Hello,

I own a 86 trans am, my 305tpi was gone.

I replaced it with a GM performance 350 engine 300HP, I installed the TPI manifold setup with the MAF sensor. A new chip from motorvation. 19lbs ford bocsh yellow black injectors. I have hooker headers, a really big aluminium radiator from becool and a standard rotation water pump.

My engine overheats.

I Checked the timing, I have 10 degrees of initial timing. ok !
I checked the fuel pressure, about 42psi. ok !
Head gaskets ok, no water leak, water pressure ok, engine oil ok !

I installed an innovate MTX L wideband O² sensor to check the AFR.

As I start the engine cold, I have between 18:1 and 20:1 of AFR ! it sucks !!! once engine hot, I think the O² sensor corrects the mixture because I have between 14.7:1 and 15:1.

On cruising the engine runs great, I have between 14.7:1 and 15:1.

As I need power, like going up the mountain, (I am far from WOT) about 20 to 40% of the throttle, the engine stays at about 14.7:1, and it starts overheating... this summer it is gone to 240°F in the hot weather !

As I am at WOT, usually it goes to about 14:1 , only once I have reached 13.7:1.

I think the problem comes from my injectors... It would seems these 19lbs are really too small.... what do you think of this ?

I saw bosch 24lbs or 27lbs injectors on http://www.southbayfuelinjectors.com

what would you recommend me ? I don't want to change the injectors twice

thanks for you help.... I need your experience !

Marc

If you went to a larger motor, but changed nothing else then it's lean because the 19lb injectors are too small. Your knock sensor needs to be changed as well. There is a difference on those too.

EDIT: Be sure to set your initial timing with the ESC wire unplugged.

I changed with the ford injectors I had, but it seems it was a bad idea !

What would you recommend 24lbs or 27lbs ? maybe I could be too rich with the 27lbs, or the ecm is able to learn enough ?

or maybe another idea for my overheating.

Ok 305tpi and 350tpi knock sensors are not the same, I will change it ! I didn't know this !

Thanks for your help

Marc

What ever injectors you go with you will need a custom chip to get the AFR.
6° BTDC +/- 3° is the nominal setting.
Are both fans coming on once it starts to overheat?

ok

I have chip from motorvation, they didn't tell me which injectors to use...

what would you recommend, 22lbs, 24lbs ? for just 300HP engine.

the cam setting was 10 degrees of initial timing, 32 of total, that's what is in the chip.

I have a single fan, it comes on at about 170°F. but as I am driving at 40 ou 50mph and the car overheating, the air flow comes, this is not a fan which will add flow during driving at a good speed.

The air damn which is under the radiator is in good shapes and send air flow to the radiator.

thanks

Marc

You need to find out from motorvation what they had planned, but 24lb was stock I believe. Good that your air dam is in tact because it's certainly needed by the car, unfortunately.

ok. I will try to check for the injectors.

I will change my knock sensor.

otherwise, it is still possible to take bigger injectors and lower the pressure on the regulator.

any other idea for my overheating is welcome !

thanks

Marc

stock injectors for a 350 are 22lb/hr. The ford 24lb will work ok, just need to lower fuel pressure from the stock 43.5 to about 42psi. I have done this myself. You may be overheating from incorrect timing, could also be a thermostat issue. WHere is your distributor timing at?

Your fan should be coming on at about 15 degrees AFTER your thermostat opens. The lowest fan setting i have seen is 176 degrees with a 160 thermo. You need to find out what settings they set up for you in that chip. Call them. Also, make sure your distributor timing is at the stock 6 degrees BTDC. You should be at about 12.0 -12-5 AFR at WOT too.

I think I have 22lb injectors. When I bought my car 10 yrs, ago (305) the injectors leaked so bad the cylinder filled up with fuel to the point the motor wouldn't turn over.
Dyno Don replaced them with used ones from member of our local car club, and his son burned a custom chip for me to get the car to run properly.
Since I've gone to a 355 but still use the same injectors. Getting the right chip is very important and buying from some company on the net is never going to anywhere close to as good as one burned to your own car.

I would start with setting the distributor timing to stock. Why is your fan coming on at 170 degrees? Stock fan comes on at like 220. What thermostat are you using? I would also find out for sure what injectors you are running. If you have 19lb,then you can increase fuel pressure to richen it up. If you have 24lb you may need to decrease pressure. So i would check timing and verify thermostat is opening correctly first.

