Is it worth it to upgrade intake manifold and carb?
 

I have a Scarab 29 with twin SBC 350. I was wondering if it is worth upgrading to better intake manifold and a Holley, Quickfuel, or Eldelbrock 4 barrel carb?

What are you looking for? If its speed the likely answer will be no. An intake and carb can't give you enough to make a worthy difference on a stock engine.

What is on it now, Q-Jets? For all the bad mouthing that some like to do with Q-jets, they are a decent carb when set up properly on a stock engine. IMO, the only thing you will see by switching to the Holley is more fuel consumption, and probably more dicking around with it. Unless you plan to also upgrade exhaust, cam, heads, etc., keep the whole thing stock and enjoy running on the water with your hatch down instead of wrenching on it in the driveway.

+1 on the stock quadrajet. Great carbs.

I don't totally agree with these guy's as far as the intake is concerned.

However, you may already have the good Highrise cast iron intakes on those motors already as many twin engine 350cid powered boats have them. If that's the case, other aftmkt intakes won't gain you anything.

Get a casting # for me or pics of your engines and I'll let you know.

I've seen modest gains on 7.4L's going from the flat, cast-iron truck intakes to an RPM Air-Gap and 4150 Holley. I would assume similar, modest gains would be seen with the small block. Key word here is modest.

Just realized the later 350 mags, could have came with a 2 barrel ''merccarb" or a 4 barrel weber. The older 260's could have the quadrajet.


SB is right, get some pics or better description of what you have there.

I will take pictures this evening and load them. The intake on it now is flat for sure and I am pretty sure its quadrajets but I will also take some pictures of the carbs to.

Yep, that cast iron high rise was essentially the same thing as the "472" intake used on the DZ302's and LT-1's by Chevy back in the day. They are pretty good, and having the cast iron is probably better in a marine application than aluminum.

I went from the "flat" standard intakes on my Chris Craft 260 to the "Z-28" iron high rises. WHAT a difference. I then added the magnum flame arresters which were 2x-3x taller. This actually slowed me down until I called the Carburetor Shope in Ontario California.
They sold me the correct jets and metering rods for my Quadrajet. This is an awesome upgrade. I gained 400 r.p.m.s and much better acceleration. There are probably better intakes now but I was "raw water" cooled at the time and needed to stay with iron.
At the time (late 80s) the iron intakes were about $130 each. The metering rods and jets were about $75 but I could have saved if I went with the Carb Shop's recommendation instead of buying jets larger and smaller. I ended up going one size up on the
primary side for a gain of 50 r.p.m.s. The gain didn't even show up on the boat's tachs but it did on the digital tach we used for tuning.
Good luck!