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View Full Version : 4.3 engine additional HP!!!



Mike Ellison
01-19-2004, 05:31 PM
Does anyone know how much additional HP can be obtained from a 4.3, and what the cost would be to obtain it?

Thanks,

mike

HyperDonzi
01-19-2004, 05:40 PM
Not as much as a 350, and will be more expensive.

Edelbrock makes aftermarket intake manifolds, I would reccomend buying Vortec 4.3 Heads/intake off ebay, that will put you to 220hp. The pistons are the same as 350 pistons.

BUIZILLA
01-19-2004, 08:15 PM
You can get the same hp per cube as a 5.7, no douibt, the only problem is, a 4.3 will always be 75% of a 5.7... wink

J

why somebody hasn't hopped upa 4.3 Donzi yet is beyond me :cool:

ToonaFish
01-19-2004, 08:31 PM
We were waiting for you to fund the R&D, Jim!

Bunches,

Celene "He's got six, do I hear eight?"

Rootsy
01-19-2004, 09:14 PM
if i'm goin down to anyone there's no better person than jim, he has me WAY outclassed... one man who has truly forgotten more than i probably know... :)

but if you wanna play hardball... i have A LOOOOOOOOOOONG way to go with my mouse :D

who wants to fund these projects wink

wonder JUST how fast the 16 will go before she develops enough lift to require FAA numbers eek!

seriously... building the 4.3 is just like putting together the V8 version we fondy know as the SBC... albiet a weeee bit more expensive but this is BOATING!!! (BOAT = Break Out Another Thousand)... put together a good combination, have meticulous machine work, use quality parts... a few tricks here-n-there and some voodoo and such and whala... 325 hp (or more wink ) is VERY EASILY obtainable in naturally aspirated form and it;ll even idle at 800 rpm :) make sure you have a balance shaft motor though... breaking crankshafts is a bitch frown

mikev
01-19-2004, 10:13 PM
i have been looking into it extensively and there are alot of nice parts gm, crane and edelbrock make some nice cams i have the edelbrock manifold and 4 bbl on mine and gained 400 rpm dennis moore makes some nice manifolds. www.mooreperforamce.org. (http://www.mooreperforamce.org.) and you can port an polish some vortec heads. dont get a balance shaft engine because there are no cams available for it and the vortec heads bolt right onto the early blocks. after all the research I have decided to build a 383 small block though because i can get allot more performance for the same amount of money. now if my engine was new with not many hours I would probably just hop up the v6.

Mike Ellison
01-19-2004, 10:17 PM
Definity more expensive..I found a place that is selling new 4.3's, 307 hp, for $8,999. Oh well, was just a thought. Lots of 4.3 Donzi's out there....Thanks, Mike

ToonaFish
01-20-2004, 05:01 AM
Rootsy:
wonder JUST how fast the 16 will go before she develops enough lift to require FAA numbers eek! Speaking of which, Cumberland Airport would like a list of low flying Donzis and their respective flight plans on file before May 5th. The new Homeland Security rules and such must be obeyed!

Bunches,

Celene "flew from Rootsy's back seat"

BUIZILLA
01-20-2004, 06:05 AM
Actually, you can build up a nasty 4.3 for nowhere's near the cost of a 5.7 setup.

IMCO has the manifolds and risers, GMPP and the aftermarket has the parts.

J :cool:

whadda ya waitin fer?

Rootsy
01-20-2004, 07:26 AM
though i have never given it much thought, mainly because i've never screwed with the 4.3... i reck you could always do a little strokin to that V6 and be a real sleeper wink

so just exactly what would you do Buz?

Verdugo
01-20-2004, 03:51 PM
Thanks for the great info. :) I have a 1994 16 Classic with a 4.3 mercury & Alph one. I am also looking to get more HP, Speed, POWER! :mad: out of it. I am running 56 57 MPH. I have kept it stock except for that I added the captains choice exhaust.(thru Hual)

What other affortable goodies are out there with out haveing to spend 6-7 K? biggrin. does any one know the exact Hp of a 4.3 stock 1994?

Also thinking of changing to a bigger block 350??

Thanks for your input from Arizona

Lowenski MG

Mike Ellison
01-20-2004, 05:34 PM
Verdugo, I'm looking at a 1994 16' that is for sale. The owner claim that it has a stock 4.3, 205 HP.

AIRGRADY
01-20-2004, 05:48 PM
One word.........BLOWER!

http://www.donzi.net/hull.cfm?id=1064696217

Mike Ellison
01-20-2004, 06:02 PM
Airgrady...What was the cost of the blower?

mikev
01-21-2004, 09:28 AM
hear is a 320hp 4.3 for 4500 complete

http://www.speedomotive.com/4.3%20chevy%20v-6%20street%20master.htm

BUIZILLA
01-21-2004, 10:32 AM
Very interesting...

