Hey guys lookin for advice.

So I picked up a complete LR4 4.8 with 65,000 miles on it from a wrecking yard. I'm gonna be putting it in my 1973 Chevy Nova with a T56 behind it. Goals are to have a nice streetable motor that revs. Goals are roughly 400 HP, 375 Tq, 6500-7200 RPM redline, and 25 MPG on the highway. Getting fairly close is good enough.

I have a complete LS1 from a 2002 Z28 donor car, but the block is shot.

I plan on:

* new bigger Cam
* Valve spring upgrade
* New lifters
* LS2 lifter trays
* HD pushrods
* new gaskets
* head bolts
* Holley 302-2 oil pan
* High pressure oil pump
* New Timing set
* Swapping on the LS6 intake, TB
* Long tube headers
* HP tuners tune

So my questions:

Heads

Should I use the 241's or 862's? The 241's would need to be freshened up as they have seen 125,000 hard miles from the PO.

1. So I can have them decked a little, but does that screw with the Intake sealing or pushrod length?

2. For my power goals is it worth the effort over the 862's?

3. Would a mild home port and polish make much difference/worth the effort? I'm not talking real agressive, just smoothing out of transitions and removing the extra flash.

Rockers

4. With my goals in mind should I upgrade the trunions?

Internal

I don't plan on taking the short block apart, but,

5. Should I upgrade the rod bolts?


6. Is any of the above overkill for what my goals are?

Any and all info/feedback is appreciated including brand recommendations for parts.

Thanks

 

Anybody? Lol

 

In my Sierra, through an a4, I made 302/288 with TSP220r, long tube headers, and a great tune through Synergy. I think switching to the 241s will drop compression, so I would stick with your stock heads, milled, and ported. My 220r is great cam, and very drive able. 400 may be a far reach for a 4.8 IMO. A more realistic goal I would say would be 350/325.

 

Was that to the wheels?

 

A mild clean up of the 862's will need you a solid gain. You can get upwards of 40 cfm by just cleaning up the bowls.

A larger intake valve will help you make more peak power as well.

If you're not messing with the bottom end, then leave it alone. They run best untouched.

 

Are you saying don't cam it?

 

Im saying don't put rod bolts in it.

 

Are the 4.8's subject to stretching like the LS1?

 

Yes that was to the wheels, truck is 2wd.

 

Less so because stress on rods is exponential based on RPM (and stroke right?) but you have a shorter stroke with 4.8.

Lots say not to install rod bolts without real machine work and that is probably the right way to go. There is a lot of discussion out there about that subject though. Seems like a high-probability lottery ticket. You do lose sometimes. But a high enough go rating that it's fun to drive fast on the odds.

 

Of all the things to start with and you start with the least displacement. I think your off to a great start, but to meet your goals I would port the 862 heads and throw the 2" valves in the head. Milling the heads will change your pushrod length. Don't go crazy on the cam especially in a truck. If you want to meet your goals throw a turbo on this sled and have some real fun.

 

Got it. My goals are to the flywheel.

 

Got it thanks for the info!

 

This is going in a car, a Nova. As far as the small displacement goes, I liked the symmetry of it, my Nova came as a 307. Also being a 73, it's the unloved year that everyone butchers to make look like 68-72. And the 4.8 is the unloved LS.

So I figured I'd take the unloved LS, stick it in the unloved Nova and make it cool.

A turbo down the line is a possibility for sure.

 

Ohh your there then!

 

This one went over 900 RWHP before the rod went out the side of the block...

Factory rod bolts won't be an issue...

BTW he towed a boat with that thing regularly too...

http://www.performancetrucks.net/for...q-4-8l-514949/

 

Awesome! I like the idea of not messing with it.

Do you guys think it's worth changing the timing set and oil pump?

 

Subscribed.

Sounds like this will be an interesting build. Hoping you share your build process here.

 

Changing the timing set will depend on the valve springs you use. The springs are where 99% of the force comes from in your valvetrain. Adding 1mm to the lobe of the camshaft doesn't beat anything to death. The force of the springs does. If you went with a small cam and springs like the PAC1218s, you could use stock pushrods, timing chain and gears. Dual springs and you'll need stronger pushrods, and an upgraded chain.

A 4.8 with even a mild cam will pull to 7000 RPMs. They LOVE to rev. Their long rods and short stroke also make them the strongest LS shortblock out there. The 4th generation 4.8s have beefier rods and a better piston design, and should withstand any beating you can toss at them.

I wouldn't touch the shortblock other than a cam. JEGS sells a 228/230 cam with just enough lift that you can use the PAC springs and not have to upgrade the valvetrain.

I've seen this cam make 440whp in a well built 5.4. You could break 400whp with this cam in a 4.8 with the right mods, or you could hit your 400 flywheel goal without trying too hard (headers, intake, good tune).

 

The valve springs determine the need for pushrods and/or timing chain. Less open pressure means less stress on the rest of the valve train.

Don't over think it too much. A 4.8 with a mild cam/valve springs, headers, ls6 intake, and a tune will make 400 flywheel on whatever heads you can scrape together.

I would personally go with PAC1218 springs, TSP 224R cam, long tubes, Edelbrock Pro Flo, and a good tune. You'll make ~450 flywheel and it'll rev to the moon.