Tinkering on the 4.3l this winter...

[Pmt133]

So I've said it in the past just don't think I have it documented here. I have some go fast parts for the 4.3l I'll probably throw on this winter then in the spring document any improvements.... The parts I think will show the most improvement based on threads here are the 4 barrel carb and Edelbrock 2519 intake. The intake is the proper marine one with the lined water passages. This was given to me so the cost was $0. The carb is actually a Mercruiser unit off a 96 marine engine. I did the electric choke conversion and rejetted it based on what most people with the vortec headed v6s jet to as a starting point. (pretty near what the service manual calls for) The carb was a trade and cost me ~$20 for the core. The rest of the peripherals and rebuild set me back another $80. So for about $100 I have the conversion plus gaskets and time.

I will be curious to see how much an improvement it is and how close the tune up ends up being. I plan to document in this thread any improvements in hole shot and top end. I suspect I will have to reprop as I am kissing the limiter with a lighter load as it is so any more power will probably have me run right into it.

The other thing I have a question on and this is again a "cheap" upgrade.... I have a set of 1.6 ratio self aligning rockers laying around. My heads have the non adjustable valve train but not the trunnion style rocker arms so it has studs. The studs on there are screw in however. For ~$50 I can snag a set of conversion studs and utilize those rockers. My question is, is it even worth doing or should I just put that towards the extra fuel I am going to burn. I figured it's cheap enough and I am right there anyway, but given these engines are supposed to be near the edge of reversion as it is, maybe I shouldn't tempt fate lol.

I plan on selling the 2bbl intake and carb and would most likely recoup any money I put out anyway but still figured that it is something to keep me busy one weekend. If anyone else wants to convince me to either spend more money or not, please be my guest lol.

 

[alldodge]

I have a set of 1.6 ratio self aligning rockers laying around. My heads have the non adjustable valve train but not the trunnion style rocker arms so it has studs. The studs on there are screw in however. For ~$50 I can snag a set of conversion studs and utilize those rockers. My question is, is it even worth doing or should I just put that towards the extra fuel I am going to burn. I figured it's cheap enough and I am right there anyway, but given these engines are supposed to be near the edge of reversion as it is, maybe I shouldn't tempt fate lol.

Other then the Merc racing motors, no factory motor is even close to reversion

@Scott Danforth should help with the rockers

 

[Scott Danforth]

the 4.3 is on the verge of reversion due to the exhaust pulses.

@Tail_Gunner did a hot 4.3 about 15 years ago on Hot Rodders. will check his old threads as he hasnt been on iBoats in about 6 months. https://www.hotrodders.com/threads/4-3-marine-upgrade.155256/

4.3 Vortec build up and traps

2000 4.3 tbi setup http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=576&sb=0 I know that cam is a bit hot for a boat but will reversion be a big issue here??? Revised to: http://store.summitracing.com/partdetail.asp?part=CCA%2D08%2D417%2D8&autoview=sku Milder duration with less...

forums.iboats.com

1.6 should be OK. However need to check total valve lift and interference with the keeper and seal

 

[Lou C]

I think for both Merc and OMC when you went from the 4.3 2bbl to the 4.3 4bbl you went from 175 hp to 205 hp so it's not a big jump but I guess comparable to what you get with the Vortec heads. My pre-Vortec came with the 4bbl Quadrajet and you can feel a definite surge in power when the secondaries open up, when you run on the small primaries it is surprisingly economical. If I could do it for the price you're getting lol I would for sure do it!
As far as being on the edge of reversion, what I have read is that this became more of an issue with the Vortec engines due to the more aggressive cam, but I guess that depends on what cam the marinizers actually used.
Not sure about what Merc did but OMC/Volvo actually changed the exhaust system twice with the Vortec V6 engines, first they changed the shape of the 90* aluminum down pipe that connects the elbows to the Y pipe, they made the angle of the down turn sharper to keep water from climbing up the down pipe due to vacuum in the exhaust pulses. Then they added one way check valves in the elbows to break the vacuum in the exhaust by letting air to enter via the one way valve. So if they bothered to spend the money to do that, I'd assume there was some kind of concern.
When I converted mine from the batwings I used the updated down pipes, thinking if I ever repowered with a Vortec it would be less likely to have a problem, I didn't add the check valves because with my current pre-Vortec it's not needed IMHO. I never had reversion problems either with the batwings or the current 2 piece later exhaust style.
I think you'll be happy with the Edelbrock intake and a 4bbl. It will wake up that 4.3 above 4000 rpm.

