Old Oct 5th, 09, Vacuum question Demon carb. Hello, I just bought a crate engine and it came with a Demon vac. Ive never dealt with a barry grant before and I noticed there are 2 vacuum hook up's on the passenger side of the carb.
I am assuming it would be ok to hook the vacuum hose up to either one of them but I am not certain. Old Oct 6th, 09, I have mine on the front, the one closest to the rad. Steve The best laid plans are those not made mine To view links or images in signatures your post count must be 10 or greater.
You currently have 0 posts. Originally Posted by pro67street View Post. Old Oct 7th, 09, Originally Posted by Steiner View Post.
That'll start a whole new discussion You might be better suited to search the discussions on ported vs. There are arguments for both sides and you may like one better than the other.
George 68 Camaro blown Rat on E Full article is on this site in many posts. My files contain the long and short versions. Now, to the widely-misunderstood manifold-vs. After years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream.
One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate where it was exposed to full manifold vacuum at idle to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at Demon carb vacuum hookup retarding spark timing from its optimum valueand these applications also had VERY low Demon carb vacuum hookup static timing usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC.
This was done in order to increase exhaust gas temperature due to "lighting the fire late" to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A. If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the degrees "total timing" at high rpm wide-open throttle to get some of the performance back.
What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT.
Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, they're not alone.
Sauron67MM is online now. Old Oct 8th, 09, We have had customers have success with it in either location depending on how their ignition was set up but our preference is the full time port. As noted though in a lot of cases the distributor will need to be recurved and you may need to change the vacuum advance out for one with a different range or an adjustable one.
To view links or images in signatures your post count must be 10 or greater. Tech BG is offline. Old Oct 15th, 09, Thank you for all the help and advise. I think I will Demon carb vacuum hookup it on both locations and see which one seems to work best The engine builder recommended that I put it on the port that only has vacuum when the throttle plate opens.
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