there you go.....100k on engine......very well taken care...probably never been touched.
Original truck.........owned by a farmer in SD and only driven from SD to Texas once a year. All highway miles and parked in a garage the rest of the year. I talked to the shop that took care of the truck He said the guy was a fanatic about this trucks care and it shows. The engine and undercarriage are spotless....So I am fairly certain the engine is like new inside....I cant believe the towed with this with at least a 14.5 to 1 or leaner AFR but the dyno operator says its typical with these vortech 454 engines. He claims there is an easy 30 to 50 hp and and 20 to 30 ft pounds of torque in this engine.
I am pulling it and doing a 496 with all fresh parts and a different cam. I want to concentrate on power from 4000 rpm and below but see if I can get this torque up and lower than it is.........somewhere around 2000 to 2500 and at least 500 ft pounds...and maybe some more horsepower down low I use it for some commuting and towing a camper.
There was no tuning with this.......it was put it on and take it off in 15 min just to see where it was at so I have a baseline. I towed with this and it was not as easy as I thought. My foot was always in it. I should be able to see another 100 ft pounds or more of torque with everything correct.injectors/fuel pump etc/new fresh 496 cubic inch etc. This engine has the original plugs and wires on it. Its never been touched. A testimony to the reliability of these trucks. I have had diesels and love them.....but fuel prices/repair labor etc can cost a pretty penny. I think I can get close to an early duramax for torque and power. Maybe not as low but close if I concentrate on air speed down low in rpm in the cyl jead and make the cam small enough. The 496 is capable of 600ft pounds of torque. Not in this engine because its not going to be optimized like say a 5500 rpm engine would be. I want to take the 4:10 gear out and make it a 3:73 or go to gear vendors
I have seen dyno testing on a 454 Vortec in a RV that gained 15 hp just following the GM TSB of regapping the plugs to IIRC 45 thousandths instead of 60 thousandths. Goes back to the what I was saying before there is power to be had with what you already have.
Those small port vortec heads can work very well, just watch out with your piston selection on the 496 build. Those iron heads have small chambers too and it would be very easy to put the compression into the race gas only range.
Also since your engine speed will be low and you are not shooting for high hp goals I would look into a set of reconditioned and flow matched 28 lb/hr LS6 injectors. If you go 0411 the injector data for the injectors that gets programmed into the computer is readily available.
You might also look into the coil per cylinder conversion. The L21 medium duty 454 Vortec engine had coils mounted to the valve covers and a LS style 24x crank reluctor. The 24x ignition system is much more reliable and made a noticeable performance change in my L31 compared to the OEM distributor and single coil. The spark timing is more accurate and the spark voltage/intensity/duration are increased.
