HI! CAN SOMEBODY ADVISE ME IF IT PAYS TO SWAP STOCK CAST IRON INTAKE MANIFOLD ON MY 73 LS4 454 ON ALUMINUM ONE FROM 69 427 L-36. IS THERE ANYTHING I SHOULD KNOW ABOUT SUCH SWAP? CAN I USE HOLLEY 750 DOUBLE-PUMPER ON THAT MANIFOLD. CAN I ONLY USE THE ONE FROM 69 OR THERE ARE OTHER YEARS THAT WOULD BE COMPATIBLE? DO I HAVE TO MODIFY IT OR IT JUST BOLT ON?
THANK YOU. :smash: :chevy

 

Since I did this swap I'll jump on in. First off the swap is worth the weight loss by itself, you won't believe how heavy the stock LS-4 intake is. The 68-69 L-36 intake is made for a quadrajet and is the only aluminum big block intake that GM made for a quadrajet and a big block with oval ports. Ithink there are actualy 3 different castings for this intake, an early and late 68 and then a 69 casting, I have an early 68 myself. I found the L-36 intake a tad taler then the stock LS-4 intake but not by much and your cowl induction hardware will still clear, mine has a brand new seal and it clears fine. You may lose a tad low end grunt with this intake over the LS-4, but it makes it up in the midrange. The L-36 intake is also much easier to do some port work on since it's aluminum, I took some advantage of this. Don't expect a major power gain on this swap, but you will pick up some power and lose a ton of weight. Now for the modifications, these are realtively minoe little things. Your divorced choke will not work with this intake (unless the later castings were different), I got a divorced choke unit off of a 68 and made a rod for the choke, it works OK, but I just have full choke and none, needs some fine tuning but works good enough for a weekend toy. The other is the water pump bypass hose, for some reason the L-36 intake is shorter in front so you may need a bit longer bypass hose to get it to work. Now for the biggest pain of the swap which is the carb gaskets. The aluminum L-36 intake had an open heat crossover under the carb, so it requires a special 3 part gasket to work, not a big deal, you just have to plan ahead if you plan to pull the carb. Other then that it's a simple bolt on. If you need any more info, just ask :D

:cheers:
Pat Kunz

 

THANK YOU 73 LS4!

 

Oh yea, here's the casting numbers for you: 3947801, 3919849, and 3937793.

:cheers:
Pat Kunz