2bbl to 4bbl

[joshljoshl]

Re: 2bbl to 4bbl

Stan, could you elaborate on more of the technical differences between the quadrajet and AFB carbs? You mentioned fuel efficiency of the QJ, which is my primary goal... what size would you recommend for a stock 220HP 305? ~500CFM? What manifold would you suggest, and why? Just looking for as many details and feedback as possible.. thx

 

[weatherz]

Re: 2bbl to 4bbl

I liked the ease of tuning with the Edelbrock, but I also encountered the same two aforementioned problems. I fixed the hard start prob. with a phenolic spacer (stopped gas from boiling into the manifold), but the off Idle stumble is not fixable as far as I'm concerned (tried everything!) just learned to live with it. Like my quadrajet though, after I epoxied the jet bores on the bottom, good as new.

 

[weatherz]

Re: 2bbl to 4bbl

Josh,<br />The easiest way to tune a carb is by reading your spark plugs. Too black: Too rich. Too white: Too lean. Tan: just right. You definitely don't want it too lean, that'l give you religious pistons. Also try to shut her down while at mid throttle under load in case at idle the plugs clean up. As far as tools, just an assortment of jets for a Holley or a jet and metering rod kit for AFB type carbs.

 

[lakelivin]

Re: 2bbl to 4bbl

Originally posted by wynter:<br />..... Also try to shut her down while at mid throttle under load in case at idle the plugs clean up.....

I was reading in another thread a little while ago that suddenly stopping and shutting down the engine is one of the ways that hydrolock might occur. If the OP does this, should he make sure to turn the boat before the wake catches up to avoid any chance of this, or are probabilities so small it's not an issue?

 

[weatherz]

Re: 2bbl to 4bbl

I guess it depends on the boat, whether or not your flappers are in good condition, etc.

 

[WSUDERMAN]

Re: 2bbl to 4bbl

i know i am late posting on this but i did this same upgrade on my 305 about 2 years ago. replaced the rochester 2bbl with edelbrock 1409 and performer intake. results where as follows...<br />pre upgrade <br />wot rpm = 4400<br />top speed = ~42 (GPS not speedo...)<br />prop alu. 15 pitch<br /><br />after upgrade <br />Had to change prop to 17 pitch stainless<br />top speed = ~50 (GPS not speedo...)<br />wot = 5000 (don't flame me i only did it once., i want a good hole shot, not top speed.)<br /><br />I do not have any restart or start problems. <br />But i do have a mid range bog if i go from idle to wot. If i keep it just under wot, no bog...<br />not sure about fuel econ because that was not a major concern. so if i burn 6 gal an hour vs 5? its still expensive...

 

[JLAfarms]

Re: 2bbl to 4bbl

I recieved my performer intake and my 1409 carb yesterday and will be installing them today and hopfully go to the lake next week to tune it in thanks for all the replys and I will let yall know how everything works!!<br />Thanks,<br />Jerry<br /><br /><br />If two people always agree, one is not needed!!!

 

[bryont]

Re: 2bbl to 4bbl

I just put on a new EDEL #1409 600 myself. It is on a 1995 350 Mag (260 hp). I just bolted it on and it runs great out of the box. I bought the tuning kits but see no reason to play with it yet anway. The 600 does have smaller primaries. Should help with cruise fuel usage. One would think. By the way what did you pay for yours? Some people may now know but I bought my marine #1409 thru Summit Racing for $303 shipped.

 

[bryont]

Re: 2bbl to 4bbl

JLAfarms; Hi, I have a 1991 monterey 20.5 ft boat with a 305 mercruiser 2bbl carb and I am thinking of upgrading to a 4bbl carb and manifold. What will the performance difrence be?

Did this for you today while I was finishing my boat up. I have a new 1409 Edel. 19 pitch SS and a 260 350 Mag in a 21 ft runabout. Results:<br />4 bbl.-- 5000 (only did it once)at 57 mph "indicated".<br />2 bbl. (secondaries disconnected) -- 4600 rpm, 52 mph "indicated". That doesn't see much but the big difference was that the mid range performance was gone. That is where the big change was. Now of course a 2 bbl. carb would probably have bigger throttle bores than the primaries on a 600 CFM 4 bbl., but that gives you something to look forward to.

 

[JLAfarms]

Re: 2bbl to 4bbl

I have completed the install and just lack modifying my throtle cable bracket that bolted to the back of the 2bbl, or is there one that I can purchase with no mods and bolt on. <br />Thanks,<br />Jerry

 

[JLAfarms]

Re: 2bbl to 4bbl

I paid just under 300.00 for my 1409 from summit

 

[Northern Eclipse]

Re: 2bbl to 4bbl

Jerry,<br /> This is what I ordered from Merc, when I installed a 1409 last year, Bracket part #805359t about $25, Stud (throttle cable mount) 16-818192 about $5, nut 1129250 (there should be 2 with that 1 part #) washer 12-20084 ( should be 4 with that part #). These are all genuine Merc parts for a Weber 4bbl set up V8 5.0, 5.7lx and 350 mag alpha one. The fit is perfect, and very little cable adjustment is required. Just check these part # with your local Merc dealer to be sure.

 

[JLAfarms]

Re: 2bbl to 4bbl

hi guys,<br />I went to the lake yesterday and I was very pleased with the proformance. I gained 5 to 6 mph on top but the big differance was out of the hole it was on plane very easy. mid range was also better than ever. Thanks for all the help from everyone.<br />Jerry

 

[vipzach]

Re: 2bbl to 4bbl

Glad to hear it! I wish I could put a 4 bbl on my 3.0, well I probly could but I geuss it would be a big waste of time. Maybe I'll try nitrous

 

[SeattleMatt]

Re: 2bbl to 4bbl

JLAfarms: what model intake did you get?