Chevy 4.3 V6 Vortec Replacement Engine..Carburator vs TBI

[dlogvine]

I just purchased a vortec 4.3 v6 block and set of heads. The engine is from a car and it had TBI. Im thinking about reusing the small block and heads as a marine engine. Intake manifold of the original engine was TBI but it was bad. So now im rebuilding this engine, cleaned and rebuild the heads, which turned out to be in excellent condition, besides being dirty on the outside. The seats and valves are in great condition, clean and very smooth. The block is now at the shop getting inspected and cleaned, also I beleive it will be in a good condition. Now, the question is, what kind of intake manifold should i get, carburated, and if yes, how many barrels or should i get similar to the original. And if yes, how does TBI fuel injector work on the marine engine? Thank you

 

[NHGuy]

I'm a proponent of using what you have. Do the engine the way the boat was before. If it's already set up with injection do that again. If it had nothing or was carburetor, do that. Make sure to use marine pieces. Car - truck stuff won't be safe. It can allow fuel vapors into your bilge.
If you disassembled the engine and it has normal flat lifters, I hope you kept the lifters, rockers, pushrods and valves in order. If not you'll need to get another cam & lifters because they are mated for life.
If it had roller lifters it can be reassembled without keeping them in the same spots.

There are many intake manifolds available. They are not marine specific. The carburetors are though. Pick a carb first, because they determine the intake. I'd do a small four barrel or large 2 barrel. Look up what Mercruisers are built with and copy the CFM rating.

 

[Scott Danforth]

If the V6 came from a car vs a truck, you will need to change the cam in addition to the head gaskets, core plugs and circulation pump.

Is the motor a true vortec headed motor (96 or newer)? I ask because GM called the 4.3 the "vortec" long before coming out with the vortec heads. I think their marketing department called it that going back to 88.

Sort of like Dodge calling the new motor a "Hemi" when it has wedge heads

If you do have a vortec headed V6, then make sure you have a marine or RV cam vs the auto cam. Set up with a nice intake and a moderate carb, you can have 260 at the crank or 220 at the prop

 

[Rick Stephens]

What was on the original? This could be fun.

 

[dlogvine]

Original was prevortec 4.3 v6. I'm rebuilding it and probably will put the original engine back in the boat. This 2001 vortex engine I bought accidentally, was purchasing a set of heads, which were much better than the original ones, and the seller asked me if I need the remaining parts of the engine, block and accessories, all together with the heads for $100. I took it without asking any questions, just cranked the engine to see if it was seized. While cranking it, it moved with good amount of torque, I saw that cylinders were in good, at list visually, condition. Walls were smooth, not much carbon buildup, the block itself had bad intake manifold, the main reason, according to the seller, of removing the engine, don't ask me why. So this engine is at the shop right now for cleaning and inspection, but I want to rebuild it completely, change all bearings, rering it, put new timing gears and gaskets and keep it until I find a boat to put it in, or just sell it. I still need to get another intake manifold and since most of the boats are carburater, I wanted to get a 4bbl intake and use one of my old Rochester carbs.

 

[achris]

Vortec engines used roller cam and rockers, stick with that set up. If you go carb, get a Edlebrock 1409 and cast iron manifold to suit. Don't use the automotive TBI system. Not 'boat safe'! Use 'one of your old Rochesters' only if it's a proper marine carb... Automotive carbs don't belong anywhere near a boat engine. Unsafe.

Chris.........

 

[dlogvine]

I always thought that the difference between the marine carburetor and similar automotive is in the gaskets. And rebuild old Rochester carburator would work in both engines. Schematicstart for both automotive and marine Rochester carb are identical. Or am I Wrong? thank you

 

[dlogvine]

As for the engine, I just got my original block Mercruiser 4.3 v6 bored 30 over, so I'm going to stick with an original engine, rebuild it completely. The heads for this engine are also getting fixed, one with deteriorated exhaust seats. Now I have another question. Mechanic I'm the machine shop told me that the only difference between marine kit and automotive rebuild kit is in the gaskets. Marine does not use steel studded, but some other type of gaskets that could withstand salt water damage. Since this boat will be used only in the fresh water, baring some major flood that will bring coastal line to Arizona, do I really need a marine kit which is about $100 more expensive?

 

[dlogvine]

oh, one more thing, I'm using the original camshaft and lifters, they were in a good shape, so I'm replacing pistons and rings, freeze plugs ( bought brass ones separately), all bearings, oil pump, timing gear and gaskets.

 

[jrs_diesel]

I can answer the carb question. There's a couple of key differences between an auto carb and a marine carb, and it is not simply the gaskets. Automotive carbs have the bowl vented externally. Marine carbs vent the bowl into the intake. If the float ever sticks open while running, the fuel would leak right out and run down to the ground on an auto. If the same thing happened on a marine carb, the excess fuel would run into the intake and flood the engine, which also stops the fuel pump (usually). Now imagine if the auto carb was installed on a boat, and the same problem happened. The fuel would leak and collect in the bilge, a very bad situation.

