I have a bbc with tunnel ram,holley 450s. The 450s have no provisions for a vacuum port with the exception for vacuum advance. Was thinking only was to drill tap manifold. Any thoughts. Thanks.
My edel. Street tunnel ram has provisions on both sides of the plenum , centered in the sides for 1/4" not fittings , that's where I connected my PCV valve . Be aware of the wall thickness that you're drilling. I've seen others use carb spacers with provisions for PCV..
I was always in mind set without pcv engine would build to much pressure. I am running vented breathers on each cover
PCV helps remove moisture from the engine & ( slightly) improves ring seal with millions of vehicles having used them for over 50 years , I think the fuel dilution argument is pretty mute .
^^^^This^^^^ PCV will help maintain oil condition and reduce tendency toward lacquer/varnish/sludge build up.
Despite the comment above, MANY racers use both the PCV AND the "pan evacuation" (headers) system to pull air out of the crankcase. If you have a well sealed engine (rings and valve seals), you won't find much oil contaminating the intake charge. Sure, find an unobtrusive location in the plenum, drill-tap, connect it to what it needs to be connected to and motor on. Mike
Just put a spacer with vacuum port under each carb, and choose whichever you want for the PCV valve hoes. Block the 2nd one off. But you shouldn't run two breathers in conjunction with a PCV valve. If you do, the breather closest to the PCV will simply defeat the PCV and cause it to flow from the breather to the PCV. If you want to keep both breathers, then plug the one nearest the PCV inside. Or remove the breather on one side, and use a grommet in the hole to install the PCV. Good luck with those 450's! They also don't have secondary accelerator pumps, but are mechanical secondary carbs. They tend to stumble when the secondaries open without a fuel shot. But they work fine on hard acceleration when you punch the throttle and they all open. May need to change to larger nozzles, and maybe larger jets too, depending on how big your BBC is, and how built it is.
In all my years running multiple tunnel ram engines I have never used a PCV valve, just valve cover breathers with an occasional oil fill tube breather cap. Don't see the need for them.
I have a set of circle track valve covers that use a crossover tube with a couple breathers, put a check valve inside the breathers which in-turn allows my adjustable pcv valve to draw a vacuum in the crankcase... Made some check ball seats out of Delrin plastic... They just push into the breather tubes... 1" nylon bearing balls cost me about $1/ea. Added a pcv valve between the breathers... The pcv valve is modified by adding a screw in it's plastic elbow, allows me to hold the pintle off it's seat to make the valve act like an adjustable orifice... Mine is a street/strip engine, using the pcv to draw a vacuum in the crankcase allows me to use a lower drag piston ring set than I would otherwise be able to. It's part of what allows me to get 20mpg without an overdrive, also the cylinder bores last longer and the engine runs cooler. I've been using a pcv to draw crankcase vacuum for many years now, oil always looks great and zero sludge build-up. Grant
Well first trip down the road ran better than the 2 650 eldebrocks I just off. Only thing I noticed was it idles up and down some. Think I will change to a 125-45 power valve.
My dual quads PCV is between the carbs and they are progressive. A correct PCV valve should have a vacuum on the crankcase of 1 to 3 inches. The smell is gone from engine and the rear seal rarely seeps any oil now which it did before installing it. I use a valve from a 65 Chevrolet (V100) into an 90* elbow in the manifold, that valve works that direction. I use the same valve on a 302 GMC 6 which has a lot of air inside. I would not be with out one.
If they're idling up and down you might want to put an O2 sensor up the tailpipe and see how lean they are? The engine oscillating idle is usually a sign of it running lean. Watch your engine temps also, especially on warm days. If it's running hotter than before they're jetted too lean.
The V100 has threads on one end I believe. Threads go into the manifold or carb spacer correct? Just curious, I have a few of those laying around that I might use.
I wouldn't chance a PVC tunnel ram ... one long traffic jam and I'd expect it would either melt or at the very least, end up heavily distorted. I understand wanting to keep the weight down but I'd be inclined to stick with the aluminum one in your pic
No he joshin ya PVC stands for polyvinyl chloride not Positive Crankcase Ventilation. I'm glad you went with the system. I was raised in a gas station in the fifties and sixties. Life got better With PCV helping the breathable air.
They are threaded on one end. That end goes to the intake. I call it a suck thru. They are metal and crimped. Originals were screwed together and ez to clean. The other end went to the rear of the blocks in 65. The can in the valley kept oil out. Years later all that was gone and the oil separator was in the rocker cover.
I have been told that a bbc with bigger cam and tunnel ram does not have much vacuum. Holley techs said change it. Some guys say change,some say not to.
Yeah i was wondering what camshaft you had. Probably not enough vacuum to run power brakes, but should pull on the pcv.
Sidewayzz , some engine I use Pvc some I dont , & some with Vac pump. Every engine tune is different, That just part of the game . Your going to have to experiment , try different things , Keep Notes, extra parts. even on a wheel dyno , Good tools to have , Read up on Carb workings / tunning & how a cab actually works (a lot need to do this) Timing light, Big face vac gauge Wide band O2 gauge
Sorry, it was a lame attempt at a joke. I'll show myself out PVC and PCV are two totally different things