Why would installing a new intake & carb cause my car to overheat???

Why would installing a new intake and carb cause my car to overheat?

The weekend before last, I replaced the 2bbl intake and carb on my car with a used cast iron 4bbl intake and a new Holley vacuum secondary 4bbl. Everything went pretty smoothly during the installation with the exception of the throttle and kickdown linkage. Since then, the car has overheated on all but one occasion since firing it up.

I took the car to work the next day. The car didn't overheat, but I ran into other issues, as one of the sidewalls grew an apple-sized bulge and I had to get a replacement.

The ride home was going well until I overheated about five miles from home. The brakes were acting funny and I was driving funny to compensate, so I didn't think much of it.

The car was layed up for a couple of days while I gathered all the parts to fix the brakes and found time to do the job. On the test run for the brakes, the car overheated in about three minutes.

Thinking that the problem was the thermostat, I pulled that out and ran the car around. I rqan it on the highway and local roads. Everything seemed peachy until I was stopped for a while at a light and the temperature gauge quickly crept up.

Earlier this evening I installed a new thermostat into the car. I fired it up, and before I could finish tuning the carb, the engine started overheating. That's where we are now.

The engine in question is a 383 Mopar big block and the car is a '65 Dodge Custom 880. Not exactly HAMB material, but more on topic than TV shows or tatoos. There is an exhaust crossover p***age in the intake, and I partially restricted it. The engine is reading 20-21" of vacuum, so I don't suspect a vacuum leak. The carb is making a funny whistling noise when you peg it. I can turn the mixture screws in all the way without stalling the car out. It'll run rough, but doesn't stall immediately like I'm used to.


Any ideas?


Thanks,
Ed

 

I am gonna say Vacuum leak.

 

Do you have to pull the distributor to change the intake on a BB mopar ?

If so, it could have ended up more retarded than before., which causes overheating.

 

Did your timming change....(retarded)...Nothing will make an engine overheat faster than retarded timming. Good Luck...H

 

Did you install a new valley pan gasket when you replaced the intake? Those have been known to cause air/vaccuum leaks.

What intake and carb, and what condition are they? New, rebuilt, or just bolted on?

 

Ed, are you sure it was a 383 intake? I think I'm remembering from back in my BB mopar days that some other intakes would bolt up but didn't have all the p***ages match.

 

running waaaaaylean?

 

Thanks for all the replies...

I went back outside after I posted the first message, and sprayed carb cleaner looking for vacuum leaks. Nothing. I'm still not convinced that it's not leaking though.

The distributor is located in front of the manifold, so I didn't have to touch it to install the intake. I'll retime it tomorrow for good measure.

I'm pretty sure that the intake matched the valley tray and the tray matched the heads...

It's getting to the point where I'm second guessing EVERYTHING.

The intake was used, and I think it was an early intake because it wasn't a spreadbore. I blasted it and then used sandpaper to clean up all the mating surfaces.

Carb was new, fresh out of the box.


Ed

 

I don't think so...but I'm second guessing everything. I don't have an A/F gauge in the car yet, so I just turn the screws until I get the highest vacuum reading. I've been tuning engines that way since I bought the vacuum gauge three or four cars ago and haven't really had any problems.


Ed

 

are u boiling over? or is the guage just goiing up? did u put on a new sending unit in the intake? i dont know mopars and not sure if there even in the intake. perhaps the sending unit u have is bad. i would geta digital tmp guage and see what the upper hose is when the guage says its over heating. or you could have some air pockets in the coolent system run it with out the cap and let u burp and see if that helps. but i would look at that temp sending unit. this is why i hate guages there useless. just make you freek out

 

3 things came to mind. 1- timing needs to be reset 2- running too lean 3- problem with auto ****** kickdown cable causing the torque converter not to lock up, thus overheating the ******. The overheated ****** fluid heats up the radiator and makes the motor not cool properly. The result, you see your water temp creep up when it's really the trans. I know this happens with ford aod's, don't know about mopars. But you said you had linkage problems, which is just what does it on the fords. Good luck

 

My Buick drove me crazy all last Summer. It constantly ran hot. I was sure I had checked the fluid level several times. I put in a new thermostat, flex fan, rad cap, and anything else I could think of to make it run cooler. The flex fan and 160 Thermostat helped a little, but it still ran way too hot for me. Then one day I decided to check the fluids again and saw it was low. I kept adding anti freeze until it had consumed almost a full gallon. My guess was that it had an air pocket in the system somewhere because it hasn't run hot again. Temps now are around 160-170. Maybe 180 after sitting in traffic. Just a thought that worked for me....

Spike

 

DirtyT - It was puking out the overflow hose last night. I'm pretty sure it's actualyl getting hot! I should replace the cap though... maybe that's malfunctioning. I doubt old factory gauges too, so I ordered a three gauge cluster from Summit.


