High riser manifold

[pike hunter]

First, I would like to say that I'm reading you're posts on a regular basis and it is a superb place to get informations and improve my poor knowledge.<br /> I got a 92 Mercruiser 5 lit. with a 2 barrels. I want to put a 4brls. I got the chance to put my hand on a manifold that was previously on 350 Mag. When I talk to the seller he mentionne: this is not a regular manifold it's a high rise and I can get more HP from this model compare to a regular manifold.<br />True or false?<br />I suppose I can use the parts of a 350 for my 305? By parts I mean manifold and carb. <br />Thank you

 

[TilliamWe]

Re: High riser manifold

this is not a regular manifold it's a high rise and I can get more HP from this model compare to a regular manifold.

Probably true.<br /><br /><br />

I suppose I can use the parts of a 350 for my 305? By parts I mean manifold and carb.

About the only parts you can't use would be the pistons, cause the 350's are larger than the 305's. Everything else should bolt right up. Just remember, small block Chevrolets do not need HUGE carbs, and a 305 would need one even less (really small pistons in comparison to other small block Chevys)

 

[Laddies]

Re: High riser manifold

the manifold will work, might have to rejet the carb, more HP. ??

 

[John_S]

Re: High riser manifold

Yep, it is a high-rise, and develops its power at the high end of the rpm range. 4000-6500 according to Dennis Moore in "SBC Marine Performance". As I researched this manifold for my 5.7L, became concerned about idle and off idle performance. I ended up choosing the Edelbrock Performer, which Dennis recommends as a good manifold for a 305. I think the high-rise will be too much for a otherwise stock 305. Consider the performer, or if you are raw/saltwater cooled, you want cast iron and might be better off with the "standard" 4 brl manifold.

 

[jimmbo]

Re: High riser manifold

Volvo uses a high rise 4 barrel manifold with a Holley 500 cfm 2 barrel carb with adapter on its 305 and 350 engines. I have the 350 and this combo has very good off idle performance and pulls hard up to 5000 rpm. At WOT, it is pulling 5.5 inches of vaccumn, so I think there still is untapped power there. I've acquired a Holley 650 spreadbore marine carb to try out.

 

[Northern Eclipse]

Re: High riser manifold

Pike Hunter You'll need be sure that the manifold will be correct for your engine since there is 3 variations for SBC, there are Vortec heads from 96 and up and from 87-95 there are center bolt and then there is your '55 -'67 styles. As others have already mentioned the Edelbrock duel plane performer works well also and a 500 to 600 cfm carb will be plenty.

 

[pike hunter]

Re: High riser manifold

Thank you all for you're fast answers. You may laugh at me but I should point some details on the reason why I want to make that change. My boat is a light 23ft. Alum. boat so power is no concern but it's always good to have more then not enough. I do a lot of trolling for salmons and lakers and I think it could be more economical using a 4 bb. Rochester 'cause of the smaller jet.<br />Also the parts I can get are stock Mercruiser. I will keep in mind the 3 variations. And before making my decision I will analyse all the answers on the board. I don't want to spend my money for nothing and I am on the right track with you guys.

 

[John_S]

Re: High riser manifold

Given your low speed use and mileage goals, I'd say all the more not to get that manifold. The good news is, if it doesn't work well for you, the manifolds are still in demand. <br /><br />See below an excerpt, from the web. Keep in mind they are talking cars, but in my mind, cars can handle it better than a boat.<br /><br /><br />===start of add<br />This Bow Tie part is the best stock cast iron (casting #14096242) 4 barrel manifold available. <br /><br />In stock form it will produce more power between 4500 and 7000 rpm than any other stock Chevy manifold. Commonly referred to as a “Marine” intake, this manifold is a cast-iron copy of a Z-28 high rise aluminum intake. The marine intake is equipped with both carburetor bolt patterns, is 1.250" taller than regular intakes and was not available – in cast iron form – on any production cars.<br /><br />In stock form this intake will out perform stock Q-Jet and 2 barrel manifolds in most applications where the engine is running between 4500 and 7000 rpm. Because of its huge internal volume, the Marine Intake lacks throttle response below 4500 rpm compared to other stock intakes. Our Modified Marine Intake will add 10 ft/lbs of torque between 4000 and 6000 rpm.<br />===end of add<br /><br />Or the whole page: http://www.castheads.com/intakes_folder/2intakesmain.html

 

[pike hunter]

Re: High riser manifold

I will like to thank you for you're answers and advises. I will take a moment to think about it now that I do have more informations.

 

[Bondo]

Re: High riser manifold

As Stated above,<br /><br />A Low-rise Manifold will be a Much Better Bet, for Your Application, for the Goals that you've set......