I have just gotten my 79 Seville up and running.

Love it, working on a custom dash using Jaguar gauges and Steward Warner gauges and an old Cal Tech Mileage Computer.

I switched out the bad TH 400 and put in a TH 200R4, it was a straight bolt in and works great. I did the same with a 79 Camaro and got 19 MPG road with a carb, so hope to do as well or better with the Caddy.

But questions are: Performance, the engine seems to run out of power too soon and feels less powerful than a four barrel carb, is this right?

Any way to get more out of it?

This is a California car so it should go closed loop, would switching the Ox sensor out with a switch make it go open loop and give more gas and thus more power?
Will this trick work on other Injected systems?

Can a large injector give more power and still give the same mileage? If so which ones?

Has anyone up graded the computer to say a late model system like a 87/93 Camaro computer and run a performance chip?

I have a RV Tuned 403 OLDs to put in any one ever tried one>> Better power sure but what of mileage? Will need to change the injectors right?

Anywhere to get replacement washer and over flow bottles, all of the ones I find locally are all dried up and cracking apart.

One last problem, the A/C blower can hard move any air even on high, I fear the evaluator is plugged, but is there a more powerful, faster fan/fan motor that will fit so I can get more air flow?? I am in Arizona so we NEED that air flow….
And is a clogged A/C coil common? Or is it something else?? Air is blowing out the dash vents not out the floor and the inside door by the kick panel is opening, so what??

Thanks.

Rich

not real sure, but are'nt these motors the same as a small block chevy? or are they the small block chevy? because if they are, you can do a hell of a lot with that motor. i say forget carberation, get an aftermarket fuel injection kit and go from there.

For being only 175 hp stock, and older technology... as it is, its not fast and never will be without mods. You'd probably be cool with dropping in say, a GM performance crate engine. Or get some nice heads, headers and intake.

but is that motor a chevy 350? or is it a cadillac version? or something else? :hmm:

Well it is a Port injected MAP OLDs 350, I think rated for about 280 HP and about 300 FP of toqure.

A strong very long living motor, I have owned and driven Carbed versions and felt more kick in power, so felt this lost of feeling was due to the injection system, which my frend said was set up for gas mileage and thus limited in WOT power.

I feeling is these are stonger that a Chevy 350.

Rich

the motor in a 79 seville is an olds 350. an 80 seville got the traditional caddy power with a 368,was front wheel drive, and was replaced later in the mid 80s with the 4100.

the injection system on a 76-79 seville is a great idea that was finalized/assembled in haste- it's not a true sequential port fuel injection at all. (semi-sequential to me would be 4 groups of 2 injectors firing twice per cycle- like a coil pack with an open intake valve fire and a waste-innitial fire for prime. this would just take double the computer and an additional 2 sensors presently not configured in this setup.

All the fuel delivery components are there,but lack the ability to descriminate between cylinders. It's basicly a throttle body with 8 injectors instead of two.
there are 4 injectors that fire at one point, then the other four, so if you stop the pulse to one the reversion might cause that cyl. to run lean, not completely die, although the cyl. next to it might completely die without an injector.
it's simply not a system that works for any performance use. I still feel that with this knowledge it's an inferior great idea that still screams carburetor.
if you put a Q-jet off of a 403 T/A (a 1705 beginning series serial starting in 1976) and a performer intake with a set of 75-80 omega/ 77-79 T/A headers, and a good street cam, the motor will be a strong runner- this is my plans with my 76. unless you are keeping it original for resale, the carb. is the only way to go.
All I do is cadillac and pontiac of this era- if you have tech questons/ ideas or restoration/service needs give me a call at my shop: Dave- D+M Enterprises (860)779-9545

as far as the A/C- check to see if there isn't mousie nest remains plastered to the evaporator- that's easy- you can see the evap when you remove the blower- a flashlight and a mirror might help you look head-on to see the 2 dimention view of the fins to determine that the airflow is jeopardized. the repair isn't exacly an easy one- depending on the length of time that it was clogged, and how much the system was used, it becomes like a plaster stuck in every groove of the core, almost glued in place- it would have to be removed, and forcefully cleaned to work properly.

This is usually a problem that happens if the cowl screen (under the back of the hood directly in fromt of the wipers) has holes, is broken or missing screen sections (typical AZ weather probably turned it to a brittle mess) or missing altogether. There is no other place (unless a damaged case) for the rodents to enter.
The way the cowl is designed, there is no way possible for an accumulation of dust to enter the A/C system and clog the evap. to the point of no air flow because a gravity trap is used in a turbulence-free area, unless forcefully moved there, or the cowl integrity itself was compromised.

Since you have overdrive, look for a posi rear axle to swap under there. Something around 2.73:1 would be nice to keep the gas mileage. This might take some fabrication but with a 403 there is no sense keeping the open differential.

The original Cadillac Electronic Fuel injection was a great setup. The idea was borrowed from European designs which had been used for several years by then. Engines never idled so smooth. Oil stayed clean forever because there was less unburned fuel. You had to look twice at the fuel gauge to see why it hung around full for so long. There are no adjustments for performance. Your injectors are the same as those used on the 425. The larger 500 ones are hard to find and expensive. The only thing that will work is to get an adjustable fuel pressure regulator and increase the pressure across the injectors by 10-15%. This will give more full throttle power but all the part throttle curves are built into the ECU so it could lower mileage. This stuff will never run right when you drop the 403 in. I tried this myself with a 425 ECU and a 500 engine :banghead:. There is hope: http://www.megasquirt.info/
If you have the skills to put a 2004R in and make it work then you should be able to pull off an ECU swap.
Only give in to the temptation of the evil carburetor when all hope is gone. :tisk:

You probably need to pop the HVAC box apart. Maybe swap in a new heater core when you are in there just for Murphy's sake. The evaporator is most likely clogged with bits of leaves. This is normal for a car this age. Had the same problem with my '77 CDV. It was a night and day improvement after cleaning the trash out.