L31 Extreme Budget Build

[L31MaxExpress]

I pulled apart the 2 bolt 880 Vortec I had at the shop this evening. It is surprisingly clean for something that sat over a year with coolant in the oil from cracked heads. I am putting this one back together with factory GM Mahle lightweight LT1 pistons and a L30 nodular iron marine crank. Also using a $100 GM steel roller cam and some form of aftermarket Vortec head that was on the 99 Tahoe when I bought it. The only markings I can find on the heads are DD where the typical GM casting number is and what appears to be a serial number stamped in the end. I think they may be Speedmaster. The castings are much heavier than even a Mexican vortec but I had to do some cleaup work on the bowls, around the vane on the guides and the very coursely cast chambers.

Was not too bad for a 110K mile engine. Very little sludge other than the coolant gunk in the bottom of the pan. The rings were still sharp and the oil control rings and bottom of the pistons near perfect. I am shocked that even the cam bearings are near perfect. The rod bearings were very clean as well. The mains look nearly perfect. I am probably going to put new rings that I had laying around the shop on the LT1 pistons, new rod and main bearings and toss it back together. I checked the new rings in a couple of cylinders, got 0.018" upper ring gap and 0.024" 2nd ring gap straight out of the package. The rings on the LT1 pistons had 0.032 upper and 0.040" 2nd ring when I checked. Ao maybe there is some truth to a heavily used engine being pre-gapped for boost from wear, lol.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

 

[L31MaxExpress]

Other than that, it is getting a stock truck intake and since it is replacing the heads/cam 6.0L I sold to a friend it is getting a 24x reluctor. It is getting a DBW LS throttle body and coil near plug ignition. Basically building this to drop in and run on the LS harness and electronics. The 6.0L was a GUTLESS fuel drinking pig in this application even with ported 862 heads and a mild camshaft. Just did not have the grunt down low that even the stock TBI 305 it replaced did. Its in a 4,500 lbs 87 G20 van with a TH400 with the stock converter because it has 3.08 gears. A good running 350 should wake it up alot where it spends 95% of its time running, sub 2,500 rpm. A friend kept bugging me about buying the 6.0L, so I gave a price that was a stupid $$$ figure and he still wanted it. I parked the van in the shop and 3 hours later it was loaded into the back of his truck.

It is getting Holley SBC 2.5" outlet cast iron manifolds.

Including the new exhaust manifolds, the new cam, new bearings and rings I will have about $500 in this 350. It is getting alot of left overs though. Set of Jegs 1.6 roller rockers, set of LS1 lifters I dissasembled and cleaned, used LS coils. The LT1 pistons & rods were out of a LT1 I stroked years ago. The 305 crank was out of a marine engine that froze with very low hours that I practically stole for parts. I sold the 059s off it for more than I had in the whole engine including the marine intake on it. Best guess is it will make 350 hp and about 400ish torque. Compression ratio works out to 10.3:1 with 1094 head gaskets. Cam is 270/276 @ 0.004, 214/220 @ 0.050, 0.452/0.465 lift with a 1.5 which is 0.482/0.496 with 1.6 rocker and 112 LSA on a 107 ICL. Even with that cam the 350 will have 50-60 ft/lbs more at 2,500 than the 6.0L. The 350 will not make 450+ hp @ 6,500 rpm like the heads/cam 6.0L but it was almost never wrapped out anyway. The only time it was ever reved that high anyway was in 1st gear.

I transfered the LS6 springs and Comp 787 retainers off the heads that were once on my 97 van too.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

 

[tayto]

I wish I would have known about those holley exhaust manifolds 5 years ago when i built my truck motor. I went through a few sets of dorman manifolds from amazon before I found an acceptable set. i opened the outlets as much as i could (2 1/4") and cleaned them up with the die grinder. let us know how they work out. with the cost of dougs tri-ys now i might still go with the holley manifolds if there is a gain over the dorman log manifolds.

Also, have you seen if you can get heat shields for them or if stock ones work?

 

[L31MaxExpress]

Some more pictures of the rotating assembly that came out of this engine. Old crank had a little surface rust from sitting with coolant in it. Oddly enough the only surface rust I found. Old bearings did have some signs of acid etching but otherwise great shape. This engine ran 110K with 5w30 Mobil One. Was in my aunts Escalade until the radiator split and it cracked both heads. She shut it off when she saw the coolant needle go into the red but it was too late for the heads. We talked about putting heads on it but she wanted a new engine. I put this engine into the truck back in 2010 when it had 190K on it. She got the truck when it had 130K on it cheap but the previous owner had sludged it up and it lost oil pressure and started knocking. Its a high mileage truck but it has always been garage kept and nearly immaculate. I paid the $100 GM core charge and kept the core when I put a new GM L31 engine in it for her.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

 

[L31MaxExpress]

I started going back together this afternoon. GM 492' cam went into it first. Crank is in it on Clevite A bearings. Main clearence is checked. Standard bearings on the mains. Caps are torqued to spec. Cam retaining plate is on and torqued. I degreed the cam and the timing sprocket is torqued. The reluctor ring is in place. I dropped #1 piston into place for the degree check so I had an reference for TDC #1. I have since dropped all the rings into the bores in multiple places. Upper ring is 0.018" end gap and the Second ring end gap is 0.024". It was dead consistent across every ring and every bore in the engine.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

Finally have an intake soaking in Super Clean diluted with water. Its starting to get very clean.

You must be registered for see images attach

 

[L31MaxExpress]

Short block is done. Tomorrow I will finish cleaning the heads and get them installed. Along with the oil pump, valve train, tinware, intake and exhaust manifolds.

You must be registered for see images attach

 

[L31MaxExpress]

Back to the cam best I can tell. The actual lobe is.
258/282 @ 0.006
200/216 @ 0.050
118/130 @ 0.200
0.3015/0.310 lobe lift
0.452/0.465 lift with a 1.5 rocker
111 ICL and 120 ECL
115.5 LSA

I will be running 1.6s on it, it will see a slight duration increase at the valves.

It has some odd specs but it is a GM steel roller cam used in some L31 application making about 300 hp. Comes new in the GM cam shipping tube for $100.

 

[95burban]

Sweet build!

 

[Orpedcrow]

Real cool build, whats different about the lt1 pistons vs l31?

 

[PlayingWithTBI]

whats different about the lt1 pistons vs l31?

LT1s are flat top giving you more compression. In an earlier post @L31MaxExpress figured ~10.3:1 compression