[hardhatz]

I have a 66 El Camino that I commute 150-200 miles a day with, 90% freeway. The 283/TH350 has gotten so tired it uses 3 qts of oil a day. Last time I checked, I was getting 20 MPG. (18 if you count the oil )
I wish to embark on a plan to improve gas mileage by 5-10 MPG.

Power was adequate for my needs, with a surprising top-end rush. I have no idea what cam it has, but it pulled nicely up to 6000, which was where I chickened out. The car is fairly new to me, and shows plenty evidence of Mickey-Mousing.

I am presently dropping in a 350/200R4 for now, but I'd like to return the 283 one day after it gets freshened up. Here is my general plan.

* full rebuild using anti-friction coated pistons (perhaps with heat barrier coat on top) floating pins, and low-drag (thinner) rings.

* compression ratio around 9 or 9.5:1

* some good heads. I am hoping for some good suggestions on what a "good" head is for a 283 where mileage is the first concern. I was thinking "Vortec", but I don't know if the TPI can work with them. The present heads have a flat bar with a triangle sticking up on the front. 3884520

* a late-80s TPI manifold. Now, here is where it gets a little fuzzy... I know that loop-controlled EFI operates at about 14.7/1 air/fuel ratio, yet max mileage occurs at about 17/1. So, I need some of you bright minds to help me figure out how to do that. Lean at freeway cruise, normal at higher throttle settings or higher RPMs. I have thought about a wide-band O2 sensor, but I have no idea how that would be made to work.

* A Ford EEC4 computer, because it easily adapts to older cars, and offers sequential fire instead of batch like the Chevy. More adaptation, and more suggestions requested....

* cam: open to suggestions. also, would roller cam bearings or roller lifters be worth it?

What I have now:
* MSD6 ignition
* headers, large pipes with flowmasters
* 200R4 lockup, 3.08 gears. later will be a T56
* serpentine belt, thermostatic clutch fan
* Q-jet, my favorite carb
* present gearing will have me spending most of my time at 1800-2000. After the T-56 goes in, that will drop to 1400-1500.

OK Wise Men... I am ready for your judgement....

[70bird]

Why do you want a 283 over a 350?

Check these guys out for some pretty trick TPI tuning gear:
Moates
Their emulsification setup is sweet. Their shirts are great also.

I have a bunch of TPI parts (everything minus the wiring) from a project I abandoned (PM me if interested).

If your getting 20MPG on a 350 trans, you must have a light foot. I can't even get that out of my 2001 Toyota 4 banger P-up (city driving).

With your driving style, a 350/200r4 will get you a little more fuel mileage. Probably pick up 6 to 8 MPG with a mild cam, cleaned up heads heads, headers, and a Q-Jet. TPI will add a little bit. The T56 will probably put you in the 30 MPG area (if you stay out of the throttle and do the speed limit). My cousin's LS1/T56 Z28 gets 32 MPG at 90MPH on the freeway (14 in town). The T56 has a .5 OD compared to an Auto OD of .8. Plus, the t56 doesn't take as many HP to turn as an auto.

[lowROLLERchevy]

tuning the eec4 should be easy w/ a product called the tweecer. its a tuning device that plugs right into the diagnostic port of the eec and takes control over the eec's processor

if i had the tweecer software on my PC right now i could take some screenshots of my buddies tune, but basically we adjusted AFR based on load

low load is set to 15:1 +
medium load is 14.7:1
high load is 12.5:1 AFR

theres a chart in the program thats load on the vertical axis and rpm on the horizontal axis, so you can adjust AFR at numerous points

now in our case there were a few functions of the stock EEC that attempted to adjust these numbers up and down, so it became a game of finding out what AFR we had to input to get the proper AFR @ the wideband

IIRC 11.3:1 = the 12.5:1 we wanted, but this will be different for everyone

and of course the Tweecer has many many more adjustments, its well worth the investment

by the way, my buddies car jumped from 25mpg to 32 mpg with the changes to the AFR .... but thats only if he keeps his foot out of the gas, otherwise the turbo spools and he gets like 8mpg

[Jmark]

Originally Posted by 70bird

My cousin's LS1/T56 Z28 gets 32 MPG at 90MPH on the freeway (14 in town). .

Really?????????????????? or is that stretched a tad? LOL

Mark

[barnym17]

I would say that is accurate my neighbors 99 with 6 speed gets over 30 highway cruising and runs in the 12 second range when bottle fed a 75 shot.

[alittle1]

A simple LSX engine/700R swap should net you 30 mpg and could be down for less than $2500.

[70bird]

Originally Posted by Jmark

Really?????????????????? or is that stretched a tad? LOL

Mark

This is according to his calcs. He said this was made an a trip to Vegas and back.

