I've owned a 1995 K1500, L05 350 TBI since 1999. The existing motor is getting tired and I'm looking to purchase a new Vortec long block through Pace Performance. I plan to purchase a conversion intake manifold and retain my TBI. I'll install a better fuel pump, increase fuel pressure and adjust fuel and spark tables as needed. Before I pull the trigger on this conversion, are there any "fatal flaws" with this plan I need to be aware of? Thanks in advance.
No "fatal flaws" that I've experienced. I did a similar conversion last year for a co-worker. The difference was, for budget reasons, we used a remanufactured L31 Vortec short block assembly, with remanufactured TBI heads. We saved some serious $$$ reusing the factory TBI heads and intake. We also saved some $$ using plain cast dish pistons used in older 5.7 liter engines. We needed to install the timing cover alignment dowels for the sheet metal timing cover. Vortec L31's use a plastic timing cover that has the alignment dowels molded into the timing cover. Another bonus to this engine build was the factory chip was nearly perfect.Originally Posted by Roadknee
dave w
I've often wondered how an otherwise stock L05 would run with the hydraulic roller Vortec cam. Was there a significant difference in performance compared to the stock L05 motor?
The stock Vortec L31 roller cam was a HUGE improvement compared to the flat tappet stock TBI camshaft! The 1990 K2500 the engine was installed in, is mostly used for towing. Climbing the mountain passes of Washington State / Oregon, some of which are more than 6000 feet in elevation, is where the biggest improvement was felt. The 3 mile ~ 4 mile 6% grade climbs are now in 3rd gear not second gear. Towing on the modest grades (3 lane sections for slower semi trucks to use) on I-5 / I-90 are now climbed at the posted 70 MPH speed limit, before 60 MPH or slightly less was the norm.
For a pickup used for towing, I feel the swirl port design of the TBI head is very effective. The TBI heads are good to about 4000 RPM, then fall flat. For all out performance, the Vortec head is a better than the TBI head. For the money, the roller cam is an outstanding BANG for the BUCK$! Some TBI blocks can be upgraded to roller cam without modification, most can't.
dave w
OP
The chambersofthe L31 heads promote good torque compared to the TBI heads. Just look at a dyno comparing the 290hp/350 and anything using L31 heads.
Cant go wrong with a $1900 L31 brand new GM 4 bolt longblock. Nodular iron crank(stronger than cast iron), PM rods (better than pink hi po rods) and hyperetectic pistons(better than plain cast aluminum). Coupled with the high flow, efficient L31 heads, stock roller cam equipped block with windage tray.
The L31 long block came stock on 1996 1 ton vans, it came with the Vortec/TBI intake manifold that GM designed for this application which was later used in the GMPP/CPP catalogues. These intakes have 2" throttle bores and the TBI injector was specific for the TBI/Vortec engines. There are marine intakes as well that use the TBI injection with L31 intake ports/bolt pattern. Even if you threw a Performer RPM Vortec intake with a TBI adapter on it would work well.
The TBI/Vortec was rated at 235hp/340 lb/ft torque. These TBI/Vortecs were also available on some export trucks as well. I used to have pics. The BRDW code was used to identify the ECM calibration.
peace
Hog
Thanks everyone for the good information. I have carefully considered rebuilding my existing engine. I have to travel about 150 miles one way to find good machine work. I'd end up spending slightly more for a rebuild with quality parts and machining as I would for a brand new vortec 350. I'm leaning toward an Edelbrock Vortec EPS intake with a throttle body adapter. It doesn't have EGR, but emission testing is not done in my area. I looked through the Tunerpro ADX file for the $0D and it is quite impressive. I should have no issue adapting the tune for the Vortec motor. If I end up pulling the trigger on this plan I'll report back once it's installed.
The 290 HP 350 crate ran some big 76cc open chamber smog heads, unless you are talking about the marine 350.
However in a low-rpm, towing application I prefer swirl ports to vortec heads.
Yes you're right. Are the heads the same between the LD and HD TBI engines? There is a decent compression difference and I thought one of them used the large 76cc chambers?
Different strokes for different folks. It all depends on your setup, I just hated towing with a LD TBI 350, great off idle, but of you ever have to drop down a gear. There is the intake manifold advantage of the swirl ports
peace
Hog
Engine building and engine theory are fun topics. Add budgets, available parts, and EFI computer controls there are going to be opinions, trade offs and compromises. The debates should, and can be fun. Wet flow vs. Dry flow. Effective Compression Ratio vs. Static Compression Ratio. Port Volume vs. Intake / Exhaust Velocities. Dome vs. Dish piston. Open Chamber vs. Closed Chamber. The lists go on and on.
