"HELP" Is there more vacuum the closer you get to the carb???

Still dealing with wierd vacuum issues. Is there no vacuum at the actual PCV opening on the top of the intake? And then the vacuum on the intake/or/carb pull the valve open? Then what is the difference if I use the Vacuum port on the back side of the SP1 intake, or if I use the one on the back of my Double Pumper? Right now the one on the intake is plugged and I am using the one on the carb.
Reason I ask, is there more "vacuum" the closer you get to the carb. Thinking of routing the brake booster from the one specified on the topback part of the intake to the one just underneath the carb on the intake. Or, use that same opening for my heater vacuum ball on the firewall instead of the carb.
One more question, does anyone use the hole on the back of the intake, and if it is plugged, is it necessary to use "brass" of some sort or a nice fitting bolt with some pipe dope?
Measuring around 15", still not enough for the brakes, but notice a spark knock at certain RPM's. Thinking timing may screw with the vacuum as well but the car runs awsome.

 

Joe,

From my "limited" experience, 15 lbs vacuum at idle, should be more than enough for power brakes. On my old engine, I had 13 lbs and had no issues. You may have another issue? Possibly a bad booster, or something?

As for the PCV valve installation on the SP1, I run that intake and a Holley 1000HP. I use the port in the back of the plenum, for that purpose, since my carb has no vacuum ports on it. T/A sells parts to adapt it, a nipple, and a hose, to angle it down to the manifold. You can probably find the correct brass nipple adapter at the hardware, or parts store. The correct hose, is a Gates #18030, small I.D. hose. I hope this helps.

Regards, John.:TU:

 

Make sure you measure your vacuum at idle in gear because this is when your brakes are needed not in neutral. 15 should work the brakes well but I bet you probably have around 9 or 10 in gear. I'm still fighting with mine but I'll post any progress I make, a vacumm canister might be my next option to go with my timing curve change.

Steve

 

Thanks on both. Your right, that is measurement is at idle. The booster does hold the vac, cause when I pull the hose there is a big rush of air. I was thinking about a can, not sure if that would really help or not? To recap, so in gear would be less I guess. Any helpful hints you guys have or figure out, definately let me know. As for plugging the plenum is fine? and run it from my carb? Also, is there more vacuum the closer you get to the carb or is that theory no good?

 

I believe vacuum is vacuum, unless your close to a leak with the connection it should be the same reading everywhere. That would make the most sense to me, but I have been wrong before. LOL

Steve

 

I researched the threads on my 290-08h cam and found that you need around 25 initial timing for the brakes to work like they are supposed to. I'm sure we can get by with them working at 75% but I'm going to try and get mine right, my car is way too fast not to have real good brakes.

I am more concerned with the noisey lifter sound, I have tried everything except replace them so that will be next I guess.

Steve

 

Same thoughts.
Did you say you ran a can on the other thread? Just curious on how much they help. If any. If so, I will order one today. I just don't rmember my stock motor pulling that much, seems like my brake were shitty back then too, just not as bad. This feels like Fred Flintstone

 

The can will only give you a reserve of vacuum but not increase its number. The key is to get the vacuum up to the amount that allows the brakes to work properly then use the can to create more volume so the vacuum drops less each time the pedal is used. I have not used a can yet though because I'm still playing with the timing curve. I was able to limit the mechanical advance to 12 degrees as stated in the other thread so I hope it will all come together.

Steve

 

Joe -

You should be able to stop with or without the booster. No vacuum booster just means lots more pedal effort. 15 psi sounds like plenty of vacuum for brakes.

If you just can't stop, maybe you have other issues - bad linings or air in the lines or a bad master.

 

The problem lies in not knowing how hard you'll have to push in a instant, we all know that there are times you have react quickly. I'm after proper working power brakes that I have a trust in, pretty simple really. Guessing how much foot pressure to use each time doesn't cut it with me so we continue tweaking. I only have 12 lbs and it is good for one maybe two pushes then it is non power.

 

Are you running regular motor oil? My lifters used to make noise until I switched over to Mobil 1... it's expensive, but I don't have to change it as often, and, there is virtually no delay in getting oil pressure in cold weather like their was with regular oil. I used to dread starting the car when it was below -10C...

 

I'm running castrol 10w-30 but I also had rotella in it before. It never gets below 40 degrees here and if it does it is for about 5 hours.

 

The vacuum numbers I spoke of, were at idle, in park. I was running 20* initial timing, in that situation. 34* total. In my new motor, I too am having some hard pedal issues, that I did NOT have before. I would not rule out the master, but I changed nothing else, but the engine, with a hotter cam. Like Steve said, I can be running 45 mph, and hit the brakes and all is great. I hit them a few times more, or slow the rpm and keep using the brakes to a stop sign, and that is when the pedal gets hard. As I said, I have some other issues right now, and am focusing on them. If I find a solution, I will let you know.

Just a thought, you may want to look into a vacuum pump. I know some people using them, and it creates extra vacuum if I understand it right. Good luck!

Regards, John.o No:

 

Hey Larry, it was great to see you at Marcus Dairy, I really like your Stage 1. Awesome guages!
Jay