305 to 4.8 worth it?

[78shortandwide]

I think all he will need to change to get it to work with his tranny is the torque converter it wont bolt to the flex plate. but someone makes the correct one that will, not sure who tho.

 

[HotRodPC]

SOME 99 4.8 and 5.3's had a small engine noise. I cant remember for sure which cylinder it is but I am thinking it was #3 cylinder. The problem was from the manufacture the castings on the heads were undersized where the push tubes go and theres been some motors reported that the push tube will rub the head.

Not saying that is 100% for sure what your noise is but it is defintly something I would look in to.

The noise you are likley talking about, actually lasted into 2001 models as far as I know. It turned out to be the skirtless pistons was the reason for the noise. If its that noise, only at start up, then its perfectly normal. Although, I think GM did start going with small skirts on the pistons just to quiet the noise because of all the customer complaints and not being satisfied with the noise being normal and no harm being done. If the customer pushed the issue, some of them even got new motors. Now that #3 noise you're talking about is something I've not been aware of.

 

[HotRodPC]

Also, on another note, if you want bucket, the 4.8 and 5.3 are the exact same block. They are even marked 4.8/5.3. Only difference is the crank increasing the stroke to make the same bore a 5.3. If you want, while its out, you could put a new bottom end it, crank and bearings and its now a 5.3. I've been told, the 4.8 is only 1mpg better than the 5.3 in both city and hwy, but the torque difference is quite a bit even the hp is only 25 more. Just something to think about.

The rods, pistons and heads are supposed to be the same too but I never confirmed that myself. I never did understand how they could have the same heads and pistons and the compession ratio stay the same on both engines with a shorter or longer stroke. Hell, if the 4.8 uses a bigger volume piston or a smaller chamber head, then put that 5.3 crank in it and have a compression monster.

 

[89Suburban]

The noise you are likley talking about, actually lasted into 2001 models as far as I know. It turned out to be the skirtless pistons was the reason for the noise. If its that noise, only at start up, then its perfectly normal. Although, I think GM did start going with small skirts on the pistons just to quiet the noise because of all the customer complaints and not being satisfied with the noise being normal and no harm being done. If the customer pushed the issue, some of them even got new motors. Now that #3 noise you're talking about is something I've not been aware of.

I wonder if that's what's up with my brother's truck.

We thought it was a valve tap. It goes away after it warms up. He religiously changes the oil in it.

 

[Old77]

I wonder if that's what's up with my brother's truck.

We thought it was a valve tap. It goes away after it warms up. He religiously changes the oil in it.

This is what is commonly referred to piston slap and is definitely wide spread amongst the newer body style trucks/SUVs with the LS motors. Some are worse than others. There is a fix for the issue but I'll have to do some searching to find what it is but it's pretty simple if I remember right.

 

[HotRodPC]

Yep, the noise I'm reffering to is piston slap. That noise is only at start up and only lasts about 5 seconds. What it sounds like and what people think it is, is when you first start the motor there is no oil to the top end. You know how you truck might sound if you change the oil and don't fill the filter before you start it up. And it takes the couple seconds to get oil to the lifters and pump them up? Very similar to that kind of noise and only lasts seconds. But its harmless and the starvation of oil is not the problem.

 

[Old77]

Yep, the noise I'm reffering to is piston slap. That noise is only at start up and only lasts about 5 seconds. What it sounds like and what people think it is, is when you first start the motor there is no oil to the top end. You know how you truck might sound if you change the oil and don't fill the filter before you start it up. And it takes the couple seconds to get oil to the lifters and pump them up? Very similar to that kind of noise and only lasts seconds. But its harmless and the starvation of oil is not the problem.

yep....that be the one There's a small part (can't remember the name of it) that is available to fix the issue. I really need to find that write up now! Google....here I come......................

 

[89Suburban]

Sunuva bitch, that's exactly what we thought it was, starving for oil at the lifters. I am glad I learned this today.


How is there a simple fix for piston slap old?

 

[Old77]

Well, what I mean by simple is that it's one part that is needed to be installed. The install is fairly involved, though, if I remember right. Still searching for the thread I was thinking of.

 

[HotRodPC]

The noise is harmless if you can get used to it.

 

[crazy4offroad]

Mine has pistons slap, sounds a little like clutch chatter. Worst thing that can happen is break a piston skirt and scar up a cylinder.

 

[HotRodPC]

Mine has pistons slap, sounds a little like clutch chatter. Worst thing that can happen is break a piston skirt and scar up a cylinder.

In your case you're right C4, but the reason these 4.8/5.3 motors have piston slap even when new, is because they are skirtless pistons. This is done to keep the rotating assembly light as possible.

 

[foamypirate]

Yeah but the 6.0's are different than the 4.8's with regards to what tranny will bolt to it, right? Will a 700R4 bolt up to a 4.8?

Only the 99-01' 6.0's. You can bolt an old school transmission right up to those, because of the longer crank flange. Any 02'+ 6.0 will need the flywheel with the spacer to use an older style transmission. Any of the old school auto transmissions will bolt up to any LS block, it's just about having the right spacing for the flywheel.

 

[89Suburban]

 

[Beatdown Z]

Also, on another note, if you want bucket, the 4.8 and 5.3 are the exact same block. They are even marked 4.8/5.3. Only difference is the crank increasing the stroke to make the same bore a 5.3. If you want, while its out, you could put a new bottom end it, crank and bearings and its now a 5.3. I've been told, the 4.8 is only 1mpg better than the 5.3 in both city and hwy, but the torque difference is quite a bit even the hp is only 25 more. Just something to think about.

The rods, pistons and heads are supposed to be the same too but I never confirmed that myself. I never did understand how they could have the same heads and pistons and the compession ratio stay the same on both engines with a shorter or longer stroke. Hell, if the 4.8 uses a bigger volume piston or a smaller chamber head, then put that 5.3 crank in it and have a compression monster.

Crank AND rods are different. If the 4.8 used the same rods as the 5.3, then the piston would be far down in the hole. The 4.8 DOES have flat-top pistons though, compared to the dished pistons in the 5.3. Now besides the piston volume, they do have the same dimensions. So you could swap a 5.3 crank/rods into a 4.8 or swap 4.8 pistons into a 5.3 for a 10:1+ compression 5.3. Been done many times...

For the mating an LSx engine up to an older transmission situation, here's how it goes. If you have an iron-headed '99-00 6.0L, then you have a long crank snout and you can bolt up any old trans without issue. If you have an '01 up 6.0L or any other LSx(4.8, 5.3, LS1, etc) then to bolt up to a older trans you have a few options:

1) Run a factory LSx dished flexplate along with a crankshaft pilot extender.

2) Run a crankshaft spacer and flat flexplate combo from a '01 up 6.0L that was backed by a 4L80E.

3) Get a custom made torque converter for your trans with a LS1 style front cover.