CAN YOU RUN REC-PORT LS3-STYLE HEADS ON A SMALL BORE 4.8L/5.3L? WILL REC-PORT HEADS EVEN FIT A 4.8L?

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Published 2023-09-21

CAN I RUN FACTORY REC-PORT HEADS ON A SMALL BORE 4.8L/5.3L? CAN I REPLACE THE 706/862 HEADS ON MY 4.8L/5.3L WITH LY6/LS3 HEADS? WILL MY 4.8L/5.3L MAKE MORE POWER WITH HIGH-FLOW, FACTORY REC-PORT HEADS? HOW MUCH POWER ARE REC PORT HEADS WORTH ON A 4.8L/5.3L? WILL THE REC PORT HEADS EVEN FIT ON THE SMALL-BORE MOTORS? CAN YOU NOTCH THE BLOCK TO MAKE THE REC-PORT HEADS FIT? CHECK OUT THIS VIDEO WHERE I DIVE INTO THE INSTALLATION OF A SET OF FACTORY L92 821 HEADS ON A SMALL BORE 4.8L/5.3L? USING THE SECTIONED ALUMINUM BLOCK FOR VISIBILITY, WE CAN CLEARLY SEE THE INTERFERENCE BETWEEN THE BIG-VALVE 821 HEADS AND THE SMALL BORE 5.3L CYLINDERS. CAN WE MAKE THEM WORK?

All Comments (21)

@DillonAuto 9 months ago

It's good to know others will still experiment, trial and error with things that are important. Like going fast in a car.
@Obshowersyndicate 9 months ago

Nothing a grinder can't handle
@GrandPitoVic 9 months ago

Wow you Def answered a question I've had on my mind for the past few years since I've been watching you. Thank you sir. More great information sir.
@loundclear9279 9 months ago

Pro maxx extreme 240 heads a rec port and for 3.800 bore That would be interesting as well. But yeah a 5.3 with a 300 plus cfm head na will be spun to the moon but will be mean on boost
@Airman.. 9 months ago

the LS Guru
@davidreed6070 9 months ago

Pro max has a rec port head that they have put a smaller valve and moved it over to work on the small bore engines. That should work well
@kimmorrison9169 9 months ago

I Wondered about this swap, Now I know. TY for showin us!
@mariotillery8459 1 month ago

Just like the 348/409 Blocks and heads swaps.
@Turbogto_guy 9 months ago

Now this was a damn good video.
@steveyoutube1709 9 months ago

Not being an ls guy EXCELLENT video
@dreece2000 2 months ago

Your my hero Richard
@Sir.VicsMasher 9 months ago

Edelbrock makes bolt on LS3 style rectangle port head for small bore LS #61319.
@bobjensen7136 8 months ago

Thanks for your demonstration. Sounds like the same problem that Chevrolet had that similar problem with the 348 and 409. Also the possibility of hot spots in the cylinders at the point of the head gaskets and a little way down the cylinder wall. In other words it would really complicate those arias nearest the valve and the cylinder walls too.
@yepyep340 9 months ago

Well HOW COOL WAS THAT! TY
@stellingbanjodude 9 months ago

A set of custom pistons could resolve some of your problems, domed pistons to bring back compression, then move the rings a little further down the piston to allow for adequate clearancing for the valve pocket. Bada bing bada boom
@peted5217 9 months ago

I solved this by trading for a 6.2 block. I used LT pistons, milled to fit chamber, and give slight compression boost. PVC MUST be ck'ed. Very tight !
@Nafskie 2 months ago

I am runnin ls7 heads on my stroked ls3, the exh valve was the main issue and we machined it to give 0.030” valve to cyl wall clearance.
@billybadass411thefirst9 9 months ago

You so are awesome!
@paulriceman3669 7 months ago

Awesome video. Would really like to see a small bore ls3 head test. I’ve got a 383 stroker in my 4th gen f body. Trying not to run a spacer plate for the LSA and pickup some power too na before hand.
@youritake8618 9 months ago

This would make for an interesting build if combined with that big bore 4.8 idea