What hp will I gain?

[Stingdog93]

Out of all of the sites that I have visited, this place has the best advice that I have found so hopefully someone here can help me. I have a 1993 Stingray 606ZP, 20'3", with a 175hp 4.3 and am looking to do some mods on it. At this time I can spin a 14 1/4 x 23p 4 blade Ron Hill Signature at 4600 RPM, at a gps of 48 mph. It is a non-vortec engine. I have a set of 1999 vortec heads and an Edelbrock performer intake, #2114, that I am planning on having match ported, both intake and exhaust. I also plan on using a good set of push rods, and a set of full roller rockers, 1.6 ratio, and since I'm this far, I was thinking of using a better roller cam like Edelbrocks Rolling Thunder Hydrolic Roller, but don't know what grind to use. I know that I will need to do some carb tuning, and open the exhaust up somewhat, but what kind of hp gains am I looking at with the heads, intake, rockers port work and cam? Just looking to go faster, but keep my fuel economy.

 

[kghost]

I would say without the right cam you wont gain much with just heads and intake and a 4 bbl carb.......maybe 20-35 hp

If you get a good cam, maybe the one you suggested you could see 50 hp easily maybe a bit more with the heads, intake and research a Barry Grant 600 cfm marine carb (4BBL) you will need the 600 cfm for that hp range.......

You also would be able to raise your max rpms up to 5200 most likely. I would think 250 hp +/- at 5200 rpms would put you in the mid 50's mph maybe higher.


I am not sure the ignition will be good enough as it is not designed for high performance but I would see what it can do before buying another.



Of course simply swapping out to a 350 280 hp would do the same..........

One issue when trying to go to fast with a boat not designed to go to fast is the possibility of fish tailing (rear end of boat dancing back and forth) due to hull design vs top speed.............

 

[bondo]

Ayuh,.... Put the Vortec heads, intake, 'n 4bbl. carb on it, 'n be Happy,.... probably 35/ 40 hp,...

Swappin' to a hot cam can, 'n probably will cause trouble,....

Unless ya change the pistons to match the heads, swappin' the cam don't help so much anyways,....

 

[RicardoMarine]

If I may chime in.

First of all, if you are running this 4.3L engine at or near 4.6K rpm for any duration, you will shorten it's life dramatically.

Secondly, the GM built 4.3L engine will be fitted with the GM style full dished pistons.

The Vortec cylinder head's combustion chamber design is great, but it will not be able to offer it's full potential with these pistons.
In other words, the Vortec Quench surface is excellent, but the full dished piston lacks the quench surface that is necessary to "mirror" the cylinder head's quench area.

Unless ya change the pistons to match the heads, swappin' the cam don't help so much anyways,....

I fully agree with Bill!


If you are after more speed, replace the 4.3L with a well built 5.7L and then change the over-all drive ratio to accommodate.




Edit:

Just for fun, I ran the calcs for CFM requirement for the 4.3L engine.
At a 100% VE, the 262 cu in engine requires only 349 cfm @ 4,600 rpm.



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[kghost]

"""""""""Just for fun, I ran the calcs for CFM requirement for the 4.3L engine.
At a 100% VE, the 262 cu in engine requires only 349 cfm @ 4,600 rpm"""""""

This does not matter if he modifies his motor,

If he cams it and reaches ~ 250 hp and puts a four barrel carb on it he will need much more than 349 cfm

Calculations or not it is only a base line

Many of your Volvo 4 cylinders use a holley 2 barrel and that is exactly 1/2 of a 600 cfm.....so that makes them 300 cfm....for a 130 cubic inch motor.

 

[RicardoMarine]

......................

Just for fun, I ran the calcs for CFM requirement for the 4.3L engine.
At a 100% VE, the 262 cu in engine requires only 349 cfm @ 4,600 rpm

This does not matter if he modifies his engine,
How much modifying can one do to a 4.3L V-6 and yet get V-8 type performance from it?

If he cams it and reaches ~ 250 hp and puts a four barrel carb on it he will need much more than 349 cfm
Even if the CFM requirement increases, what would your estimate be?



Calculations or not it is only a base line
Agreed! Do you not use base lines?

.

