Intake manifold compare?
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Intake manifold compare?

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    Default Intake manifold compare?

    I have a super vic now and am having trouble launching off the line. Once going runs great. So I figure I'll change the intake first. In searching I can't find any info on what makes them different. Each manufacture will tell me they make the best. Is there some way to compare them like with heads runner volume cfm rates and the like. Hate to buy 3 or 4 to find the one that works best. Any info would help. Thanks.

    Tim

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    Senior Member cyclone's Avatar
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    Quote Originally Posted by River Rat 005 View Post
    I have a super vic now and am having trouble launching off the line. Once going runs great. So I figure I'll change the intake first. In searching I can't find any info on what makes them different. Each manufacture will tell me they make the best. Is there some way to compare them like with heads runner volume cfm rates and the like. Hate to buy 3 or 4 to find the one that works best. Any info would help. Thanks.

    Tim
    Do u have carbs or injection? Jet or vdrive?
    Sounds like a tuning problem to me

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    Senior Member EVILFORCE's Avatar
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    OK. I will say it. What are all the specs on the motor? RPMS it turns ci, c/r, head size carb size. Yes could be to much intake or carb or both.

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    I've posted this problem before. Thought most would remember.

    OK.....468 bbc, 12.5:1, Brodix 2+ non cnc heads, Comp cam [email protected] 286in 294ex. lift .775in .748ex and a Quik Fuel 1050 carb. This is in a kurtis 500 drag hydro with 37% in box and 31 split in lenco and a 11"x16 prop. I launch at 1500rpm,(don't know how high rpm the dogs can handle) shift at 7500 and cross the line at about 7500. I'm having trouble with a bog off line, but runs fine after it launches. Turns 9.00 no problem, just lossing at the launch. I've done all the tuning I've been told to do except to remove the 1" open spacer.(ran out of weather) I know this is a miss match of parts, so I'm thinking of starting with an intake change first. I'm looking for a little more bottom end and not lose much up top. It takes about 7900 to run the 1000' in 7.00.

    Tim

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    Distinguished Member David 519's Avatar
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    Quote Originally Posted by River Rat 005 View Post
    I've posted this problem before. Thought most would remember.

    OK.....468 bbc, 12.5:1, Brodix 2+ non cnc heads, Comp cam [email protected] 286in 294ex. lift .775in .748ex and a Quik Fuel 1050 carb. This is in a kurtis 500 drag hydro with 37% in box and 31 split in lenco and a 11"x16 prop. I launch at 1500rpm,(don't know how high rpm the dogs can handle) shift at 7500 and cross the line at about 7500. I'm having trouble with a bog off line, but runs fine after it launches. Turns 9.00 no problem, just lossing at the launch. I've done all the tuning I've been told to do except to remove the 1" open spacer.(ran out of weather) I know this is a miss match of parts, so I'm thinking of starting with an intake change first. I'm looking for a little more bottom end and not lose much up top. It takes about 7900 to run the 1000' in 7.00.

    Tim
    Looking at your combo, I doubt an intake will fix a bog off the line. That said and to answer your qustion, IMO I'd have chosen a Victor Jr (454R) if I was starting from scratch for your deal. While there are "better" manifolds out there for specific combos, either a Victor Jr or Super Vic will cover most performance applications and a good baseline start. Getting a single dom to launch is a trick. Ours took a bunch of pump shot and an engine that builds torque very early. Good luck, hope you get it sorted out. Would be tough to race it with a stumble....
    Quote Originally Posted by gn7 View Post
    ....... David 519 is 100% correct........

    Quote Originally Posted by fuelinmyveins82 View Post
    .....I think people forget that racing is supposed to fun. Losing shouldn't be discouraging it should motivate you work on your pile to make it faster.....

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    My two-bits is that you spend some time testing on the dyno to sort out a few things within your engine, have several props and work on how the boat leaves!! Sounds like your chasing your tail big time, find someone that will give you the straight poop and stick with them, quit going around and round getting opinions going no where.

