87 trans am
Motor swap from stock 305 TBI to a 5.7 L 350 Carburated

Was sitting for about three monthes due to a bad carb, bought a new Summit 750 cfm Carb, and new Summit intake manifold...

After I put the new intake on I noticed that it didn't have a coolant hose port in the back next to the distributor like the stock one did. So I plugged it hoping it wasn't important. Now I have over heating problems. I'm not sure what that hose does but its attached to the heater core hoses that go into the fire wall. If I can take a pic, that might help you guys figure it out. I know there's some very smart people on this site so I'm sure you all can help me fix this problem... I'm hoping its not that hose but I have a feeling it is. Is rather buy a new water pump and radiator than take that manifold off for the fourth time.... Pain in my ***....

Thanks

 

Whats the problem? highway? idle overheating? be more descript.

 

Overheats driving around town and on the highway. I took out the thermostat to see if it would still overheat and it did... After about 2 miles of driving in the range of say 25 and 60 mph it will start to heat up, after about 5 miles is when it starts to get HOT. Like 240 250* hot...

 

1. enough water/coolant?
2. Air flow? check all radiator air flow directions
3. Pressure tested system?
4.check water flow, can you see the water flow correctly in the radiator? (this will rule out reverse belt issues where the water pump is pumpin backwards)
5. What is known of the motor installed?


MY experience is that if all the above have checked out than the other issue may be an extreme lean mixture at cruise.I would check for vacuum leaks etc. then make sure the carb is jetted correctly........if all the above check out.

 

Also check the timing.
the hose you blocked off can b run right off the water pump if it has the port on the top to do that..

 

Damn good catch TTOP! I totally forgot about that. Retarded timing will saturate a motor with heat instead of sending it out the exhaust pipe!

 

Wow, I had no idea the timing could lead to over heating, that helps a lot guys. Thanks

 

Still have the air deflector under the car?

 

Air deflector? Never heard of it

 

Was just recently playing with my timing, plotting the curve and getting it to run at the edge of pinging across the rpm range (carb + non-cc hei dist). Also changed to manifold vac advance instead of ported as part of the deal.

Ended up with noticeably lower temps as an added un-expected result.

Big flap bolted under the bottom the the rad, to deflect air up across the rad. Needed for extra airflow at speed.

 

[QUOTE=Big flap bolted under the bottom the the rad, to deflect air up across the rad. Needed for extra airflow at speed.[/QUOTE]

Yep. Your issue sounds exactly like the deflector is gone. Could be something else but this is the easiest thing to check. Just look under the car, should be a black plastic panel bolted under the radiator support in back of the air duct work that goes up into the radiator

 

On the firebirds its a multi part deal. our lower part goes across the bottom from side to side..

 

http://compare.ebay.com/like/3903619...Types&var=sbar


Here's one if yours is gone.

 

Oh ya I have that, thought it was a rock deflector.... Haha

 

And speed bump and gutter catcher

 

Lean of air or fuel? I'm trying to figure out why its still over heating. I took off the rad. Cap and water was flowing through like it should. Also felt it flowing through the hoses. It doesn't make sense....

 

Get a laser heat gun and see if your car is truely overheating.
the sending unit/gauge may be messed up.
thes cars do run warm from the factory.

 

do you got a bypass from the intake to the water pump? some used the heater core the the bypass back to the raditor

 

I had an issue where the gauge kept going back and forth between 190 and 220 while going down the highway on my old engine that was jacked up to begin with. Changed everything. Nothing worked. I changed to an Autometer gauge and there was temp was fine. It was a bad gauge as I had changed the sending unit as well.

 

I'm sure its getting to hot, when I got home it was steaming and coolant was spewing out of the old hose... I replaced both hoses upper and lower, new radiator cap, new coolant filled to the brim. Still gets too hot. I'm thinking its the timing and fuel ratio, seeing as how I can't find the timing marks on the crank its just timed by ear. Same with the carb....

 

My heater cor has two hoses going into it, one of the two has a smaller hose coming off of it into the intake, but my new intake doesn't have the port for that hose. So I plugged it with a bolt and clamp. Il take a pic soon...

 

The small hose going off to the right was connected to the stock intake, this manifold doesn't have the port for it so it is now plugged.. also seeing as how there's no thermostat in it, how would it still be getting so hot?!

 

If Your running the computer distributor, you have to unplug the set timing connector to set the timing properly.
fix your timing first. Make sure you have the correct balancer and timing cover so they work together.

the little hose doesnt really have to be there.

 

Do any of your fans come on?