 

[Stingdog93]

Thanks guys. Kghost, I agree with you on the V8 swap, but I have kids and with the V6, I can make my 37 gal fuel tank last 3 full days of pulling toys and doing water sports, with a V8 I think I would loose that. I would love to build a 427ci sbc stroker when the kids are gone, I'm pretty sure the hull can handle it as Hot Boat Magazine tested this hull in 1996 with the 235hp 5.7 and it ran 61.3 on radar. I still have the magazine that my boat model was in and in 1993, Hot Boat caught it on radar at 53mph with the 175hp 4.3. I just want to maximize what I have now without spending $3000+ and killing my fuel economy. Also, my engine has the 4 barrel carb, just not sure of the size as I have not checked on the numbers yet. I was told that there is a rev liviter in this engine, is there? What rpm would it kick in at? I have spun this motor with a 13 3/4 x 21p Lazer 2 at 5300 for a short run and it did not kick in, got rid of the prop, too small.

 

[Stingdog93]

In the 1993 Hot Boat article of my boat model, it states the prop as a 15 3/4 x 23P Lazer 2. Does that sound right? That sounds like a mighty large diameter for that gear case, my 14 1/4 x 23P 4 blade is very close to hitting the zink skeg now.

 

[kghost]

There are lots of factors that make two identical boats run at different speeds.

The X dimension is the most critical. That is how high the whole is cut through the transom for the outdrive to mount.

1/2" higher on one boat and it will run significantly faster so the boat article is just that......you don't know how the boat was prepped!!

As far as prop size........I am no expert.....don't really play with props. your zink "skeg" is called a trim tab. If it is not flat then you could install a flat one and see if there is enough space for a larger diameter prop like the one in the article. A larger diameter will move more water so a higher speed will be obtained But it may take longer to get there.......


As far as a rev limit..........I don't think there is one on a carbed motor.

Your motor should not exceed 5000 rpms in stock trim. I said 5200 if modified.

So, without a cam change don't expect much from port matching........not going to give you much. Roller rockers are nice but not needed for a basic "street" motor that will not rev over 6000 rpms.......and no need for "special" push rods either......nothing to be gained.

All that "hot stuff" is for high revving motors to stabilize the valve train..........you are not going there so don't waist your money.

A real good multi angle performance valve job, with of course you port matching and the right cam should get you well over 200 hp.

Not sure what carb you have but I would strongly recommend one with more adjustability if you modify your motor. You will need to richen it up some.

If you have a weber carb I am not sure what parts are available to modify it. No experience with weber performance. Maybe a comparison to one run on a 350 and see what the jetting and any other differences may be. If the information is in the manuals....not sure.

So in the end if you bump up the power you will sacrifice economy. no way around it.

One thing to remember..........this site most people here do or have done repairs on boats. Not modifications. Speaking for myself, I fix what is broken with 99% of the time OEM parts. I don't change cams, pistons, or any other parts with high performance parts. I don't have nor do I want to spend the time FU CK ING with some ones boat to make it go faster than the way it was built. I simply tell them to go buy one that was designed to go faster.

If I were to rebuild a motor for performance one thing is for sure, I would have it dyno'd so I would have 100% confidence that it would be tuned properly and turn key.

I would not simply swap parts and tune on the fly..............Who has time for that anyway..........summer is to short to be wasting time tuning instead of drinking!

 

[bondo]

As far as a rev limit..........I don't think there is one on a carbed motor.

Ayuh,... A '93 oughta be a T-Bolt IV ignition, so no rev-limiter,....

The T-Bolt V, does have the capability,....

If this is a Weber carb, or any of the Carter AFB clones, Edelbrock performer is the same exact carb, 'n uses the same exact parts,....

 

[RicardoMarine]

Just looking to go faster, but keep my fuel economy.

It's highly unlikely that you'd be able to have both "go faster" and "keep my fuel economy"....... it just doesn't work that way.

The whole idea behind modifying an engine is to some how get the engine to breath better, of which means pulling in more fuel/air, and then to compress it under greater pressure for a more effective fuel "burn", etc.
This almost always involves more fuel consumption.

