My wife's 5.3L in her SUV spun a rod bearing so my son and I will be rebuilding the 5.3L into a 383 as soon as parts start arriving next week. My fuel systems guru was redeployed overseas three weeks ago to somewhere he could not tell me, so I'm currently without a reliable source to ask this question:

What set of injectors would complete this buildup?


-4" Forged Eagle crankshaft with 24 tooth reluctor ring
-6.125" Forged Eagle H-beam connecting rods with ARP rod bolts
-T6 Hypereutectic aluminum Wiseco dished pistons, 15cc of dish
-Wiseco ring set
-New main, rod and cam bearings
-GMPP top end set = .052" OEM head gaskets, head bolts, valve cover gaskets, exhaust manifold gaskets, intake manifold gaskets
-My custom grind Comp Cams camshaft, (261*in/267*ex advertised duration, 208*in/214*ex @ .050", .554"/.559" on a 113 lsa and 111 intake center line)
-Freshened up 5.3L heads, milled to 61cc (from 61.15cc), stock valves, LS6 valve springs, new intake/exhaust seals.
-Pushrod length will be checked during pre-build, most likely will end up with 7.400" rods
-I'll check the lifters after tear down, if they need replacing LS7's will go in
-Obvious spark plugs, wires, water pump gaskets, oil pick-up tube o-ring, timing chain, tensioner pulley and serpentine belt.

Extras:
-Stock exhaust manifolds and piping, but a new Magnaflow 22" Case 3" In/Out will replace the OEM factory muffler. Factory cats.
-The SUV has the 28" standard 1/2 ton radiator right now. It will get a new 3/4 ton 35" radiator, along with the oil cooler adapter and lines. I'll have to find a new shroud for the fan/radiator, but I'll still use the clutch fan.
-Cheap-o eBay intake, stock air box. (cleans up the image a little)
-It currently has the 145A alternator, I'm having a 210A replacement made
-4L60E will be rebuilt by my son this week to handle the power
-Transfer case will be untouched, but the fluid will be changed.
-Rear end is currently open, if I can find a G80 in my time frame I'll put that in as well.

All in all, the 383 should be sitting at 9.95:1 compression. It's designed to run on mid-grade gasoline but I'll tune the low octane spark tables to accept old 87 octane as well just in case my wife forgets. In all honesty, I'm not troubling myself with horsepower and torque numbers. I know it will do the job. If I had to guess, I'd figure the motor could probably make a little less than 1hp/cubic inch because of the small duration camshaft and 5.3L heads. Torque will be through the roof, which is why my son is rebuilding the transmission.

 

42 lbs. marine injectors are a direct replacement.
I will probably be getting rid of mine in a couple weeks if you are interested.

 

Sounds like it is going to be a fun little Tahoe. My wife's Yukon has 100+ on it and I am thinking about building up a 6.0 for it and maybe tossing on a TVS

 

I found a few quick Google calculators. Plugged in between 360-375hp, figuring a .50 BSFC and no more than an 80% duty cycle with 8 injectors and the calculators are spitting out between 29.5 and 31lb/hour rates. I did that with three different online calculators. I've been informed there are 31lb/hour injectors from the 8.1L big block.

"Too small or just right?", as Goldie Locks would say. The horsepower output of the 8.1L and this 383 is about the same. 340hp/455lb-ft of torque for the 8.1L. I'd imagine this 383 will be close to that at the flywheel with 20lb-ft less torque.

 

80-95% is a good range to stay within. Don't want to go too big, it will screw with the idle. Nothing wrong with running 90-95%. Hell, I've seen several run 110% with no problems. I had 42s in the vette at around 95%. Only went to the 60s after a few more tweaks.

 

To anyone who might find this thread later on in a search. I just ordered a set of 31lbers for the build. I'll report back after tuning.

 

I just wanted to know how this project turned out. Hope to hear some results, thanks.

Russ

 

I am also curious how this build went? I am in the process of having a machine shop build my LM7 based 383.

 

No matter what please post your results. I really want to know how much the 4" stroke fills in the low RPM's. With the right cam, heads, intake I don't know how you could be much below 450/450 with a metric *** ton of torque at 2000 rpms.

Good luck with yours

 

I'm running the 30 PPH injectors from an 8.1 L big block right now. When I was running my 212 218 114 cam, my max injector duty cycle was 78% @ WOT at about 5,300 RPMs. That's with my current displacement of 364 CID. Your 383 won't be much different. You've chosen a good cam for this task in my opinion.

I also have a set of new marine 42 PPH injectors that I bought from Magnusun on eBay a couple of years ago. When I finally build my 408, I'll check the duty cycle first with my current 30 PPH injectors. Then, I'll go to the 42 PPH units only if necessary as I do believe that the idle quality will likely be better with the 30 PPH injectors. What kind of lobes are you using on your cam. I've been thinking about almost your same cam on a 112 LSA with 112 ICL, or a 208 208 112 LSA 112 ICL.