 

[Pmt133]

the 4.3 is on the verge of reversion due to the exhaust pulses.

@Tail_Gunner did a hot 4.3 about 15 years ago on Hot Rodders. will check his old threads as he hasnt been on iBoats in about 6 months. https://www.hotrodders.com/threads/4-3-marine-upgrade.155256/

4.3 Vortec build up and traps

2000 4.3 tbi setup http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=576&sb=0 I know that cam is a bit hot for a boat but will reversion be a big issue here??? Revised to: http://store.summitracing.com/partdetail.asp?part=CCA%2D08%2D417%2D8&autoview=sku Milder duration with less...

forums.iboats.com

1.6 should be OK. However need to check total valve lift and interference with the keeper and seal

I actually thumbed through tailgunners threads not long before posting this. The hotrodders one seemed to go off on tangent but the iboats one was pretty good though had some gaps.

I think somewhere I have a box of the offset keepers for a vortec as well if that does become an issue. But I seem vaguely to recall my shop machining down the guides when rebuilt anyway... but obviously I'd measure lift while apart and do the calculations.

I think for both Merc and OMC when you went from the 4.3 2bbl to the 4.3 4bbl you went from 175 hp to 205 hp so it's not a big jump but I guess comparable to what you get with the Vortec heads. My pre-Vortec came with the 4bbl Quadrajet and you can feel a definite surge in power when the secondaries open up, when you run on the small primaries it is surprisingly economical. If I could do it for the price you're getting lol I would for sure do it!
As far as being on the edge of reversion, what I have read is that this became more of an issue with the Vortec engines due to the more aggressive cam, but I guess that depends on what cam the marinizers actually used.
Not sure about what Merc did but OMC/Volvo actually changed the exhaust system twice with the Vortec V6 engines, first they changed the shape of the 90* aluminum down pipe that connects the elbows to the Y pipe, they made the angle of the down turn sharper to keep water from climbing up the down pipe due to vacuum in the exhaust pulses. Then they added one way check valves in the elbows to break the vacuum in the exhaust by letting air to enter via the one way valve. So if they bothered to spend the money to do that, I'd assume there was some kind of concern.
When I converted mine from the batwings I used the updated down pipes, thinking if I ever repowered with a Vortec it would be less likely to have a problem, I didn't add the check valves because with my current pre-Vortec it's not needed IMHO. I never had reversion problems either with the batwings or the current 2 piece later exhaust style.
I think you'll be happy with the Edelbrock intake and a 4bbl. It will wake up that 4.3 above 4000 rpm.

Kind of why I'm doing it lol. Merc calls the 4bbl crate 4.3l around 225 hp. I'd say the edelbrock intake may be a little better than mercs production manifold but I haven't seen the aluminum one they're using lately. Figure 230hp with intake plus rockers lol.

 

[Scott Danforth]

Not sure on Merc, however both Volvo and Edelbrock marine come out of the same mold at Barr

 

[Pmt133]

One other thing noted I'd have to check... the 4.3 pushrod slots look like they could get pretty tight if I increase the ratio.... Might need to clearance them a tad if I end up using the 1.6 rockers....

 

[Pmt133]

So I did some checking today. It would seem I am quite close to coil bind with stock valvetrain. I have to swing the engine out in a few weeks to figure out where my leak is. I may toss it on the stand and better measure out everything. Might be able to use the beehives and offset keepers I have laying around if I choose to do this still.

