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engine vacuum
https://www.slantsix.org/forum/viewtopic.php?t=50191		 Page 2 of 4
Author:  kielbasa [ Fri Oct 26, 2012 9:10 pm ]
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Brand new actron. Never used a vacuum gauge, no reason to check vacuum on a vw :-P
Author:  kielbasa [ Fri Oct 26, 2012 9:20 pm ]
Post subject: 
It was suggested by joshua skinner. He said it would be a good choice for what i was looking to do with it. I just wanted a very mild stock motor. As i asked of there was cam that was close to stock but more efficient, 125 is what he gave me. It runs really great driving. My issues i have are the idling. Yes its 225. And I'm still wondering if i should be checking vacuum with distributor tee'd in

From what i figured a couple months ago I'm getting about 20-22mpg. Kinda hard to figure with a wonky fuel gauge
Author:  ceej [ Fri Oct 26, 2012 10:08 pm ]
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From an economy standpoint, it should deliver.

Is your speedometer/odometer reading accurately?

Base your fuel economy on averages of fill gallons to miles. Fuel gages are always wonky! :lol:
The only true measure is to divide miles by gallons used.

The Hooptie gets right about 20 mpg when I check it. I'd hazard a guess you aren't any lighter with a street car. I've got the Hooptie down to 2800# without my pudgy butt in it.

If I pulled the Carter AFB and went back on a Holley 390, which chokes my particular build down significantly, it would likely go back up around 23 mpg out on the freeway. I could probably pull just shy of that with the vacuum secondary Holley 600. Next carb going on the Hooptie is my 600 double pumper. Got to feed the 183 somehow. :roll: I'll have to go back on the stock rocker shaft to keep the valves away from the pistons though.

CJ
Author:  kielbasa [ Fri Oct 26, 2012 10:21 pm ]
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Speedo goes crazy sometimes ot will read steady. Its 2 mph faster then my gps says. Odometer is exact couldnt be any more acurate vs my gps. Motor pulls hills. I live in the valley so lots of hills. And it doesn't struggle one bit. Doesn't even need to kick down on the real steep ones. So motor does as its suppose to. Its just the idle is so rough, i thoughtte choke was my problem but guess vacuum is a factor as well.
Author:  ceej [ Fri Oct 26, 2012 10:41 pm ]
Post subject: 
Tee'ing the vacuum line in will tell you quite a bit.

I run a vacuum gauge in the car. It's fairly accurate. I use it to tune circuits in the carb, but it's handy for keeping fuel economy in check was well. The deeper the vacuum, the better the fuel economy. You want to keep out of the enrichment circuits when going down the road.

I pull vacuum off the carburetor on the manifold vacuum port. If your on the distributor port, that is ported vacuum. It is going to be lower than manifold vacuum. When the butterfly closes, it masks the port to keep advance out.

Though the runner vacuum port isn't ideal, if you have no choice, hook your vacuum gauge to that. I have an idea it will read higher, but will be less stable due to location.

CJ
Author:  kielbasa [ Fri Oct 26, 2012 11:13 pm ]
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I've been reading off the small vacuum port where dist plugs in. Should i be going off the pcv port?
Author:  Reed [ Fri Oct 26, 2012 11:38 pm ]
Post subject: 
Quote:
I've been reading off the small vacuum port where dist plugs in. Should i be going off the pcv port?
The small port where the distributor tees in is not a good port for a vacuum gauge to use. Tee into the line for the choke pulloff diaphragm.
Author:  patrickhenryhague [ Fri Oct 26, 2012 11:40 pm ]
Post subject:  vacum
The dist. port is the incorrect one to use you'll get an incorrect reading. A stock good running slant six will be pulling 18 to 20 on your vacum gauge at idle. Use the manufactures suggested valve lash setting, I don't know if your cam is Hyd. or solid so I cannot tell you how to adjust the valves. If Josh suggested that particular cam I'm sure he would know best.
Author:  kielbasa [ Fri Oct 26, 2012 11:47 pm ]
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I had just ran outside to recheck using pcv port. I'm getting a steady 19", not sure if i need to tee into the port but i just removed pcv from carb and plugged my gauge in. I'm at 10degree timing 750rpm steady 19"

Now i need to figure out why i can't get choke pulloff set correctly. With it adjusted to its maximum towards passenger side, still revs up as i close choke plate.
Author:  Reed [ Sat Oct 27, 2012 12:00 am ]
Post subject: 
Quote:
I had just ran outside to recheck using pcv port. I'm getting a steady 19", not sure if i need to tee into the port but i just removed pcv from carb and plugged my gauge in. I'm at 10degree timing 750rpm steady 19"
It is more accurate to check the vacum with the PCV plugged in and working.
Quote:
Now i need to figure out why i can't get choke pulloff set correctly. With it adjusted to its maximum towards passenger side, still revs up as i close choke plate.
This suggests that closing the choke is pulling the fast idle linkage which, in turn, puts the fast idle cam under the fast idle screw, as it should. Adjust the carburetor according to the carb spec listed on this site. Specs and adjustment procedure are available in THIS POST for stock carbs.
Author:  kielbasa [ Sat Oct 27, 2012 12:06 am ]
Post subject: 
I dont have a great way to tee into that big a hose at the moment. I talked to slant dan and he helped me with adjusting info. Infact there is no write up for early piston style pull off. But i have bent the bracket as far as it goes and seems it still needs more.
Author:  kielbasa [ Sat Oct 27, 2012 12:39 am ]
Post subject: 
Ok i teed into the pcv. Two different ways with two very different readings. Confused on how it should be done

Pcv disconnected completely: 19"
Tee'd into pcv at valve cover: 13"
Tee'd into pcv at carb: 1"

Here are pictures of how i done it (unsure how exactly it should be done.)
Image
Image

Image
Author:  ceej [ Sat Oct 27, 2012 7:47 am ]
Post subject: 
Teeing into the pcv isn't ideal. You need to find a better place to measure. The Positive Crank-case Ventilation system is an engineered vacuum leak to provide sweep air for the engine.

Reed suggesting tee-ing in at the choke pull-off. That would be better.

If you haven't found true manifold vacuum yet, and you don't have the tell-tale miss, leave the valve lash where it is. If you are getting the periodic "Poof" out the tail pipe, then loosen them up. OCG and Erson both spec too tight lash settings.

Patrick; The #125 is a mechanical cam. Hydraulic slants don't have adjusters. I disagree with Josh on that grind. That's the first time I've found anything to disagree with him on though. :shock:

CJ
Author:  kielbasa [ Sat Oct 27, 2012 10:31 am ]
Post subject: 
I don't have a vacuum pod pull off. I have the piston type. I dont notice any poof from tail pipe
Author:  Reed [ Sat Oct 27, 2012 10:41 am ]
Post subject: 
If you have no other options, tapping into the vacuum at the #6 runner is better than checking vacuum via the PCV line. However, sourcing your vacuum signal in any one intake runner will lead to a fluctuating vacuum signal.

You must have a 60-63 Carter BBS if you don't have a vacuum operated choke pulloff diaphragm. Use your vacuum gauge to find a port on the carb that has vacuum at idle.
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