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First pic is an example of the heat transferred through those exhaust runners (note burnt paint). The second is the damage caused by the hot slot if the carb isn't mounted correctly. Carter AFB 3721SB.
Wow, I haven't taken my carb off yet so I hope it's not ruined like that one! So they did that on an AFB also, thought it was just common to a Quadrajet.
Two more questions and I'll leave y'all alone.
1. What locktite do I use on the rivets?
2. When installing the manifold, do I use the rubber seals at the ends or just use red RTV silicone?
Two more questions and I'll leave y'all alone.
1. What locktite do I use on the rivets?
2. When installing the manifold, do I use the rubber seals at the ends or just use red RTV silicone?
Well, I thought I knew what I was doing until I got your note. I think my intention was to reduce carb heat even though percolation is not a problem. Will the choke not work at all?
Here is a pic I found on the forum (can't find the location now) of someone who did plug these holes. Any idea for what purpose?
This is a picture of the intake manifold off my 67 after I had a machine shop shop peen it and I installed the plugs to block off the hot slot under the carburetor.
The best approach IMO is to block off the hot slot like shown in the picture and use some loctite to seal the threads because there can still be a internal vacuum leak if the carburetor does not seal perfectly in this area so seal those threads.
You will not find this leak externally, it will be internal so my suggestion is to use the base gasket for the hot slot, stainless shim then another gasket above MADE JUST LIKE THE STAINLESS SHIM so the primary venturi holes seal into a gasket. If the carburetor base is not perfectly flat the stainless shim will allow a internal vacuum leak around the primary carburetor venturi holes and pull air from the hot slot around the installed plugs.
Also, leave the exhaust crossover open and wire the heat riser open in hot weather as this heat will help the cast iron manifold, in cooler weather you will probably want the riser to work as designed.
Thought I was done with this thread but still need some help on getting everything hooked up after installation. I would prefer to be environmentally responsible and use a PCV system rather than venting to atmosphere if it's possible. So I need to install a PCV system with this manifold and Quadrajet carb.
How do I run the hoses? Where do I install the PCV valve? There is no breather hole in the 350 block and the manifold and I don't want them in my valve covers (original Corvette covers). Do I need to change the oil fill tube to the type that has a hose bib and use a non-vented cap? Then what?
If the installed manifold is the one pictured with the oil fill tube then change it or modify it to the 1967 style with the PCV valve that screws into the side of the tube. Connect that to full manifold vacuum and keep the breather on the valve cover. The PCV will pull out while the breather will allow clean air in.
If the installed manifold is the one pictured with the oil fill tube then change it or modify it to the 1967 style with the PCV valve that screws into the side of the tube. Connect that to full manifold vacuum and keep the breather on the valve cover. The PCV will pull out while the breather will allow clean air in.
Is there another way? I don't want to put a breather in the corvette valve cover.
You might try a post here asking that question, I am sure if you are willing to modify something there is another way to vent the engine.
Your are half way there with the breather tube, IMO, valve covers would be the easiest way to complete the circulation path. It's very important to have a good PCV system on the engine.
Try the post and see what others have done, I am sure you will get some good ideas.
I don't know anything about your engine configuration and I'm not going through this whole thread to find out BUT, if your block has the old road draft tube hole in the back behind the distributor, you could configure an old RPO-242 open PCV system with a vented oil breather cap, and an adapter in the road draft tube hole and the PCV valve in the base of the carb. That's what I run on my '61 original motor.
I don't know anything about your engine configuration and I'm not going through this whole thread to find out BUT, if your block has the old road draft tube hole in the back behind the distributor, you could configure an old RPO-242 open PCV system with a vented oil breather cap, and an adapter in the road draft tube hole and the PCV valve in the base of the carb. That's what I run on my '61 original motor.
That's my whole problem, Frankie, I don't have this draft tube hole. It's a '69 engine. I don't really want to burger up a set of good Corvette valve covers by adding a breathing hole, got to be another way.
Yeah - I know they make adapters to raise the original-style valve covers for roller rockers and IIRC there may have been an option to put a breather port in some version of those. Can't recall exactly -- however, if you have the staggered bolt valve cover pattern then I'm not sure there is anything suitable out there...
I looked at my 75 blazer's pcv sys. Left vlv cover has hole forward with pcv valve into the gromet, hose from valve to the fwd carb base. Right valve cover has hole aft with gromet for a tube that goes to the air cleaner. So in your case, pcv valve into the valve cover gromet, hose plumbed to fwd vac port on front of carb. Your oil fill with nipple would be plumbed to air cleaner for the freash air intake. Correct gromets are availabe in the HELP section at your local parts store. What air cleaner are you using?
Brgds,
Rene
10-17-2014, 07:18 AM
