Doc's dual plane mod and port matching stky

Discussion in ''Da Nailhead' started by doc, Mar 24, 2011.

  1. doc

    doc Well-Known Member

    With a ebrock carb all you have to do is put a heat shield under the carb and bolt it on.... I would do the Doc dual plane mod on the intake manifold while I had it off..... see the sticky.....
    I make my own spacer/heat shield because I use holley carbs and they have a different bolt pattern.... and I make them the same as the doc modded intake flange..... and I make them out of 3/8 hot rolled steel.... in your case , I would say just make sure of the size of the carbs bores and make the shield match them.... or you can make the shield match the doc mod intake,,, either one will work fine,,,,,
     
  2. chefcg1

    chefcg1 New Member

    Got the dual plane mod and port matching done over the weekend. Pretty simply job, although it wore my arm out with the saw cutting out the manifold. Whole job took about 4 hours from disasembly, porting manifold, port matching, dual plan mod, putting it all back together and clean up. Haven't driven yet as I'm doing headers next. Big thanks to Doc for the shaving cream idea, worked great!
     
  3. Aussie V8

    Aussie V8 Well-Known Member

    I need to get a 4 BBL intake for my project 401. I know where there is one and it's had the Doc modification. It has been port matched to a set of heads which went with another engine. Would this intake be OK to use as is with my stock heads or will I have to now port the heads to match the manifold ?
     
  4. doc

    doc Well-Known Member

    well,, Ken,,,, if the guy doing the port matching used the stock intake gasket for a pattern,, it should work just fine....
    I have a manifold laying around my shop that is done and painted up,, in fact the one that is pictured in the sticky....
    I would take a hundred bucks for it.... not really trying to sell it though..... It is easy to port match the heads ,, just fill the intake runners with arisol shaving cream and do the grinding , the shaving cream catches the metal chips,, then you slurp the stuff out with your shop vac... no need to pull the heads... have someone hold the shop vac hose real close to the carbide burr while you are grinding... cools the tool and cuts the chips to a minimum....
     
  5. Aussie V8

    Aussie V8 Well-Known Member

    PM sent.
     
  6. 66GS425

    66GS425 Well-Known Member

    Hi Doc:
    I can't believe this has taken me 3 yrs but I am finally doing the intake mod. What do you mean by making the air cleaner and side exhaust more efficient?
    Best, Paul
     
  7. Bigpig455

    Bigpig455 Fastest of the slow....

    I dont know how often Doc is on here anymore, but I think I can tell you what he'd say....

    As far as the air cleaner on a stock GS ( and perhaps big car as well ) there is a baffle inside the air cleaner where the snorkel meets the housing that is extremely restrictive. He likes to see that removed, I've done it on mine and I think he's right.

    On the exhaust side, he probably means you need a good performance exhaust. In my case that means a 2.5 inch mandrel bent dual system, and I incorporate an X pipe on top of that. It also helps to port match the exhaust manifolds, but I dont recall that being something we spent a lot of time talking about.

    Good luck with the manifold, and I'll attach a couple pics of one that I did for reference. Looking back, I understand I shouldnt have ground off the "buttons" on the floor of the plenum. I think at the time we confirmed this was worth a tenth or two with back to back track testing.
     

    Attached Files:

  8. doc

    doc Well-Known Member

    As you think about the air/fuel mixture getting into and out of a engine,,, anything you can do to make it less restrictive helps..... and that makes more power.... bigger pipes/mufflers on the exhaust side... and have you ever taken a hard look at a factory air cleaner assembly ???????:grin: they expect a big cube engine to breathe thru a very small snorkel /funnel affair that is not 2 in. in diameter.... so you need to make it easier for air to get into the air cleaner assembly.... that is why the factory put 2 snorkels on the super cat air cleaners.... so you need to also.... and take out that stupid baffle that is in there too.... it is there to reduce noise.... you need at least a 4 in. area that draws cold air from outside the underhood area for a cool air source.... that alone is worth a bunch of power,,,, and along that line,, have you ever noticed how your car will run better on a cool morning ??? the cool , dense air coming in is why.... so why not have that all the time....just keep the intake hot enough that the gas will flash into vapor so it will burn....
     
  9. Bigpig455

    Bigpig455 Fastest of the slow....

    Hey Doc! Good morning.
     
  10. 66GS425

    66GS425 Well-Known Member

     
  11. doc

    doc Well-Known Member

    Hey,, Rhett,,,, good morning to you also too.....

    Paul,,, between those 2 mods you should pick up quite a bit.... then attend to the air cleaner and the exhaust system..... these changes dont add up,,, they multiply.... :Brow::laugh: The horsepower wont change that much,,, but how quick the engine gets what it is gonna do,, will change a bunch....
     
    300sbb_overkill likes this.
  12. 66gsconv

    66gsconv nailhead apprentice

    I haven't started my nailhead in almost 4 years now. But when it was running I tried the doc mod. Worked great. Then I got a drop base KnN air filter with flow through top. Not sure if that helped , no room. my 66gs was able to fit a 1/2 inch 4 hole spacer and then I tried a 1/2 inch open plenum. I felt like the doc mod with a open spacer lost no bottom end and was for sure better in the mid and top end performance. I think it's all about getting more plenum. Nailhead is starving for air and doc mod gives it some
     
    Harlockssx likes this.
  13. Bigpig455

    Bigpig455 Fastest of the slow....

    Hey Bob! Have we ever flowed any other manifolds than the one you did for me? I'll throw a pic up here for illustration, but that was a bit more than a Doc mod, the whole plenum was CNC'd wide open, and I think I recall that was worth a 10th or two on top of everythng else... the plenum idea certainly seems to hold true...

    IMG_4463.jpg
     

    Attached Files:

  14. Daves65gs

    Daves65gs Member

    Hey Doc, Have you tested these? if so, do You have any of the single four barrel intakes that are already ported for sale? Just checking

    Thanks
    Dave
     
  15. doc

    doc Well-Known Member

    +Yes, actually I have the DDP manifolds on all my cars,,, there is a good increase in power .... but you have to keep the heat in the manifold to get good response from them... and..... I do have a manifold that I have done on my bench... I will take $75 plus shipping for it... it has the casting flash ground off the outside and is painted red.... but there is a buuuunch of dust on it... ;);) it also has been port matched to the metal intake gaskets....
     
    300sbb_overkill and Harlockssx like this.
  16. Daves65gs

    Daves65gs Member

     
  17. Daves65gs

    Daves65gs Member

    woops didnt mean to do that, I would like to buy it from ya do I send to a paypal address or mailing address, can you figure the shipping to Joy Illinois also

    Thanks
    Dave
     
  18. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Good to see you posting again Doc!:)

    Clicked on your avatar the other day and it said the last time you were seen on v8 was January and I got a little worried.:eek:

    How the heck have you been?
     
  19. doc

    doc Well-Known Member

    I am good Derek,,,, cept for old age... ;);) just been busy... working around the place,,, finally finished my driveway,,, sold the skylark GS... still have the 64 Riv... aint drove it much in the last year because I was so busy with the driveway project.. maybe now I can get it out and clean it up and drive it some... also cleaned up my shop... that only took 8 full days... :rolleyes::rolleyes:..... but I have been lurking... :):)
     
    300sbb_overkill likes this.
  20. doc

    doc Well-Known Member

    Let me contact UPS and see what it will take to ship... box wise and money and I will advise...
     

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