Cornholio7979

iTrader: (1)

I rebuilt my 89 TPI 350 a year ago, after which I had my transmission rebuilt (discovered it was unhappy after the engine was running.) I have been keeping meticulous records of my fuel economy ever since, and haven't been able to get it above 15mpg in the city. I usually drive the car as it was intended, but have tried a few tanks of gentle driving to see if I am that aggressive with the pedal. I replaced damn near every component & sensor when I rebuilt the engine, as well as cleaning every electrical connection and replacing a few connectors. I'll list the upgrades below, but I built it to be a clean-burning example of how a stock 89 Camaro can still crush the competition. My brother took a new STI (had to be a horrible driver), and a new Mustang GT from a dig about a month ago and said it was not close either time. He did own a factory freak 97 Camaro for 7 years (which I learned to drive on) and knows how to race, so you can tell it's running well.

C5 wheels 17" front/18" rear
MSD 6AL2
SLP Runners (Couldn't find any without a large dent in the junkyard)
Removed baffling below the air filters to attempt a gain in airflow & mpg...
Southbay Orange 22Lb Injectors

If I think of anything else, I'll edit again.

Please help me fix this, as I cannot figure out what is dragging its efficiency down so much.

-Cornholio

Cornholio7979

iTrader: (1)

Thought I'd update and get some attention at the same time. I just smogged my car and it passed on the first try.

Still no clue why it's getting poor mileage. I have noticed that the intake manifold gets so hot it has been cooking the underhood firewall material onto the aluminum plenum. I've been thinking about installing a separate cooling pump/radiator for the throttle body to cool down the intake manifold/throttle body temps. I doubt I can cool the incoming air, but maybe just the intake manifold itself alone will help.

I would really appreciate some advice as I have the car running smoothly, but the mileage doesn't make sense to me. I remember getting at least 15mpg in the city before the engine rebuild. That was also with stock everything and dented runners.

The car also blows a plume of blue smoke on cold starts, and also has a rough time starting cold. The only suspects I can imagine are the original catalytic converters, but I'm not certain since the car passed smog so easily. When my engine was rebuilt, the guy that had done it was a 25+ year veteran at raceways (and his son currently competes) and said the bottom end was so well maintained it didn't need to be bored over. He put the money into chromoly rings IIRC since I was a friend of the shop owner. Hope I didn't get taken advantage of, but maybe you guys can shed some light.

I've tried to keep the vehicle as stock as possible and raise my efficiency as much as I can expect with the TPI induction. If I had the money, I'd get some Dyno Don headers, but that's a ways away...

Ideas anyone?

Green89IROC305

Well in regards to the blue smoke, that is oil burning. It is quite common on small blocks. Valve stem seals usually fix that. The 350 really was only rated 17-18 highway and 15 City though.

The intake manifold should not get hot enough to melt anything. What temp is your thermostat?
I have noticed improved mileage, although slightly by putting in a 180 degree thermostat. 195 is a bit hot, but it was done for emissions reasons.
An engine that is running too hot can cause mileage issues, as excess heat can cause detonation, causing the computer to over compensate with timing adjustments. Also improper base timing can effect that a lot.
I personally removed the coolant hose that routes coolant through the throttle body as it heats the incoming air. It really is only for deicing the throttle plates in really cold climates.
Also the car is tuned for 245-50-16 tires. Increased tire size means more rotating mass you have to overcome. Unless you have made sure to have the proper tire ratio for your larger rim diameter chances are your speedo is incorrect.

Total tire height with the rim should be about 528.9 milimeters or 52.89 centimeters. So by having an incorrect speedo you could be going faster or slower than you think. If you are going faster that could account for decreased mileage. I have seen comments of people burning proms to compensate for different size tires

Are you by chance throwing a code 32? If so an egr that is not functioning can easily reduce highway mileage.
Other things you can check is your plugs. Some plugs don't get along with SBCs. Pull one out and check the color of the plug. As I recall a white colored plug indicates a lean condition. Also check your vacuum, any vacuum leak can cause poor mileage. What baffling did you remove? The curved plastic piece that directs airflow through the fog lights to provide a type of ram air? I am not sure why removing that would increase mileage, that is intended to direct and force air into the engine. Or the air damn? That is needed for proper cooling.
I have found that my IROC prefers Plus 89 octane over Premium 93. It gets better mileage on plus. Although the manual calls for 91 octane for Vin F and 8.
There are people better equipped than I to answer this. But I thought I would throw some info out there.

Cornholio7979

iTrader: (1)

I don't feel like the blue smoke is normal on startup, at least for a healthy engine. I use Royal Purple 5W30, so I have taken into account if there is the smallest opportunity for oil to get by the rings or valves, it will with that awesome oil. That being said, I use the same oil in my GMPP 350 HO crate motor in my firebird, and it never blows smoke out of the exhaust. That car is also smog exempt, so without a catalytic converter (since my 5 year old Catco collapsed internally and was removed) the engine has more opportunity to clear its throat yet still doesn't show smoke.

I know the difference isn't great, but 13 is the best mpg I"ve seen since rebuilding the motor, when I also replaced nearly every sensor. It's usually closer to 11, which isn't right for an engine that operates as efficiently as the TPI should.

