Upgrade 2b carb to 4b on 4.3L for hole shot power

[df909]

I have a 1992 4.3L with an Alpha 1 drive. It has a 2b carb on it now and it takes a little time to plane. I'm not a small guy and plan on skiing, so the boat is going to have to work to get me up. Will I notice much power difference if I change carbs? Any other ideas to help with getting out of the hole vs. top end? I don't care about going fast, but I like to get to cruising speed quickly.

Thanks.

 

[EddiePetty]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

....actually, I suspect if you up-grade to a four-barrel, especially one with mechanical secondaries, you will lose your ventrui signal during a severe hoyshot causing a bog.
FWIW....Ed in 'ol Virginny

 

[ENSIGN]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

Try a smaller pitch prop

 

[Bondo]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

Ayuh,... Going to a smaller pitched prop will get you out of the hole...
The 4bbl. coversion will give you about 30hp or so...
Marine carbs use Vacuum secondaries...

 

[df909]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

Ok, so I should be ok with a new carb and not have problems with vacuum?. A 30 hp gain seems like a pretty good improvement. I think I might try that before a new prop to see what the difference would be. What does FWIW mean? I've seen that a few times. Thanks for the replys.

 

[Fishermark]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

I'm not a small guy and plan on skiing...

It seems to me that a smaller pitched prop would be your better bet - as mentioned above - if skiing is the primary purpose and use.

What does FWIW mean? I've seen that a few times.

FWIW = For what it's worth.

 

[Maclin]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

Prop pitch is the easiest and best bang for the buck for what you want, unless the pitch is already pretty low. You need to find what pitch you have and what the speed and engine RPM is at WOT (Wide Open Throttle) before you begin prop tuning.

Going from a 2bbl to a 4bbl in general will not help holeshot, as has been mentioned.

I have seen better low end response when going to a Quadrajet from a 2bbl. That comes from the primaries on the Quadrajet being even smaller than the 2bbl and thus more responsive to engine needs at lowend when the throttle is pushed to wide open on a holeshot. Marginal at best though, probably not worth the hassle and cost.

Stick with the same carb for now and try the smaller prop pitch and I bet that does what you want.

 

[cpubud]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

to get the most out of going to a four barrel carb you would have to have the heads done and cam . You cant just pull off a two barrel and put on a four barrel.

 

[Bondo]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

to get the most out of going to a four barrel carb you would have to have the heads done and cam . You cant just pull off a two barrel and put on a four barrel.

huh,..??

The Difference between the Merc 2bbl.'ed 170hp, 4.3l,+ the 4bbl.'ed 205hp, 4.3l, is the Manifold,+ Carb....
Nothing more,... Nothing less....

Btw,...
The Merc/ Weber/ Edlebrock performer carbs used on the 4.3l Is in fact a semi-spread bore carb...
The Primaries are Considerably Smaller than the secondaries...
The Larger version used on the HP 350s,+ BBCs is a true Square-bore carb...

 

[180shabah]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

You cant just pull off a two barrel and put on a four barrel.

Sure you can, that is exactly how the factory does it, for a 20hp (at the prop) increase on a 4.3L.

Yes, head work and a new cam can make bigger power, but there is really not much wiggle room when selecting a cam for a 4.3, without getting into reversion. Stick with the factory cam. As for the heads, don't waste time with porting, get a set of vortecs.

Bottom line, a 2bbl pre-vortec 4.3 makes about 155php. That same engine with stock cam will increase to 175php by switching to a 4bbl. With vortec heads, and a performer intake manifold with 4bbl, a solid 220php, without sacrificing durability.

OP - after all of the above, I still suggest you skip all the power upgrades(for now) and start with a prop change. A hustler/legacy is a great all around prop that won't break the bank. Of course there are alot of four blade props out there, that just love to yank the arms off of skiers.

Start a new thread in the prop forum, with the following information.
Boat, engine, drive, current prop dimensions and condition, and current WOT performance data. That forum will help you select a prop to do what you want.

 

[wca_tim]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

the 4bbl will be worth a noticable amount of power once jetted right, but as others have recommended the first thing I would do is go with a good quality stainless prop that puts your wot at max rpms for the engine AND has adjustable vents / vent plugs. even if that means you run the sam epitch prop you have now.

The vents dump exhaust gas along the leading edge of the prop at lower speeds (on take off) and let it slip more which in turn lets the rpms spool up to where the engine makes more power, the net result when set up properly is that you get a LOT better holeshot and still aren't propped so low that you have to be careful not to overrev the engine when you're running wide open.

the merc props with the inserts have larger holes and interchangable plugs with several different hole sizes. the larger hole plug you use, the more exhaust gets dumped along the prop blade on take off and the more slip / effect you get out of the hole. At higher speeds it doesn't have much impact at all and will not slow you down. It's sort of like running a stall converter on your street rod...

Cheers!

 

[bonzoscott]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

FWIW- mine is the 205hp 4 barrel, does well but I tend to think it's at top end. My dealer told me the only difference was about 7-10 on top end. I think prop is the way to go. You could get in a mess of money with little satisfaction on the carb/manifold.

 

[df909]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

Thanks for all the help. I think I'll stick with the prop and see how that does. What's Vortec?

 

[180shabah]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

Vortec is actually just a fancy marketing name from GM(dating back to '87), but in '96 they redesigned the cylinder heads on the 4.3 and larger engines. They flow substantially more air then the heads they replaced. These new heads are commonly referred to as vortec heads.

 

[vegasphotoman]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

a 4 blade stainless 19P would give ya great pull.....
buy one new $400 used $150 on up

 

[45Auto]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

a 4 blade stainless 19P would give ya great pull.....
buy one new $400 used $150 on up

Now that's pretty impressive, to be able to recommend a new prop without having any idea what he's currently using!!!!!

What prop would you recommend for my neighbor's boat?

 

[180shabah]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

Now that's pretty impressive, to be able to recommend a new prop without having any idea what he's currently using!!!!!

I was thinking the same thing....

 

[ENSIGN]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

Call some local shops,they may have a assortment of test props that you could borrow or rent,that way you'll know for sure.(It never hurts to ask)

 

[jtybt]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

I was checking for a friend for the 4bbl holley 4175 Q-jet replacement. There used to be a guy selling 'em for about $225. Anybody know where he is?

 

[180shabah]

Re: Upgrade 2b carb to 4b on 4.3L for hole shot power

donno, try ebay....