Found Pontiac GTO 2006 243 heads nearby my home, will they fit my gm 5.3 engine?

The 5.3 block is just back from cleaning/honing, the engine is being used for a engine swap in a Chevelle.

Thanks
Jim

 

Yes they should 799 heads come off of 5.3L and 799 and 243s are the same

 

Id get them milled a little bit to bump the compression up. But other than that they go right on.

 

Thanks!
The heads was sold, so I will search for 243 or 799 heads, ls6 intake.

 

Some 5.3 engines, like the LH6, came with the 243 heads.
The intake runner is designed for the 6.0 LS2 engine however.
I think there's a reason TEA starts with 706 heads for the 5.3 engine.

 

All 243 heads are all the same aside from the Z06 243 heads that came with the lightweight hollow stem valves and valve springs the ls6 where blue and the ls2 had an orange stripe down them that being the only difference. Even the front wheel drive LS4 had 243 heads that are the exact same head. TEA uses the 706 heads to start because they are great at bumping compression up.

 

In my opinion the 706 doesn't bump the compression for a 5.3, but the 243's lowered it. Next to that, with the increased intake runner volume, the air velocity went down.

I know the 243's flow better in stock form, but I think the 706 has more potential for a 5.3, starting with the smaller chamber and intake runner,

 

799 heads and 243 heads are identical castings, just different factories where they were produced. I recently purchased a set of 799 heads with Manley Pro-Flo Valves from another member. 799s can sometimes be found in junkyards as well and make them a great score. Very similar flow numbers to 317 heads (Stock LQ4/LQ9 Heads) with a much smaller chamber size. Compression gains will be very rewarding, plus great flow. My 799s were milled between .020" and .030" to provide a 60cc chamber.

 

Back in the day when only Z06s had 243s and were thus expensive, the 5.3 heads had an exhaust port which flowed better than the LS1 casting and a smaller to bump up the compression.