2bbl to 4bbl...

[kewlkatdady]

In the process of ordering a 4.3 longblock from Rapido Marine...and want to upgrade my current setup from a 2bbl to a 4bbl...

Seems to be a pretty simple straight forward addition of about 30-35 HP's.

With that said, I'm going to have Raul throw the 4 bbl intake on the longblock, before he ships it...

now the big questions is...
which Carb? I know i need to be somewhere in the 600-650 CFM range...
marine carb for sure...

Holly, Edlebrock, Merc?

PROS and CONS?

TIA...

 

[Howard Sterndrive]

Re: 2bbl to 4bbl...

In 1999, Mercruiser marketed the 4.3 2 BBL as 190HP, the 4BBL as 205HP, and the EFI 4.3 as 210HP

It's easy and straightforward and worthwhile, but only 15HP net gain

 

[metalwizard]

Re: 2bbl to 4bbl...

Howard is right, only a small change in top hp and that is at a certain RPM. a 2 barrel will give better throttle response, and better low end torque (in most situations)

remember no matter how much fuel you throw at any motor. it does NO good unless you can get it ALL burnt and out of the motor (exhaust) without having the motor work hard to do so.

that being said. Best bet get a VACUUM Secondary Holley 600 cfm is more than enough for a stock 4.3, maybe even too much. I recommend the Holley because they are simple and reliable. if you are a do it yourselfer, they are easy to work on.

Good luck

 

[zbnutcase]

Re: 2bbl to 4bbl...

1409 Edelbrock vastly superior to any Holley, and get the 4.3 calibration kit they sell for it also. And MUCH easier to work on.

 

[kewlkatdady]

Re: 2bbl to 4bbl...

ok...so is the swap even an upgrade or worth the $$$?

I'd be very disappointed to spend the time and $$$ and not really notice much of a change...

Thoughts?

 

[zbnutcase]

Re: 2bbl to 4bbl...

Keep the 2bbl

 

[John_S]

Re: 2bbl to 4bbl...

It is more like 20-25hp with no other changes. You get a couple more wot mph, but also some better low-end acceleration and throttle response.

The edelbrock 1409 and kit mentioned would be the best for people that do not want to do allot of tinkering and tuning.

 

[kewlkatdady]

Re: 2bbl to 4bbl...

the boat could definitely use some low end power...

WOT mphs are not a big concern.

I'm prolly going the edelbrock route...

performer intake vs. GM 4bbl intake comparisons?

worth the extra $$$.

the GM intake will cost $200 and the edelbrock 2114 (i think) roughly $260...

is the extra $60 going to be worth it?

 

[John_S]

Re: 2bbl to 4bbl...

I'd go with the performer, unless your boat in salt or brackish water with raw water cooling. Worth it? This is boating, there isn't a positive ROI.

The 2114 is for the 4.3L vortec engine.

 

[sethjon]

Re: 2bbl to 4bbl...

In 1999, Mercruiser marketed the 4.3 2 BBL as 190HP, the 4BBL as 205HP, and the EFI 4.3 as 210HP

It's easy and straightforward and worthwhile, but only 15HP net gain

But with a 4.3 thats a big deal. If it was a small 8 I'd advise against it.

 

[Aloysius]

Re: 2bbl to 4bbl...

If the manifold is a spreadbore, use a spreadbore carb. do NOT use an adapter.

 

[sethjon]

Re: 2bbl to 4bbl...

ok...so is the swap even an upgrade or worth the $$$?

I'd be very disappointed to spend the time and $$$ and not really notice much of a change...

Thoughts?

Depends on what you are looking for. A few more MPH? Then go for it. Better for skiing? Doubtful.

 

[kewlkatdady]

Re: 2bbl to 4bbl...

Depends on what you are looking for. A few more MPH? Then go for it. Better for skiing? Doubtful.

better hole shot and overall performance

 

[kewlkatdady]

Re: 2bbl to 4bbl...

I'd go with the performer, unless your boat in salt or brackish water with raw water cooling. Worth it? This is boating, there isn't a positive ROI.

The 2114 is for the 4.3L vortec engine.

thought the 2114 was right...thanks

freshwater only...

I'm learning that ROI and boats are like oil and water...

pardon the reference back to the water in my crankcase

 

[Harte3]

Re: 2bbl to 4bbl...

An old saying in the automotive world..."Race a Holley, drive an Edelbrock." On the plus side, the Holley is very adjustable. On the negative side, the Holley is very adjustable...and easily maladjusted. If one doesn't mind tinkering, the Holley is fine. Otherwise, go with the Edelbrock.

 

[wca_tim]

Re: 2bbl to 4bbl...

go with the edelbrock 1409 and performer manifold, I did on a previous engine and was very pleased. I would also order the long block with the non-balance shaft, roller cam bottom end and newer vortec heads. Again, that's what I did, overall it made great power for a stock 4.3.... just my experience.

 

[dvandsm64]

Re: 2bbl to 4bbl...

we thought of doing same swap on our 1997 5.7L 2 barrell. would he have to change intake manifold? or are the 2 and 4 barrel manifold the same?

 

[jkust]

Re: 2bbl to 4bbl...

we thought of doing same swap on our 1997 5.7L 2 barrell. would he have to change intake manifold? or are the 2 and 4 barrel manifold the same?

I looked into moving to a 4bbl to my 4.3 as well but it seems that it is a 15hp gain in reality. I did all the research including starting a thread here. Of course I don't know how much torque the 4bbl will add. I was going to point at the article where they swapped a vortec 5.7 2bbl to a 4bbl to absolutly rave reviews on a 21 foot Rinker and Dvandsm64 goes and asks about his 5.7. I can't recall the specifics now but it was a big mph and power gain. I've posted the article before here called something like "why buy efi when you can get more hp for less" or something. It was written before MPI when EFI was still the standard.

 

[John_S]

Re: 2bbl to 4bbl...

we thought of doing same swap on our 1997 5.7L 2 barrell. would he have to change intake manifold? or are the 2 and 4 barrel manifold the same?

If you have a Mercruiser, you have to buy an intake. If you have Volvo, there is a chance you don't have to. Volvo SBC V8's used 4brl intakes with the 2brl carbs. They might of done similiar on the 4.3L.

 

[dvandsm64]

Re: 2bbl to 4bbl...

thats exactly the question i was wondering, thank you. its alot cheaper just buying a 4 barrel, than buying a carb and intke. wish you knew the exact thread for that swap. i think the merc manual shows going from 210hp to 260hp, thats alot i think. ours is a merc