Unexpected rebuild
 

99 Z28, M6, 853 heads, long tubes, lid and filter, unknown tune, stock cam, underdrive pulley, stock 10 bolt and gearing

Unknown mileage as speedo was unhooked when I bought car last year. Previous owner said it’s around 170k. Various leaks and internal wear are in line with that. Developed very noticeable squawk puttsing around town. Ruled out accessory drive so figured it was lifter. Upon tear down found 1 lifter tray cracked and allowed 1 lifter to rotate sideways. Just ruined the roller on the lifter and corresponding lobe on cam. Cam journals and bearings don’t show any signs any trash went thru the oil (engine ran maybe 15 mins total trying to track down noise). I haven’t had a chance to remove main or rod caps to look at those. When parked engine had excellent oil pressure so hoping bearings are all clean.

Future plans have been accelerated, didn’t plan on rebuilding for a couple years. Being realistic with myself I am shooting for 400hp at crank, to wheels would be bonus. Daily driver when weather is nice, can’t say I wouldn’t go to the drag strip a couple times of year, but street would be 90% of use.

I am confident i could open up the heads w hand porting. Just can’t decide on opening up the 853s or if I should brave the cold and rip some 5.3 heads out of a truck and open those up. Drawback there is machining for 2” intake valve. Looking at cams but I think I should know which heads I am going to run (to know compression) before I pick one. With cam, better flowing heads, and the long tubes I think it makes sense to look into a used LS6 intake manifold as well. After work is complete would take it to a good tuner.
Just looking for some advice on head selection so I can move on with putting it back together.

Thanks

Stock 243 heads
tsp 228r cam
Ls6 intake
Speed eng 13/4 headers
Tune
400 rwhp

Sounds simple enough to me. Can stock injectors handle 400 or would I be on borrowed time with those? From what I can see in the intake runners on the head they were all spraying well/evenly.

I know the 853 heads are frowned upon. I know the 243 are a better casting and people love them. What in particular lends them to flow so much better? Runner cc or shape? Finish? I wouldn’t mind sitting down and doing my best for 25-30 hours working with the 853s. The only ‘good’ thing I can say about these in particular is they don’t have the pry location cast in to them. I guess I’m just wondering what area of the 853 would need the most attention to get it to flow equal to or even a little greater than a STOCK 243.

Dont mean to come across as cheap. I enjoy taking things I already have and making them better. I have no problem spending the $ where necessary.

thanks for the quick response!

The best porting on heads nowadays is done CNC, as it is repeatable forever. Hardly anyone hand ports anymore.

No reason to hand port 5.3 heads . Just wasting your time imo .

katech charges 500 for a Cnc port work. But then again a stok 243 flows more and can get them for $300 all day.

Go check my built thread out m I'm running 5.3 heads . A baby cam and an og fast .

We maxed the injectors and stock fuel pump out at 5000 rpm . Lol it has alot of Information you might need/want to read .

Its Mavns summit cam build thread.

99-00 fbody LS1's have 26# injectors. New ~ 450 whp was possible with the stock system. Injectors were static and spraying with intake valve closed.

My 99 TA made 418 whp and ran that way for 15 years & 130,000+ mile. ​​​​​However the stock fuel system definitely wasn't able to support that in the later years. The car "woke up" with a new Racetronix fuel system probably because the old stock fuel pump couldn't maintain the pressure at higher rpm.

I wouldn't trust a 99-00 LS1 stock fuel system in a 20 year old car to be able to support a good heads and cam package. New better fuel pump, filter and bigger injectors will help make sure the car makes good hp & keeps making good hp in the years ahead.

As Mavn said I skip the hand ported heads. You'll really have no idea what you've got unless all 8 ports are flow tested. There are a lot of good CNC probably and a few exceptional ones. You might get lucky and find a good set of ported used 5.3's with 2 inch or better valves or used ported243's on the classified section. Some 5.3's were prone to crack so be careful with getting a used 5.3 heads either ported or unported.

Looking forward to you'd build.

228R cam from TSP is your best bet.

You can mill your 243's .030 and still run that cam and have PLENTY of clearance.

I like the 228/232 split better. Or a Cam Motion Titan 2. Split cams tend to carry power a bit higher. Pick your poison.

Whichever combo you pick,, it has to be tested by hand on the block, once you change cams.
Don't need the crank in, but you put the cam and valve train & heads in/on,, and check the valve sweep on every single one.

Some will say not necessary but I've been burned twice with "stock" heads with different pocket heights,, and not just a little off..

Example I did my 4 cylinder jeep head, had to cut 6 of the 8 spring pockets for a Clay Smith .560(IIRC) lift cam. YMMV..

I love my summit cam I put in my trans am in my build thread . I'm liking it more and more every day!

Maybe it should be more for what you want than a bigger cam .

Just my $.02

Our high lift asa and milled (.030) unported 243s made 430/420 on a 99 m6 ta.

We also carry all of the rebuild/rering/reseal parts for the best price out there. Mix and match.

Our high lift asa cam and pac beehive springs are also on sale for $499 as well.

Great price, one stop shop, and everything you need. It has a 110 lsa so it has a very aggressive idle but will also peak a little sooner and give you much more useable power! Seems like exactly what you want.

Look for 799's as they are identical to 243's and are in most pickups with a Gen IV 5.3.