Then you must consider what increased cylinder pressures may cause to an engine fitted with the GM style Full Dished pistons!
Keep in mind...... there is No Quench Effect possible with this piston.
No Quench = reduced ignition advance in order to avoid detonation.
Reduced Ignition advance = a lazy LPCP.
A lazy LPCP = less torque.


In part, going to a 5.7L engine just may prove to not burn any more or less fuel than what a modified 4.3L may burn.
If hell bent on a modification, your best bang for the buck will be in modifying something other than the 4.3L.



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[kghost]

It's highly unlikely that you'd be able to have both "go faster" and "keep my fuel economy"....... it just doesn't work that way.

The whole idea behind modifying an engine is to some how get the engine to breath better, of which means pulling in more fuel/air, and then to compress it under greater pressure for a more effective fuel "burn", etc.
This almost always involves more fuel consumption.

Then you must consider what increased cylinder pressures may cause to an engine fitted with the GM style Full Dished pistons!
Keep in mind...... there is No Quench Effect possible with this piston.
No Quench = reduced ignition advance in order to avoid detonation.
Reduced Ignition advance = a lazy LPCP.
A lazy LPCP = less torque.


In part, going to a 5.7L engine just may prove to not burn any more or less fuel than what a modified 4.3L may burn.
If hell bent on a modification, your best bang for the buck will be in modifying something other than the 4.3L.



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Agreed............with exception of the piston story...........haha.........

 

[RicardoMarine]

Agreed............with exception of the piston story...........haha.........

Understood and that's OK...... you do your builds.... I'll do mine!


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[Stingdog93]

Your points are all well taken, thank you for your advice. Since I kinda got the cart ahead of the horse and the parts are already here, I'm debating going ahead on the project. If I do continue on, I will post the data here so that maybe it will help someone else. If not, I guess I will sell it al and have to be happy with what I have till the kids leave and that 427ci stroker is built. Thank you all for your time and advice, Happy Boating!

 

[kghost]

Don't waist your money on a motor build for that boat.

There are much better boats with more space, better hulls, and much bigger motors already on the market.

Back in the mid 90's the shop I worked at sold a 22 foot with a 454 bravo 1 and it did 67 mph all day every day............

 

[sandkicker]

Going from 4.3 to 5.7.....

Well, my 23 ft Deep V came from the factory with a 283/185 HP SBC with a 4BBL carb. It burned 10 gph @ cruise. With any passengers on board, in order to get it onto a stable plane, the back 2 BBls opened. I swapped it for a 5.7 260 HP factory MERC w/FWC. Max speed went to almost 40 and fuel burn @ cruise dropped to below 7 gph. Boat has a wide range of cruise speeds, i.e., nicely on a plane @ 2400 RPM up tp 3200 RPM. Cruise speed @ 3100 is 30 mph.

Soooo.... a bigger, more modern larger engine can give you higher speed with less fuel burn vs an older smaller displacment engine. ( Part of fuel improvement is the ability to increase engine operating temp to 165/170 F with a FWC engine, vs 135/140 F raw water cooled.) While I can top 40 mph in my high deadrise 4000 lb dry weight boat, in the waters I boat in (Barnegat Bay and environs), going much over 30 on anything other than the rare flat as glass water days is punishing. Boat does fine, knees and back less so. Most summer afternoons feature a 3 to 4 ft chop, often with breaking tops out of the south, i.e., up the full fetch of the bay driven by 15 to 30 mph winds. Spacing between waves is "short" ... :-}.

A boat's ability to run fast improves as the waterline length increases... that's why the "big boy- go fasts" are so long. You want the waterline length to be rather longer than the distance between the wave crests. You want the beam to be relatively narrow as well. When you push Deep V hulls close to the designer's top end, the hull will "porpoise".... i.e., do the "Miami Vice" opening scene thing. Been there, done that... not a good mode to be in unless you have a longish boat. Sticking your nose in a wave @ speed, while it looks cool to the observer, is dangerous, and getting "air" also looks cool, but race boats have a throttle man dedicated to dealing with this.

It's your boat and you are entitled to go as fast as you want, however, in my experience ( USCG 50Ton Captains License, 1986-2013), there are more than enough "unconsious" (a.k.a. stupid) boat operators on most water ways who don't watch where they are going or who is around them, to make "going fast" under most conditions, too risky.