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Old 01-26-2002, 02:12 PM
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Post Tunnel ram woes

We are building a 51 merc pickup with a 400 chev small block sporting a dual quad tunnel ram with 2 - 450 holley carbs. we are running progressive linkage with the primary carb being the rear.
Where would we drill the intake to have vacuum ports? Any other helpful info would be appreciated
that would help us get this nostalgic setup working properly

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Old 01-30-2002, 01:01 PM
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You want to take vaccuum sources at the base of the carbs, thus you'll have to add a 1/2"-1" spacer below the carbs that have been tapped for fittings. Also, you may find out that you'll have to run the carbs 1-to-1 to keep the fuel curve in line.
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Old 03-20-2002, 08:03 PM
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You all have no clue how happy i am that you were talking about this. I just bought the exact same setup up for my regal and had no clue and couldnt find anyone that knew what to do about the vaccumm situation. I never even thought about that. thank you very much.
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Old 03-22-2002, 05:49 AM
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I have the same setup on my 69SS nova and I used the 1" spacers under each carb as mentioned above and it will work ok. The only problem that I had was my cam was to big to supply enough vacumn for power brakes so I had to run a canister. Good luck with you project.

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Old 03-24-2002, 04:55 PM
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You can drill a 1/4" npt fitting on the top and get the correct manifold vacuum. I had to do this on my cross ram intake, this is for my breaks,trans and heater. Works fine. If you look at any intake theres a place for vacumm port it's there on the top.You mite want to put some 50cc acceleator pumps on those 450s, because the secondaries dont have squrters to help with any lean spots. It depends on the cam that you run.
You can have lift but go with about a Compcam 280 I just put a cross ram on my 406 and WOW does it lite up the tires to easy.You also need a vacuum line to carb to carb to equalize the vacuum between the two. You want to use a lower duration cam on a street driver, or else with a bigger cam , you have to use a 3,200 stall converter at least, the intake make's power in the 3,500 to 7,500 RPM range . You also need a good set of heads like Dart Pro 1s with 230 on the intake side.If you want a hot setup use 600 carbs,The 280 cam will make it more driveable. If I'm wrong , PLEASE anyone let me know . I do NOT want to give the wrong info to anyone. Please plan your motor out on the parts before you buy them,you want everything to match if you want it to run,and if you cant afford it wait until you can, because you wont be happy and end up buying what you wanted in the first place. Talk about cost.
Thanks George

[ March 25, 2002: Message edited by: 1BAD80 ]

[ March 25, 2002: Message edited by: 1BAD80 ]

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Old 03-24-2002, 05:09 PM
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Wouldn't the better set-up be to go with mechanical secondaries. I can't imagine that you will have enough vacuum with a tunnel ram and correctly matched cam to pull in the secondaries, even with a canister.
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