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Spacers Isolators etc
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Author:  68barracuda [ Wed Dec 05, 2007 9:00 am ]
Post subject:  Spacers Isolators etc
Hey Chaps

I am using a 1/2 inch small to large boltpatern spacer converter. 4 hole type
for a holley 4150

Had some heat soak issues so I added a 1/2 inch phenolic resin isolator big bolt pattern between carb and isolator BUT

here is the rub - it has one BIG hole - but strangely my fuel distribution has improved.......

Comments please
Author:  Joshie225 [ Wed Dec 05, 2007 1:35 pm ]
Post subject: 
What manifold and how is the carburetor oriented? Pictures?
Author:  68barracuda [ Thu Dec 06, 2007 5:38 am ]
Post subject: 
This is where it gets funky

It is a Chrysler SOuth Africa 4BBL manifold designed for the small boltpatern Carteer afb.

In lay out and runner design a lot like the cliffor effort

The carb is at this stage not yet turned 90 degrees wich I would like to do

I even pulled my plugs again - and all seem evenly slgthly dark coloured
Author:  slantasaurus [ Thu Dec 06, 2007 10:35 pm ]
Post subject: 
With the open "one BIG hole" spacer, you've increased the plenum volume more than with the 4 hole spacer. That along with the drop in fuel tempature (I'm guessing it's cooler....somewhat at least) would acount for better fuel distribution. From what I've found with most engines, a bigger plenum is usually a good idea. At least until clearance or distrubution problems start to occur.
Author:  LUCKY13 [ Fri Dec 07, 2007 6:41 am ]
Post subject: 
Quote:
With the open "one BIG hole" spacer, you've increased the plenum volume more than with the 4 hole spacer. That along with the drop in fuel tempature (I'm guessing it's cooler....somewhat at least) would acount for better fuel distribution. From what I've found with most engines, a bigger plenum is usually a good idea. At least until clearance or distrubution problems start to occur.

Good call on the plenum size & cooler fuel.


With the bigger plenum size the fuel & air has less velocity, this helps the fuel & air mix make the turn to go to each cylinder easier. It also changes the demand on the boosters & has a effect on jetting. Most of the time it has a leaning effect on jetting.

Inside of the intake manny there is a lot going on and many things can effect the outcome of how it works. I have always liked
a phenolic spacer to, it takes a lot of heat away from the carb itself leaving the fuel much cooler.


In the end when it comes to spacers there seems to be no major rules. Each setup will like its own arangment of spacer & types of holes. Sounds like you found what your setup likes, run with it and enjoy.


Jess
Author:  68barracuda [ Fri Dec 07, 2007 9:58 pm ]
Post subject: 
Thanks

The strange thing still is that usually I wold go for a 4 hole adapter + 4 hole isolator, or big hole + big hole. but as I said I have the 4 hole adaptor on the manifold, the "big hole" isolator on top of that and then the carb - cause I couldnt find a 4 hole isolator - I tried the combo for fun and it works

Wonder if the big hole on top of the 4 hole does not act as a sort of mixing chamber, before all is divvied out through the 4 hole spacer :?:
Author:  slantasaurus [ Fri Dec 07, 2007 10:08 pm ]
Post subject: 
The only time I've used 4 hole spacers was on V-8 engines with single plane intakes that already had open plenums. The 4 hole seemed to help the signal to the booster in the carb. I'm not saying the open, then 4 hole idea won't work though. I like to experiment too, try it both ways and see if there is any difference or what the engine likes.
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