jonmark1985

i have an 89 lo3 firebird that i basically just replaced the short block in

• i went .060 over on an ~78 305 block
• fresh deck on the block, not on the heads
• im running the .420/.443 204/214 cam at 2 degrees advanced
• im running my vaccum advance on the low port of 4160 carb
• timing is "ear shot" around 12*, i have no audible spark knock
• im running 18* of dwell for the points
• ~25% antifreze 75% water
• im running the 11 lbs of fuel pressure into the carb directly

the car heats up to 220-230 at highway speeds, but at idle and in town driving the car runs around 160*

so far i have;

• flushed and cleaned the radiator
• unpluged the compresser and unplugged the "pressure valve?" up by the accumulator
• hotwired the fan relay to run all the time
• removed the 160* thermostat and eliminated it
• unhooked the vaccum advance all together
• advanced and retared the timing

i know not all of these ways are the proper ways to do this stuff, please don't correct me on that part of it, most of this was used as diagnosis, all came to no avail im running short of optioins on what my problem could be,

my questions are;

• Do i need to run an overflow tank? Right now i have it capped off, i plan on hooking it up after i find a better spot for my starter solenoid.
• Are the 305 blocks a thin casting and don't like to be overbored?
• Do these cars come with a fan shroud or just the part that holds the fan up?
• Could the excessive fuel pressure be causing a rich condition that makes the car over heat, like a stuck on choke?
• I tricked the fan into running by flipping the air on, but the compressor is unhooked and not spinning, could this still heat the condesor?

i plan to set the timing with a light, watch the water in the radiator while the car is running to look for air bubbles, replace the thermostat,check compression for a bad head gasket, inspect my water pump for a worn impeller, putting a fuel pressure regulator with a return on, and get an overflow tank of some sort hooked up

thanks in advance guys

jonmark1985

ok, just tryed running ported vaccum, still gets around 220

five7kid

iTrader: (14)

Points????

jonmark1985

yeah, i got the car converted to a points dizzy

CG_1985_Z28

if u took out ur thermostat put it back in, and try running stright tap water with a bottel of redline or royal purple water wetter.... some times if the antifreeze is eather old or not mixed properally if wont cool right at higher speeds. i just ran the Hot Rod magizine power tour from clevlant to arkansa and back with just tap water and a bottel of the redline and my temp never went over 185 with a 180 thermostat..... good luck

five7kid

iTrader: (14)

The dwell on the points should be more like 30 degrees (28-32 is what I recall).

Not sure if that's related to your hot running, but you should at least get that right. Set the dwell, then the timing. With a timing light. With the vacuum advance disconnected.

bilms01

Hot at highway speed and good intown
Where have I heard this before




Front air dam? it it where it belongs

jonmark1985

ok, we just set the timing at 12° (inside joke) the car runs a whole lot stronger before it was off the tab it was so advanced, my buddy thinks cooler, but im not sure yet, also the black plastic panel under the nose of the car is removed due to damage, i could see about getting another

Stekman

You need an air dam.

raptor80dad

AIR DAM

jonmark1985

Does anyone make a repo unit, or are they still available from GM? I would rather not put a ratty one on. I may just try to fabricate one from a thin sheet of aluminuim or galvinized steel mounted 2 or 3 inches off the car and put a bend on it at 45° angle aimed towards the radiator. If i do i'll make sure to post a pic.

Supervisor42

You want a nice new one? Here you go:
AIR DAM
The air dam is a MUST if the engine makes more than 150 hp.
EDIT:when you get the air dam on, put the thermostat back in and un-hotwire the fans. It's costing you gas mileage.

dirtgta

88 gta car runs 230 at highway also air dam is there all original car same things done new pump fans radiator etc still runs hot?!?!

ThreeOhFive

what is normal opperating temp for a thirdgen then? i thought 180-220 the normal opperating tempature range on a 305.

dirtgta

yes 220 is normal but with no t stat should be around 160 i have a 92 rs that stays at 160 my gta is a tpi and just recently started doing this its ran at 200 210 all the time until 2 weeks ago it just goes up on the highway

red30011

I've heard you can get them cheaper,or was I wrong. Thought I remember reading somewhere you can get them for like $20? I think I need one as well(will know as soon as dial up loads the picture in that link).

Supervisor42

I feel like holding a class called "Cooling Systems 101".
The fuel feedback engines (anything with an oxygen sensor) are equipped with a 195° thermostat from the factory.
This limits the minimum temperature of the coolant.
They did this for emissions and fuel mileage. The coolant will not begin to flow thru the radiator until this temerature is reached. This is NOT a bad thing. As the temperature of the coolant rises, more flow thru the radiator is needed the more the thermostat opens.
The radiator and the air flow thru it removes the heat.
The thermostat will be completely OPEN at 210°. IF the cooling system is working properly the normal temp of the engine will be between these temps.
If the temp is above 220° (let me say this very slowly) a 160° thermostat (or no thermostat) won't make any more difference than the factory thermostat because they will BOTH be completely OPEN at 210°.
Yes, thermostats fail. They won't open, they get stuck, or won't close. Taking one out that won't open or won't open completely, will get you home. But that is the only good reason to remove one.
There are plenty of fire-breathing 383's running around with the stock radiator keeping their cool just fine.
Let's talk about cooling systems that overheat at cruise speeds.
There are only 4 reasons that this happens.
1: inadequate flow of coolant thru the radiator.
2: inadequate flow of air thru the radiator.
3: too much heat being added by the engine to the coolant. (rare)
4: inefficiency of the radiator to remove the heat with adequate coolant and air flow thru it. (ie: too small) (also rare)

Next we'll list the causes of the above conditions with the most common ones first.