    I'm not a guru at anything but by this time I would think I would have had this sorted out by trying things and listening to constructive criticism and not taking anything personal. If money is the issue maybe you need to back off for a bit and regroup, so your not pissing $$ down the drain!! I've posted on your previous thread and I'm not sure why I keep doing this, so I'll not comment again!

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    Just a very quick and easy question that I think I asked the first time around. What kind of cranking cylinder pressure do you have with your current cam and the intake closing point that it is now installed?

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    X2 sounds like not enough initial fuel, pump shot, squirter, etc. launch higher?

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    Wideband that data logs(barring that a dyno is out of the question), Learn what the issues are before you start chasing your tail. That being said a Dom with a cam that big being launched at 1500 and you get a bog does not surprise me. I'm pretty uneducated in boat stuff but in a car you'd be looking at a minimum of a 3500 stall

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    OK.....I understand what you guys are saying. And I also know that if this were in a car I'd have no trouble because I could launch at 3500 or even 5000. I know how to compare cams and heads, but theres nothing I can find on intakes other than rpm range. And all seem to be 3500 to 8000-8500.

    As for a single dom being hard to launch without a stumble, then how can it be easier with 2. You now have twice the cfm to cover at the hit of the throttle. And yes you have 2 more squirters but you have 4 more barrels. I've watched boats launch with t rams a 2 doms at low rpm and they leave.

    As for cranking pressure, I don't know. The card says the intake closes atb 73* abdc. It's ground on a 110 center line and is installed at 108.

    Tim

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    Quote Originally Posted by River Rat 005 View Post

    As for cranking pressure, I don't know. The card says the intake closes atb 73* abdc. It's ground on a 110 center line and is installed at 108.

    Tim
    Borrow a cylinder compression test guage from your buddy, pull one spark plug, screw in the compression guage, ignition off, carburetor open and with a well charged battery spin the engine over about five pumps on the guage. Read the PSI and report back. Initial response is highly affected by the relationship of the closing point of the intake valve with the crankshaft rotation and compression ratio of a given engine size.

    While you are at it, it might not be a bad idea to pull all the plugs and repeat procedure on all eight holes to see if all cylinders are reasonably equal. This can indicate the condition of your ring and valve seal, etc.

    If this thing is less than 190 lbs cranking pressure it is going to be be hard pressed to come out of the gate at low RPM with any intake manifold. Preferably you would want to see 210 to 240 psi in my opinion to have decent throttle response. It could be as simple as advancing the phasing of the camshaft. Larger camshafts do make more power up high, but a proper size/phased cam will always accelerate quicker and if you are drag racing.... an engine/vehicle that will not come out of the hole will seldom win

    I hope this helps

    Gear

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    FYI - Back to your original question - I do have several BBC rectangle single four intake manifolds extra that include a large Dart, Brodix, Holley Strip Dominator and Victor 454-R Victor. I would consider swapping one for the Super Vic if that would help.

    Gear

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    Quote Originally Posted by River Rat 005 View Post
    I have a super vic now and am having trouble launching off the line. Once going runs great. So I figure I'll change the intake first. In searching I can't find any info on what makes them different. Each manufacture will tell me they make the best. Is there some way to compare them like with heads runner volume cfm rates and the like. Hate to buy 3 or 4 to find the one that works best. Any info would help. Thanks.

    Tim
    Is this Deja Vu or haven't we chase this tail 6 six months ago for FIVE PAGES
    The differences in the manifolds is runner cross section and plenum volume for the most part. Both of which were explained in that privious thread.
    Its too little motor, with a ton of head port, shit load of canshaft, along with a huge intake plenum and gigantic ports. Leave everything else the same and add 100 inches and the thing will probably work bitch'n.



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    Last edited by gn7; 03-17-2013 at 03:48 PM.

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    With my work I only have weekends to work on it. I have the compression gage. I'll need to set the valves. This will be next weekend.

    As for the manifolds, I was leaning towards the victor 454 figuring it might have a smaller plenum and runner cross section than the super. I was looking at the Brodix because I have thier heads. Some of the intakes have extended runners in the plenum while others don't. Was thinking this could help low end also.

    Tim

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