Rochester Quadrajet

[BrockR]

i recently bought a 1977 Century Raven that came stock with a 228 Mercruiser. the motor was supposed to be locked up no biggie i am pretty mechanically inclined i can build a new engine. So i bring my new baby home start the rebuild and i find out this is no locked up 305 this is a 350 bored 40 over 202 heads hi-perf cam with a fried starter okay sweet. so to be on the safe side i tore it down checked everything had heads checked, rebuilt carb and so on. I got her running but im not real sure about the mixture screws on the carb seems like she may be a little sluggish at times idk any advice would be greatly appreciated.

Also i figured this engine is pushing at least 300 hp at the very least how much hp can a pre alpha handle or what should i check to see if the outdrive has also been beefed up if thats even possible???

 

[Bondo]

Re: Rochester Quadrajet

or what should i check to see if the outdrive has also been beefed up if thats even possible???

Nope,.. It's got the same 300hp limit as the Alphas...

 

[BrockR]

Re: Rochester Quadrajet

thanks for the quick reply bondo one less thing to worry about

 

[Bondo]

Re: Rochester Quadrajet

Ayuh,... No Prob,... Have you downloaded the Factory Manuals for your rig yet,..??..??
They're available in the Adults Only section at the top of this forum... free...
You'll probably find diagnostics for that Carb in there...
I know the throttle shafts are known to Leak when they get Old,+ worn...

 

[BrockR]

Re: Rochester Quadrajet

yeah i have them all downloaded i will have to take a closer look thanks for the help

 

[6meter]

Re: Rochester Quadrajet

A problem you might have there is since you have other upgrades to the motor, the cam might not be for a boat. Car and boat power curves are different. Idle mixture only make a difference at idle. They do nothing off idle. 1000's possibilities with it not being stock or knowing history.

 

[Alpheus]

Re: Rochester Quadrajet

the mixture screws are for idle only. Here is how I adjust them.

If you are planning on doing hole shots or pulling people and want to get up on plane as fast as you can. follow this procedure.

1 get engine up to normal operating temp making sure that the choke is open full.

2 Turn you air mixture screws all the way in till they just bottom out and turn them out again 2 turns.

3 adjust your idle to around 600 to 700 rpm, or as low and stable as you can get it.

4 You can do this by ear,vacuum gauge or with a tach.
Turn your air mixture screws out until you start to here or see (tach or vacuum gauge) the engine rev just a little and just when it starts to bog down a little turn in until max RPM is achieved. Do this with both needles one at a time.

If you are looking for better fuel economy and are just spending your days cruising around and not at WOT all the time follow the first 3 steps accept this time turn your needles in till the engine revs a bit and the starts to bog and turn out till you are at maximum RPM.

5 After your needles are set return the idle of your boat to around 700-750 RPM

The reasoning on this is just that the mixture curve is a little small but you can choose which end you want to run at. For hole shots you want to be at the rich end just for that little bit of extra fuel before the carb switches to the primary circuit. And for cruising you can run a little on the lean side as not to waste the extra fuel dumping at idle it also dosen't carbon up the plugs as fast.