power of 5.7 GS with Holley 4bbl carburetor

[R.N.]

Hi
I was looking at ways to increase the power of 5.7 GS PLKD (96 or 97) , from what I read in this forum it was "normal" to be a 2 bbl Holley .
I checked the carburetor and it looks like the carburetor is 4175 spread bore Quadrajet (80310-2 stamped on it ) i think this is rated 650 cfm
Before i realize it is a 4 bbl i was thinking to upgrade to Edelbrock 1409 at 600 cfm.

Does it even make sense to go Edelbrock now that i know this?

Should this still be 250 HP with the 4bbl?
By the year of manufacturing i dont think the heads are vortec but i will look into that .

 

[Scott Danforth]

Your carburetor is a 650 CFM model 4175. The rebuild kit for your carburetor is a 703-34.

with a change in cam (required) and rocker arm ratios you can get up to 300-330 out of the motor and carb at the prop any more than that you gotta add more motor

your probably 250-260hp right now at the prop (280-290 at the crank)

I wouldnt change to a 1409 - no point
I would buy a Comp Cams XM270HR cam and do some mild porting and polishing to your heads

 

[jimmbo]

The Vortec heads and intake are a very cost effective upgrade for hp increase per dollar spent. A VP 5.7 with Vortec heads and a Holley 2bbl was prop rated at 260hp.
I added the 4175 650 to my 2002 VP 5.7 and gained 10% in rpm and mph. Swapping a 22" prop for the 20" brought the rpm almost back to where they were with the 20" and the 2bbl. I don't know what intake VP used for the 2bbl 96/97, but in 2002 they used a very well engineered 4bbl intake with an adapter for the Holley 2bbl.

 

[Jbart19]

The Vortec heads and intake are a very cost effective upgrade for hp increase per dollar spent. A VP 5.7 with Vortec heads and a Holley 2bbl was prop rated at 260hp.
I added the 4175 650 to my 2002 VP 5.7 and gained 10% in rpm and mph. Swapping a 22" prop for the 20" brought the rpm almost back to where they were with the 20" and the 2bbl. I don't know what intake VP used for the 2bbl 96/97, but in 2002 they used a very well engineered 4bbl intake with an adapter for the Holley 2bbl.

Hi Jimmbo and RN. I just bought a 25' cruiser with a 2001 VP 5.7 GS and the stock 500cfm 2bbl is ready for either a replacement or rebuild. I am leaning towards replacement with Holley 4175. Looking for feedback on any items that needed alteration such as fuel lines or vent hoses.

Did either of you replace the flame arrestor with a higher flow model? Holley suggests a 3" model and my stock unit is about 2".

IIRC there is a 1/2" spacer between the manifold and the carb. On another forum someone switched it out for the recommended 1" phenolic spacer and they said it definitely made a difference.

The jets on the current 2bbl are 75 and with the primaries on the 4bbl being 61 I am hoping for better economy when cruising. With just me on the boat I am currently running about 24mph @ 3200 rpm and 40mph @ 4700 RPM with a 14.5 x 14 SS 4 blade SOLAS HR4. I haven't really had it long enough to get GPH or MPG numbers but it seams like there is more to eek out of this old girl.

I'd like to be able to move up to a 15 x 15 and hopefully cruise around 26mph @ 3000 rpm running on just the primaries and conserving some fuel.

I would love to hear more details of your swap and how both performance and economy improved. Stock RPM range is 4400 - 4800 for carburated but the fuel injected range is 4600- 5000. Does changing the carb effect the optimal RPM range and make it OK to go up to 5000 ?

Thanks for any insight you or anyone else could provide

 

[GA_Boater]

Hi Jimmbo and RN. I just bought a 25' cruiser with a 2001 VP 5.7 GS and the stock 500cfm 2bbl is ready for either a replacement or rebuild. I am leaning towards replacement with Holley 4175. Looking for feedback on any items that needed alteration such as fuel lines or vent hoses.

Did either of you replace the flame arrestor with a higher flow model? Holley suggests a 3" model and my stock unit is about 2".

IIRC there is a 1/2" spacer between the manifold and the carb. On another forum someone switched it out for the recommended 1" phenolic spacer and they said it definitely made a difference.

The jets on the current 2bbl are 75 and with the primaries on the 4bbl being 61 I am hoping for better economy when cruising. With just me on the boat I am currently running about 24mph @ 3200 rpm and 40mph @ 4700 RPM with a 14.5 x 14 SS 4 blade SOLAS HR4. I haven't really had it long enough to get GPH or MPG numbers but it seams like there is more to eek out of this old girl.

I'd like to be able to move up to a 15 x 15 and hopefully cruise around 26mph @ 3000 rpm running on just the primaries and conserving some fuel.

I would love to hear more details of your swap and how both performance and economy improved. Stock RPM range is 4400 - 4800 for carburated but the fuel injected range is 4600- 5000. Does changing the carb effect the optimal RPM range and make it OK to go up to 5000 ?

Thanks for any insight you or anyone else could provide

Please start your own thread. The OP, RN, left over a year ago.

Closed.