TBI/Carb intake Brake booster question

**Coronaburb-19** · 02-06-2021

Alright, new guy here but I've got the first of many questions. Switching to the edelbrock vortec 2116 manifold, I lost the original manifold port for the brake booster. I know I just need a dependable source of manifold vac, and there are multiple options, however, I rerouted my PCV through a catch can, which freed up the large port on the front of the tbi... which is 3/8 and just so happens to be the same size as my brake booster line. Would that pcv port on the tbi be a dependable source of vacuum for brakes?

**tayto** · 02-06-2021

why are you not running vacuum on your PCV system? there's a vacuum port on the manifold why can't you use this?

**Coronaburb-19** · 02-06-2021

Originally Posted by tayto

why are you not running vacuum on your PCV system? there's a vacuum port on the manifold why can't you use this?

I have my crank case routed through a remote catch can. The fumes circulate out of a breather and any moisture/oil is trapped in a reservoir.

The vacuum port on the manifold is already occupied, but it could work if I buy a T. The T would have to have two different sized hose barbs, or I would have to cobble something together. It would be easier to just hook to the available port on the TBI if that's a possibility. It's the right size and everything

**tayto** · 02-07-2021

i see no benefit or point in running a catch can the way you have it. you might as well just put one of those filtered breathers on each valve cover. your catch can should go like this: vacuum source->catch can->PCV valve in valve cover. i perfer running the other side either into the air cleaner or if you must have a filtered breather. you want to pull vacuum on the crank case, helps ring seal (to a degree), gaskets won't leak and cleaner oil. your engine will live much longer and happier life.

I believe they make T fittings with different size nippels, this is the route I would go. Check Summitracing, hardware store, etc

**tayto** · 02-07-2021

I assume you are running a carb to TBI adapter. if it's thick enough you could drill and tap it to run a nipple for your brake booster if you can't find a T fitting.

**Coronaburb-19** · 02-07-2021

Okay this is making sense. A buddy of mine told me I should set up a catch can in the non-vacuum format, but now I've been reading into it and I'll probably go with vacuum. I was trying to completely avoid any sludge buildup in the intake runners, but at this point if there is any, it's the catch can's fault. Thanks for the pointers, I'll have to figure out a different place to hook up my brake booster ��

**tayto** · 02-08-2021

I was half incorrect. apparently the "best" setup is a separate catch can for the pcv side and another one for the crank case vent. I think in the pcv side is best because the crank case vent is suppose to bring in fresh air then pulled through pcv before going back into intake. however at shut down oil fumes would come through the vent. i put an inline canister filter on my caprice when I had a carb hat on it. it looked like the gm tbi fuel filter but had 3/8" nipples on either side.

**1project2many** · 02-08-2021

I was trying to completely avoid any sludge buildup in the intake runners, but at this point if there is any, it's the catch can's fault.

"Sludge" being hydrocarbons that build up in the runners and on the valves? You're in for a good challenge there. While the engine is running, especially at low speed, the intake contains a mixture of atomized (small liquid droplets) and vaporized (gaseous) fuel. Fuel is primarily HC in composition. Heating atomized fuel causes some or all of the droplets to vaporize. The amount of fuel vaporized depends heavily on the "weight" (or complexity) of the fuel molecules and the heat in the manifold. During this process, lighter HC molecules can vaporize quickly while heavier molecules can deposit on the manifold walls. Over time, this can lead to heavier molecules building up and leaving a deposit.

One way to help prevent this is to use a fuel which is not composed of an HC blend. Ethanol, Propane, and CNG are great examples of fuel which do not exhibit large amounts of "sludge" buildup over a long period of time. Race fuel is another way to go as the fuel blend is much more specific than "pump gas" for retail market.

**tayto** · 02-12-2021

http://mewagner.com/?p=2207

never used their product, but some good reading on the importance of having a PCV and why the factory one might not be the "right" one for your engine.

**kenh397** · 02-14-2021

There has to be a place to drill and tap for a fitting as tayto mentioned. This would be my solution. Maybe drill and tap where the OEM brake booster location would be??

Ken

**tayto** · 02-15-2021

i think original TBI intake had a fitting on the front drivers side, below the TBI unit. then it was a hard line from there to the back of the engine. like I mentioned before, if the port on the intake runner is in use, I would just drill & tap your carb to tbi adapter plate if it is thick enough.

**PlayingWithTBI** · 02-15-2021

Originally Posted by tayto

i think original TBI intake had a fitting on the front drivers side, below the TBI unit. then it was a hard line from there to the back of the engine. like I mentioned before, if the port on the intake runner is in use, I would just drill & tap your carb to tbi adapter plate if it is thick enough.

The port for the PCV valve is on the Throttle Body (the large one in front), the port for the brake booster is in the manifold. Here's a picture of the Edelbrock 3704 manifold but, it's just about the same as OE.
IMG_0676.jpg