts between our two cars.

Getting rid of that car is something that bothers me so much (I think about it constantly), even though I do plan on getting a C5 in about 2-3 years. The problem now is that my 95 Formula is only worth about $8000 CDN, but had I kept my 98, it would've been easily worth $15,000. So I could've gotten my C5 sooner due to that fact too.

 

[MB289]

Thanks for the reply Patman. I did something similar. Before the LS1 I had a 96 Caprice with the LT1, which I think is a better engine than the LS1, that I sold. I miss the size and power of the car, but with 131k miles I thought it time to sell.

BTW, GM is not the only vehicles with piston slap. Couple of weeks ago I was driving an 04 Crown Vic at work and it had audible piston slap until it warmed up.

One more thing on the oil consumption problem with LS1s. I believe a significant amount of oil is sucked through the PCV system. I have 2 oil catch cans on mine and I empty about 1/3 qt between OCIs. Even with 2 catch cans, some oil gets into the intake. About 3 times a year I have to clean the throttle body and plate. It's usually gunked heavily with oil and crud. If your LS1 is idling rough, clean the intake. It always solves my idle problems. At least I don't have any noticable pinging like some.

 

[JohnBrowning]

I have seen to many broken sintered metal rods to belive that they are stronger then forged rods!
I remember when all of the Home improvment shows like "This Old House" were touting engineered lumber i.e. joices and struss's as stronger then dimenional lumber buit pieces. Seems that alot of these products had problems with saging. Seems like the few tests that showed them to be stronger then diemensional lumber did not show the entire picture.

I also have plenty of experince with sintered metal gun parts that wear out much faster then their forged counter parts.

I have fractured cap rods on my little Toyota and mine are forged. The problem with fractured caps is that they are not machineable latter on.

I would be willing to go along with sintered metal parts being close to or equal to the rigidity of forged parts but the cost is now cheaper then forged. Sintered parts lack the toughness. I was under the impression that weight saveing and material working costs were the driveing factor for sintered metal parts.

Now if you wanted a really tricked out laminated rod with different alloys layered in a specific order that would not be weldable or castable due to differing working temps then the new powdermetal equipment is definately the way to go. I belive that this is how they safely make berelium rods and such for F1 engines? This is about the only way I could see powdered metal or sintered parts being stronger then forged.

No matter how you slice it the LS1 and LS6 are made with inferior materials and manufactureing tecnology. The T5 Aluminum is not the hot ticket and niether is a cast crank and powdered metal rods. Even in the 60's and 70's they knew forged steel crank with nitride coating and forged steel rods were the way to go. High Nickle,silicone and titanium content hollow sodium filled valve, forged pistons etc.... Remember that the LS6 and LS1 are supposed to be flagship engines! Likewise the Northstar is supposed to be a Flagship engine. When you look at the price of the vechiles these engines are being placed into they are not that impressive. Piston slapping, oil consumeing,gasket leaking, distributor failing noisey engines do not impress me at this price level.

Now if these engines were placed in $17,000 cars I would probably over look all of their short comeings without question and smile every time I pushed the gas pedal to the floor!

 

[MB289]

Hi JohnBrowning, I agree that GM has some flaws in their LS1s as I stated earlier. However, the problems I've had with my LS1, ie noise, is only a nusiance. The engine runs great and is the fastest stock engine I,ve owned. I plan on driving mine to 200k. Since I only paid 14k for my Z28 with 34k miles, I'm happy.

Also, lets not forget GM is not the only manufacture that has had cold startup noises or piston slap. Ford has had a huge problem with piston slap. I've driven many new 04 crown vics with the 4.6L engine and all have startup noise and some piston slap until warm. As for oil consumption problems, many other vehicles as stated on this board, use oil. My LS1 at 5 to 6k per quart is OK.

BTW, I'm not familiar with any ignition problems (no distributors on LS1s) with LS1s. LT1s did have problems with their early optispark ignition, however, when I sold my LT1 Caprice it was working fine at 131K.