Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

[Spivy30]

I have a 1991 1900 Glastron with Merc 5.0 with Alpha 1 with a cracked block. I am going with a reman long block, everyone is telling me to go with a 5.7 which makes sense but what should I do about the carb? I'm pretty sure my 5.0 has a 2bbl, should I go to a 4bbl i'm not really looking to build a speed boat, if the 4bbl is only gonna give me 2-3 mph I dont think its worth it i'd rather save some fuel.

Any input?

 

[Spivy30]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

If i'm gonna switch to a 4bbl i'd have to buy a new intake and carb so I was thinkin I should just buy a motor with vortech heads and just replace the fuel pump.

 

[Bondo]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

so I was thinkin I should just buy a motor with vortech heads and just replace the fuel pump.

Ayuh,....

Even with that Plan,.... You'll need a new Intake manifold......
It still should give you 250hp or so...

 

[180shabah]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

If your going to get the vortec heads, then you can geta 4bbl manifold (aftermarket aluminum) for less than an iron 2bbl manifold. It would lessen the sting of buying a new carb to go with it. That'll put you in the 290-300hp range and still be very durable over the years.

 

[JIGGER]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

You should be able to find a 4bbl intake for a quadrajet fairly easy. Deff worth the coin. There 2bbl werent worth a hoot! Wouldnt worry about vortec heads though. That was the factory diff between the two. Valve size and such. A 350 can be built for about 1000 bucks!

 

[69seabreeze]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

to put it simply... yes

 

[dan t.]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

any auto wrecker will have lots of cast iron intakes for q-jet cheap.not too much demand for them any more. these will not work with vortec heads but can be made to work with 87 to 95 tbi heads, you have to grind out the 4 middle bolt holes so the holes in the head will line up. you also need to make up a tapered sleve to go under the bolt head so the bolt has proper clamping force. I know this works as I have an intake manifold made for a carter afb from a 66 chevelle 327 mounted to 92 merc 305 in my boat , it has worked perfectly for 6 years

 

[180shabah]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

There is NO reason to use the "TBI heads" unless you already have a perfect pair AND you will never reach past 4000RPM. They do not breath well and power drops off quickly as revs climb. Those heads were the primary reason that TBI 350's put out less than 200hp(net at crank) from the factory. Great off idle throttle response, but no power.

A 350 with vortec heads(cheap and plentiful in junk yards - Or still available new for just a little more money) and a 4bbl will give you an honest 320-330hp depending on intake selection. Subtract 30hp or so running through the drive and that will still net you 290-300 at the prop. Youcould add in a more aggressive cam for a little more power, but remeber that this is a boat with wet exhaust and you really don't want to have any reversion problems. Besides, I think you will be more than satisfied with the nearly 100hp increase over your current setup.

 

[TilliamWe]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

Kalina Machine in Peoria, IL sold me a reconditioned Vortec head for $179 plus 8% tax. They reconditioned my other one for $150, no tax. This was in the summer of 2005.

 

[180shabah]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

GMPartsdirect has NEW vortec heads priced between $400 and $600 depending on engine(V6-BBC)

 

[Spivy30]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

I just want to verify...If I get a motor with pre votec heads, and get vortec heads they will bolt up? Then I just need a different intake and carb? Will my current manifolds from the 5.0 bolt up?

 

[Spivy30]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

Any suggestions for the intake and carb if I go with the vortec heads? 19 foot boat, 5.7, mostly used for water skiing tubing cruising etc but still want to put the throttle down sometimes and I dont want to have to stay close to a fuel tanker.

 

[Bondo]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

I just want to verify...If I get a motor with pre votec heads, and get vortec heads they will bolt up? Then I just need a different intake and carb? Will my current manifolds from the 5.0 bolt up?

Ayuh,.... That's Correct...

Eldebrock performer series is a Great set up,...
Not much Saltwater in Wisconsin,... An Aluminum Manifold will work just Fine...
I think the carb you need is the 1409...

 

[TilliamWe]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

Just to add in regards to a carburetor. Don't go crazy with a 750 Double Pumper Holley. A 650cfm carb will be more than enough. Heck a 600cfm would get it done too. It is easy to over carb a small block Chevy. Dual plane intake manifold with a 650cfm is the way to go.

 

[Spivy30]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

If I dont go with vortec heads does anybody have any suggestions for carb intake combos?

 

[Bondo]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

Ayuh,... Same Answer...

 

[captmello]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

Bond-o

Eldebrock performer series is a Great set up,...
Not much Saltwater in Wisconsin,... An Aluminum Manifold will work just Fine...
I think the carb you need is the 1409...

Thats the best if your buying new.

 

[dan t.]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

in reply to 180 shabah ,look in a merc manual, a 96 350 lx 4bbl is rated 250 hp at the prop. these are a tbi engine with a carb. admitedly tbi heads arent the best, I was trying to suggest a cheap way to put a 4 bbl on a 87 to 95 engine which will probably come with stock heads.

 

[John_S]

Re: Swaping 91 5.0 to a 5.7 should I go from 2bbl to a 4 bbl

in reply to 180 shabah ,look in a merc manual, a 96 350 lx 4bbl is rated 250 hp at the prop. these are a tbi engine with a carb. admitedly tbi heads arent the best, I was trying to suggest a cheap way to put a 4 bbl on a 87 to 95 engine which will probably come with stock heads.

My '96 1/2 5.7L had 14096217 heads: 350 285HP, Crate motor, 1.94-1.5, 72? intake bolts, 64cc, center bolt VC.

As far as I know, Merc used these heads from '88 to replacement with vortec heads.

If you had TBI heads on your boat engine, likly it had been replaced at some time.