Can a 350 Horsepower engine be built with 250 cubic inches or less with a budget of $1000 or less? Maybe Desktop Dyno can help?
dave w
NOPE...I can tell you the 8.75:1 version has longer, deeper dishes that total 18cc vs. 12cc of a standard LD 350. The TBI chambers are like 65.3cc IIRC on 191, 193, and 810 head castings. The HD 810 heads are set up for rotators on both intake and exhaust valves and have larger stem incol exhaust valves.
I just put a franken engine in a 1978 Camaro and slapped a marine TBI on top. It started life as a rebuilt long block that was pulled out of a 99ish Express that I got for core value with coolant/oil mix. Found out it only had bad intake gaskets and the lower end was in perfect shape. It was a 4-bolt main block, with 12cc dished pistons, "X" rods and was bored .020" over. A while back my brother and I had robbed the heads and put them on a friends 71 chevy truck that had a GMPP 290 HP 350 in it. Made some money on that deal. That old truck RUNS with the vortec heads, GM vortec carb intake, long tubes, and the L82 cam thats in that engine. Well the shortblock got a pair of 810 casting TBI heads tossed on it and a set of leftover 1.6:1 roller rockers. It was going to go into a 91' Firebird, but we decided that car was too far gone to save after tearing into it. We kept the 700r4 and TBI harness from it. Let me just say that a Vortec shortblock with TBI heads and TBI on it runs a hell of alot stronger than an 8:1 smog head flat tappet cammed carbed 350, EVERYWHERE in the rev-range. With the 4.3 stalled 700r4 it gets about 50% better mileage on a day to day basis. His mileage has jumped from 12 mpg city to 18 mpg city. The car really doesn't see long highway trips, although I bet highway milage is definately improved as well. It almost never has to downshift at highway speeds. The car has some retarded gearing as well. Runs about 1,600 RPM @ 70 mph. Even shifting at the stock 4,600 rpm shift points, it runs out about 45 mph in first and close to 90 in 2nd and never feels flat in any gear. It runs side by side with a 4.6 3v mustang with a CAI, Exhaust, 3.73s, and SCT custom tune. I would say that it probably makes 270 HP/350 ft/lbs through the larger 2 1/4" outlet 91 G-van cast-iron manifolds with the performer RPM intake and big block TBI. For anyone thinking of doing the swap, it was very driveable on the stock 1992 AWLD "299" 350 TBI tuning with only a timing tweak and some extra fuel pressure. Although 1978 is not checked for emissions here, we installed a highflow dual in/single out catalytic converter and ran that into a 3" exhaust and into a crossflow muffler like stock. The goal was to keep everything as stock appearing as possible and be as reliable as possible. Not to mention for some reason girlfriends never seem to like the unburned hydrocarbon smell getting in their clothing. I did not find this a bad build for a spare parts build.
Last edited by Fast355; 01-02-2014 at 05:06 AM.
12520270 -5.7L 350CID (LO5-K) 1987-1995 Chevy & GMC Full Size Trucks & "G" Van & 1996-2002 "P" Van - Over 8,600 GVW
It uses the 14102191 heads which have a 76cc chamber
Specs
1986 and up 4 bolt main 1 piece crankshaft seal block(no mechanical fuel pump provision)Nodular iron crankshaft
Powdered metal connection rods
Dished hypereutectic pistons
8.75:1 Compression ratio
High volume oil pump
Morse link type timing chain
12568758 - 5.7L 350CID (LO5-K) 1987-1995 Chevy & GMC Full Size Trucks & "G" Van-Up to 7,200 GVW- Uses 14102193 heads with the 65.3cc chambers
Specs on this engine are as follows:
- 1986 and up 2 bolt main 1 piece crankshaft seal block(no mechanical fuel pump provision)
- Nodular iron crankshaft
- Powdered metal connection rods
- Dished hypereutectic pistons
- 9.25:1 Compression ratio
- High volume oil pump
- Morse link type timing chain
Not sure if that info is correct,its from PAce Performance.
peace
Hog
Bad information on the TBI heads. While the compression ratio is lower it is the pistons that make the difference.
I've only measured one set of the 191 TBI heads and one set of 193 TBI heads, both were about 65cc.
dave w
The 810s I have cc'd about 65-66 as well.
Just wanted to catch this:
I've only spoken to two people that who claim to have found OE TBI / L31 engines that I believe. In both cases the engines were installed in P chassis step vans. The G van (old body style) carried over to 1996 in cutaway chassis cab configurations with the L05 for >8600 lb emissions, and the new Express/Savanna vans came with a complete L31. The only calibrations I've found for the hybridized engines are marked as export emissions as well.The L31 long block came stock on 1996 1 ton vans, it came with the Vortec/TBI intake manifold that GM designed for this application which was later used in the GMPP/CPP catalogues.
Posting Permissions
Reply With Quote
Bookmarks