trev511T

Hey, I am going to be building a big CID engine using an aluminum 6.0 or 6.2 block and I'm going to be using it as a race engine. I just bought a pair of 243's from a member on here and I want to know what I should use for springs and rockers because I am hoping for a lot of hp. And yes, I will be porting the heads. I'm just trying to figure out the best route to go about this. Any help would be great, thank you.
Trev

lemons12

iTrader: (71)

Who is doing the porting?

1lejohn

iTrader: (9)

There are better head choices then the 243's. My choice would be the PAC springs 1518,1521 look them up on their site. Alot of people run the patriot golds.

Stock rebuilt rockers are fine as well as the stock GM LS6 valves. Ran the 243's for many years they developed small cracks on the intake throat ,and leaked water into the engine. I had them repaired and sold them.

The Ls3 heads or an aftermarket casting would be better then a 43 head.IMOP.

trev511T

I will be porting them in head class at SAM.

I have looked up some of the aluminum type rockers like the patriot golds and some others. is PAC the name of the company or does it stand for something?
I would go aftermarket on the heads, but I figured I could still get some flow out of these 243s by porting. Haven't heard of them cracking in the intake throat. That's interesting.
I'm still trying to decide whether to rebuild stock rockers, or go with some patriot golds.
Thanks for the help guys.

Tainted

iTrader: (9)

I'd go with LS3 ported heads, stock rockers with trunioin upgrade and double springs with a custom cam

1lejohn

iTrader: (9)

They will make some power. Yea it was the GM cnc heads that I had problems with. They were paper thin in some areas. PAC is the name. Put bearings in the stockers, its the way to go. We made in the 450hp range in our 383 with the 243's and a Fast 102.

87silverbullet

iTrader: (11)

^^^This is what I have done on my motor.

PRC LS3's, trunion upgrade, PRC double springs, EPS custon cam

trev511T

Where would I get some bearings for the stockers? I looked on PAC and when I tried to open the page with drag springs and ls springs, some of the pages wouldn't load with results?

I am now changing to iron block and going to bore .060 over, still undecided on efi, or carb. But I know I want at least 600 hp, (if that's possible).
Thanks!

SOMbitch

iTrader: (8)

Bearings for the rockers come in the truinion upgrade kits sold by many of the sponsors. Harland Sharp and Comp both make them.

Not enough info provided for anybody to help out with a spring choice but thinking just a good stout dual will more than likely work well.

trev511T

Ok, it sounds like I will be using the truinion upgrade.
I will be using aftermarket steel rods, and pistons (obviously).

Thanks!

1lejohn

iTrader: (9)

600 FWHP, or RWHP? Not going to make 600 RWHP with those heads, and its going to take big cubis inches to do it with aftermarket heads. 500+ RWHP is doable with those and other GM heads like the LS3's.

lemons12

iTrader: (71)

You could do it with a nice (expensive) stroked l92/ls3 setup.

1lejohn

iTrader: (9)

Show me one. I haven't seen any myself yet. BSE built a 434 and it made in the 7's on an engine dyno with $$$ parts. It was a year or 2 ago. Things may have changed. They were runner up in the Engine Masters Challenge with that build.

trev511T

I've been told by some people here at the school that it shouldn't be too hard to make 650+ hp with a nice big cam.
Also the situation changed and I'm just going to bore it .030 over and put a 4" stroke crank in it which will make it a 408 CID.
With those 243 heads I will have to put in bigger valves and port. Any idea on how big of valves you can put in 243's?

getonit

iTrader: (3)

Dude seriously its going to take more than that to make 650+. You will never reach that on the factory cast 243's. You are going to have to run some afr or trick flow heads or something. I wouldn't listen to your buddies at school.

1lejohn

iTrader: (9)

A 408 is going to be hard pressed to make 550 let alone 650. Its gonna take more cubes and LS7 heads if you stay with a GM castings. It might make 600.
Like I posted above a 434 with PI heads and intake ( now Mast) only made 713FWHP which say taking away 16-20% for a chassis dyno equals 599 to 571RWHP.

The 243's are a nice head if you have them already but 450 should be your goal. It's not worth doing alot of work to them like changing valve sizes etc. Porting them would be good if you can get it done cheap. Don't get me wrong I like running factory castings the 92's that I'm running now have 2500.00 in them. That includes the price of the bare castings , valves, seals , and porting. There are better heads out now for that kind of money. Good luck with what ever you build.

trev511T

I don't know how long I will use these heads. I'm getting ready to go back to the school to have someone flow them to see what cfm they flow.
I know a guy with a 377 CID back home that built a big cam engine that made 704 hp on the engine dyno. His heads flow 340 cfm.
Like I said, I'm going to port the heads and see what cfm I can get out of them. I will let you all know how much my heads flow later on.
I will keep you all updated too.

87silverbullet

iTrader: (11)

Everybody, just let him go. He is adamant and hard headed.

Katech did make 725 fwhp with ls6 heads on a 4xx cube motor but none of us here could ever reproduce what they did.