monte383sbc

iam swapping out my quadrajet carb for a holley 4150 or 4160 carb but have a couple questions. my boat is a 22' century with a mercruiser, the engine is a small block chevy 355 cubic inches, have a comp cams marine flat tappet camshaft, 10to1 compression, eagle crank, eagle rods, keith black hyperutetic pistons, 2.02/ 1.60 cable hump heads, gm performance cast iron intake, and a alpha one gen II v8 outdrive i beilve its 1.50 ratio?, so now thats i told you about my engine a little, help me decide what carb to purchase and or build and marineize my own 4150 or 4160 carb, i do know that the 4160 only has one metering block on one size and the 4150 have 2 metering blocks and more tuneability, also i dont what a huge carb cus theres no reason for it so iam looking at 600-650 cfm, now when i do decide on a carb, what size jets should i start off with, how many cc accelerator pumps to install, should i have vaccum secondarys or mechanical secondarys, duel feed inlet or single feed inlet, j tubes installed, and throttle linkage bracket? just wanted to get pointed in the right direction, any info is apprciated thanks matt...

GPM

You may want to look at the Edelbrock 1409

monte383sbc

not a fan at all of edelbrock carbs, trying to stick with what i know and what has proven power and tuneability, but i apprciate the help, thanks

gmhdfan

Mechanical 650 double pumper would be cheap & easy to find. If not a marine one you can buy J tubes. I would change to a square bore intake. Nothing wrong with a good working Q-Jet though. Good Luck

monte383sbc

well if its to much work to marineize regular holley carb, iam looking at the 4150 part# 0-80559 w/mechanical secondarys or the 4160 part# 0-80551 with vacuum secondarys, what yall think?

Budman II

iTrader: (1)

Personally, I think the Q-jets get a bad rep just because so few people really know how to tune them. I will say this - once you get one set up, they are rock solid, trouble free, and for an application like yours can deliver just as much cfm (and power) as a Holley, and probably do it more efficiently. I ran a Q-jet for years on my warmed over 454, and it never gave me any trouble. I just had to change to a set of fatter metering rods and main jets to richen it up a little, and off I went. I miss those days now, as I am having to mess with the Holley that I am running a bit more than the Q-jet. Why did I switch? because I stepped up to a 489 with a much more aggressive cam and AFR heads. A Q-jet just couldn't feed it without major mods that are beyond my capability.

IMO, if you HAVE to run a Holley, there are plenty of square bore 715 and 750 CFM marine versions out there, or you may want to go with a spread bore Holley. I have a 715 cfm marine Holley that needs a kit that I would let go for a very reasonable price. Good luck!

NightHawk

+1

Simpler, reliable and easy as hell to tune while on the water. Try that with a Holley and you'll either paddle home or explode.

Budman II

iTrader: (1)

Monte, honestly for a 355 small block with GM heads and (I assume) stock Merc exhaust, I think you will see little if any performance gain by switching to a Holley or even an Edelbrock. If the Q-jet is running OK and not giving you driveability issues, I would leave well enough alone. If you are a tinkerer (like most of us here), and just want to play around with different combo's, then go for it, but I think it may turn out to be a waste of time and money. Now if you were running a stroker with good aftermarket heads and performance exhaust that really needs to breathe, then that would be a different matter.

The fact that you are running 10:1 CR with stock iron heads and hyper pistons concerns me. In a car, this would be just fine, but a marine environment puts everything under much more extreme loads. Couple that with the questionable gas that is often available on the water, and you could find yourself with a detonation issue, which could be disastrous for those hyper pistons. At the very least, err on the side of caution when jetting a different carb, and make sure you are running at least 91 octane fuel at all times. Also, be careful not to overprop this boat - that too can lead to detonation. Much better to run a lower pitch prop and let it wind out a bit.

Budman II

iTrader: (1)

GMHD, I was under the impression that the GM Performance cast iron manifold he is running has a dual pattern flange on it. If so, this might keep him from having to swap the intake.

MILD THUNDER

iTrader: (3)

Keep the quadrajet. Going to a smaller 600 or 650CFM holley will do nothing for you.