Carb Recommendations for 5.7L Vortec?

[76SeaRay]

So the fun of building an engine from scratch is getting all the right parts to fit properly. It turns out that my Rochester QJet carb has the fuel inlet in the front of the carburetor so the fuel line runs right into the thermostat housing as set up with my closed cooling system. Looks like I need to buy a replacement carb with starboard side inlet so looking for recommendations. This is a cruising boat so I don't need a super high performance carb. Looking for good fuel economy, easy to set up, and reliable.

Thanks....

 

[Bondo]

Ayuh,..... Edlebrock 1409,....

 

[Scott Danforth]

I like a Holley 4150 (715 CFM 80309 is what VP put on many engines)

 

[76SeaRay]

Thanks for the model numbers. I will check them out. I did find a right angle fuel filter inlet fitting for the QJet but not sure it will clear the TStat cover either. I also am not sure I like the design of it.

 

[tank1949]

So the fun of building an engine from scratch is getting all the right parts to fit properly. It turns out that my Rochester QJet carb has the fuel inlet in the front of the carburetor so the fuel line runs right into the thermostat housing as set up with my closed cooling system. Looks like I need to buy a replacement carb with starboard side inlet so looking for recommendations. This is a cruising boat so I don't need a super high performance carb. Looking for good fuel economy, easy to set up, and reliable.

Thanks....

EDELBROCK 600 cfm

 

[76SeaRay]

Is 600 cfm sufficient for a 5.7L vortec engine? Old school Rochester QJet's were typically 650 cfm on a stock 350 engine. I have the Xtreme Marine Comp Cam with a bit more lift (.488/.495). Again not looking for high performance.

 

[Scott Danforth]

guessing your boat is about #4000 dry, about #5000 wet

the cam you have will require more CFM from mid-RPM up

I would definately go bigger. you have more cam than I had with my vortec headed Small Block and I was feeding it with the 715CFM holley running larger jets pushing my 3600# dry, 4400# wet hull (now I am running a big block with an 850)

I would suggest 650 CFM at a minimum

 

[Bondo]

Ayuh,..... Once calibrated, the 1409 is plenty of carb,....

The 1410 is overkill, 'n more of a big block carb,.....

 

[achris]

Even at 5000rpm the 1409 (600cfm) is well within it's capacity..

 

[76SeaRay]

Hey, that is pretty cool. I assume the Racing Carb CFM calculation is for engines with higher lift cams then since the Xtreme Marine cam is higher than stock lift.

 

[Scott06]

Hey, that is pretty cool. I assume the Racing Carb CFM calculation is for engines with higher lift cams then since the Xtreme Marine cam is higher than stock lift.

Yes - basically they factor a higher volumetric efficency for racing engines vs street.

Most of the outfits like Michigan Motorz who sell partial or complete engine packages use a 1409 600 cfm on 5.7 engines so these must work well. Not to foncuse the issue- I have never been able to figure out is why Merc uses a 750 cfm on the 357 alfa and bravo reman bobtails they sell. ..

Either way get the merc part number 805359T throttle bracket. All the linakages and any electrical components (mine has the slave relay and 50 amp CB on it) will bolt right for a clean install.

 

[Scott Danforth]

Most of the outfits like Michigan Motorz who sell partial or complete engine packages use a 1409 600 cfm on 5.7 engines so these must work well. Not to foncuse the issue- I have never been able to figure out is why Merc uses a 750 cfm on the 357 alfa and bravo reman bobtails they sell. ..

It stems from the performance group at Merc Racing.

Ilmor, Indmar, and VP also had 715/750's on their 5.7's

 

[76SeaRay]

I haven't bought a replacement carb yet but was wondering if the standard Mercruiser fuel line fits either the Edelbrock or Holley carbs recommended above. If not, what do most people do for the line from the fuel pump to the carb?

 

[Scott06]

I haven't bought a replacement carb yet but was wondering if the standard Mercruiser fuel line fits either the Edelbrock or Holley carbs recommended above. If not, what do most people do for the line from the fuel pump to the carb?

Depends on what you have for standard. The fuel line off the 357 alpha and bravo engines will work if you have a mechanical fuel pump. I used the original fuel pump, filter and brackets off my original 4.3 wih a mercarb a d stretched It to fit my 5.0 with an edlbrock.original line had metal ends with a rubber flex section in the middle was about 3” too short, i was able to cut the swaged clamps on ether end off and use a longer marine fuel hose with good hise clamps on the end to lengthen the line 3-4” needed

there are some universal fir marine rated fuel lines with swaged ends sold like this https://www.michiganmotorz.com/fuel-line-hose-3-8-fuel-pump-to-carburetor-31-length
And this

Fuel Line Hose - 3/8

For fuel pump to carburetor connection Replaces copper or steel tubing 3/8" x 25" 25" long PTFE composite hose with 5/8"-18 male inverted flare straight one end; 5/8", 90 degree on the other SAE J1527 type A1

www.michiganmotorz.com

 

[76SeaRay]

I don't have a fuel line yet from the mechanical pump to the carb. I prefer hard lines but will go with hose with swaged fittings if I can find the right length.

 

[Rick Stephens]

I don't have a fuel line yet from the mechanical pump to the carb. I prefer hard lines but will go with hose with swaged fittings if I can find the right length.

Once you pick a carb, to get the OEM fuel line you just need to find a year engine using that carburetor that used an electric pump as well. For the 1409 that would include the Weber version of the same carb. That's how I plumbed my V6 and it came out really clean.

 

[76SeaRay]

Thanks for the pic. I am going to run the manual pump but your comment applies equally to that I would think. But not sure if there is that combo for the Edelbrock or Holley in the parts diagrams anywhere.

 

[Scott06]

Thanks for the pic. I am going to run the manual pump but your comment applies equally to that I would think. But not sure if there is that combo for the Edelbrock or Holley in the parts diagrams anywhere.

If you are running a mechanical pump the fuel line for the 357 alpha or bravo , which uses a Webber carb (identical to edlebrock), would be as close to a bolt in as you can get

 

[76SeaRay]

Great, thanks for the info...

 

[76SeaRay]

Seems to be a shortage of carburetors. Both new and reman seem to be out of stock almost anywhere. I did find a 1410 in stock and assume it would work fine on the 5.7L.

Oops, that one is out of stock too...