chevy 5.7 performance

badley · February 22, 2005

I have a 1998 chevy 3/4 tun pickup with the 5.7 350 in it. The truck is a crew cab and is quite heavy and i was wondering what i should to it to get a couple more ponys out of it. thanx

Marty46127 · February 22, 2005

Hey Badley,

It is quite heavy, I have the 1 ton version . Headers / tubular exhaust system will help quite a bit (oem headpipes on the L31 are crimped and restricted). On the intake side, a K&N will allow a bit of additional airflow. Cylinder head work / aftermarket heads provide some additional opportunities. With stock heads headers, aftermarket exhaust, cam, roller rockers, KN air filter + a PCMforLess tune (Bryan is awesome to work with), I have gained ~ 70 HP and considerable torque (Truck feels a lot lighter!!). If you really want to perk it up, how 'bout a Powerdyne Supercharger?

GREG 418 · February 23, 2005

Badley sorry about butting in here but......Marty I was eyeing up your combo on this thread and another which you posted your cam specs. I was just wondering how much better or worse your mileage got? Also what kind of tune did you get, I mean was it a towing tune, and for what grade of fuel? Lastly did you do any port work to your heads and intake or is that all still stock?

Thanks

Greg

Marty46127 · February 23, 2005

Badley sorry about butting in here but......Marty I was eyeing up your combo on this thread and another which you posted your cam specs. I was just wondering how much better or worse your mileage got? Also what kind of tune did you get, I mean was it a towing tune, and for what grade of fuel? Lastly did you do any port work to your heads and intake or is that all still stock?

Thanks

Greg

<{POST_SNAPBACK}>

Greg & Badley, gas mileage with the OEM totally stock setup was ~ 12 MPG for a mix of rural/urban driving (with the tired and leaky 122K mile original engine). I decided to do a fresh build (GM Goodwrench new long block scored from eBay for $1100 swayed me ) rather than open up the old to rebuild. I installed the new cam, roller rockers, roller timing chain etc.. into the new long block, hoping to increase torque (have a 2 horse trailer). Mileage dipped slightly to ~ 11 MPG (more air = more fuel), vehicle felt MUCH stonger across the board. Bryan Herter (PCMforLess) and I met at a dyno shop in Reading PA a couple weeks back to tweak the PCM... We found the OEM calibration to be a) extremely lean and b) non-aggressive from a timing advance perspective. Baseline pull on the dyno suggested that I gained ~20 HP over stock from cam, rockers, headers etc.. After 27 pulls on the Dyno (don't ask!) we coaxed another 50 hp out. Bryan richened the mixture, advanced the timing significantly, removed torque management, firmed shifts etc.... I do have an issue to still work out with Bryan (after 4-5 pulls on the dyno, engine cuts intermittently at 5000 RPM as if it has hit a rev limiter - need to inspect/replace my spark plugs and recheck the indexing of my distributor). Mileage (from advanced timing) has jumped from ~11 MPG to 13 - 14 MPG! Not a bad compromise....50 HP + 2 - 3 MPG. The dyno tuning was done with 89 Octane.

If you are running with a stock 1/2 or 3/4 ton L31 (2 bolt mains, light duty Vortec heads), your gains will likely be better than mine. I am running stock L31 Vortec HD heads that are fairly restrictive (HD valve seats, stems etc..). If I had it to do over again, would like to use Edelbrock e-tecs or Pro-Topline Vortec replacements. Hit me with PM if you need more details.

GREG 418 · February 24, 2005

Thanks for the info Marty.

Yes my truck is just a K1500 Z-71 so it would have the lighter duty heads I guess. I didn't know there was even a difference. I don't want to dive to far into my engine since it only now has about 70 000 miles (114 000kms) so if I do anything internal it will be limited to a camshaft. Also I am on a limited budget for the work I am planning so that leaves heads out.

I would just like a little more accross the rpm band, and a little improved fuel mileage would be nice......

Greg

Marty46127 · February 24, 2005

IMHO, with a limited budget you will get the best bang for your $$ with Headers, Exhaust, KN Filter and a PCM Tune....That should fatten it up across the board and based on my experience, give you a couple of MPG's..