dobbs187

Has anyone ever done this if so what was the results looking to build this motor out of leftovers from building a cast iron l33 i have all leftover parts to use 5.3 pistons in the 4.8. Would this make a good turbo motor?

KCS

iTrader: (20)

I don't see why it wouldn't work. Whats the point in swapping them?

steves86ta

iTrader: (5)

to my knowledge, most 4.8's are flat top and most 5.3's are dished

atleast my 5.3 is

so it owuld essentially lower the compression.

dobbs187

The point is it would be an extra motor built out of spare parts that would also be turbo charged so the lower compression wouldn't hurt I wouldn't think but that's just my thoughts looking for reasons why this won't work and if anybody has ever done this what the outcome was

MuhThugga

The pistons are interchangeable since the rod lengths maintain the factory compression height with the different stroke cranks.

Just remember that you lose compression with the shorter stroke, so if your 5.3 pistons are dished, you are going to have even less compression than a comparable LM7. Out of boost, the engine will be a dog.

68Poncho

iTrader: (1)

Using the 5.3 piston would be a great way to get the motor Turbo ready. The smaller stroke of the 4.8 will also compliment the turbo idea. Remember the rod length for the 4.8 is longer than the 5.3 so you will need to verify PTV if you use the either rod. You would then just need to decide on what heads to use. The 317 will have a lower compression than a 243/799, but there are places out there that has all the specs for all the different heads. If it were my motor I would want larger chambers and larger runners to promote lower compression and better flow numbers.

KCS

iTrader: (20)

Have you calculated the compression ratio yet? With 4.8L dished pistons and a 317 is stupid low.

dobbs187

I was planning on 862 heads and ls9 gaskets the pistons come out of the block 0.011 the gaskets ive read torque to 0.051 so 0.040 clerence my cam is 560 lift

MuhThugga

That would be .040" quench. The quench doesn't guarantee piston-to-valve clearance.

Mercier

iTrader: (15)

We've discussed this quite a few times but I think we come down to balancing throwing the budget off. Last time we were talking 5.7 pistons and rods in a bored 5.3. Would we run into the same issues here? That is, it'll fit but unless you invest in proper balancing at a machine shop, it would rattle your teeth out?

truckdoug

iTrader: (25)

haha i just recently put a motor together with gen 4 4.8 slugs, gen 4 5.3 rods and a gen 3 5.3 crank. right after we were talking about and iron 5.7 i decided to try an iron L33

the floater 4.8 slugs were 425-430g compared to the 415-440g 5.3 press-fit slugs

i did not weight the rods or the wrist pins.

i'm guessing it'll rattle like crazy. or maybe not?

Mercier

iTrader: (15)

Well Doug, I'm about to change out the fluid-filled engine mounts in the V..maybe those will insulate you from the vibes a bit? Only 100K. Sell them to you CHEAP! ;-)

stinaores

The smaller stroke of the 4.8 will also compliment the turbo idea

JoeNova

Nobody ever mentioned using anything other than the pistons from the 4.8..

Mercier

iTrader: (15)

The short stroke of the 4.8 crank is what is referred to I believe. Turbo is a little out of my wheelhouse(but have my project 4.8 ready when my wallet is ready) but I believe the (longer?) piston dwell time is what makes the 4.8 so good for boost. Hot Rod mag did a project with a 5.3 that was stock bottom end, even had some rust in a cylinder. Made something like 1100 horsepower without it blowing up and THEN discovered it was actually a 4.8 all along! After reading that I hit Craigslist for a 4.8 the next day. You know, because I'm stupid and don't have enough junk in my garage already. ;-)

JoeNova

I know what he is talking about, I think it sidetracked me a little when talking about trying to lower the compression with 5.3 pistons to suddenly talking about the stroke of the 4.8.