4.3 2bbl to 4.3 4bbl
I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?Any input would be greatly appreciated. |
crystalguy
Oct 7
2006
|
| and it takes 15hp to gain 1mph! What are you trying to do & why? "crystalguy" <cbollinger48818@yahoo.com> wrote in message |
Lost
Oct 9
|
| As everyone said should be an easy swap, do you really want to pump more gas
through the boat for a slight increase in power? I went through the whole thought process with my 4.3. Decided against the 4
barrel due to cost/ gas/ and minor performance increase. THEN I had water in my oil, found the 2 barrel manifold cracked. Replaced
it with a 4 barrel manifold, bought an adapter plate, rejetted my two barrel
and gained about 10-15 hp. Top end only improved very slightly, but low end
torque and hole shot are a lot better. |
GOP=Gas
Oct 9
|
| Depends on the 4 barrel. The quadrajet has smaller primaries than
secondaries. The holleys have 4 equal sized. The secondaries on the quadra
jet are vacuum actuated so they open as the engine demands. That will be
under higher loads but that is not some specific throttle position.
Obviously it tends to be the more open throttle positions. The holley can
be had as a vacuum or mechanical secondaries. The main reason for a bigger
carb is to deliver more air/gas at wide open throttle. The holley typically
is not the best choice for fuel economy but is preferred for perfomance.
The holley is also so common that they are easy to find parts for. |
James
Oct 8
|
| for all I know. Yes, it is a matter of intake and carb. Of course your
throttle linkage[s] may need some rerouting, but I don't think it's
that much of a chore. The manifold should bolt right on. crystalguy wrote: |
tschnautz
Oct 7
|
| That's basically it. You can use an aftermarket automotive aluminum intake
buit the carb needs to be marine. For that engine I'd stick with a 600 or
650 cfm max. Any bigger would really be overcarbed. Don't expect any
overwhelming performnace leap. Maybe 3 mph or so more on the top end. "crystalguy" <cbollinger48818@yahoo.com> wrote in message |
James
Oct 7
|
| The other three things that may contribute to higher horsepower are the cam,
compression ratio and valve size. You should check out those things before
you go to the trouble changing the carb.
LD
"crystalguy" <cbollinger48818@yahoo.com> wrote in message |
Lee
Oct 7
|
| I do agree, that you probably wouldn't ahve that much ore to gain, but
I suppose it depends on what you want. For pulling a ski , i would
think you could get a better hole shot, and plane out quicker. But I do
agree,t hat you probably wouldn't notice that much difference on top
end.
But even so, arn't the fron two bbls. usually smaller on a 4, and the
bigger back two usually kick in at 3/4 to WOT? |
tschnautz
Oct 7
|