I have a 160 thermostat, my fan goes on at 170. I have tested it in water and it opens at 160

ok, I will take 24lbs injectors ! and one adjustable fuel regulator on southbayfuelinjectors.com

I already tried with only 6 degrees of initial timing, it overheats again more. the more timing I put, the less it overheats, but still too much... Itried everthing on the timing... I checked I had the good marks for the TDC...

I would wait til you get those injectors installed and fuel pressure regulator. Then run it again and see.

I just ordered the injectors and the regulator, I let you know once it is changed.

If you have other ideas, these are welcome !

Thanks for your help

Marc

Hello,

I changed the injectors with the 24lbs, I installed the adjustable fuel regulator. It was set at the minimum at 45psi.

I tried on the road, it was better, but not enough !

I adjusted the pressure to 50psi. It seems to be great.
It is not a too high pressure ?

thanks for your help

Marc

I really sounds like you may still be running on the 305 chip. If you installed 24lb injectors then you should have to lower the fuel pressure a little bit. Stock fuel pressure is 43.5 psi. Try another fuel pressure gauge first. 50psi is ok, but usually 50 psi along with the stock 22lb injectors is like using 24lb injectors with the stock 43.5 psi setting. Yet any pressure above 50 psi is not good for your fuel pump. Re-check the fuel pressure with another gauge and try to confirm if your chip is made for a 350tpi.

just curious. Have you changed your fuel filter lately? Do you hear any whining noises from the gas tank?

What is the broadcast code on the memcal the 3 to 4 letters ?

ok Perhaps should I try to lower the pressure of one or two psi ? to be sure not to damage the pump.

My pressure gauge is a new one...

My chip has be made by motorvation for my 350tpi, but maybe they missed something ! :s

I changed my fuel filter last year. I did about 1500 miles.

there is not any strange noise from the fuel pump. just the usual noise of the pump priming as I turn the key.

Here are pictures of the computer


Marc

do you have the means to read the .bin or the eprom ?

No, I have nothing to do this

thanks for your help

Marc

Have you changed the computer to work with the 160 degree t-stat?

I'm not an expert, but I've been told: If you run a t-stat too cool for the computer than you will have problems. I doubt its the cause of the problem you're having now, but you might want to switch up to a 180* unless you've told the computer otherwise.

Perhaps someone more "in the know" can elaborate.

I had a 180 thermostat before and the same problem.

The 160 thermostat temp is programmed in the chip to have the fan at about 170.

Marc

I am adding to this site here, any help would be great.
I recently purchased a 1987 Trans am with a 5.7. This car runs great but the temperature gets to high and the vehicle loses power. I have replaced water pump, radiator and the 2 electric fan motors. The fans do come on when the temp rises over 240. I had one of these years ago and the temperature never hit the 220 mark on the dash. I tried the 160 thermostat and that did not work at all. I proggrammed the fans to come on earlier and the car is still going over 240. Please give me some ideas. Thanks to any one who can help. Nick

Did you check your ignition timing ?

Thanks for the reply.
Yes , THe timing is perfect at 6 degrees before TDC. I am stuck on this. I have checked everything twice, replaced the thermostat with a 195, 180, and 160. same problem. this motor has been done before from the looks of it as the block has been painted. What could it be? Should i make the timing different, if it is running too lean?

Did you just buy the car with this issue ?

Purchased the car and drove it my shop.
Never noticed anything anything the first day.

The injectors may be too small but they are not causing your problem because once you are in closed loop you ar holding 14.7 AFR which is fine. the WOT AFR should be 12.8 to one. Either you need a custom chip that uses the 19lb injectors or change them to 22 lb injectors and you should be close. What are the fan temperatures set for?

Have you checked your water pump to make sure it is circulating water and looked at your radiator to make sure it is not plugged up both externally or internally? You also need to verify that you have the correct water pump for the application some SBC water pumps were designed to rotate backwards and if you have the wrong pump on this could be an issue. (I know you said this is all new but verify that it is all working correctly)

The stock radiator in these cars will keep the cool in most cases. My 406 runs 170 degrees with a stock radiator in the summer, your be cool set-up should have no issues.

You might have a bad thermostat.

I have changed the thermostat now 3 times!!! :/

wire a switch to the fan and turn it on manually at about 200 degrees or so. See how it does.

Already tried that. had both fans turning on at 185 and the temperature still went up.
Car looses power when it gets hot.