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Thread: Carb suggestions for TR

  1. #1
    Senior Member
    Join Date
    Apr 2010
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    2,920
    Looking for some input on carbs for a tunnelram. Motor is a 500 hp BBF and I'm currently running a Weiand TR with a pair of Holley 660 center squirters. I'm getting killed at the pump and want to make a change to something a little more miserly on the go juice.
    Prior to the tunnelram I was running a Weiand Stealth dual plane intake and a single Holley 850 dp. Since I gained absolutely nothing (except for the piss poor mileage) by making the change to the TR, I figure I could pick some carbs that would put me around that same 850-900 cfm mark.
    I'm toying with the idea of vacume secondaries, or possibly the Holley 450
    4160 mechanical secondary. I see where Summit and Jegs are selling that 450 for $193 so the price is right. The question is............will I be in the same position I am now (right next to the gas pump) or is the linkage more progressive than the 660s I'm running? Does anybody know about this particular carb? It states in the ad This has a mechanical secondary, but no secondary accelerator pump circuit. It is designed for a mulitiple carburetor application ONLY, it will not function properly on a single carburetor application.
    It sounds perfect and the linkage looks to be a lot more progressive than my "all or nothing" on the 660s.
    http://static.summitracing.com/globa...hly-0-9776.jpg
    Link to the Holley 4160 carb (http://store.summitracing.com/partde...5&autoview=sku)
    I have buddies that are running BBFs with tunnelrams and 600 vac sec carbs. They work o.k. for them and their fuel mileage is way way better than mine so I reckon the vac secs would be o.k. but I'd probably go a bit smaller.
    Any thoughts or comments on these two choices. Or any other possible choices to recommend.
    Input appreciated.
    Thanks
    Dan

  2. #2
    sanger rat
    Dan, I've been really happy with my 600 dp's. I don't think you will be happy with the 450.

  3. #3
    wsuwrhr
    Wouldn't a vacuum secondary carb in a TR application cause a lean/rich condition due to the later opening of the secondary butteryfly?
    I bought that combo deal from Summit years back for the jetboat and later returned the carbs because I didn't realize the carbs the combo came with were vac. secondary.
    Brian

  4. #4
    QuickJet
    I have yet to see ANY vacume secondary carb work from a performance standpoint. I had 660's on my BBC in a jet AND in a v-drive and they worked great. Maybe it's what's under the carbs that not giving you what you need. What series intake is it? I'd switch the intake before messing with the carbs. The only thing a Weiand intake is good for on a boat is to fill it with concrete, tie a rope to it and use it as an anchor. Or you could fill it with potting soil and make a nice planter out of it. Wife might like it.

  5. #5
    Senior Member
    Join Date
    Apr 2010
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    2,920
    Not a lot of choices on tunnelrams for BBFs. As for the carbs, the secondaries are tipping in at 3000 rpm. I hardly ever run my boat that slow which means I'm sucking some major fuel.
    The boat runs great, it's just a gas hog.
    http://jetboat.homestead.com/carbs_done_copy.jpg

  6. #6
    Blown 472
    If you gained nothing why not go back to the 850?

  7. #7
    OverKill
    Dan
    Don't even think about swaping motors LOL.

  8. #8
    DUCKY
    We used to run an 850 Holley DP on an Offy single carb T/R (10:1 BBF) in my Dad's jetboat. When he sold it, he wanted to keep that carb, so we put on a 780cfm vacuum secondary Holley. After spending some time tuning it, the overall top end loss was only 150rpm, and the throttle response and economy were both drastically improved. The 450's could be made to work, but it will take some tuning time, and some mods from the way they come out of the box. One key to a pair of vacuum carbs is drilling and tapping the vacuum cans and running a balance line between them, and adding the secondary metering blocks so you can change the jets on the sec. side is also a really good idea. I have done a couple using primary blocks that have idle screw and power valve provisions, and that makes for a nice smooth pull from idle to WOT.

  9. #9
    DUCKY
    Wouldn't a vacuum secondary carb in a TR application cause a lean/rich condition due to the later opening of the secondary butteryfly?
    Brian
    Not if the primaries are jetted right, and have the right power valves.
    I am not professing to be a Holley master, but I have played with quite a few, and it seems that most people automatically discount a vacuum secondary carb, due to a general lack of understanding. They can and do work when they are tweaked right, and I don't mean putting in the lightest spring you can find and throwing away the check ball, or even worse putting a screw in the little arm. The most drastic mistake that most people make with a V/S carb is trying to force the secondaries to open early. The motor will open them IF it needs the air.... Oh yeah, and another good one is when people slap that vac. can together without paying attention to the diaphragm, and tear it with the screws If there is a leak, you can forget about the secondaries ever opening... (I am speaking from personal experience, having made ALL of the aforementioned mistakes )

  10. #10
    Senior Member
    Join Date
    Apr 2010
    Posts
    2,920
    If you gained nothing why not go back to the 850?
    I've sold all the other pieces parts. I still kick myself in the ass for that one. Let em go way too cheap too.
    Not if the primaries are jetted right, and have the right power valves.
    I am not professing to be a Holley master, but I have played with quite a few, and it seems that most people automatically discount a vacuum secondary carb, due to a general lack of understanding. They can and do work when they are tweaked right, and I don't mean putting in the lightest spring you can find and throwing away the check ball, or even worse putting a screw in the little arm. The most drastic mistake that most people make with a V/S carb is trying to force the secondaries to open early. The motor will open them IF it needs the air.... Oh yeah, and another good one is when people slap that vac. can together without paying attention to the diaphragm, and tear it with the screws If there is a leak, you can forget about the secondaries ever opening... (I am speaking from personal experience, having made ALL of the aforementioned mistakes )
    I completely agree with this statement. Right down to tearing the diaphragm on the vacume pot, and messing around trying to turn a VS carb into a mechanical linkage.
    I know the VS carbs can be made to work on a tunnelram and might even prove to be more fuel efficient than the the little 4160 mech carbs I'm looking at.
    Personally............ I still prefer a mech sec carb though.
    The 450's could be made to work, but it will take some tuning time, and some mods from the way they come out of the box.
    We're talking about modding the VS carbs too so that's not a huge deal. I didn't really expect to bolt em on and have em work perfectly.
    Dan, I've been really happy with my 600 dp's. I don't think you will be happy with the 450.
    I appreciate the input, but can I ask why? The only downside I can think of is if I build the 557 stroker that I want so bad, I'd have to make another change later on.

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