383 carb choice
#1
Guest
Posts: n/a
![Default](/forums/images/icons/icon1.gif)
I am sure a few of you saw my other thread regarding my 383 stumble and I was wondering if maybe before I spent the time and effort to set up the car right if I should look into a different style/ size carb.
I am running a 650 double pumper now mainly cause I had it. But for a boat what is best? Mechanical secondaries or Vacuum? 650 or 750.... and so forth.
Keep in mind the boat is not a cruising boat. She is a little hot rod that is used for 1/2 hour blasts. Acceleration and speed are more important then fuel economy.
Chris
I am running a 650 double pumper now mainly cause I had it. But for a boat what is best? Mechanical secondaries or Vacuum? 650 or 750.... and so forth.
Keep in mind the boat is not a cruising boat. She is a little hot rod that is used for 1/2 hour blasts. Acceleration and speed are more important then fuel economy.
Chris
#4
Registered
Join Date: Oct 2000
Location: On the river
Posts: 3,372
Likes: 0
Received 0 Likes
on
0 Posts
![Default](/forums/images/icons/icon1.gif)
On my 383 which is not used for crusing either
I am running a 750 holley vac. secondary. Its in the GM parts book. I put it on and haven't touched it since works great... But it is not a marine carb..
![Big Grin](/forums/images/smilies/biggrin.gif)
#6
BEACH PARTY
![](https://www.offshoreonly.com/forums/images/icons/platinum_member_star.gif)
![Default](/forums/images/icons/icon1.gif)
I'm using a 750 QuadraJet on my 383 with the jetting done by yours truly. It works REALLY well and has no stumble.
I would suggest looking for a vac 750... is your carb stock out of the box?
Tom
I would suggest looking for a vac 750... is your carb stock out of the box?
Tom
#7
Registered
Join Date: Oct 2000
Location: Ochlocknee Bay, Florida
Posts: 138
Likes: 0
Received 0 Likes
on
0 Posts
![Default](/forums/images/icons/icon1.gif)
I run 600 Holley Marine vacuum secondary carbs on each of three 383 engines. One 383 is in my X-18 Donzi and a pair are in my 27 Magnum. All are propped for 4800 to 5200 RPM. I did try a 750 cfm carb on the 383 in the X-18 an found no difference in top end.
#9
Registered
Join Date: Oct 2000
Location: Cleveland, OK
Posts: 410
Likes: 0
Received 0 Likes
on
0 Posts
![Default](/forums/images/icons/icon1.gif)
I run a Barry Grant 750 vac secondary on my 383 in my car. I don't know what is better for a boat but I know they will tell you that you need a 650 mechanical and 750 vacuum.
#10
Guest
Posts: n/a
![Default](/forums/images/icons/icon1.gif)
On the dyno my brand spanking new 383 tried both 750CFM and 650CFM Carter carbs.
Results:
750CFM flowed a max 511 CFM at 5400 RPM and made a max HP of 398 at 5100 RPM and a max torque of 438 at 3600 RPM. Jetting was on the money with BSFC in the .45 range and FA lb/hr in the 165 range
650CFM flowed a max 503 CFM at 5100 RPM and made a max HP of 387 at 5200 RPM and max torque of 432 at 3800 RPM. Jetting was rich with BSFC in the .51-.52 range and FA lb/hr fuel comsumption in the 180 range.
conclusions: leave the 650 on for breakin and then after 10-15 hours rejet it to the 750 specs, and pick up some HP and fuel economy. This is a case where bigger insn't better....
I'm looking for 400+HP once dialed and broken in
Should push my 2400lb bow rider very nicely with the addition of a new Alpha 1 SS drive I'm getting today.......
Results:
750CFM flowed a max 511 CFM at 5400 RPM and made a max HP of 398 at 5100 RPM and a max torque of 438 at 3600 RPM. Jetting was on the money with BSFC in the .45 range and FA lb/hr in the 165 range
650CFM flowed a max 503 CFM at 5100 RPM and made a max HP of 387 at 5200 RPM and max torque of 432 at 3800 RPM. Jetting was rich with BSFC in the .51-.52 range and FA lb/hr fuel comsumption in the 180 range.
conclusions: leave the 650 on for breakin and then after 10-15 hours rejet it to the 750 specs, and pick up some HP and fuel economy. This is a case where bigger insn't better....
I'm looking for 400+HP once dialed and broken in
Should push my 2400lb bow rider very nicely with the addition of a new Alpha 1 SS drive I'm getting today.......
![Stick Out Tongue](/forums/images/smilies/tongue.gif)