Marine carbs are also designed to run at more extreme angles without stalling or flooding the engine.

 

[achris]

Use the marine gaskets. Your steel gaskets will still be subject to 'lake' water. In a car those gaskets are only subject to non-corrosive coolant. Lake water is still corrosive. Less that salt, but they will still corrode.

One other thing you need to replace with marine is the engine water pump. Again, automotive pumps are assembled with a steel seal and back plate, marine are with stainless seal and back plate.

Other things that need to be marine are the electrics. Externally the starter motor, alternator, distributor etc look the same, the difference is internal. Marine electrics are designed, tested and certified to not allow any internal spark to get out and be the source of a fire or explosion. Neither of which are good in a car, but are devastating in a boat.

One more difference between automotive carbs and marine. Marine carbs don't have a fast idle cam. Can you imagine what would happen to the drive if your engine was idling at 1400 or 1500 revs and you dropped it in gear? or your passengers?

Chris

 

[dlogvine]

I know I'm in the wrong forum, Bt I just can't find an answer to this question on the Web or in chevy forums. This engine that I bought as a replacement, it had a bad intake manifold. Since I decided to go with the original mercruiser engine and had it bored and will rebuild it , the replacement vortec engine I decided to restore as a car engine. Damaged intake manifold is easier and cheaper to replace than to fix and the upper unit still could be reused. The engine is from 2001 chevy blazer or s10, so is the manifold. The one I found on ebay is from 1998 chevy s10. The question is, where can I find if these manifolds are compatible? I tried chevy dealer but they were not helpful and we're not even able to find the parts by the cast numbers, tried chevy forum, but got no response. So I try this forum. as my last resort. Any help would be appreciated, I just need some direction on where can I dig the answer, I have part numbers for both manifolds if needed. thank you

 

[Scott06]

If the years you list are correct they should both be vortec manifolds thus can be verified by confirming they both use 8 bolts to attach the intake to the heads. If so they will fit. There may be other minor differences in coolant or carb/throttle body connections that you need to see them to confirm

 

[Scott Danforth]

I know I'm in the wrong forum, Bt I just can't find an answer to this question on the Web or in chevy forums. This engine that I bought as a replacement, it had a bad intake manifold. Since I decided to go with the original mercruiser engine and had it bored and will rebuild it , the replacement vortec engine I decided to restore as a car engine. Damaged intake manifold is easier and cheaper to replace than to fix and the upper unit still could be reused. The engine is from 2001 chevy blazer or s10, so is the manifold. The one I found on ebay is from 1998 chevy s10. The question is, where can I find if these manifolds are compatible? I tried chevy dealer but they were not helpful and we're not even able to find the parts by the cast numbers, tried chevy forum, but got no response. So I try this forum. as my last resort. Any help would be appreciated, I just need some direction on where can I dig the answer, I have part numbers for both manifolds if needed. thank you

the manifolds from 2001-2004 are different than 2000 and older. the whole fuel injection system is different.

 

[dlogvine]

I looked on ebay and there are several intake manifolds for GM 4.3 v6 vortec engines, they mention that these units are good for 96-05 engines
This is a used OEM intake manifold for a 1996-2005 GM Blazer/S10 with a 4.3L V-6 Vortec engine. Part #25170759.
or
96 97 98 99 00 01 02 03 04 05 S10 BLAZER INTAKE MANIFOLD 6-262 4.3L
So im a little confused, part numbers listed are different from each other and from my original, but they look similar to what I have, the bolt pattern is definitely correct. How much different are these manifolds?

 

[makanik32@yahoo.com]

Are you looking for a carb intake or an injected intake? If the carb is the way you wanna go, then it shouldn't matter ... The injected option kinda would be more about what vehicle you want to put it in....the biggest thing to consider is the mounting bolts ... The true vortec heads, the bolts are perpendicular to the intake. Pre vortec the bolts went in perpendicular to the cylinder head.

 

[dlogvine]

I'm trying to use the fuel injection intake manifold, like the original one. Original.had a hole in the lower unit and the quote on its repair was way too much, $200 at least. I'm not sure about what was the original engines chevy truck Vin number, I think it was 2001 blazer or s10, and upon checking with machine shop I found out that even in the same year 2001 there were at least a couple different part numbers for the manifold and thease part numbers don't even match the casting numbers. I just bought a 1998 intake manifold that had the same bolt pattern and will put it on the block. I decided to use an original 1993 engine on my Bayliner. vortec engine I'll rearing and put new gaskets, and just try to sell it as a car engine.