mississippirat
New member
Ok I have an 89 starfire with a 4.3 would mind more power would I be better off building the 4.3 a bit or swaping to a v8?
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build 4.3 or 5.7 swap
- Thread starter mississippirat
- Start date
1989checkmate
Active member
I had a 1989 starfire with a 4.3 and it ran around 50mph. What color is yours?
mississippirat
New member
White with red stripes identical to the one in the brochure pic on here. Playin around with props now when I bought it had a 21pitch 4 blade I put an 18 pitch on it now but around 50 is what I'm getting
jumbofordman
Well-known member
Probably cheaper to get a 350 (5.7) than build the 4.3.
Jimway
Well-known member
RNGRDVE
Well-known member
Do they make shoehorns that big?
mississippirat
New member
sounds like v8 is the best option room isnt really and issue theres lots
mississippirat
New member
Ok realizing that this will take time and work I want to go ahead with the project with some much needed tech help from the brains here. First few questions being when I do this do I have tto change gears I'm my alpha one out drive and secondly should I find a mercruiser engine or can I rebuild a junk yard 350
karzrus
Well-known member
Lots to consider.
You will want/need to do the gears or you getting a prop with the needed pitch may be an issue.
Rather then a junkyard block, you may be better off getting a rebuilt marine engine from one of the venders here like MKHammer or venders on the web.
If you got a junk mercruiser complete you would have manifolds/starter/carb/alt/brackets.
What kind of budget do you have. Is the 4.3 worn out/needing a build or you just want to go faster?
wired
Well-known member
A 4.3 is just 3/4 of a 5.7. Same pistons,lifters, valves and a lot more of the internals interchange. This is one of the few motors where its cheaper to build the V6 than the V8. Good engines.
go 350 or bigger small block, no question.
If you look into building the 4.3, you'll quickly realize that to make any really substantial gains, the cost per performance very quickly gets much more attractive for a 5.7. use the right parts and you won't gain weight over your 4.3. Remember, it takes 10-15 horsepower for every mph top end gain in a typical boat. Gains of 30 or 40 horsepower that are easy to get with a 4.3, won't make the major difference you're probably looking for. Been that route too...
A few more random thoughts off the top. (do a search on here, lots of good information posted for this kind of a conversion...).
You DON'T have to change gears! The 1.84 / 1.87 gear set in your drive is strong and will work fine. With that gear set and a 27-29" prop (readily available), you can go a LOT faster than you'll have the power to go. I'm betting you would need a 25" range prop to pin max hp at wot rpms with that gear ratio. I've run 1.84, 1.61, 1.5 and 1.32 gears behind a 383 in a small check and have had no problems finding props for all of these combinations and speeds 60's well into the 80's.
As long as you use marine parts for starter, alternator, etc, etc. etc... you're ok with a block from wherever. I would go with a crate engine or build your own depending on your experience and desire to do the work. If you can find a 400 that might be the best bet. I might just go with a crate engine for overall cost.
Almost all of your accessory parts from the 4.3 will fit a small block, but you'll need exhaust and will have to move the front engine mounts a little. Alternator, distributer (with new cap and rotor), ignition (with different module, but your v6 module will be easy to sell to performance boaters and a 5.7 module will be easy to find for same or cheaper price), starter, coupler, steering cooler, etc... that you have should work on a small bock with no problem.
Either way, budget 2-3 times more than you think it's going to cost just to be safe...
Good luck! (and enjoy your project if you do it).
If you look into building the 4.3, you'll quickly realize that to make any really substantial gains, the cost per performance very quickly gets much more attractive for a 5.7. use the right parts and you won't gain weight over your 4.3. Remember, it takes 10-15 horsepower for every mph top end gain in a typical boat. Gains of 30 or 40 horsepower that are easy to get with a 4.3, won't make the major difference you're probably looking for. Been that route too...
A few more random thoughts off the top. (do a search on here, lots of good information posted for this kind of a conversion...).
You DON'T have to change gears! The 1.84 / 1.87 gear set in your drive is strong and will work fine. With that gear set and a 27-29" prop (readily available), you can go a LOT faster than you'll have the power to go. I'm betting you would need a 25" range prop to pin max hp at wot rpms with that gear ratio. I've run 1.84, 1.61, 1.5 and 1.32 gears behind a 383 in a small check and have had no problems finding props for all of these combinations and speeds 60's well into the 80's.
As long as you use marine parts for starter, alternator, etc, etc. etc... you're ok with a block from wherever. I would go with a crate engine or build your own depending on your experience and desire to do the work. If you can find a 400 that might be the best bet. I might just go with a crate engine for overall cost.
Almost all of your accessory parts from the 4.3 will fit a small block, but you'll need exhaust and will have to move the front engine mounts a little. Alternator, distributer (with new cap and rotor), ignition (with different module, but your v6 module will be easy to sell to performance boaters and a 5.7 module will be easy to find for same or cheaper price), starter, coupler, steering cooler, etc... that you have should work on a small bock with no problem.
Either way, budget 2-3 times more than you think it's going to cost just to be safe...
Good luck! (and enjoy your project if you do it).
on a stock or near stock 350, the stock v8 curve is best. with a larger duration cam that wants more advance at idle, the v6 curve is sometimes helpful to give more advance at idle without too much timing at full advance. My understanding is that rhe folks who need the v6 curve the most are the ones running blowers... where too much timing is an instant death sentence...