Stud - It overheats at idle just sitting in my garage. That isolates the problem to the engine. I'm going to check the timing tonight after work.


Spike - I didn't touch the fluid level during the intake swap. It was only when I swapped out the t-stat that I had to drain the radiator.



Did anyone read above how I set the A/F mixture? Is it a good technique? It's worked for me in the past, but like I said I'm second guessing everything right now.



Thanks again,
Ed

 

PS- Is there any way to check a water pump?

PPS- Other than looking for white smoke at the tailpipe, how can you check for a blown head gasket? Someone suggested that I might have loosened up on the gasket when I replaced the intake.

 

Ed, try changing your rad cap. Mine went bad in my roadrunner when I was breaking in my 383. Or it could be the wrong thermostat(temp wise)in there. There is a couple years of those motors where they used a 160 degree thermostat in them. I'm running one in my 383. Hope this helps. later shawn

 

I was told to watch for bubbles in the radiator when the car is running, as a sign of blown headgasket.


Check for play in the pump shaft by wiggling the fan back and forth. later shawn

 

My thoughts are:

1. You've got an air lock and the engine is not full of coolant even though the radiator is.
Feel the upper hose when the engine is warm to see if the hose is warm as well.
You can get rid of the air lock by cracking open a fitting - temp sender, block off plug or heater hose ****** - and letting air escape until coolant comes out.
Or, best of all, pull the thermostat and drill a 3/32 - 1/8" hole in the flat area of the thermostat so air can bleed through during the fill process. It won't flow enough coolant to impinge on the warm-up process.

2. Is it possible the thermostat is upside down?

3. Do you have a vacuum advance ignition? If so, where is the distributor vacuum line connected?
On the GM engines if you don't have the distributor vacuum connected to full time vacuum (manifold vacuum) so the vacuum diaphragm can advance the timing at idle, the engine overheats.
That could be true for your Mopar as well. I'm not sure where the vacuum advance connects on those. Regardless, if I was running Mopar or Ford and the engine was modified I would set the engine up with a GM type advance curve.

Getting back to the GM engines if you connect the distributor vacuum advance line to ported - or venturi vacuum - you won't have vacuum advance at idle and that could cause your overheating problems.

Generally speaking, vacuum advance problems usually take a while for the engine to overheat. Perhaps 5 minutes on a hot summer day.

One off the wall thought that may not apply to you - did you use a Mopar specific thermostat?
I ran into a problem with a Cleveland 400-M when I learned the only thermostat available for them was 197 degrees. I found that a 160 degree Chevy thermostat would drop right into place. Where I fooled myself was the Ford thermostat has a block off ****on on the bottom of the thermostat that closes off an approx 3/8" hole at the bottom of the thermostat well when the engine is warm. When the engine is cold, the ****om is open and that forces cold coolant to flow through the byp*** hose thereby speeding up the warm-up process. When the engine is warm, the thermostat opens allowing coolant flow to the radiator and at the same time the thermostat ****on closes off the 3/8" hole in the thermostat well which ceases coolant flow through the byp***.

The Chevy thermostat had no such block off ****on so when the engine was fully warm the stat would open and the byp*** was still functioning which led to an overheating problem. It wasn't too bad and the pickup was usable, but it was worrisome.

Cured the problem by tapping the hole at the bottom of the thermostat well and installing a flush allen driven pipe plug. Granted, the byp*** no longer functioned and it wasn't a big deal in Southern California, but It did cure the overheating problem.

 

I'm not familier with BB Mopars, does coolant run through the intake? If so, I've seen different brands of gasket that had the coolant p***age holes punched to small. In that case I opened up the holes some to stop water restrictions.

C9- For future reference, on 351c 351/400M if you want to run a thermostat that is 160 or 180 use one from a Ford 429/460. I used to run 160 degree thermostats in all of my 351C, never had a problem. They use the same setup.

 

Coolant does not run in the B and RB intakes,it was overheating before you drained the coolant ,that isn't the problem.
I am 90% sure it is a va***n leak . When I worked at a Mopar dealership we could buy thin paper gaskets that would sandwich the tin gasket to help the manifolds seal .This was a big problem especially with aluninum intakes.

My way of checking for va***n leaks is to use a propane torch.Crack it open and run around all the top side stuff ,carb also. If nothing changes put it in the valve cover hole and if the bottom side of the gaskets is bad it will pull the propane in and the rpm will go up.You do know that the torch is not burning when you do this stuff ,right?

Another thing, I have seen several engines ruined by blasting intake manifolds and not being able to get them clean enough inside,the rings do not like that stuff. If you must blast a manifold ,use duct tape to mask it so it won't get anything inside.
Hope this helps.