1: Coolant leaving the system (leak or radiator cap not holding pressure). Thermostat stuck (or partial opening). Slipping fanbelt driving water pump. Clogged radiator core coolant flow (scale, rust, stopleak, silicone, etc). Flow path thru bypass hose, heater circuit, etc. that coolant is going instead of thru radiator. Wrong rotation water pump inatalled (serpentine verses v-belt). Collapsed radiator hose.

2: Air dam missing, (fans can only remove heat produced at idle). Bent fins on A/C condenser or radiator core. Radiator air path clogged with dirt.

3: Blocked exhaust (clogged cat/muffler). Pulling the 30 foot trailer with my race car on it, uphill, in August, when it's 100, with the A/C on. Early ignition timing. Fuel mixture too lean. Late ignition timing or malfunctioning engine (have to hold it on the floor to go 50).

4: "Painting" or "Plating" of the inside of the tubes in the radiator core from contaminated coolant or stopleak. Excessive heat load from transmission oil cooler being dumped into coolant. Too much heat being dumped into the airstream before the radiator by the A/C condenser.
Spent all of my money on the "502" and thought I could get by with a stock radiator.


I have left off a few causes. Can you list them?

Next week: How to use a hand-held non-contact thermometer($29) to troubleshoot cooling system problems...

Supervisor42

Aw c'mon. Anyone, anyone, anyone....

oil pan 4

iTrader: (1)

Do you have your coolant bypass hooked up?
(You know the coolant lines that go to the heater core).

Project86B4Z

So does my 85 sport coupe with the 2.8 MPFI...with z28 gfx and air dam...like dirtgta says mine runs around 230 to even 240 at speeds up to 70mph and gets down around 220 between 30 and 50 MPH. Got new antifreeze and 195 thermostat which for what ever reason seems to open around 240 to warm up. Water pump and hoses are good no flexing or leaking on acceleration...

Supervisor42

Well, I guess 2 years is long enough.

1.2: Leaking of combustion gasses into cooling system displacing coolant IE: bad head gasket. (coolant reservoir gets "full")

1.3: Coolant being "consumed" by the engine causing the system to lose pressure IE: head cracked at intake valve seat. (coolant reservoir gets "empty")

@my85sportscoupe> Sounds like you may have a gauge/sender problem. Get someone with a handheld thermometer to verify the actual coolant temp; especially if the gauge reads above 210 at idle.

89bird2.8

i have the same problem with my 2.8. replaced the water pump, thermostat, hoses, radiator. had to hot wire the fan to run at all times. air dam got messed up so took it off, but it still ran hot when it had it. hills really kill it, cant hardly drive it in the summer.

Supervisor42

RTT=
Read
Tha
Thread.

89bird2.8

ill get a new air dam and see if that helps. also i changed the tranny fluid and filter. after that it wants to hesitate and spit and sputter. didnt not do it before i changed it. i put a new fuel filter and checked pressure and run some lucas fuel injector cleaner thru it. still no change. if i hammer it itll take off fine, but easing in the throttle when it does it

Supervisor42

Is the check engine light on? Hooked up and working? 'Smog pump' still on it?
If possible, set the ignition timing to remove it from the list.

Joe Tag

iTrader: (4)

Air dam and 180* thermostat. I had the factory 195* in my car, though it never boiled over, it got too hot for me to feel comfortable. I wanted a 170* but the choices I had at the time were 160 and 180. I opted for a 160 and it honestly runs a little too cool now. Also, any mixture more than 50/50 antifreeze will inhibit cooling.

rusty vango

.60 over is a bit much.it makes the cyl walls too thin, which contributes to overheating. and a thermostat is a flow control device. as well as a temp regulator. not having one causes the coolant to flow too fast through the system, thusly, not removing enough heat as it passes through. and points!!?? HEI makes a hotter spark .more reliably. but if it makes you happy, WTH right? and ,yes, there is NO way for it to cool properly with out a air dam.

Supervisor42

Jonmark was working on his car 7 years ago. He's probably got it fixed by now....

mmadden55

If you have to, go to Lowes or those other guys that don't sponsor Jimmie Johnson, and get some 6 inch wide vinyl baseboard strips and make one. Cheap easy and hard to tear up on driveways also cheap to fix if you do.

rusty vango

I find it ok to post to old posts BECAUSE........ there are junior members who read through these to gain information. lurkers if you will.

aramirez121

also another big thing that was a problem for these cars is the lower radiator hose sucks in on its self when you hit the throttle for some of them out there

rfoster23g

yes^^^^make sure you get one with a spring in it

89bird2.8

yeah my bottom radiator hose exploded Friday going up a mountain. Wasn't runnin hot yet cuz I'd only been drivin maybe 5mins. Damnest thing

aramirez121

how old was it?? vuz after awhile pressure builds up on it and will blow it if its the original it happened to mine going up a hill last year

89bird2.8

a year or so old. I'm startin to think I have a cracked head or gasket on the exhaust side

aramirez121

well only way to find out is check the pressure build up on it also if you have a bad w/p it will cause a huge pressure build up ive installed a few that were like that and the pressure was gone so you might wana check that first

89bird2.8

blown head or gasket. got a new bottom radiator hose on it and it started spewin water out of the top hose round the thermostat. never done that its new checked the oil...... full of waterrr