Factory Alpha 305 Quadrajet vs 350 Quadrajet

[Biggyniner]

Hey guys,

As I mentioned in another, post I am swapping my 305 out for a 350 long block. I noticed that the carbs for the 305 and 350 are two different part numbers. It appears that the 4bbl option for the 305 is the same 4bbl for the v6 Mercruiser. I am assuming the only difference is jet size. Does anyone know what jet's I need to make it equivalent to the 350 qj?

305 part no: 1347-804623R02

350 part no: 1347-804624R02

 

[Biggyniner]

I found this post but this is for a mid 80s quadrajet, mine is a 93

 

[alldodge]

This is from Manual 17 page 5C-2 which can be found in link below
http://boatinfo.no/lib/mercruiser/ma...cruiser17.html

Here is the page



If you go to page 5D-2 is for the weber carb

 

[harringtondav]

I spent some time poking around at '87 260 305 and 350 and found your 1347-804624R02 (1347-804626R 1) listed for both.

I poked further on Chevy forums and read where similar carbs use a limiting tab on the secondary air valve to reduce CFM.

"Some that come on smaller motors like 305s have a tab on their air valve that limits its travel, thereby "lowering" their CFM "rating". However, grind or bend that tab, and then they're the same "rating" as all the rest."

Looking at AllDodge's chart, the two look identical. So look at your 305 carb and see if this CFM limiter exists. If so, remove it.

I poked a little further and found this at Boatinfo. This also shows similar jets. Maybe this will help guide you
http://www.boatinfo.no/lib/mercruiser/manuals/mercruiser9.html#/472

 

[Lou C]

Cliff's High Performance Quadrajets is also a good source of information for tuning this carb. They have a forum where you can ask questions.

 

[Biggyniner]

Thanks Everyone!

 

[Biggyniner]

This is from Manual 17 page 5C-2 which can be found in link below
http://boatinfo.no/lib/mercruiser/ma...cruiser17.html

Here is the page



If you go to page 5D-2 is for the weber carb

It would appear the only difference is the secondary metering rods... Outstanding... Probably not even necessary but i found a decently priced used pair I will pick up

 

[alldodge]

They are necessary, to make the fuel mixture a bit richer. If it leans out the piston gets burned