318 manifold on a 360........

[dodgetkboy78]

So this isn't an A body engine question, but I need some opinions.

I have a Boat, with a 360 in it. It has the little single plane 4bbl manifold on it from the 318 it replaced. What effect do you think the little port manifold has on the big port heads? I have put 318 heads on 360's for hunting buggy's, and low low rpm work engines, but never a small port manifold on a big port head.

My only main question, since I am happy with the power, (The boat cruises at 8kts, 2000rpm, throttle barely cracked) is what it is doing to the economy. What do you think I would benefit if I put the dual plane 360 marine manifold on it?

 

[dodge freak]

Boats drink fuel up fast, go to http://www.marineengine.com/discus/messages/12490/12490.shtml lots of info on Chrysler boat engines.

As for small port intakes, should not be a problem for your use. Holley street dominator intake was a small port single plane and was listed as a high performance intake for street use on all SB Mopars. They did make a big port and called it the strip dominator

Only thing I recall on marineengingines about getting better fuel economy was to replace the Carter carb with a Edelbrock, many claim a difference. Same carb I always thought.

 

[1wild&crazyguy]

Sounds fine for a boat, they don't turn very many rpm's, like what ..3000-4000 rpm maybe?

 

[dano]

Hook up a vacuum gauge, if your pulling Zero vacuum at your 2000 rpm cruise speed, then motor is working as hard as it can. The economy you might just need to measure.

 

[moper]

I run one on my truck for torque and economy too. That thing nver sees the high side of 4K.

 

[dodgetkboy78]

Actually, LOL, it's cruise speed is 2000..........

SHould be just fine, eh?

I was wondering what effect the port mismatch had.

 

[1wild&crazyguy]

Small to big no issue other than possibly flow and slightly turbulent dead spots just under around the transition.

Big to small=suspended fuel that doesn't all make it cleanly into the port, some crashes against the margin around the smaller port entrance and you can end up with a lil puddling at drastic rpm drops.

This issue becomes more relevant in bad combos of carburetors and intakes in relation to cid and application.

My thoughts on it.jmo

 

[dodgetkboy78]

makes perfect sense, and kinda goes along what I was thinking.

As far as the EB getting better MPG than the carter? That really doesn't make sense, putting a bigger EB on it, and getting better MPG.

I'll have to check into it.

 

[dodge freak]

I agree but many were posting that they notice a improvement over the old Carter carb they had on their boats. Maybe the Carters were worn out..like by the throttle shafts area and were leaking air.

You can not use any carb, needs to be coast guard approved (this is one area I agree even if you have no law enforcement, the gasoline vapors can build up in the engine bay and just one little spark from a plug wire--even static electricity and kaboom)