Need to replace my engine.

Skybreeze

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I currently have a 431A volve penta V6 driving a DPA1 stern drive. The motor is stuffed and needs to be replaced. I have been recommended to get a remanufactured engine but upgrade to the newer vortec engine. I have been lead to believe it will bolt straight up to what I have. Firstly is this the case. What parts will I be able to reuse off my existing engine and what extra parts will I need to get. My current engine is rated at 205 HP and I don't want to drop back in HP. All the reading I have been doing tells me that the vortec engine will be less HP with the 2 barrel carb but more than I have if I have a 4 barrel carb. Can anyone verify what the HP ratings would be with each carb. I am currently running a 4 barrel carb on my existing motor. Any other info to help me decide on an engine would be greatly appreciated.
 

smassey22180

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On a newer vortec 4.3, a 2 barrel is 190 HP and a 4 barrel is around 210. You can probably re-use your 4 barrel carb but you will need a new intake that is 8 bolts. Your current intake has 12 bolts connecting to the head. 8 bolts lets you know it is a newer Vortec. Don't go by what it says on the valve covers.

Also, I believe your current 205 HP was rated at the crank. Newer engines are rated at the prop.
 

Skybreeze

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Thanks for the info.
You mention a newer vortec. Is there a difference between the older vortec and newer vortec engines as far as HP or do you mean newer vortec because its a newer engine in relation to the engine I have. Also can anyone verify the HP ratings of each engine to whether they are rated at the prop or crankshaft
 
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Bondo

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Thanks for the info.
You mention a newer vortec. Is there a difference between the older vortec and newer vortec engines as far as HP or do you mean newer vortec because its a newer engine in relation to the engine I have. Also can anyone verify the HP ratings of each engine to whether they are rated at the prop or crankshaft

Ayuh,...... Count yer intake manifold bolts, if there's 12, ya Don't have a Vortec headed motor,.... Vortec heads use an 8 bolt intake,...

The Vortec heads, give ya 'bout 20 more horsepower over the non-vortec heads, with whichever carb ya use,...
 

bruceb58

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There were some engines early on that were called Vortec but was just a marketing name that meant nothing. Around 96, GM came out with the Vortec heads which actually makes a difference. As Bondo said, you count the intake manifold bolts to see what you actually have.
 

Skybreeze

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I think everyones missing my point. I already know that my motor is not a vortec. I want to replace it with a vortec. I know there where some motors that had vortec on them that weren't. What I'm trying to establish is when the true vortec came out were there any changes that occurred in later years that may have increased the HP. What I need to know is the HP rating with a 2 barrel carb and a 4 barrel carb in comparison with my existing motor. My existing motor is 205 HP but when I replace my motor I don't want less HP than what I already have. It was mentioned that one may be measured at the crank and one at the prop. Is anyone able to clarify this. Also will the vortec motor bolt straight up to my existing stern drive. What parts can I use off my existing motor and what will I need to change motors.
Hope this clarifies what I need to know.
 

bruceb58

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Vortec motor with the true Vortec heads came out around 1996. You will have to replace your intake manifold. Everything else should bolt up fine.

No other changes were made so you should have more power now than you do with your current motor if you use the same type carb.
 

Scott Danforth

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the changes to the Chevrolet V6 and V8's in 1996 was the vortec combustion chamber, which is actually the LT1 combustion chamber on a head set up for proper direction waterpump (vs the reverse flow for the LT1/LT4).

as indicated, this is on motors produced by the engine plant for the 1996 model year, however some 1997 boats actually have 1995 or 1996 motors in them (left over stock). this is why you need to count the intake bolts.

your 205hp motor is a 4 barrel motor. A vortec V6 4-barrel is about 215-220hp. The vortec heads add between 10-20hp on the v6, and about 30-40hp for the V8. a change in the cam can help to a certain point, however there is only so much power you can get out of the V6
 
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Skybreeze

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My current engine is a 431A which was in production from 1989-1991 well before the vortec was introduced. Not concerned about the year my boat was built as it is not a production boat. It was custom made and the engine bought for it.

My situation is that my current non vortec engine has had it. I have been recommended to buy a remanufactured engine but upgrade to the vortec engine rather than rebuild my existing engine. I don't want to have less HP than what I currently have. A bit more is always nice to have. My current engine is rated at 205 HP. Don't know whether this rating is at the prop or crank. From what I have read and concluded from here is that the replacement engine I intend to get being a vortec is only rated at 190HP with a 2 barrel carb. Does this mean I will have less final HP at the prop because its only rated at 190HP compared to my current 205HP or will I have more because one is rated at the prop and the other at the crank. Or will it be about the same. If I go to the 4 barrel carb it looks like I will gain 10 to 20 HP. Again is this gain a direct comparison to my current set up or is the 215 to 220 HP claimed rated differently to my current set up. Hope this clarifies the situation and someone can help me with my questions.

I need to replace my intake manifold but can I use my existing 4 barrel carb (its a rochestor #17088142) or will I need a different 4 barrel carb to suit the intake manifold as well as the fuel and air requirements of the vortec engine. Will the new engine bolt straight up to my existing stern leg or will there be other parts I need. My current engine has a mechanical fuel pump will this need to be changed to electrical. Things like fly wheel and starter motor. Any other info greatly appreciated.

