SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: challenger76 on September 15, 2014, 12:21:33 PM
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I have a bbf 71 block dove heads 180h magnum cam lifters 850 holley and lightning headers I run a dual plane intake now just wondering if a single plane would be better seems like thats all I see on jet boats any info would help
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Single plane-
Dual plane is for tow trucks, motorhomes and boats with a prop. (more low-end needed)
Dan'l
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Any good recommendation on a single plane manifold for my set up
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I went from a torker to a performer with no difference. I added hp an now run a rpm. I hear a stealth is good.
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Alot of my ford friends run the trick flow one
http://www.trickflow.com/partdetail.asp?part=TFS-53400112 (http://www.trickflow.com/partdetail.asp?part=TFS-53400112)
i run a stealth on my sisters 460 , changing it out in the winter :thumbup:
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Any good recommendation on a single plane manifold for my set up
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Is this a race boat? What RPM are you pulling now or expect to be pulling? Single plane intakes like the higher RPM range as they like the runner velocity. Dual plane would probably do everything you will ask of that motor unless you like to make pass after pass and squeeze every horse from it. Weiand Stealth is one of the most recommended dual planes and seems to good power even on BBF's over 500", just my $.02.
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Its not a race boat it runs 5200 rpm now.. with the rpm air gap manifold I have on it... I just see a lot of single plane manifolds thats why im curious to see what everyone thinks
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Its not a race boat it runs 5200 rpm now.. with the rpm air gap manifold I have on it... I just see a lot of single plane manifolds thats why im curious to see what everyone thinks
What intake do you have currently? You may save your money and run what you have currently, unless you want the look of a single plane you may not see a noticeable difference.
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Its not a race boat it runs 5200 rpm now.. with the rpm air gap manifold I have on it... I just see a lot of single plane manifolds thats why im curious to see what everyone thinks
What intake do you have currently? You may save your money and run what you have currently, unless you want the look of a single plane you may not see a noticeable difference.
im running a eddlebrock rpm air gap
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Keep it on for now...
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That's a pretty good intake, I'd keep it. Are you looking for more power or speed?
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Try an open carb spacer and see if your engine likes the extra plenum volume. They are available in 1/2", 1", and 2".
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Or just mill the divider down a bit...
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Or just mill the divider down a bit...
^^^^^
This is a good answer here. I'm a believer in a good dual plain unless all your doing is full speed passes. To me, you may just run your fuel bill up trying to find that extra power you think your giving up with the dual plain. All your parts need to work together for max gain otherwise you just become a "Bolt on Barney". If your heads and/or cam aren't going to want the higher velocity of a single plain then your just pissing money away. I would try Flusher's idea adding carb spacers and see if the engine likes that.
Here's a video with dyno numbers showing what the basic differences may be in the 2 manifolds.
Good FYI info,
https://www.youtube.com/watch?v=i2DvnoHWagk (https://www.youtube.com/watch?v=i2DvnoHWagk)
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Milling the divider is difficult to go back, it is difficult to put the material back in. The AirGap RPM already has part of the divider milled down.
Be careful milling the divider, it is actually possible to lose power or not achieve the desired results. Typically, the divider will be milled down anywhere from .200 to .500-inches. The cut could also be biased towards the rear of the plenum and not centered. I have seen a lot of manifolds that have had the entire divider removed, but I have read a lot about that being a bad idea and actually hurting power. I have not found any documentation on modifying an AirGap RPM and I didn’t have the resources to develop mine before changing directions.
You might also consider trying a 2-hole and a 4-hole spacer. You might see some benefits from increased plenum size while keeping the two planes isolated as it will keep the velocity of the air and fuel up, promoting better atomization and therefore a more complete burn with increased power and efficiency. To do so, you will need to fill in the portion of the divider that has already been removed.
If you do feel the need to modify your divider, either leave the remainder of the divider square or put as large a radius as possible. DO NOT sharpen it to a point, it causes shearing of the air and reduces flow. A large radius will help airflow transition around the sharp bends.
Hope you enjoy the attached reading, I think it is a good start to understanding induction science. You may find that porting your existing manifold would be a better option for your particular usage. Keep in mind that runner length (relative to cam timing) and cross-sectional area (relative to cylinder volume and RPM) are key to having a good performing engine. Shorter runners as well as larger cross-sectionals area favor higher RPM.
Just be advised that each change you make will probably require rejetting the carb to see any real benefits. Each configuration will require “developing a tune” and evaluation to see if there is a gain or a loss. Take good notes so that you can go back to what worked.
Cheers,
Joe