deuce_454

darn.. here i thought i made such a strong argument fro the above block... good luck with it though..

SynergyV8

iTrader: (1)

I was typing my response during your post. I have a soft spot in my heart for old school motors and carburetors, but my daughter on the other hand, being 14, does not. The only carburetor she's ever seen is the triple setup on top of one of my 1200cc race sleds. If I'm going to use this build to teach her things she can use in the future, I'm hoping a fuel injected motor is a wiser choice. Eventually, I see carburetors being phased out by fuel injection within the race scene during her life time, so I'd like to take her down that road for this motor.

Old SStroker

If spend you money wisely, especially on heads, I think you can make a killer engine. I wouldn't worry about an even mm size bore. I wouldn't push the 5.00 L displacement just in case they check. Just use the pistons you need to make the power. Get professional help on the heads/valvetrain from someone who has been there on smaller LS engines and don't have any pre-conceived ideas of what works or doesn't.

Not cheating the rules is a good lesson to teach your daughter. So is spending money on the things that make power and not overkilling the OEM stuff that's plenty strong.

If the rules, or your personal preference keeps it under 7000, it should be a piece of cake.

Jon

SynergyV8

iTrader: (1)

I know it spins off the line pretty bad, but that '96 Ranger will still do a flat 13 second 1/4 mile around 98mph. I'd like her to be able to beat it, but not by much. I'm just not sure I feel comfortable with her driving much over 100mph yet, which is why Papa is setting a 6500rpm limiter for now. Our driveway at home is just over a 1/3 mile in length and she'll take one of the 4-wheelers down it at WOT but gets scared around 65mph. Hopefully an enclosed feeling without the wind blowing in her hair will ease the tension at high speed.

At any rate, I just got off the phone with my good friend at the machine shop. He said what I'm building is no trouble at all and I can drop the motor off for a full blue printing and overbore. Guess that means tomorrow I have to call Wiseco and fill out a custom piston application and hunt down a used 4.8L.

Question 1:
Is a sub-13 second goal reasonable with this 5.0L?

Question 2:
Where to find stronger 4.8L, 6.278" rods?

5.3LJimmy

iTrader: (10)

At a race weight of 3200lbs a heads and cam 4.8 will go high 11's - low 12's easy. Given you have traction and the correctly setup drivetrain of course. The few extra cubes you are adding is probably going to put her near mid 11's. My jimmy with the stock 5.3, stock 4l60e, stock converter, 3.42 open diff, and race weight of 3600lbs went 13.0's.

deuce_454

if you are getting custom pistons anyway i would go with 6.200 rods like the below, the rod baearing dimension is about the only thing an SBC has in common with an LS motor... but in this case it saves you about 1000 bucks.. http://cgi.ebay.com/ebaymotors/CARRI...Q5fCarQ5fParts

briannutter

Good rings are available in a 3.838 bore size (.5mm increments). Just get the custom pistons done.... put some compression in it while you're at it.

omore001

iTrader: (1)

Custom pistons on a 4.8 or a destroked 5.3, Go solid roller with some LS3 heads and get quality valvetrain components to spin some serious rpm's. Put the motor in a 2nd gen RX7 or worst case, Fox Mustang, both are relatively easy projects. With slicks, 4.10 gears and a dialed suspension, it should be good for high 10's.

Old SStroker

Brian makes some good points, as always. I'd go to him for pistons when you need them. From the performance you are looking for, I really like the stock EFI system.

How about this for your 13 second entry level: Buy a complete stock 4.8 from a salvage yard, with the OEM computer. Use the stock (5.3) heads tweaked by a good shop, but not "ported", stock valvetrain with good pushrods and springs, more compression and the correct HR cam matched to the entire engine/vehicle combination. You may actually have to detune it to keep it to a 13 sec/100 mph vehicle, but that's easily done in the computer.

Then in a year or two, if you need to turn up the wick, a 5.0 L shortblock with ported heads, a different cam and and more rpm could up the power a whole bunch.

FWIW, there is a stock 6.0 L shortblock with 5.3 heads (2.00 intake valves), and a single plane running 7800+ every run with a HR cam, stock lifters and stock rockers. Your 6500-7000 rpm 4.8 will be a piece of cake if you get the right folks doing it.

