2thousand2

I have a new Edelbrock RPM Air Gap intake on my sbc in my 1969 Camaro. We are having some really cold weather in the STL right now. My temp gauge will fluctuate from 180* sitting still and then go up to 240* when driving and then drop between the two temperatures on the highway. It looks like the t-stat is opening and closing a lot. My temperature sending unit is on the drivers side cylinder head (auto meter gauge). I am still messing with it checking the coolant level and all that, I was just wondering if the really cold air passing under the t-stat is making it act weird. It is a new 180* thermostat btw, maybe there are some air pockets working their way out. Everything seems ok when the temp outside is warmer. Also my carb is staying soo cold with this new intake the choke keeps closing going down the road (cowl induction hood and k&n lid doesn't help im sure).

Also the car is a manual trans, lunati .480/.480 230/230 cam, and 670 street avenger carb....is there anyway to get away from a bad stumble when the car is under a load under 3k rpm?

Thanks for any suggestions.

1997bird

iTrader: (2)

You can adjust your choke themostat on your carb to go ahead and open the choke flap up a little bit. The temp change sounds like the themostat is not operating properly. Even though they are brand new they can be bad off of the shelf. I worked at a parts store for almost 11 years before opening my own speedshop. We used to warrenty quite a few thermostats that were brand new off of the shelf. Try boiling the thermostat in a pan of water so that you can watch what it is doing. You will nead a themometer that can read the temp, like a candy thermometer.

2thousand2

I have the choke adjustment going all the way to the stop to make it come off as quick as possible. Yeah I have worked in parts for 7 years and have had some bad thermostats too. This one worked before I took the intake off so maybe its just some air.

Any ideas on the stumbling? It seems like its too much fuel when you hit the gas under a load.

1997bird

iTrader: (2)

How much manifold vaccum do you have at idle? What is you air fuel ratio in vaccum as well?

joewee350

Maybe you just have a faulty temp gauge or temp sending sensor.

darom

iTrader: (2)

Did you check your t-stat in a pot with boiling water to see if it was opening? As a habit, I always do it on my 67.

You might be right about the air pocket in your engine. You can use a $35 dollar special from Harbor Freight tool with laser remote temp sensor, verify the temp with your Autometer gauge, then point the device at your cylinder head where the sensor is installed (there is going to be a bit of discrepency).

2thousand2

Ill check the vacuum and let you know. I do not have an air fuel ratio gauge tho or any way to check it.

2thousand2

at 2k rpm vacuum is at 18in holding steady. At idle it jumps around a little with the cam but stays around 10-12in.

I topped the coolant off so I think the temp fluctuating problem is taken care of. I prob shouldn't be spoiled with a heads/cam LS1 that has perfect driveability...then I wouldn't pick on this car so much lol.

Villain281H

iTrader: (5)

Temp gauge usually will be a little higher reading from the head versus the intake on placement from cases I've seen, just an FYI.

I think all the other comments have you on the right track, good luck!

Derek

1997bird

iTrader: (2)

With your car at idle, start adjusting the A/F set screw on the passenger side of the car (looking at the car from opening the hood) in and out until you get your highest vacuum reading. Then go to the A/F set screw on the driver's side of the car (by the throttle linkage) again start adjusting the screw in and out until your vacuum gauge needle levels out. Sometimes you may need to go back and slightly re-adjust the set screw on the pass. side to completely level out your gauge reading. Ideal vacuum reading is at 14.7", I usually try to set mine at 15.0", depending on your combo you may have less than this. Set it as high as you can if you can't get any higher than 10-12". If this is the case you may want to bump up your intial timing a few degrees and then reset your idle. There are alot more variables than this, but should get you close to getting your car running like you want it to.

2thousand2

Thanks a lot! Ill give it a try and let you know how it runs!!!

2thousand2

Ok set it with a vacuum gauge...a lot smoother and better idle. I can tell its set a lot better...thanks for the tip!!!!

The car still has a dead miss from 2-3k rpm I have no clue what is going on. Cylinder 4's terminal inside the ignition cap was like new where the others had normal wear tracks. I checked spark on that cylinder through the rpm range and it is making a nice spark. I checked compression on that cylinder and it was 140. I did a check on all the cylinders about a month ago and it was 140-150 on all of them. All of my valves are tight and the wires are on the correct cylinders. The cam has changed since the problem and the carb has changed since the problem so im gonna start looking more into those areas I guess. I thought the carb was putting too much fuel out when you hit the gas (making a stumble or a miss) but if you hold the throttle steady it will still miss in that rpm range. Very weird situation.

1997bird

iTrader: (2)

Take your manifold vacuum and divide that by 2. That should be the power valve size. Stock it is going to have a 6.5 in the carb. You also may want to put the lightest vacuum secondary spring into it to let the secondaries engage sooner. If this doesn't help, you may need to advance your intial timing a few degrees.

Nate81Camaro

My 81 camaro has an air gap on it, and I've drove it in -5 degree weather without any of the problems you're having...it just runs really cold (160ish). With a 2 core aluminum radiator, a fan that pulls alot of air, and a 180 stat I wonder why (Above 20 degrees, it heats up to 180 and doesn't move above that...even in traffic). Hope that info helps ya.


-Nate

onebad82z

iTrader: (1)

Do you have vacuum advance set up on the distributor? Hooked to full manifold vacuum or ported if so?

If , when it is stumbling at that rpm and steady throttle, you mash it does it pick right up and go without the miss?

2thousand2

We had it set before with a timing advance analyzer to max advance at 3k rpm with no vacuum (a friend set it for me, he did it on his and it was great). After having the intake off I didn't have that type off timing light so I set it at 12* vacuum capped engine hot at 1k idle. Then I drove it with and without the vacuum advance connected and it still misses hard. It is hooked to ported vacuum when I have it connected.

onebad82z

iTrader: (1)

So the cam and carb was swapped and then the problem began (if I read right in post #12)?

I would shoot for more initial timing myself with that combo...say 16-18 and of course limit the mechanical advance to keep total around 36.

What type of distributor are you running..HEI, MSD Billet, etc? What springs do you currently have in the distributor?

1997bird

iTrader: (2)

Did you have your vacuum advance hooked to the carb, or directly to the manifold? If it was hooked to the carb which vacuum outlet did you have it connected the passenger side or the drivers side? B/C it souds like it is going to full advance too soon.

2thousand2

I will try more timing. I have a gm points distributor converted to electronic with a crane fireball setup. The advance springs are stock. I have a nice spark (I doubled the gap distance with a spark tester and it still fired) throughout the rpm range.

2thousand2

I have tried it with no vacuum advance at all and it will still miss. When it is hooked up I have it on the passenger side (ported) of the carb.