VP 5.7 GL caruburetor swap to 4 barrel?

[awalkertx]

New thread and I apologize for bringing up the old one.

I've got a 1997 Cobalt 200 with Volvo Penta 5.7GL PLKD motor and DP-S 1 out-drive... Counted the intake bolts and it's a first gen SBC. Obviously the Vortec is a superior head design and as such a better power plant, but given that mine's a 350 should a 4bbl swap be something to undertake? I have no desire to swap engines (or heads) at this time because it's all original and low-time.

I've looked at the specifications for the 5.7GL vs the 5.7GS and see a 215HP v. 250HP for the two. I have the shop manuals, which includes both power plants, but it only shows that the GS has a 4V carburetor vice the 2 on the GL. I have googled far and wide for any other differences between the two engines and really can't come up with anything other than carb and hp rating.

Boat has been dormant for a very long time and rather than rebuild the carburetor I was thinking about doing a swap to a four barrel. Earlier posts suggest that the Holley 4175 might be a good option, at least in the thread for the Vortec 5.0 that I should've left dead.

Looking at the parts catalog for my 5.7 liter engines model "LK" it looks as though the intake is shared between the GL and GS.... I'm assuming Volvo used a common one with an adapter like they did with the Vortec motors. VP 5.7GS calls for a P/N 3855279-0 Carburetor assembly... as far as I can tell, that's a Holley 4175 based on my googling but much of that is just based on advertising being bumped to the top.

Thanks for any input from the gray beards (or any slick-faces that happen to know). I'd sure like to go from 215HP to 250HP if it's a simple carburetor swap.

PS, again I can't tell a difference between the GL (limited power) power plant from the GS other than carburetor. Page 5-35 from the workshop manual gives same specs on cam, rocker arm ratio, base timing etc...

 

[Bondo]

Ayuh,...... As you've discovered, the difference is the carb,......

Go for it,..... You'll "Feel" the difference 35/ 40 hp makes,.....

 

[Lou C]

If what you have is actually a GM cast iron 4bbl spreadbore intake (there may be an adaptor for the 2bbl you can remove) then the Holley 4175 will fit perfect because its a spread bore carb, no adapter will be needed and because Volvo also used this carb the throttle hook up should be simple.

 

[awalkertx]

Gentlemen, thankee much for the input. As far as I can tell the manifold is common between the two power plants. As of material I'm not sure, but based on the newer Vortec that was aluminum with brass coatings... that being the 8-bolt. Just my guess, mine is iron (magnet store is my next stop). In the parts catalog for the 5.7 "LK" engines it does in fact specify a carburetor to intake manifold adapter (P/N 3853278-4). I can find no information on the specs for this plate or what I should use as a non-VP substitute.

Thank you again very much. I do plan on doing the swap. At least with the larger displacement of the 350, I'd expect that it could use the 650CFM carb at least to 75% at 4800 RPM just based on the basic math.

 

[Lou C]

http://www.volvopentastore.com/Fuel...on_id.521957171--store_id.366--view_id.780887
fuel system

here it shows the 4160 style carb (square bore) with the adapter plate, they may have changed from the spread bore 4175 at some point..
I find VP catalogs maddeningly complex and confusing with the plethora of model numbers etc, best bet is take a good pic of what you have.
If you have a GM 2bbl manifold then you have to get the right intake for the 4bbl
If you have a GM 4 bbl manifold with an adapter for the 2bbl carb, then remove that adapter, and you can likely use either a spread bore Holley (4175), with no adapter or a square bore Holley (4160) with the adapter shown in the VP catalog.

 

[awalkertx]

Wilco good sir, I'll report back when I pull the carb and see what I've got! Thanks again!

 

[jimmbo]

I did the 2bb to 4bbl on my 2002 5.7, using the Holley 4175 650 spreadbore. My engine is a Vortec, and VP did put a very nice 4bbl intake with an adapter for the 2bbl. I gained around 500 rpms. The smaller Primaries of the Spreadbore will help retain Torque at the bottom end as you will probably have to increase Pitch to keep the engine within the WOT range after switching to the 4bbl.

 

[awalkertx]

Jimmbo you've sold me, but there's a curveball... My engine for absolute certain has an intake manifold that does not have an adapter... it will only support a 2V carb... the VP parts catalog was untruthful

I'm bummed, but i'm still for sure going to do an upgrade. I guess the question now is what intake manifold do i choose? I"m contemplating the edelbrock 2506

https://www.michiganmotorz.com/edelbrock-marine-performer-intake-manifold-wbrass-1987-p-3761.html

and still thinking about 4175 b/c thats what VP used. Though I did just happen upon an interesting Holley solution: the Holley Sniper EFI quadrajet. No more vapor lock on super-high ethanol california gasoline! If only money grew on trees!

