Jseal52

i built a 4.8 with a set of 243 heads that were milled to increase cr and tsp can the stage 3 truck cam with high lift.
What kinda hp numbers could I see with this combo?
https://www.texas-speed.com/p-5072-t...-camshaft.aspx
cam specs

MrHorsepowerLSx

iTrader: (13)

How much were the heads milled?
Head gasket thickness?
Long tubes or manifolds?
Intake?
Trans?
RWD/4x4?
Injector size?

All those factors will help determine rwhp number

Jseal52

Drspencer

iTrader: (1)

Well...might get flamed for this...but if you don't have plans for forced induction, shoulda kept the 862s. I've been wrong before but when Super Chevy did their test and the 706/862 head made more power than the 243, my only thought was the 5.3 just isn't maintaining the velocity to validate the 2.00" valve. That could be the same with the 4.8.


But anyway, cutting 243s .030 may only yield a drop in 4cc (1cc per .007). What year is the stock truck intake? Those manifolds are holding you back. If we're taking shots in the dark, you're probably only doing somewhere around 320 at the crank.

Vortec350ss

iTrader: (20)

The 706/862 made more power due to higher compression. The 4.8 doesn't need the larger valves and better flowing heads, but in the right combination it will help. They will help your cam pull to higher RPM but you're going to have to spin it to see gains.

lowering compression however is tough to overcome. Having been decked they should be similar to stock, I think. Not positive.

As far as HP estimates I really have no idea.

Jseal52

Drspencer

iTrader: (1)

I do understand what you're saying, but in the article, it states


"The chamber volume on the 799 heads was within 2.5 cc’s of the 706 heads, but the dyno indicated this did not translate into power on our test engine. The peak numbers were certainly close (473 hp vs. 471 hp), but the graph tells the story best. The 706 heads were simply better than the 799 heads through most of the curve. "


Surprising HP Numbers From Our Stock LS Cylinder Head Test


This is all a little moot considering the goals. Turbo, ok got it, 243s should, again, in theory, perform better. It may be a little bit of a pig before you get that turbo on there, though....

Vortec350ss

iTrader: (20)

The 243's could benefit from a smaller cam. Their ability to flow more air would make a "smaller" cam perform better.

To be clear, I am not disagreeing with you.

I have 243's on a 4.8 that has a 2.9 whipple. I thought I would benefit from the larger heads with a motor that will be running 20psi and is spinning 7k.

MrHorsepowerLSx

iTrader: (13)

I’m saying 300/310(if you tune it aggressively)...... but that’s about all that pooch is going to make

A smaller cam would indeed help the motor not be such a dog down low. A bigger stall and 4:10+ gears would really help make the truck feel like a rocket ship

07NBSChevy

I agree with above. Milling the head .030 wont really had to much Hp by itself without porting. So that itself maybe added 5 rwhp and a nice little bump in lowend torque with good tune.

My shop recently built a Gen4 4.8 with the TSP 220R cam, Ported Heads, and milled to 59cc chambers, along with all the other goodies like headers and so on. It made 323 rwhp.
It lost a bunch of torque below 2800 rpm.
So being a slightly smaller cam and no porting, maybe 300 rwhp.

The 4.8 with High Compression Pistons and a Compression Ratio of 11.0 to 11.5:1 would make a nice difference.