What am I looking at?

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danielb927

danielb927

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Been trying to troubleshoot a vacuum leak / really horrible idle so I had the carb off the car today. I never looked real close but just under the carb there's this bolt like thing on one side, and a straight up hole in the other. What the heck are these for?

p1020705p.jpg
 
That's kind of what I was thinking too but I couldn't say for sure. I've got no idea where the manifold is from, the engine is a 1975 but the original thermoquad on there was later so it could be the case. I've got a Holley and been using a carb adapter too, I think I'll probably just pony up for a new manifold at this point.

So now the question is, LD340, performer, or air-gap?
 
I would get an air-gap. They are quick and easy to find. LD340 would be next. Performer would be my last choice out of the three. would be
 
I just realized these holes would explain the carbon buildup on the carb secondaries especially on the side with the hole and no fitting (or whatever that is) on it.
 
I'm trying to decide between an LD340 (one on eBay for a pretty decent price right now) versus the air-gap. The air-gap doesn't have the exhaust crossover and it does get cold around here in the winter. However, I never drive the car in the cold and I wouldn't do anything but fire it up for a little tuning unless it's above 55 or 60. Am I really going to need the crossover for the way I drive it? Or is it only really needed for daily-drivers when you need to drive it in the cold? Don't really know if "cold" means freezing, or just not warm out.
 
Are those the same intake with and without the gap? I'm liking the 35 dollar price difference for the non air-gap.
 
Im using the same cast iron intake on my 318. I built a blockoff plate for the EGR then tapped and plugged those holes. I then milled the center devider, then radiused all the sharp edges in the plenum. I am very happy with the way the manifold runs! much stronger than a performer intake above 1500rpm , and was CHEAP!!!
 
Moturbopar's intake mod is a good one. That intake is a EGR manifold. Leave the EGR disconnected (No vacuum hose to it) and do what he said he did to the intake. The OE 4bbl. intakes are preety good and there price is right. While a RPM or LD340 would be better, your wallet may not lke it. You can live with this one for now if need be. It is a capable manifold.

The fitting on the right (Called a jet) is removeable. You can get a plug for that spot via a local hardware store/plumbing store. Tap the otherside and plug it. I myself would re-look into the TQ. You can bend AFB rods 3/4 of an inch shorter to fit them inplace of harder to find TQ rods.
 
get a air gap you will be very happy but if your have no money do the plugs and take the center down trick dose work good.
 
Thanks for the tips guys. I'm going to plug those holes up at least and see how it runs, definitely want to try the cheaper option first. Don't really have the equipment to grind down the center divider at the moment, though.
 
Got them tapped out and plugged. Definitely runs better now, I will say that I think there might still be a vacuum leak everywhere but I've sure sprayed carb cleaner everywhere I can think of and haven't found it. Could just need some tuning too, it runs well once it's warmed up so I can live with it. Will re-check timing and all that too, and might get new plugs since a couple of the current ones got pretty fouled up with how badly it was running lately.
 
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