My brother pulled the 4.8 out of his 99 RCSB and installed a 6.0 and t56. I am going to get his 4.8 and 4L60E to put in my 72 2wd blazer. I want to put a 5.3 crank in the motor but will I need to change rods or use the 4.8 rods. A 4.8 has flat tops pistons, right? I have 3:73's and I am running a 295/40/20 on the back, I want to run a large cam with a real noticeable idle since this is a show ride and not a DD. How much stall would I need? Which heads would be a good choice (ls1,LS6,Etc)? I will also be putting a ls6 intake on the motor, headers, and a mail order tune. I know you are going to say put a 6.0 in it but the money is tight and the 4.8 and trans is dirt cheap, plus the trans only has about 20K on it. Thanks in advance.

 

From what i understand, the rods are the same, and yes the pistons are flat top. It will be a direct swap to put the 5.3 crank in. at that point you'll have a lil more compression so power will of course be better than a stock 5.3 . As for cam the tR220 tends to be the biggest power maker, and it lopes a ton. 3000 stall is the unit of choice for cammed 5.3's. Heads will make power, but stick with your stock 5.3 units, have 'em shaved ported and polished. too big of a valve has shrouding issues on a 5.3 because of the small bore. the ls1/ls6 etc. heads have big combustion chambers so compression will become an issue without a ton of shaving..

that combo is a proven, reliable, easy setup

 

Do you mean stick with my 4.8 heads? I think this combo would perform pretty well since the blazer weighs a lot less than a truck. I am not going to the drag strip with it but I want something that will smoke some tires. Thanks for the info.
Thanks, Kade

 

4.8/5.3 heads are exactly the same casting. just have 'em ported/polished/shaved if you want those extra ponies

 

btw.... you'll have no issues with tires. by the time you do all that, your issue will be traction.

 

the 4.8 and the 5.3 have diffrent rods.
to use the 5.3 crank in the 4.8 block
you will need rods from a 5.3, 5.7, or a 6.0.

now if it was me, and going to all of this trouble
to make a 4.8 in to a 5.3, i would go a head and
pick up a stock set of 5.7 ls1 pistons and build an iron block ls1.

 

So get a 5.3 crank and rods from a 5.3,5.7, or a 6.0 and have it bored to a ls1 bore and use stock ls1 pistons? Still use the 4.8 heads? Whould this make good numbers with the mods I listed?
Thanks

 

yes, the 4.8/5.3 heads will up compression.
the 4.8 block at 293 cubic inch, will be up to 346 cubic inch.
along with your cam should be making some very nice numbers
at the rear wheels.

 

Turn that 4.8 into an iron 5.7 with a lumpy cam and it will run quite well...

 

are you positive on that? from past research i'd like to say you're wrong. But, if you're not, i'd like some info to back it please. My buddy is actually getting ready to do this right now. I'd like to help save him from making a mistake.