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Technical Tunnel Ram PVC question

Discussion in 'Traditional Hot Rods' started by sidewayzz69, Jun 14, 2021.

  1. sidewayzz69
    Joined: Aug 9, 2020
    Posts: 172

    sidewayzz69
    Member

    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. 20210609_193059.jpg 20210612_180358.jpg
     
    Deuces likes this.
  2. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,317

    2OLD2FAST
    Member
    from illinois

    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..
     
    Atwater Mike likes this.
  3. birdman1
    Joined: Dec 6, 2012
    Posts: 1,186

    birdman1
    Member

    Why put a pcv on it? All it does is deteriorate the fuel mixture with oil fumes.
     
  4. sidewayzz69
    Joined: Aug 9, 2020
    Posts: 172

    sidewayzz69
    Member

    I was always in mind set without pcv engine would build to much pressure. I am running vented breathers on each cover
     

  5. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,317

    2OLD2FAST
    Member
    from illinois

    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 .
     
  6. Blues4U
    Joined: Oct 1, 2015
    Posts: 5,579

    Blues4U
    Member
    from So Cal

    ^^^^This^^^^ PCV will help maintain oil condition and reduce tendency toward lacquer/varnish/sludge build up.
     
  7. Mike VV
    Joined: Sep 28, 2010
    Posts: 2,354

    Mike VV
    Member
    from SoCal

    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
     
  8. 1971BB427
    Joined: Mar 6, 2010
    Posts: 6,783

    1971BB427
    Member
    from Oregon

    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.
     
  9. Joliet Jake
    Joined: Dec 6, 2007
    Posts: 506

    Joliet Jake
    Member
    from Jax, FL

    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.
     
    Last edited: Jun 17, 2021
  10. Weedburner
    Joined: Nov 16, 2010
    Posts: 207

    Weedburner
    Member
    from Wa State

    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...

    [​IMG]

    Made some check ball seats out of Delrin plastic...

    [​IMG]

    They just push into the breather tubes...

    [​IMG]

    1" nylon bearing balls cost me about $1/ea. Added a pcv valve between the breathers...

    [​IMG]

    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...

    [​IMG]

    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
     
    Last edited: Jun 14, 2021
  11. sidewayzz69
    Joined: Aug 9, 2020
    Posts: 172

    sidewayzz69
    Member

    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.
     
  12. sidewayzz69
    Joined: Aug 9, 2020
    Posts: 172

    sidewayzz69
    Member

    Thanks for all the help to everyone.
     
  13. jimmy six
    Joined: Mar 21, 2006
    Posts: 9,073

    jimmy six
    Member

    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.
     
  14. 1971BB427
    Joined: Mar 6, 2010
    Posts: 6,783

    1971BB427
    Member
    from Oregon

    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.
     
  15. sidewayzz69
    Joined: Aug 9, 2020
    Posts: 172

    sidewayzz69
    Member

  16. 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.
     
    sidewayzz69 likes this.
  17. 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 :)
     
  18. sidewayzz69
    Joined: Aug 9, 2020
    Posts: 172

    sidewayzz69
    Member

    Are you saying the intake would be damaged by the heat coming in
     
  19. Tow Truck Tom
    Joined: Jul 3, 2018
    Posts: 115

    Tow Truck Tom
    Member
    from Clayton DE

    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.
     
  20. sidewayzz69
    Joined: Aug 9, 2020
    Posts: 172

    sidewayzz69
    Member

    Thanks man.
     
  21. jimmy six
    Joined: Mar 21, 2006
    Posts: 9,073

    jimmy six
    Member

    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.
     
    wraymen likes this.
  22. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,317

    2OLD2FAST
    Member
    from illinois

    Power valves don't affect idle unless you have close to none .....
     
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  23. sidewayzz69
    Joined: Aug 9, 2020
    Posts: 172

    sidewayzz69
    Member

    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.
     
  24. Lloyd's paint & glass
    Joined: Nov 16, 2019
    Posts: 4,521

    Lloyd's paint & glass
    ALLIANCE MEMBER

    Yeah i was wondering what camshaft you had. Probably not enough vacuum to run power brakes, but should pull on the pcv.
     
    sidewayzz69 likes this.
  25. sidewayzz69
    Joined: Aug 9, 2020
    Posts: 172

    sidewayzz69
    Member

    .680 .685 286 duration 107 lsa
     
    Lloyd's paint & glass likes this.
  26. Lloyd's paint & glass
    Joined: Nov 16, 2019
    Posts: 4,521

    Lloyd's paint & glass
    ALLIANCE MEMBER

    Yeah that ain't big enough, go bigger :p
     
    sidewayzz69 likes this.
  27. SS327
    Joined: Sep 11, 2017
    Posts: 268

    SS327

    660s would have been better on the big block.
     
  28. 19Eddy30
    Joined: Mar 27, 2011
    Posts: 1,190

    19Eddy30
    Member
    from VA

    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
     
    Last edited: Jun 15, 2021
    sidewayzz69 likes this.
  29. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,317

    2OLD2FAST
    Member
    from illinois

    Put a vacuum gauge on it & find out what the vacuum is before you start changing things..
     
    sidewayzz69 likes this.
  30. Sorry, it was a lame attempt at a joke. I'll show myself out :oops:


    PVC and PCV are two totally different things
     
    sidewayzz69 likes this.

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