I have a Straight 8 (53 Special) with a 1942 dual carb setup. There's a vacuum line tapped into the middle of the manifold and runs directly to the distributor. Is this vacuum line necessary on a dual carb Straight 8 engine? Can I cap it and eliminate the vacuum? Is there any benefit to keeping it or eliminating it?
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The vacuum line is there to give the proper advance when cruising. This will greatly improve the fuel consumption. Not used in racing as the throttle is normally fully open or closed.
There are many threads on the subject.
Trackless
I found a thread on this forum where someone was adamant that Straight 8 engines do not need manifold vacuum. He said V8 Buick engines yes but Straight 8 engines no. Which leads me to seek second opinions on the topic.
I found that post. Team member Jyrki stated "I would not tap the vacuum advance system into straight manifold vacuum. Some hot rodders do this because it helps the engine idle and generate some vacuum with a radical camshaft. The S-8 doesn't have problems with idle or poor vacuum. And it doesn't like too much advance at idle (it'll start popping in the exhaust) " Any thoughts on Jyrki's post
You may have been misinterpreting Jyrki's post. He isn't saying to run with no vacuum advance at all. What he is saying is to use PORTED vacuum rather than full-time vacuum. In other words, connect your vacuum advance to the port on the carb which is made for that purpose instead of to the manifold.
Ray
You always come through Ray. My car is a rat rod. I have dual Stromberg 97's for carbs, a Buick 1942 compound manifold, a freshly rebuilt Straight 8 engine with pistons bored on a 53 Buick Special. I run straight linkage, stock distributor, with no windshield wipers.
What brought this post on, I'm in the middle of installing my intake and exhaust manifold gaskets. In the process of installing my vacuum line on the intake manifold I sheared the vacuum line. Hence my curiosity to poke around the forums and do some research on vacuum or no vacuum.
Just so I'm correct here, in my particular car, I can cap the vacuum port on my Buick 1942 compound manifold and connect the very same vacuum line from my stock distributor to my Stromberg 97?
Yes, connect the distributor vacuum line directly to the carb. I don't think you would want to plug the connection on the manifold though. That's where your windshield wiper would connect, or rather the vacuum line to the fuel pump if you have a double action pump.
Ray
It appears I need to run my vacuum from the distributor to my carb and not my intake. My intake and exhaust are currently off and both carbs. Before I disassembled everything my vacuum from the distributor ran to the intake and the car ran. When I reassemble everything and run the vacuum to the carb will my car start and run?
No windshield wipers but the fuel pump part I'm curious about. My fuel pump only has a fuel line coming out of it. I noticed a photo of your car Ray, and you had a line running from your intake manifold that headed towards the fuel pump. My car doesn't. Should it? Why does it work without it? If I should have one, what kind of adapter do I need coming off the intake and where does it plug into the fuel pump? I have a stock fuel pump.
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