72ScampTramp
Scamp Tramp
I have a Weiand D port Tunnel Ram! motor build in progress. i have 2 600 cfm VS holley carbs! Now these run off vacuum but there isnt a port in the tunnel ram what do i need to do?
Question on Dual Carb vacuum
- Thread starter 72ScampTramp
- Start date
-
OldmanRick
Well-Known Member
The secondaries are pulled open by increased air flow, with rpm, thru the venturies creating vacuum at a small port just above the booster area. They act independent of engine vacuum. No manifold vacuum signal needed.
It would be a good idea to reference the two pods together so both carb secondaries open simutainiously. You can use a kit, like below, with a piece of vacuum hose between the two, to accomplish that.........
http://www.summitracing.com/parts/hly-20-73/overview/
It would be a good idea to reference the two pods together so both carb secondaries open simutainiously. You can use a kit, like below, with a piece of vacuum hose between the two, to accomplish that.........
http://www.summitracing.com/parts/hly-20-73/overview/
moper
Well-Known Member
You can buy two vacuum pod tops with a nipple for that connection right from Holley.
72ScampTramp
Scamp Tramp
Ok! I think I understand the vacuum created by increased RPM will pull the secondaries open. And with that Kit will pull them open at the same time? So just like DJVCUDA's set up run a vacuum line from one port to the other?
OldmanRick
Well-Known Member
I think you got it....
This pic, although a Demon carb, shows the tiny port that air flowing thru the carb uses to create vacuum to activate the secondaries....
View attachment 1118.jpg
And these are the tops that "moper" was talking about. Downside with them, there quite expensive seperately and don't allow for quick changing the springs.
View attachment 11132.jpg
One other thing that's kinda cool, you can bench test to make sure the secondaries are activating. If you have a small tipped blow gun, locate that tiny port and while holding the primaries wide open, hold the gun about 1/8 to 1/4 inch above it and blow air past that hole and the secondaries will actually open if everything is good with the diaphragm and spring.
moper
Well-Known Member
Rick - look close at Dave's pic... The new ones are phenolic and are quick change tops... ;)
Chameleon
Dart Conissuer
Mine looks like this, Weiand and 2 600's.
OldmanRick
Well-Known Member
72ScampTramp
Scamp Tramp
So lets go a step further. Much appreciate you guys helping me. My first build and very little tinker time with engines. Now i have a Vaccuum advance distributor. Where does that tie into?
OldmanRick
Well-Known Member
Depending on your preference.....ported or manifold vacuum.......
Ported is on the primary metering block and manifold would come off a port on the baseplate........
72ScampTramp
Scamp Tramp
http://www.summitracing.com/parts/maa-4757801. Thats the distributor I have should i just go ahead and run it as a mechanical advance instead?
OldmanRick
Well-Known Member
Sorry i haven't been here as much as i used too, so i haven't kept up with your build or how much street/track time you will use it for. My opinion is, if it's any different then mostly track and very limited street....run the vacuum advance. Ported or manifold vacuum can open a whole can of worms here
, but either way it should help you run cleaner on the street with that carb/manifold setup.
72ScampTramp
Scamp Tramp
Sorry i haven't been here as much as i used too, so i haven't kept up with your build or how much street/track time you will use it for. My opinion is, if it's any different then mostly track and very limited street....run the vacuum advance. Ported or manifold vacuum can open a whole can of worms here
Appreciate all the help maybe a run down on the combo will help. This will be a limited use street car maybe some track time. IVe been building this car for about the past 3 years a quest i set on with literally 0 knowledge of mopars.
Alright guys combo set...
72 Scamp
.030 440
Lunati 60341 Solid cam (see cam card)
Real close to 9.7:1 compression ICON forged Pistons
Mildly Ported 452 heads Flow sheet attached
Dual carb Weiand Tunnel Ram 2x600 Holley carbs
Pro Parts 2" headers
Stock Stroke crank and rods
4.10 D60 rear
est.. 3500 stall vert.
OldmanRick
Well-Known Member
Thanks for posting all your numbers. I really like your combo. With the mild cylinder heads and compression, that cam looks pretty sweet. That intake duration and the fairly early close on the intake side, along with the built in advance, should give you good cylinder pressure thruout the rpm range. I still think running a vacuum advance will help with the street use, but you will need to experiment with the timing to find what works in the real world. Once you get the carbs dialed in, that car should be a beast between 4000 & 6000 rpm's. The trick to some serious low et's will come with how well the converter works and how much bite you have at the track. I think deep 11's is a reasonable goal if everything works out right. I hope that's not a disappointment, but for a street/strip car, i think that's extremely strong.:thumrigh:
72ScampTramp
Scamp Tramp
So I can hook the distributor to the port side on the metering block? And thanks glad you like the combo! I beat myself up over and over to get to the final combo. With the help of others.
OldmanRick
Well-Known Member
I think the easiest way to get it going/on the road, would be to start around 12*BTDC with no vacuum to the dizzy and check your total advance to see where it tops out at about 3500 rpm's or so. You probably wont want to go past 36* total. Once you get her broken in and running decent, you can experiment with the initial to see what it likes and then restrict the total back to the 34*/36* range if need be. It may like as much as 20* initial. That's just part of the dialing in process. Once you know what the engine likes as far as initial and total, you can try to run the vacuum advance and dial that in. I know it sounds like alot of work, and it is, but that's what seperates the men from the boys...:mrgreen:.
-
