I have a 73 ls4/th400 coupe. When I purchased car...the only information that the seller could tell me was that her husband had parked the car behind the barn in the mid to late 1990's...He passed away a couple of years before I bought the car. 73,xxx miles.
The long story short is/was...at some point the heads were off the car and rebuilt. Nice thick bronze guides installed. However...I suspect the machinists math was off just a hair as there were 4 frozen intake valves. When I say frozen..I am not kidding. I pulled the springs off all valves...and all but 4 valves between the two heads were easily removed as were the 4 bent push rods. I hammered out one valve...screw it...the other three can stay there. As I did not feel I wanted to rebuild cast iron heads...I went with AFR's.
As this 454 is low compression with flat tops...I decided to purchase aftermarket aluminum heads. went with AFR 265's...yes, I am assuming the bottom end is ok at this point.
With the heads off I can bar over the crank. Cylinder walls look good or at least no gouges are scoring.
My question is related to the install of the AFR's. I can set the heads on the block...I can insert all of the ARP head bolts...minus the rear most on either side. One on the driver side will not clear the PB booster. One on the passenger side will not clear the heater box. Is there a trick I am missing on this install? Do I have to remove the brake booster on the driver side? What can I do on the passenger side? Do I have to pull the block, install heads and then stab it back in? Can I remove the engine mounts of the block, use my cherry picker to lift/pull the block forward a bit to slide the two head bolts in? What about pulling the engine mounts from the block and lowering the block in the chassis? Or pull then engine mounts and rotate the block slightly to either side to gain clearance? I have spent a lot of time trying to find somebody/anybody who might have been down this road before and could offer up some tips..surely I could not be the only fool to try to swap on aftermarket aluminum heads on a 454 while the block remains in the chassis...or maybe i am the only fool to try this...but any/all information, experiences would be greatly appreciated! As I said..my goal is to get it running and just be able to drive the car. Thanks in advance for any guidance or insight. Gus

 

I have a 71 with power brakes and this is what i did. after you get everything cleaned up and you are ready to install the heads get a rubber band or something similar and tie it around the head bolt (that is under the pb booster) about 1/2 to 2/3 up from the bottom of the threads then put sealer on the threads - i use the brown liguid permatex aviation form a gasket - i forgot the part # and drop it in the bolt hole before you lift the head on to the deck. the rubber band will keep the bolt from dropping all the way in the hole. when you set the head on the deck reach under the booster and remove the rubber band and the bolt will drop down and you can screw it in. this has worked for my original 820 heads and merlin oval port heads and on my current brodix race rite heads. on my 71 i had no issues with the pass side head.

Pat

 

I've used this same rubber band method on several different vehicles with similar head clearance issues (think 4.6l SOHC in a Thunderbird or Mustang). The bonus here is that you are going back with AFR heads, not the ultra heavy cast iron heads your LS4 came with. For a trial run, you could cover the deck surface with some poster board (to protect the heads and deck) and try the fitment dry before you install the head gasket and goop up the bolt. Once you know you can snake it all in there, install the head gasket, install the bolt, Permatex #2 or #3 Form-a-Gasket, rubber band up the bolts, and set the heads in place. I went with bolts on my big block instead studs just in case I ever needed to pull the heads in the car. Good luck and let us know how it goes.

 

Pat/Big Block: Thank you from the engine bay of my car...I was looking at things from the perspective of setting the heads on and dropping the bolts in...
I have never had this issue in the past as there has generally been plenty of room(other vehicles)...Thank you for changing my perspective and saving me a lot of time and grief...!

I love elegantly simple solutions to self inflicted complications.

Again, thank you.

gus