Timing, overheating, new edelbrock carb.

[nickeboy]

Hey CB. I changed my carb to an edelbrock 650 from a Holley 750. It didn't run very well at first so I adjusted the carb. I was then told I should adjust the timing first. I didn't, I adjusted the carb and began driving it. It tends to overheat only when idling at a long stop light on a hot day (90*).
So I just put on a timing light after reading a few tech articles and the timing looks to be right on the 10 marker. (Maybe closer to 11). Anyhow should I change it? Should I just buy an electric fan? Would love your 2 cents.

 

[DirtDonk]

If that 10 degrees is accurate, I would not think that is your problem. Should not cause it to run hot until you get much lower in my experience.
But what has changed? You're likely either running too lean or too rich. Did you change anything else at the same time? Such as the PCV valve or other stuff?

And it can't hurt to play with timing. You could see if raising it to more like 12 to 14 changes how it runs. Listen for any pinging, rough running or hard starting when hot, but normally our engines don't mind that much.
However, 10 is the sweet spot for many of us.

Hmm, on a side note, is your vacuum advance connected to full manifold vacuum, or the timed port?

Paul

 

[nickeboy]

I've changed quite a bit. Including radiator.
It's an MSD ignition and I don't think it has vacuum advance.
I'm going to try and check total timing (3000 rpm) and see where it sits. I was told 32 is the sweet spot. Any different advice?

 

[DirtDonk]

Every engine is different. Some don't like more than 30, some can tolerate up to 45 and not complain.
Too bad about the lack of vacuum advance though. Not the best for a street engine. Even a race engine driven on the street can benefit.

Paul

 

[blubuckaroo]

What carb adjustments did you make? Just the idle mixture and speed?
An important adjustment on an Edelbrock carb is to use the correct metering rode pull-up spring for your engine's manifold vacuum. If the spring is too soft, the engine is going to run lean, ping, and overheat. It acts like the timing is too far advanced.
If you don't have an owners manual for your Edelbrock carb, it's available online on the Edelbrock site.

 

[B RON CO]

Hi, you changed quite a bit so let's make sure it is all set up properly. You set timing first because adjusting the timing will change the idle. You should have a vacuum advance on your distributor, and most guys use ported vacuum, some like direct vacuum. Overheating means what? A little temp rise should not be a problem. What temperature are you seeing? It should idle in your driveway all day with no problem. If you have a temperature gun you can see the actual temp at the thermostat housing. Does your new radiator have a shroud? Is the fan 1/3 in and 2/3 out of the shroud? What temp thermostat is in it. Check out the basic stuff and see what happens. Good luck

 

[JSBX]

My son had this problem last year while we were at OCBR. He changed out the carb with a rebuilt one before we left home.. Drove it down the road a mile or so and everything was fine. When we got on the trails it started overheating and running bad. We did not have a timing light so we advanced the timing and it got worse. Backed off on it and bingo, stopped overheating and started running great. Stil have not put a light on it to see where it is at. May not be your problem but it is easy and free to play with the timing.

 

[brianz426]

I was having the same problem with my Bronco this fall. Completely stock with a fresh rebuild and stock carburetor. The only thing that's changed since the problem started was removing and rebuilding the carb. I was told timing should be the first thing I check. As soon as the weather improves and I can get out I'll report back with my results.

 

[Rustytruck]

How many blades do you have on your fan, is it the factory fan and are you using a fan shroud. The best fan Ford used in the Bronco was a 7 blade model used in the later models. Is your idle speed at least 700 rpm?

with a carb change and adjustments I would pull the plugs and check color to make sure your not running lean.

 

[jckkys]

There's far to little information. To offer useful suggestions we need to know where you were before you changed quite a bit and where you are now. What engine do you have and how is it set up? Is it a 302, 351, or 408? What cam, intake, heads, exhaust system, and ignition system do you/did you have? A high revving large displacement engine would be the only place a 750 CFM Holley would make any sense. If you put a new radiator in, that would be the first place to look. What other parts of the cooling system were changed? What fan, shroud, radiator do you/did you have? Edelbrock AFBs made for universal applications are on rich side of A/F mixture in idle, transfer and cruse modes. Lean mixtures do tend to run hot, but that's not likely with a new AFB. What do you mean when you say you adjusted the carb? Retarded timing is another common cause of over heating. When you talk about 32 degrees timing at 3000 RPM is that total ie initial + centrifugal or simply centrifugal? At what RPM does the centrifugal advance start? Here's a good article on setting up a timing curve;http://www.fordmuscle.com/archives/2000/03/timing/index.shtml. As blubuckeroo pointed out, the Edelbrock owner's manual gives you step by step process that would really be adjusting your carb.

 

[brianz426]

I'm way overdue on this update. In my case running lean was my problem. It was very strange how well my Bronco was running, but once I put a vacuum gage on it and readjusted the mixture screws and idle (stock 2bbl) my overheating at idle went away.

 

[DirtDonk]

Great news Brianz! Thanks for the update.

Paul

 

[nickeboy]

This is great news. My overheating problems are getting better. I need to dial in my Carb and Timing to see if I can make it even better.