 

[Scott06]

I actually thumbed through tailgunners threads not long before posting this. The hotrodders one seemed to go off on tangent but the iboats one was pretty good though had some gaps.

I think somewhere I have a box of the offset keepers for a vortec as well if that does become an issue. But I seem vaguely to recall my shop machining down the guides when rebuilt anyway... but obviously I'd measure lift while apart and do the calculations.


Kind of why I'm doing it lol. Merc calls the 4bbl crate 4.3l around 225 hp. I'd say the edelbrock intake may be a little better than mercs production manifold but I haven't seen the aluminum one they're using lately. Figure 230hp with intake plus rockers lol.

225-230 is a fair estimate. As mentioned closest spec merc engine would be the 4 bbl reman at 225 hp. Should be a nice punch over the 2 bbl 190 hp you have now.
would be careful of thinking the intake alone is going to add too much HP. Unless the cam is done or the higher ratio rockers, just cause the intake flows more doesn’t mean the heads and cam will.

I would put the intake and carb on get the prop worked out and then you can always do the rockers later.

I found when doing a 4.3 to 5.0 repower (with a edlebrock 1409) that the mid range throttle response on the 4 bbl is fantastic compared with the 2 bbl. If you take the merc throttle bracket #16 in the attached you will get a nice clean install. https://www.marineengine.com/parts/...p/carburetor-and-throttle-linkage-four-barrel

 

[Scott06]

So I did some checking today. It would seem I am quite close to coil bind with stock valvetrain. I have to swing the engine out in a few weeks to figure out where my leak is. I may toss it on the stand and better measure out everything. Might be able to use the beehives and offset keepers I have laying around if I choose to do this still.

Also check the retainer to seal clearance, this can be done with the head still on the engine

 

[Pmt133]

225-230 is a fair estimate. As mentioned closest spec merc engine would be the 4 bbl reman at 225 hp. Should be a nice punch over the 2 bbl 190 hp you have now.
would be careful of thinking the intake alone is going to add too much up. Unless the cam is done or the higher ratio rockers, just cause the intake flows more doesn’t mean the heads and cam will.

I would put the intake and carb on get the prop worked out and then you can always do the rockers later.

I found when doing a 4.3 to 5.0 repower (with a edlebrock 1409) that the mid range throttle response on the 4 bbl is fantastic compared with the 2 bbl. If you take the merc throttle bracket #16 in the attached you will get a nice clean install. https://www.marineengine.com/parts/...p/carburetor-and-throttle-linkage-four-barrel

I actually have part 16 on my work bench lol. I didn't feel like fabricating a throttle bracket.

From everything I have found, the 190 and 225 and EFI all use the same grind cam per the merc parts book so in theory, slightly better flow may equal a couple more ponies? (Being optimistic)

Also check the retainer to seal clearance, this can be done with the head still on the engine

Actually checked that this morning. Miles of room. the spring is just near coil bind at max lift which looking at the merc service manual, makes sense. My shop cleaned up some stuff but still more or less built to factory spec. I thought I had the cam grind in the paper work from the rebuild but I don't just a note on the bill for marine spec cam. I went down there last week and asked if they remembered off the top of their heads what was in it. They said it was the same as what came out. Only number I could find on it was 692 which sounds right... 96 truck engine camshaft. I think I may scrap the whole rocker arm thing for now. Seems like more work than it'll be worth. Maybe down the line I'll just do a cam swap as that's the only real way to gain any sort of power beyond what's there. Or I'll be totally happy with the 4bbl and leave it be.

 

[Lou C]

I think in your size/weight boat you'll be happy with the 4bbl. Keep it simple, less possibly for problems down the line. Think about stepping up to the Mercruiser/Quicksilver 25/50 syn blend oil. I think it tests out better than 15w/40s on UOAs from what I have seen as far as holding its viscosity range, has more zinc and phosphorus than most of them but it is expensive. With the 4bbl you'll be tempted to run it at higher rpms than before!