 

I just drove it down the street to get lunch. subway = mmmm..... Sweet onion chicken teriyaki is bomb.
Anyway, it got a little warm but I didn't drive it far so it didn't have a chance to over heat. It was about 2 miles there 2 miles back at about 30 mph. Got up to 200 - 220* fans didn't come on that I know of. Didn't hear them, and when I got back to the house it wasn't hissing or anything.
Possibly just the coolant temp sensor?

Just wanna say thanks everyone for the help so far. I appreciate it

 

My car doesn't get anywhere near 200 - 220 in a few miles. Check the tech article on this site about the fans, I think the secondary fan should be on at about 220 or so, which means the primary should be on already.

I suspect the gauge is not reading correctly though, 220 after a few miles doesn't sound right.

 

I don't think the fans are coming on at all...

 

The ECM switches the primary fan on, you probably don't have the ECM or its sensors anymore since you switched to a carbed motor, do you? The secondary is mechanically switched by a temp sensor/switch in the passenger side of the block, between the 6 and 8 cylinders.

This sounds like the cause of your overheating problems, you need fans.

 

Should I make a relay so the fans are on when the car is on? They'd be on all the time but I think it'll keep it from heating up, right?

 

I'm pretty sure I only have one fan, not duals

 

You could count them to make sure. Two comes immediately after one.

 

Yes, lots of people do this. The car runs quite cool but unless you live in a very cold place you should be OK. You could put, say a 200 on 180 off switch in the passenger side block and have that switch it. There should be a switch there already or something plugging it.

 

I'm sure the ecm is still there, I have all digital gauges so there must be an ecm somewhere, right?

 

I don't have a digital cluster, but I doubt the ecm would have anything to do with it - engine control only. Sounds like you need to figure out exactly what you've got. If it's a motor swap with a Summit carb, and presumably a vac advance dist, the ecm will not be doing anything, even if it's still there.

Agree with Cosmik, the fans gotta run - pretty basic. You will likely get overheating withing 10 mins from cold, if the fan(s) don't kick in. Make sure the shrouding around the fan(s) is there too.

 

Yeah, the fans are veeery important...

 

How would I wire it to a key on constant

 

ground the sensor wire,

At highway speeds your fans wont do much at all because the air flow should be more than enough to cool.

In traffic and idle thats were they count.

I think fans kick on at 223degrees

 

The ECM might be there but are any of the sensors connected to it? You have replaced the engine, did you put all the original sensors on the engine and hook them up to the original harness?

 

There is a green wire in the original harness that connects to the temp switch in the block on the passenger side between 6 - 8 cylinders. If you ground that wire the fan will come on.

 

I didn't put that motor in it, looks like someone who barely knew what they were doing put it in. I bought the car from a buddy who drove it for a couple months, then it stopped running. I bought it and put a ton of money into to get it where its at today, only problem is the over heating...

 

I can't find the wire you guys were talking about, do I have to get to it from underneath the vehicle?
I found one black wire going into the block around the same area as you said but when I grounded it it didn't do anything.... I'm laying underneath my car looking at another mystery wire that plugs into the block right above the oil pan... Is that it?

 

That would be your knock sensor.

 

Then Where the hell is the sensor I'm lookin for?

 

what kinda engine do u have?
cause i haven't found it either but stock 305TBI have it on the drivers side and have a whire or 2 I know around where it is and looks like this..

http://www.autozone.com/autozone/par.../N-ii76iZ9gsmf

 

I replaced my 305 with a 350. I too had what I thought was a hot coolant condition. I went to a local parts store and bought a new electric water temp unit. engine temp was fine. When I looked at the size of the GM sending units for the 305 and the 350 they were different sizes with different internal resistance. This is difference in internal resistance was causing the higher temps.

 

I doubt fans are his only issue, as he has said it overheats (not just runs warm) on the highway as well. Without fans a car might run warm, but shouldn't overheat cruising on the highway with the fans off, unless another issue is also at work. With his cooling system missing the bypass the new intake removed, I would check the system for air pockets where steam could collect. Basically, if you have an air pocket somewhere, the system can't pressurize, which keeps the boiling point of your coolant lower than it should be. Once it flashes to steam, it is supersaturated with heat and no longer has any ability to cool. Add to this the fact that the water pump is incapable of pumping steam, and a possible trapped pocket of air, and you have a very bad situation. I suggest you do a thorough going over of your cooling system, burp all air out of the system with the car off, cold, and the cap off, adding coolant as necessary, then start the car and let it warm to operating temperature with the cap still off and burping as long as you can before putting the cap back on. This should effectively remove any trapped air and ensure your most basic part of your cooling system is working properly. I would suggest doing this before playing with any other possible cause.