If it runs well, tell people it's built 5.0L.

My $.02.


Jon

SynergyV8

iTrader: (1)

I like where this is going. I let my daughter read this thread, and she said, "Papa, you talk to some pretty smart people on here. Think they'll be able to help with my Algebra homework?" So, we just got done doing her homework for tomorrow and here I am now planning the 5.0L.

briannutter brought up a good point. Ring availability. If there is a good set of rings available for the 3.838" bore, and another good set every .5mm increment, that leaves a 3.858" bore (97.985mm). 3.858" is a very close design to the stock LS1 bore of 3.898" (more on this later). 3.858" x 3.268" = a 306ci 5.01L. Perfect.

I spoke with my machinist this morning about the head work I'd like to have done. We spoke at great length specifically about the valve size. At first, he didn't think a 2.00" valve would be worth installing into the 5.3L head over its stock 1.89" valve. After some explaining and persuasion, we agreed the 2.00" valve would work well in this setup because it's closer to the LS1 bore with stock 2.00" valves compared to the 4.8/5.3L with their small 3.780" bore. He is going to cut in the 2.00" intake valve and finish off with a 3-angle seat at 15°, 30° and 45°. He is going to port match the intake and exhaust runners, smooth out the bowl around the intake valves and finish up with milling the heads .020", or down to 59cc chambers.

This means the pistons will have to be slightly domed to bump compression. On a 59cc chamber, stock head gasket and a 0cc flat top piston a simple compression calculator tells me 10.08:1 with this setup. I'd like a little more compression than this, as the motor will be run on non-oxy 92 octane only and I feel the camshaft will be a bit radical compared to most in the same displacement category.

Camshaft selection for this particular bore and stroke combo has proven difficult thus far. The bore:stroke ratio for this motor is higher than any other production LS motor mainly due to the very short crank throw. I'm having trouble coming up with a cam that will suit this 5.0L for a 2000-7000rpm operating range that wont be a total bear to tune. I started looking at Chevy 302 and 307 cams from the old school small block days. Many of them are in the 22x/23x range with moderate lift. Though a custom grind will most likely be the final decision, I'm thinking the Comp Cams XER273 will be close.

It's a 273/279, 224/230, .581/.588 on a 114 lobe separation angle and 112 intake centerline. Thoughts on this?

NemeSS

iTrader: (127)

currently there are .060 over pistons avaialble for 4.8/5.3 motors, these are inexpensive hyper. pistons for use with stock rods.
the size up will bring u closer to 5.0. a 4.8 from 06+ silverados alredy come equipped with 243/799 heads. a conventional inexpensive truck manifold with a stock cable driven 78mm tb would prolly be the best induction since the truck intakes are know to favor tq. some midlength headers or even hi flowing c6 manifolds would work well, even the stock non egr truck manifolds would perform well. i know my 4.8 rcsb sierra moves out, and i have a cai and cutout, ive ran down mustangs and lt1 camaros from digs and a roll.
im really impressed by the way the 4.8 revs and sounds with a cutout,
i will take my 4.8 over a lt1 car anyday. my truck has 260k rough miles,
doesnt drip,or **** any oil or coolant....yet

NemeSS

iTrader: (127)

a .060 over 4.8 will put u just under 5.0L
imo 243 heads with a 90mm truck intake will prolly be the best performer
along with a proper use cam. the 4.8 does sound good at 7k rpm

GIGAPUNK

iTrader: (2)

I think that you're going the right direction by keeping the stock stroke. You wouldn't be able to spin the engine high enough to utilize it if you went any shorter. With the stock 4.8 stroke, your pistons are only moving at 3811.5 fpm at your proposed 7000 rpm. Theoretically a well built, forged, drag motor should be able to spin at 5000 fpm; with your stock 3.267" stroke that would be over 9100 rpm. You don't want to go shorter/spin higher than that.

dug

iTrader: (10)

for reference, my '05 sierra with 4.8 a4 ran 14.90 @93mph. Only mods are 4.56 gears, no cats, catback, and tuning. It still has some torque management in the tune to save the trans. raceweight is around 4700lbs.

With a mild cam (under 220 duration), headers, and boltons they typically dyno 300rwhp.