 

[Pmt133]

I think in your size/weight boat you'll be happy with the 4bbl. Keep it simple, less possibly for problems down the line. Think about stepping up to the Mercruiser/Quicksilver 25/50 syn blend oil. I think it tests out better than 15w/40s on UOAs from what I have seen as far as holding its viscosity range, has more zinc and phosphorus than most of them but it is expensive. With the 4bbl you'll be tempted to run it at higher rpms than before!

True. Though my cruise is ~3300 RPM and 33 MPH already. That's a comfortable speed. The top end just feels choked. It freight trains up to 4000 then noses over.

 

[Scott06]

I actually have part 16 on my work bench lol. I didn't feel like fabricating a throttle bracket.

From everything I have found, the 190 and 225 and EFI all use the same grind cam per the merc parts book so in theory, slightly better flow may equal a couple more ponies? (Being optimistic)


Seems like more work than it'll be worth. Maybe down the line I'll just do a cam swap as that's the only real way to gain any sort of power beyond what's there. Or I'll be totally happy with the 4bbl and leave it be.

yes they use the same cam just changing carbs and or for injection and would assume ignition timing on later MPI models.

I think what you will find is the gains are pretty small and if you really want more after doing the 4 bbl put in a 5.7. When I did my repower my sea ray 200 was originally sold with 4.3 and 5.0 engine options. The stringers and engine compartment were sized for both engines making it an easy swap.

 

[Pmt133]

yes they use the same cam just changing carbs and or for injection and would assume ignition timing on later MPI models.

I think what you will find is the gains are pretty small and if you really want more after doing the 4 bbl put in a 5.7. When I did my repower my sea ray 200 was originally sold with 4.3 and 5.0 engine options. The stringers and engine compartment were sized for both engines making it an easy swap.

When I did my rebuild I left the mounts 4.3 sized for a reason lol. It's more than adequate for the hull. A 5.7 would be too much imo. Even though it was offered with the 350 mag back in 84.

 

[Scott06]

When I did my rebuild I left the mounts 4.3 sized for a reason lol. It's more than adequate for the hull. A 5.7 would be too much imo. Even though it was offered with the 350 mag back in 84.

Have yet to own a boat with with too much power ... but fair enough. All that matters if it works for how you use it.

 

[Pmt133]

Have yet to own a boat with with too much power ... but fair enough. All that matters if it works for how you use it.

I think it's more I'd be near the limits of the hull design at those speeds more so than too much power. Remember, I'm coming from a 3.0l pushing this thing around. She scoots just fine now. And I don't really want the stern sitting any lower than it already does. And of course I would have to have through hull exhaust because why not... see, this is why I tied my own hands. I have a ~330 hp 350 that would be a drop in for it if I wanted. And it's an excuse to build a new engine for the corvette.

 

[jimmbo]

230 out of a 4.3? maybe at about 5700 rpm

205-210 would be about the limit and still have any bottom end torque

 

[Scott06]

I think it's more I'd be near the limits of the hull design at those speeds more so than too much power. Remember, I'm coming from a 3.0l pushing this thing around. She scoots just fine now. And I don't really want the stern sitting any lower than it already does. And of course I would have to have through hull exhaust because why not... see, this is why I tied my own hands. I have a ~330 hp 350 that would be a drop in for it if I wanted. And it's an excuse to build a new engine for the corvette.

I also came from a 3.0 powered boat its a nice upgrade.

I think most people get tired of the trough hulls pretty quick. Captains Call is probably the better bet.

 

[jimmbo]

. I have a ~330 hp 350 that would be a drop in for it if I wanted. And it's an excuse to build a new engine for the corvette.

If that is an engine out of a Car/Truck, it is not going to be much use in a boat, until some Changes are made to it.