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Old 10-27-2008, 10:35 AM
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What intake for Low End Torque

I have a question on Intake Manifolds. I think that I have put the wrong Intake Manifold on my boat, over the past Winter and am wanting to change it to get more torque.

Here is what I have"

1994 Stock Mercuruiser Chevy 305 without Vortech Heads. Not sure which heads I do have. It came with a 2bbl Rochester Carb.

I removed the Intake and Carb and upgraded to an Edelbrock 1409s 600CFM Carb and Professional Products Crosswind Manifold 52025, which makes power from 1500RPMS up to 6500. I need it to come back down to Idle Up.

Here is the Model I have.

CROSSWIND® for 23° Heads
1957-’95 Small Block Chevy V8

Polished Satin Real Chrome
52025 52026 52022

The new CrossWind Manifold is a special version of the 52020/52021. While it is the exact same height, it features an open area under the plenum chamber. This provides for a flow of cooling air which keeps the temperature of the air/fuel charge lower thus producing more power and torque. The interior plenum and port design are identical to the 52020/52021 and will provide somewhat better overall power than the 52020/52021 due to the special air gap style design.

From this Page http://www.professional-products.com...uctSBchevy.php

Can anyone Give me a great Recommendation as to which manfold would work that I could just swap iwth and get better low end. My Top is great, the low needs some work, till the 1500 rpms.


Thanks,
Bryan

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Old 10-27-2008, 11:29 AM
How fast is fast enough?
 
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You can go with a Edelbrom Perfromer, or even a factory piece. THe first choice will give you a little more midrange though.
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Old 10-27-2008, 11:53 AM
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I was thinking the Edelbrock performer would work good. Just did not know if there were any other good ones that I am not aware of. Such as some by Weiand or any other company.

Thanks,
Bryan
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Old 10-27-2008, 10:22 PM
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performer dual plane works well on boats. When you have done that and want more put in a 350, and when that is still not enough build a 383 . Been there done that.
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Old 10-27-2008, 10:57 PM
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A early 327 350 hp Aluminum intake off Corvette will give you lots of low end torque over any aftermarket intake. This is the best low end intake I've every tried.
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Old 10-28-2008, 05:49 AM
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the early 327 intake was cloned by edelbrock and is know as a C3B , about 100 bucks compared to the factory unit. it works well, but I would go with the performer. and maybe a quadra jet.smaller primaries ,and more port velocity. my 2 cents.
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Old 10-28-2008, 08:32 AM
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Ok,
So it sounds as if I do go with the Performer Intake over the one that I have now. Is there any other way to help this out? I know someone said something about the Quadrajet with Smaller Primaries.

Is there any way to stay with my Edelbrock 1409 and make any changes to it, for more Torque? It is running like a champ now.

The boat did have some decent torque with the old tiny 2bbl carb and older intake, but the 4 bbl and new intake helps quite a bit in Midrange and high end, over that.

I just need to get a better low end intake on there and I think I will be happy till a 5.7 goes in down the road.

Bryan
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Old 10-28-2008, 08:39 AM
How fast is fast enough?
 
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well, a cam would get you more low end- at the cost of top end. A really good cam may leave you with more of both though... What do you have in it now?
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Old 10-28-2008, 08:41 AM
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Its all stock, other than then Intake and New 4bbl I put on it last Winter.

How hard is a cam to install? I am trying to learn, also the thing that I have read/been told about boats is that when messing with Boats, you must watch our for Reversion, where the water will come back in the Thru Hull Exhaust and into the Valves. So this would be something that I must watch out for.

Bryan
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Old 10-28-2008, 11:45 AM
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Quote:
Originally Posted by FEDDO
the early 327 intake was cloned by edelbrock and is know as a C3B , about 100 bucks compared to the factory unit. it works well, but I would go with the performer. and maybe a quadra jet.smaller primaries ,and more port velocity. my 2 cents.
Yeah But the C3C and C3BX got two oblong holes and The GM Corvette got One Oblong hole and Two round Holes...
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Old 10-28-2008, 12:27 PM
How fast is fast enough?
 
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For a cam I would call up Crane and get one with their H-206/288 lobe on the intake and exhaust, get it ground with a 114 LSA and advance it 2 degrees.

Break in is especially important with this cam, and I would recomend always running racing tyupe oils that are higher in ZDDP- they're not as expensive as you would imagine. 1.6 roller tip rockers would really make this thing purr.
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Old 10-28-2008, 01:09 PM
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Just a thought, don´t boat guys swap propellers out for more "bite" in the water, different blade pitches ?
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Old 10-28-2008, 01:41 PM
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the stock 2V carb cfm and stock 2V intake runners cc's and stock "2V specific" cam duration and the heads I/E ratio for the exhaust are a matched parts set engineered to make (almost) best possible low end TQ with the most Hg and A/F velocity possible at low piston speeds when cylinders don't get a 100% fill,,,,

due to the larger intake runners and larger 4V carb venturi's you have less Hg signal and less velocity now so the cylinders are getting less charge to make power...

it "all" has to be designed to work together especially in a boat that puts so much TQ load on the motor....

if you do change the cam to work with the 4V intake and carb you will likely need to buy a different prop to match the new TQ curve and rpms.....

within a reason,,,, motor cubes=motor max TQ so swapping to a mild 350 or basic 383 is a good choice...to gain 50-80ft/lbs of TQ for acceleration out of the hole and top speed

a boat doesn't have the TQ multiplying capability for acceleration power that a car tranny gears ratio's plus rear gears ratio does,,,it's a totally different ball game....
(drive away from a red light in 4th gear (1:1 tranny ratio) to see what I mean, even with the 3.XX rear gears multiplying the flywheel TQ it is yuch!!!)

Last edited by red65mustang; 10-28-2008 at 01:51 PM.
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Old 10-28-2008, 02:25 PM
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Bry-If you haven't done so yet, search "305 marine vortec" on this site and quite a bit of info comes up. I've had a few threads talking about your exact topic (1 exception-the Vortec part).

I've gone your route and as stated earlier, you may want to hold off on any major purchases until you can get a vortec 350.

You can put quite a bit of money into your motor and only achieve a little bit of noticeable power improvement. Just make sure your boat is in a good state of tune and prop it for what you want it to do (hole shot or top end).
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Old 10-28-2008, 04:17 PM
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The only mismatch I see is the intake. The carb is fine, the engine is fine. Qjets were put in a very rare few marine applications, so finding a marine Qjet isn't easy, and a few of the parts are different meaning you'll have some trouble.

You can't go wrong with a good old fashioned GM aluminum marine intake. They are a direct copy of the "performer-like" intake that GM ships with crate engines. They are cheap on Ebay and work great on marine applications. Do a little searching and you can even find the marine version without EGR and they are cast with bronze liners in the water passages.

If you're going to swap cams, be super careful if you have a wet exhaust. Too much overlap can suck water right back in the exhaust valve with tragic results. DON'T USE THE CAM MANUFACTURER'S GUIDELINES. For instance if you call Comp's tech line and ask them, they will recommend a cam that has been known to consistently damage engines from sucking in water. If you ask them about a wet exhaust and reversion they'll think you're smoking crack and sell it to you anyway.
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