[schnitz]

I'd love to know how. Unless the rear gears get him zero to 60 in 40 minutes (with a good tailwind of course...) I just don't see it. Maybe he forgot a fuel stop in the calculations. However, my in-law's minivan got 120+ mpg at 70 mph, though. It was on my car trailer, being towed by my truck which got 12 mpg. Averaged out pretty good for the two vehicles....


In a while, Chet.

[70bird]

2001 z-28 LS6 intake, tuning mods, free flowing exhaust, front valance for reduced drag, .5 od, 3:73 gears. I'll admit he probably wasn't doing 90 the whole trip but an average of 75+ is realistic.

Just speculating but we was probably turning not much more than 2000rpm.

I turn just under 2900 rpm at 100 mph with 3:70 gears and .62OD.

[hardhatz]

Originally Posted by lowROLLERchevy

tuning the eec4 should be easy w/ a product called the tweecer. its a tuning device that plugs right into the diagnostic port of the eec and takes control over the eec's processor

if i had the tweecer software on my PC right now i could take some screenshots of my buddies tune, but basically we adjusted AFR based on load

low load is set to 15:1 +
medium load is 14.7:1
high load is 12.5:1 AFR

theres a chart in the program thats load on the vertical axis and rpm on the horizontal axis, so you can adjust AFR at numerous points.........

Wow.. This is very technical.. I see I have some homework to do. If you could elaborate a bit (for Dummies like me) that would be great. So, the tweecer will let me run a wideband O2 sensor?

[baddbob]

Wow, this thread makes for some good reading and I hope you guys offer more info on the EEC4 conversion. Makes me wonder what a properly tuned 283 in a light car like a vega and freeway gears would get for gas mileage.

[F-BIRD'88]

Rob a complete good running 5L/305 Vortec motor and electronics from a 96+ pick up truck and swap it in your 66. No mods or reprogramming nessessary.
These motors make a ton of torque and power for a 5.0L engine and are pretty good on gas especially when in a much lighter weight, more aerodynamic vehicle.
Pretty straight forward. The 2004R could work very well with it too.

If I was going to swap a TPI induction onto a 283 I would use the stock small chambered TPI heads also. I would look for a 305/5L TPI system. The 58cc 5 L TPI heads are casting #416 up to 86 and #081 87+. Home porting is very, very effective on these heads for improved power.
The required "Vortec" TPI aftermarket manifold is expensive. If you're going to use vortec heads, use a QJET carb or the whole OEM Vortec EFI top end.
You have to consider the total cost of the project against any potential fuel mileage savings. I would use a "complete EFI system swap" approach be it TPI, TBI or Vortec or LT-1.

[F-BIRD'88]

If you were to add the L-31 vortec heads and a properly tuned Qjet and a mild near stock small "RV type cam" to your 350 and dial it all in with a Wide band AFR meter and dial in a HEI distributor for it properly, you'd probabily find no need to go back to a 283 or the need for EFI.

[hardhatz]

Originally Posted by F-BIRD'88

If you were to add the L-31 vortec heads and a properly tuned Qjet and a mild near stock small "RV type cam" to your 350 and dial it all in with a Wide band AFR meter and dial in a HEI distributor for it properly, you'd probabily find no need to go back to a 283 or the need for EFI.

Right now the 350 has an Offy dual-port, Q-Jet, a Comp Cams 256 XE cam, Rhoades lifters, HEI distributor fired by MSD6, and Camelback heads. I just drove it for the first time yesterday, so I don't know know what it will do. My reasoning for looking back at the 283 is strictly for gas mileage.

If I stay carbureted, I will stick with the present fuel system. I feel the Q-Jet can be dialed in very well without any feedback. I'd only go computerized if I put on the TPI. I think using the TPI as-is with 14.7 AFR would result in an MPG loss, but with a slight torque increase. Without the AFR modification, I would not expect the TPI to deliver outstanding MPG. I figure the MPI would-however-allow me to set the AFR quite lean without miss-fire, especially with the MSD & the sequential injection discussed earlier. This is where the theoretical MPG gains would come from.

BTW, the small displacement of the 283 should solve the problem of strangulation that TPI cars experience, giving it some performance potential as well...

Oh.. One last little detail:
After all the above is sorted out, I will embark on the next phase: attempting to run the engine on part gasoline, part HHO gas....

[F-BIRD'88]

BTW, the small displacement of the 283 should solve the problem of strangulation that TPI cars experience, giving it some performance potential as well...

You'd just be strangling the 283. The TPI induction system is a low rpm system by its natural long runner tuning length. The power is ultimately limited by the limited air flow (small runner cross section) The motor will be a lot like a TPI 305 reguardless. Doesn;t mean you can't improve the power, just don;t expect it to become a high rev'er.

The cam in your 350 is too big for high fuel mileage.