My thermostat is a 180, but I disabled the coolant flow into the throttle body a while ago. I don't believe the lack of 180+ degree coolant in the throttle body would contribute to the overheating of the intake manifold. Before it showed signs of this level of heat, I planned to design and install a separate coolant system for the throttle body to see if it could help anything.

My base timing is on 6 BTDC with proper technique (unplugging EST and jumping ALDL) and I have checked it repeatedly to ensure its position is static.

I understand the difference in circumference on wheel/tire size. I have used Corvette wheels with appropriately compensated tires to make my speedo correct. My speedo is currently dying (internals need to be rebuilt) and isn't something that I take into account of my mpg since it would be such a small difference.

I have no codes, otherwise I would be pursuing those viciously. I also put 91 octane in my cars, as the options in Las Vegas are 87, 89, and 91; with 87 and 91 only at some pumps.

I have replaced all vacuum lines and continue to monitor their health constantly. I use Platinum AC Delco plugs rated for 100K miles. I've seen my plugs twice since I've put them in and they are happy. I'll get an exact coloring from #1 today.

The baffling I removed is directly underneath the air filters. It blocked airflow in the center, and routed the air 180 degrees down, then 180 back up, with another set of plastic tabs. I think it was more for preventing debris from entering the air filter area. The air damn for the radiator and air intake is still fully intact, I just removed pieces in the way of the air filter, which I understand could possibly speed up air flow slightly. Looking at it though, it didn't seem like it would help deliver air as much as having no impediment would. I do want to add the ram air funnels eventually, but don't want to give up my fog lights. The plastic behind the fog lights is also still fully intact.

I am curious at this point, if the brand of MAF sensors would contribute to my problems. I have been reading that my Autozone brand MAF may be the very slight problem in my mpg challenge. I am not excited by the thought of experimenting with a $200+ sensor I can't return...

I will continue to dig deeper to find the problem(s) here. Thank you for the help so far. Come on experts, lets get some knowledge dropped on my thick skull!

usetaboost

iTrader: (1)

I managed 16mpg in town on a very tired tpi 305. THis was of course back when you could get 89 with no ethanol. THe car had over 160 with rings that were getting bad and a bad harmonic balancer.

djtricia

iTrader: (4)

I would try advancing the timing a bit more.

rusty vango

MAF sensors from auto zone come from china via "cardone". they are junk right out of the box. I know this because im on my 7th one. a new one from the dealer is $1,093!! and get this ,,,its made in china for GM! im gonna try and find one NOT rebuilt using rice ***** and wasp nests.

alex722607

iTrader: (3)

Any chance someone figured this out??

I am having similar problems.
-Stalling at stop lights -- occasionally (20% of the time)
-white sparkx (running lean) but am going to replace them with E3's in the next few weeks
-?possible fuel pressure regulator?
-running 89 prom for a 350 with an 88 style tpi (have not deleted cold start injector yet)
-Lousy gas mileage -- over 60 mph I get the feeling it chuggs gas because of how quickly it goes
highway mpg is around 13 (should be around 20-22)

-and it pings
- idle is 75% of the time at 500

rusty vango

I have a TPI 5.0 that is completely stock, manifolds and all .im getting 20mpg in town and 27mpg on the freeway.something must not be right,those extra 45 cid cant be making that big of a diffrence

85Special

I work at autozone. Just had A run in with cardone. Burned out a MAF in 4 months. There is a lifetime warrantee available for $150 100% brand new... But from china of course. Though I'm not so loyal an employee to waste my money on crap from china. I'd love to see if anyone has a recommendation on a good MAF I won't have to dick with every few months.

alex722607

iTrader: (3)

So I did the fsm fuel pressure reg. test and turns out it wasn't holding pressure after the fuel return line was pinched. (slowly and gradually the indicator needle fell) So I gotta check my injectors. I guess I am going to have to pull all the spark plugs and figure out which one is not running lean. BTW, the injectors were purchased re-manned.

rusty vango

I bought a NEW MAF from oreilleys. $450. its made by "richporter" part # MA157. so far no dreaded code 33,34. now, I have a 86 Camaro,so there may be a difference .but I understand that MAFs from 86 to 88 are the same,but I could be wrong.my car hated the MAFs from "vato zone" seriously ,I had one fail before I even got out of their parking lot. went thru 7 of them in about 6 months. these cars are also picky about the relays running them. im using ones from oreilleys .burn off # R-3009, power # R-671. I can say that once you get this area of your car working right. throttle response and fuel economy go up noticeably. I hope this helps,and good luck

JP86SS

iTrader: (1)

If it is pinging with good fuel and timing that low, your EGR is not functioning properly.
EGR will reduce cylinder temps to allow timing to be advanced without pinging.
You should be able to run higher than 6* base (as that low can add additional heat) and get better response and power.
Seems to me the EGR is the best starting point with everything else you have tried.
Maybe the solenoid for it is not functioning.
You could try just running it to the manifold vacuum as a test run (after warmed up).
Hth

alex722607

iTrader: (3)

I forgot to post, but I found my issue: leaky injectors. I got a factory reman set and apparently they dumping more fuel than necessary

I popped in E3 sparx and she runs a bit better. Now I have to save up for injectors.