 

[Scott06]

Would recommend the regular performer vs the performer rpm you sent a link to. https://www.michiganmotorz.com/edelbrock-marine-performer-intake-manifold-1987-p-3262.html

rpm range for the performer is idle to 5500 vs the 1500-6500 for the performer rpm. The link you posted had conflicting rpm ranges in the text and specs below... I’d just make sure you are getting the performer with the parts combo you have

 

[awalkertx]

Scott06,

Thanks much for that post. Not only is it in the lower RPM range, but it's $200 cheaper. I do wish it had the copper-jacketed water passages that the other one had, but oh well! Thanks for the catch.

FWIW, I started down the path of research on the Holley sniper EFI solution, and realized that unless I really wanted to spend money, it's probably best I stay carbureted. Need for new fuel pump, dry exhaust manifolds if I wanted to do closed loop O2 sensor, etc etc.

 

[awalkertx]

Greetings boat swamis, gurus, and graybeards,

I just pulled the trigger on something that maybe I shouldn't have. Found a cast iron GM high rise "marine" quadrajet 14098242 bowtie intake on ebay and got it for $150 right as the auction was ending. I just came across it and didn't have a lot of time to do research. Just seeing "marine" and GM and casting in 1995, also looks stock and super clean - I jumped thinking it would've been what VP or Merc would use on their pre-vortech 350's... the listing even mentions merc/vp.

Buyer's remorse: my research now shows folks are using these intakes under high-RPM automobile applications (due to it's large volume and nostalgia for the early seventies Z28 intake), rather than any marine applications. Further, I can't find any cross reference from the GM casting or the VP parts guide. Will it be a wasted time/effort putting this thing between a Holley 4175 spread bore and a completely bone stock 87-95 350?

Ugh, I wish I knew more only being a car-tinkerer until now! Face palm!

Adam

 

[awalkertx]

All,

Meant to report back sooner. Carb swap went great and I ended up using the stock iron bowtie spreadbore intake that would've been on the boat had it been a GS. I ended up propping up to the F6 stainless props that would've been on it, and the boat seems like a different animal. Love feeling the large secondaries open. Instant improvement out of the hole and the boat tops out at 55 now on smooth water with the RPMs right in the 4800 range.

Thing even does better on fuel when I'm just cruising. I don't find myself staying at 3600 RPM though. It'll drink gas when I want it to! Wish I'd done this sooner.

I appreciate all of the great input.

Adam

 

[Lou C]

Glad it worked out for you. On a GM marine V6 or V8 I’d always want a 4bbl carb. Years back my family owned a 72 Chevy Impala 350 with a Rochester 2bbl and a 75 Olds Delta 88 with a 350 with a 4bbl Quadrajet. The Olds was a lot more responsive from the midrange to the top end. I’m running a Quadrajet on my 1988 4.3. I rebuilt it with better parts from Cliff’s High Performance and it runs great.

 

[Swmoose]

I did the 2bb to 4bbl on my 2002 5.7, using the Holley 4175 650 spreadbore. My engine is a Vortec, and VP did put a very nice 4bbl intake with an adapter for the 2bbl. I gained around 500 rpms. The smaller Primaries of the Spreadbore will help retain Torque at the bottom end as you will probably have to increase Pitch to keep the engine within the WOT range after switching to the 4bbl.

did the throttle cable and fuel line hook up easy or did you have to get creative? I have a 1999 vp with the 4bb intake spreadbore like yours

 

[jimmbo]

I used a Holley carb to replace a Holley, but I did have to use a different anchor point for the Throttle Cable(still on the stock anchor block)[Black Arrows], and adjust the Length of the Cable, and did have to transfer and flip the Cable Connector Adapter on the Throttle shaft(White Arrow). The Throttle Lever on the Boat, now rotated an extra 30 degrees before Full Throttle was achieved.
I think I swapped the Fuel Line end for end, and used an adapter at the carb.
This obviously is the 2bbl, a couple of years before I installed the 4bb. Same Intake was used as VP put a very decent 4bbl Intake on and used a plate to mount the 2bbl

 

[Lou C]

Holley also sells brackets that you can use to mount your throttle cable to, that use the carb mounting nuts/bolts

Search The Holley Website

www.holley.com

 

[WIMUSKY]

Shut the thread down. 1.5yrs old...