My son and I finally got a new carb installed. This time it's a brand new Edelbrock 1404 500cfm Performer AFB. The carb is working great and seems to be a much better match for our engine.

However, a few things that jumped up at me was how fast the engine is heating up now, I lost 2 lbs of vacuum at idle and for the first time I notice oil in the air cleaner.

Gaskets on the carb are all new, really no reason to think the carb is leaking, maybe you get a lower vac reading with a smaller carb??

After doing a little research, must guys point to the PCV valve when talking about oil in the air cleaner. Makes some sense, PCV valve is connected to the new carb...... I replaced both the crank case vent filter and PCV valve to no avail, still alot of fumes from the crank case filter into the air cleaner.

I can't help think both high temp and oil in the air cleaner are related and have something to do with the new and much smaller carb. (formerly a Carter 600 cfm)

Any idea's what this could be all about?

Thank you
Joe.

 

Joe -

How does the vacuum feel from the hose connected to the PVC, and what's the reading now?

Also sounds like you might be running a little lean, how do the spark plugs look?

Archer

 

The vacuum from the PCV valve is strong, will stick to your finger easily. Have not check the vacuum with it unplugged or blocked off, I will do that.

Also will look at the spark plugs, would running lean make it heat up? Now that you mention it, I think I have read that before.

Will do those check tomorrow afternoon and report back,
Thank you
Joe.

 

A carb won't change intake vacuum

DID YOU CHANGE anything else? Intake? Did you have the distributor out? Change the timing?

The only way that a carb could cause overheating is if for some reason it was a LOT "too lean" IE jetted too lean or sticking metering pistons/ rods, etc, but the metering rods/ pistons operate independently of each other.

Something causing the engine to overheat could cause more blowby, or the opposite--if you cracked a piston/ ring, etc, that would cause more blowby, it might also cause the engine to run hotter

DID YOU change the timing?

Just to be correct, vacuum is measured in inches of mercury, not pounds per square inch, although I guess it could be. In really rough figures, the relationship of inches Hg to psi is 2 to 1, because atmospheric pressure is just less than 15 lbs / sq in and just below 30" Hg

(Conversion is .491 to convert "Hg to psi, and 2.036 for psi to "Hg)

 

Hey Archer,

as weird as it sounds, no change in vacuum from PCV normal, PCV pulled out and PCV plugged off. Go figure......

Plugs look different than I have ever seen them. In the past they were if anything carbon covered. Now are very dry with a rusty color.
Pic below is typical of the three I pulled.




440roadrunner, thanks for your reply.
Seems that anything that changes the way the engine runs would effect the vacuum. But it might not be possible to just say "smaller carb, less vacuum" I don't know.

I did not change the timing.

On my carb the metering rods and pistons do work together as they are attached to one another.
Yea I know the difference between inches of vacuum or Hg and lbs of pressure. My mistake.

Thank you
Joe.

 

Joe -

Looks like over heated / lean mix to me.

Archer

 

Thanks buddy, I have a spring kit left over from tuning the last carb.
I will try a little stronger spring to try and get the metering rods up out of the jets more. This should richen up the mix some.

Of coarse after I clean up those plugs, looking at that picture... darn that looks nasty

Thanks again
Joe.

 

Okay the sun is finally shining
and our plugs are all cleaned up and we are going for a road trip to the city.

My idea is to try and read the plugs after an over all city and highway drive and see how they look.

New or should I say improvised fan shroud has been installed to help with the heat as well. Let's see.........

Joe.

 

That plug does not look lean to me. A lean plug will be calk white to very light grey (almost white) A normal plug will be light grey to tan. That orange color is normal and caused by additives in the gas. That plug would be tan without the additives. There is however some carbon build up on it so you are using a little oil.

I watch the weather and have noticed it's real hot this year east of the NW. Is it super hot where you live? Very high air temp may also account for the loss of vac. Not sure on this one but it makes a little sense...hot air is less dense and may pull less vac.

Pull all the plugs for a good check. You could still have one or more that are running lean.

Oil in the air filter? Are you using a stock air cleaner with the vent tube running to a valve cover? Blow by through this tube would oil the filter, other wise I have no clue.

 

I agree with duster on the plug colour. Here is a chart I hope will help.
http://www.verrill.com/moto/sellingg...colorchart.htm