I'm intrigued by the though of piecing together a 328" L motor. In another post, BigTex mentions using a 6.0 block with a 4.8 crank to get a short stroke free revving 328 (101.6mm x 83mm B/S) with a B/S ratio that of the original 327 (a great motor). Where can I find info such as deck heights for the 4.8/5.3 and the 6.0 blocks (are they the same)? On the surface, it appears that a 4.8 crank and rods coupled to 6.0 pistons in a 6.0 block will work, but good solid specs should answer that. Another ingredient, would be to know the trapped volume of the different motors to determine cylinder head CR configurations. Of course custom pistons are a viable option, but I was wondering if it could be done with factory parts. Would the bob weight difference (assuming there is one) of the 6.0 pistons have much affect on balancing requirements?
Andy

 

The deck height is the same for all LS1 based engines at 9.24". This includes the 4.8, 5.3, 5.7, and 6.0L. Stock pistons are outta the block anywhere from .006" and I've heard as high as .012-5" The most common number used is .007-.008" above the block though.

I would imagine that hanging a considerably bigger diameter piston on those rods/crank would throw the balance off enough to need a little metal added to the crank. I don't know any of the weights though so really no help there. It would probably be best if you did this setup to take it to a machine shop and get it checked.

One other thing I'm not sure of is if the pin heights are the same for the 6.0L pistons and 4.8L pistons. I can't see any reason why they wouldn't be though which would make putting the 6.0L pistons on the 4.8L rods/crank fine.

Let me see if I can get an engine builder in here to help ya out.

Here is a good calculator for figuring out CR.

http://www.smokemup.com/auto_math/compression_ratio.php

 

the stock 5.3 is 325 ci...what's wrong with that?

 

The 4.8 uses a 6.2+ inch rod while the 6.0 uses a 6.098 rod ( i think). Not sure if the difference in stroke exactly offsets the sifference in rod length. If not, then the pin height will be different between 4.8 and 6.0 pistons. I'd suggest just getting a custom lightweight 4" piston and strong rod. Then you could spin the heck out of that baby.

 

Tex - You know the exact length of the 4.8L rod? The pin height is easy to figure out with that, the stroke length, and deck height.

Zapata - A 328 like above is better for several reasons. It has a longer rod than a stock 5.3L which creates less friction/side loading and it also has the bigger bore so bigger valves/better heads can be used. The short stroke would also lend itself to some high rpms. The engine above is not destined for a heavy truck but, a lightwieght car.

 

Insightful answers, so far. It would be nice if the technical info was available, i.e. pin heights as BigTex mentions, trapped volume or perhaps -/+ volume displacement, and piston to deck specs. Does a 6.0 use a dished piston like the 5.3?

I know these motors don't have a long history of gained knowlege and development like say the SBC, but I suspect this info is out there. As XLR8NSS mentions, these questions probably best aimed at a performance truck engine builders.

I realize it may be asking a lot to stick 6.0 pistons on a 4.8 rotating assembly and expect it to be all nicely balanced, so someone compelled to try this out should end up at the balancing shop to make sure. If the rod and crank on a 5.3 is the same as on a 6.0, then it would seem that the piston of the 6.0 should be the same weight as the smaller diameter 5.3 so as not to mis-match the crank throw weights. Pure speculation, but that's the logic....Did I miss anything?

The 4.8 has a very favorable rod ratio (about 1.8, from memory), as compared to that of the 5.3. This puts it into the performance engine catagory very nicely. Too bad the cranks aren't forged to boot! Keep the good info flowing!!

Andy

 

Its a 6.278" rod on the 4.8. Thats a 4.572 mm longer rod. Take the 4.8L 83mm stroke from the 92mm 6.0 stroke to get 9mm then divide by 2 to get 4.5 mm. Thats only a .072mm difference, or .0028". Looks like the same pin location.

You will need it rebalanced. I'm sure there is a good difference in piston weight. Just buy the parts, take some measurements and you'll know the answer (then you can tell us the real answer).

Displacement is neat identical to the 5.3, so with 4.8 heads (61cc chambers) you'd be in under 9.5:1 CR. The 6L pistons have a bit larger dish than the 5.3 pistons, and your gasket area is a bit larger. I'm guessing 9.25:1 using stock gaskets.

 

Sounds perfect for a high revving FI LSx engine

 

Yeah, pin height works out to within .004" between the two setups.

4.8L pin height

9.24" - 6.278" - 1.635 = 1.327"

6.0L pin height

9.24" - 6.098" - 1.811" = 1.331"

These assume a zero deck height for the piston but, that is not really important. Most LS1's are around .007-.008" outta the hole.

Compression ratio using stock gaskets and 4.8L heads.

61cc chamber
4.08" gasket bore
.054" gasket thickness
-8 or 9 cc dish
4" bore
3.27" stroke

The cr for that setup comes out to 9.5:1 almost exactly. Perfect for absolutely reliable operation in any condition on pump gas.

OH!!! and rod to stroke ratio on that is 1.92:1

 

i see...thanks XLR, i was just wondering what the differences would be.