Edelbrock 1406

[Robert Collier]

Do I need the original spacer with the new Edelbrock 1406?

I did not plug up the intake holes in the "gutter" will that be an issue with the new carb?

Last question, is the vacuum advance for the distributor a full time vacuum or is it a part time vacuum?

Thank you everyone for your time

[Jason Edge]

Air Ticking sound from under the intake. Also remove the choke cap and see if it is smut black with a burnt look to it. Choke itself will most likely be damaged and not work anymore. You could also, take external choke tube out and inspect tube inside with pin light.

[Jason Edge]

The original choke tube is prone to cracking and rotting out and leaking which releases fire hot exhaust gases under the intake on the open end, and causes a ticking sound and can be a fire hazard, and into the chock assembly for the stock carb choke.  If running an Edelbrock it is best to completely block the center intake exhaust port.  At first I only blocked the 4 access holes (2 in top channel and either end of the choke tube) but ended up also blocking the intake as seen below as the center of the intake was still firing up to 300+ degrees even when I was running dual exhaust and didn't have a heat riser.  You will want some type of spacer regardless beneath the carb. I used a 3/8" insulator spacer. You can read about my carb/intake project at this link: http://6364cadillac.ning.com/profiles/blogs/jason-s-carburetor-inta...

[Jason Edge]

Just to add, the overall ignition advance on a 'ported' setup has potentially two advance curves..... minimum vacuum at idle (less advance), then more vacuum (more advance) as you go off idle, then less vacuum under acceleration (less advance), then under high rpm (more advance).  Kinda need in the way it all works together to control overall ignition advance.  

[Jason Edge]

David, it is indeed a quite fuzzy subject, and I think the off idle type ported advance may be the simple type we had. I do recall some that had temperature sensors (probably modern carbs) that also adjusting the timing of allowing the vacuum at the ported. I can't remember if a hot engine allowed it quicker or slower?? Memory is fading on this one! LOL

 

[Jason Edge]

David, I believe there has to be at least some advance on idle for stock setup else we wouldn't have to unplug the vacuum advance when setting the timing.  I am not sure where you read or determined that the original vacuum is ported. I do remember there were different flavors of ported, and some have a temp sensor that controls the amount of vacuum in addition to rpm?  It's been a long time since I've had a stock carb but would be curious to know what type of vacuum anyone is getting on idle from that port.  There were some flavors of "ported" where as soon as you give it gas and it comes off idle the vacuum is opened to the port...some faster than others.  The stock setup may be ported in that fashion.  Regardless, the more vacuum advance that gets to the distributor vacuum advance the more it will advance timing. With engine idling or coasting with carb butterflies you have the most vacuum. Punch the throttle and then you have little or not vacuum as the top end of engine is now open.  I also remember the ported vacuum having to to with smog and emissions control and hot rodders almost always switched over to the full vac advance on later model cars.

[Jason Edge]

Tony, Actually the vacuum advance is working most at idle since that is when you have the most intake vacuum.  At idle and low load there is a lot of vacuum and the dist vacuum advance will be advancing the timing the most. As you accelerate and put the engine under load vacuum decreases, to the point where under Wide Open Acceleration there is basically no vacuum, at which point at high rpm the mechanical centrifugal advance weights on the distributor take over and provide timing advance. There is a ton of info on this on the web but here is a simple explanation I found at one of the Corvette sites:

"At idle and steady cruise, engine load is low, and intake manifold vacuum is high due to the nearly closed carburetor throttle plates. Under acceleration, the throttle plates open wider, and intake manifold vacuum drops. It is essentially zero at wide-open throttle. As a result, intake manifold vacuum is a “free” indicator of engine load, which correlates nicely with fuel mixture being supplied – lean mixture at high vacuum, and rich mixture at low vacuum."

[Robert Collier]

Awesome thank you. I will not be using the heat riser on the exhaust.

I have went through the help topics I don't think I have missed anything else.

I did not understand the importance of blocking of the exhaust channels on the intake. I think maybe this blog could be put in the help topic under the "carb and intake", so it is understood why the passages need to be blocked of.

Thank you again for your help.

[Jason Edge]

I used small pieces cut from 24 gauge (not the thin 29 gauge usually sold) 5V galvanized steel roofing panels I had left over from re-roofing our 101 year old cook house.  I used tin snips to cut to size and I used copper spray sealant to keep in in place. 

I am pretty sure the gasket kit inserts are not as thick as what I used but they don't really have to be since you are only blocking passive blow by gases.... again, assuming you do not have a heat riser blocking the Left Side exhaust exist on startup.   You can see the pieces I cut with copper sealant in picture above which is in this album: http://6364cadillac.ning.com/photo/albums/jason-engine-rebuild-proj...

(NOTE: there are 4 albums full of pictures from my engine rebuild last year)

Here is the next picture showing the intake gasket on top of the plates:

 

[Chris McBride]

robert,

Olson gaskets also supplies an intake manifold gasket which blocks the center exhaust

http://www.olsonsgaskets.com/

i think it's about $30

hth

Chris

[Robert Collier]

That is very interesting Jason, I think I will just block of the exhaust ports. I want to make sure I do this right.

What gauge steel did you use?

Did you just cut it to fit the opening on the head or is it slightly bigger?

How do you keep the cut piece of metal from moving around, did you use some sealant?

Did you use any copper seal or anything on the gasket? 

Sorry for the all the questions, I definitely do not want the exhaust gases going through the intake, since there is no need for it.

Thank you for the information