Sometimes its hard to explain exactly what it is you are after.
 

achris

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Your 205 is at the crank. The 190 (for a 2 barrel on a vortec) is at the prop. The 4 barrel on a vortec 220 is also at the prop. Your current engine would be around 180 at the prop. Apart for the heads and intake, everything else on the engine is the same. And if you upgrade to a serpentine belt, don't change the water pump. The impeller is cast brass, and is already bidirectional. Just change the pulley. Same with the alternator.

Chris.....
 

Bondo

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My current engine is a 431A which was in production from 1989-1991 well before the vortec was introduced. Not concerned about the year my boat was built as it is not a production boat. It was custom made and the engine bought for it.

My situation is that my current non vortec engine has had it. I have been recommended to buy a remanufactured engine but upgrade to the vortec engine rather than rebuild my existing engine. I don't want to have less HP than what I currently have. A bit more is always nice to have. My current engine is rated at 205 HP. Don't know whether this rating is at the prop or crank. From what I have read and concluded from here is that the replacement engine I intend to get being a vortec is only rated at 190HP with a 2 barrel carb. Does this mean I will have less final HP at the prop because its only rated at 190HP compared to my current 205HP or will I have more because one is rated at the prop and the other at the crank. Or will it be about the same. If I go to the 4 barrel carb it looks like I will gain 10 to 20 HP. Again is this gain a direct comparison to my current set up or is the 215 to 220 HP claimed rated differently to my current set up. Hope this clarifies the situation and someone can help me with my questions.

I need to replace my intake manifold but can I use my existing 4 barrel carb (its a rochestor #17088142) or will I need a different 4 barrel carb to suit the intake manifold as well as the fuel and air requirements of the vortec engine.(Either, or, the vortec fuel requirements are the same, different carb could mean different linkages, depends on the intake ya buy) Will the new engine bolt straight up to my existing stern leg or will there be other parts I need.(All the bolt holes are the Same, except the intake manifold) My current engine has a mechanical fuel pump will this need to be changed to electrical.(Yes, 'n use a relay or Oil pressure switch for safety) Things like fly wheel and starter motor.(Flywheel diameter, 'n starter bolt patterns follow each other, if ya got a 12" flywheel, ya need the straight across bolt pattern drillin's in the block, if ya got the 14" flywheel, ya need the staggered pattern starter bolt hole pattern drillin's in the block, some but not all blocks come with Both drillin's done) Any other info greatly appreciated.

Sometimes its hard to explain exactly what it is you are after.

Ayuh,.... You'll see an honest 10 hp increase goin' that way,....

A custom motor, with d-dish pistons that mirror the combustion chambers, 'n deckin' the block to get .043" quench, puttin' the compression ratio at just under 10:1,....
You'd see an honest 20/ 30 hp increase,.......;)


And it'll run just Fine on regular gasoline,...
 
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Skybreeze

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Now I'm getting the needed answers. Must have explained myself more clearly. So at the prop my current engine is about 180HP. So going to a vortec engine with a 2 barrel carb I should see 190 HP at the prop an increase of 10HP. Going to the vortec engine with a 4 barrel carb I should see 220HP at the prop. An increase of 40HP. I know which way I'm going.;):D

Interesting comment regarding the flywheel. So I may not be able to use my existing fly wheel and starter depending on what replacement engine I get. Is there any advantages or disadvantages regarding the different size flywheel. If I'm going to do the engine upgrade I might as well go the best way as far as flywheel goes
 

Scott Danforth

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the cranks changed in 1986 from 2-piece rear seal to one piece. your existing flywheel and starter will work fine with the new motor, assuming they worked with the prior motor. the only difference is potentially the diameter, and that is determined by the starter mounting ears. however I believe the v6 only came with one diameter flywheel
 
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smassey22180

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Also, If you add 30 additional HP, you may need to re-prop. My 2 barrel 190hp 4.3L easily hits 5k rpm with a 19p prop. I just ordered a 4 barrel carb and intake and I expect that will add another 200 RPM to my max.
 

Saline Marina

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I wouldn't worry too much about the change to where the dyno is hooked up. The two bevel sets are a pretty efficient gear drive, nothing like a torque converter in the middle.

The "old" 4.3 (LB4 RPO code in GM) is definitely what I call a tractor motor. It had an impressive amount of torque right off idle and above 3krpm you were pretty much done other than making more noise in a vehicle. The RPO code L35 "vortec" 4.3L was a nice step forward, retaining almost all of the torque off idle but a lot more midrange in the vehicle.

When one designs a pushrod motor there's a basic tradeoff between mixture motion in the combustion chamber which correlates with low-end torque and the restriction that is created in the airflow (which is needed to push the torque curve higher into the RPM band and increase HP). Basic low end torque is all one really needs in a truck but advertised HP is what sells vehicles as people tend to shop numbers as if comparing appliances.
 

captmello

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My current engine has a mechanical fuel pump will this need to be changed to electrical.

newer blocks do not have the mechanical fuel pump mount, so yes you most likely will need to switch to an electric fuel pump.
 

Skybreeze

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Got my old motor out and looking at what parts I need to order. I have the old 12" flywheel. I have been told I need to go to the new 14" flywheel with the starter to suit as the old starter won't fit with the new vortec engines oil pan. IS THAT CORRECT ?. Also was there 2 sizes of bell housings one for each size flywheel. My bell housing is exactly 14" across on the inside and my 12" flywheel measures slightly bigger than 12" so if the 14" flywheel measures slightly bigger than the 14" it won't fit. Can someone please confirm whether a 14" fly wheel will fit or not fit my existing bell housing. Aslo the drive plate that bolts to the flywheel. Will that bolt directly to the new 14" flywheel or will it have to be re-drilled.
 
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