Want to build a 1990 5.7 to a proven chip. Not high performace

[kenh397]

As the title states I want to rebuild my "90" C1500 5.7. I'm not looking for high performance. I just want a nice clean running engine with a possible boost in mileage. What I propose to do.

Replace flat tappet cam with a roller cam (stock vortec or somebody suggested an L98 cam?????)

Roller rockers (not high on the priority list)

Flat top pistons

Clean up the stock swirl port heads by removing all the sharp edges and boogers in the intake and exhaust ports and combustion chamber. (already done when I replaced the head gaskets and cracked head)

Bump the oil pressure "somewhat" Would like to run 40+ PSI at cruse speed.

That really is about it. I'm really looking to increase mileage if possible and any HP gain is icing on the cake. As i mentioned, if somebody has done something similar and has a chip burned to match something close to this I see no need to reinvent the wheel. I have a blank slate to work with as I still have the running but tired engine in my truck now.

Thank you in advance for your advice.

Ken

[dave w]

I seem to remember that most TBI heads have about 64cc - 66cc combustion chambers. I'm thinking that flat top pistons with TBI heads would be close to 9.5:1 compression ratio (CR).

Summit Racing compression ratio calculator https://www.summitracing.com/newsand...ion-calculator

Back in the day (without Ethanol polluted fuel) the rule of thumb for cast iron heads Octane fuel rating vs. CR; 87 Octane fuel rating = 8.7:1 CR - - - 92 Octane fuel rating = 9.2:1 CR.

dave w

[tayto]

I built a 10.3:1 TBI headed 355 with Flattops. Kept the quench tight 0.035" and had the heads pocket ported (and cleaned up casting flash on the runners). 213/217 @ 0.050" 112LSA cam, made 325 FWHP @ 5200 rpm and 394 fwtq @ 3000 rpm on the engine dyno. I suspect torque was higher, but pull only started at 3000 rpm and up. This was on "pure" 91 octane. I had to tear engine down because of lifter bore issue and everything looked great. Maybe in high heat or towing the higher octane might be required but I confident I can use a lower grade of fuel without issue. I got 16 mpg on a 1000 mile trip, 2 people with about 1000 pounds of camping gear in the rocky mountains. This was on a Qjet and gm hei distributor that have had no tuning done to them. I wouldn't bother with a bumping oil pressure. Set your clearances correctly and run a mellings 155 pump (3/4" pickup vs 5/8) with standard spring.

[kenh397]

I know I will be close to that 9.5 CR. When I worked on the heads my work in the combustion chamber amounted to smoothing and rounding off the big lump of the spark plug boss, cleaning up and un-shrouding the intake valves, cleaning up around the exhaust valve and getting rid of the lip that leads into the quench area. I didn't CC the heads but estimate I gained two to four CC's easily. That should play a roll in controlling to much compression. On another forum (GMT 400) I was advised to keep the quench at or under .040". Quench plays a much bigger role in anti detonation than I ever knew was possible.

I'm an old motor head from back in the day but it's been so long since I've done this I've forgotten everything ever knew! haha My biggest concern is getting the computer to control the upgrades. Hence my question about somebody doing what I have done and advice on what to do with the chip in the computer. I know it will also need an upgrade!

Thanks for the tip on the oil pump! AND all the other tips

Ken

[dave w]

About 15 years ago, I "built" a SBC for a 1993 K1500. At that time, it seemed a Plug-n-Play chip would be readily available. Back then there were "Claims" all over the Internet with the cleaver wording, "Tell everything you did to engine and we will sell you a custom chip". Back then I fell for the "Claim" Hook / Line / Sinker. My take away from that experience reminded me "If you want something done right ... Do It Yourself". I've been a laptop user long before laptops were USB only. I have "Tuned" hundreds of TBI engine since I tuned my 1993 K1500 about 15 years ago.

I think myself and other gearhead-efi members could "Burn a Chip" that would get you in the "Ballpark" even if technically speaking the parking lot is at the ballpark. Maybe some people are happy only being able to hear the crowd cheering from the parking lot? It's unlikely myself or another gearhead-efi member would "Burn a Chip" that's technically speaking "on the playing field" of the ballpark.

I think data logging was "developed" to ultimately fix the "Claim" tell everything you did to the engine.

If you have a laptop, your just a few data logs away from "Chip Happiness"

Things can go horribly sideways if you copy / paste a chip "Tuned" for "the same engine specifications".

dave w

[WASyL]

skip roller rockers as they are snake oil and overpriced ones, go with stamp steel ones but 1,6 ratio, summit els ones for about 65$. as for cam, stock LT1 is best one. add S10 4.3 2200 stall speed converter, electric fan and with propper tune you will gain both performance and mileage.

beest regards.