I would do the cam at 212-214 on a 112 LC though.

J

Mike Ellison
01-21-2004, 06:00 PM
Thanks for the info. Mikey
Anyone know what approximate top end would be with 320 hp. 65 mph maybe?

Rootsy
01-21-2004, 09:41 PM
with the weight savings... and some prop testing so you can hang onto it without messing your pants... yeah... MAYBE 63ish with the GEN II... figure you give up 8 - 10% of your crank hp for frictional and mechanical losses, etc through the sterndrive... so 320 crank would get you 290 or so... put you low 60's

Verdugo
01-22-2004, 06:40 AM
well if with a 320 Hp power plant you are obtaining 63MPH. Question then with a stock 205HP engin what is the average MPH speed specifications. My odometer is at 56-57 maybe it wrong. Help

Mike it seems to me that your quite serious about adding some POWER eek!

correct me if iam wrong it seems to be a cost of about $1,000.00 per mile per hour. I am on the fence :confused: thinking of maybe upgrading to a 22-classic

Lowenski MG

Verdugo
01-22-2004, 06:44 AM
OH 22 Classic 502 70+ MPH anyone looking to trade :D

Rootsy
01-22-2004, 07:30 AM
First of all i do all of my own work therefore this is just a component cost...

roughly...

3500 in the engine
2200 in the sterndrive
600 in propeller

Gain... 25 mph...

Verdugo
01-22-2004, 08:25 AM
Hey Rootsy!!

Thanks for the valuable info!

Lowenski

mikev
01-22-2004, 10:15 AM
what i am looking at is a stock 350 will produce the same horsepower for $1000 less and be a whole lot more reliable

see this link

http://www.1800runsnew.com/gmpp.htm

HyperDonzi
01-22-2004, 04:00 PM
I do have a 6-71 blower sitting in the garage.... Anyone think this could work? Will have to take it to a shop tonight :)

MOP
01-22-2004, 04:09 PM
Someone checked this out http://www.ebasicpower.com/engines/base/ said it made 320 or 325Hp Price is real right. Or my favorite crate job is the 377 on this site http://www.powertorque.net/engines.htm decent dollar.

Speed-Racer
01-22-2004, 09:07 PM
Verdugo,

What is the HP of your 4.3?? Is it Carburated? Etc?

Ours is a 4.3 Carb. 190HP 23p Mirage+ (thur-Hull exhaust)...only running 52 on GPS...

Wondering what your set-up was, and how u get the speed reading, etc?

bjh517
01-23-2004, 12:35 PM
Verdugo,

I have a 1995 16 Classic that had a strong 4.3L, Alpha Gen II. I just replaced it with a new 350 Magnum MPI. It reached no where near 57 mph with the 4.3L. Have you tested the speed with a GPS?
I'm really curious if there is that much of a difference, or if your speedo is off.

Let me know.

Verdugo
01-24-2004, 08:53 PM
Well truthfully I have had the 16 Classic for under 2 years. I love it very much but have not had the chance to test speed with GPS.

I currently come from the big Fishing machines. This is my first fast performace boat. I currently get my MPH readings from the fish finder Speedo, The follwing is what it what she carries

Engine 4.3 LX with 4b carb
CID 262
Out Drive Alpha one
Prop Quick Silver 48-16320 A4 23P
I think per web this is a Stock 205 HP

The only addition I have done was install the Corsa Chaptain Choice.(Thru Hull exhaust).

Because I am on the fence of upgrading to a 22 C am looking for tips to increase SPEED:mad: with out to much $$$$

I will repost once I try GPS. Hope this helps

MOP
01-24-2004, 09:37 PM
Just a thought, drop Waleye a note he is doing Pro Chargers, hey take it with you when you buy a 22C. Bolt on Blot off:D

Rootsy
01-25-2004, 09:21 AM
BJH517,

how is that 350 mag running in the 16?

Speed-Racer
01-27-2004, 06:55 AM
A stock 2B 4.3 for 1996 is a 190HP. A stock 4.3 today is still 190HP!

BUIZILLA
01-27-2004, 08:16 AM
In the readers comments in the back of the March 2004 Car Craft magazine I received yesterday, reiterates what I have been saying all along about the 4.3 potential. They observed a documented 288-300 hp on pump gas for less than $2500, using an existing engine. Why buy a 350??

Jim

bjh517
01-27-2004, 10:06 AM
Rootsy

I have been going crazy. I just got the boat back from the mechanic a couple of weeks ago and I have been battling a kidney stone ever since! I can't wait to get it on the water, but I'm just not up for it. If I could just pass this damn stone, I will be flying around the ICW with a huge grin on my face!

The install was tighter than we thought. We had to remove the insulation on the firewall as well as a layer of plywood to give it room up front of the engine. I also had to remove the plastic air cover and just run with the flame arrestor. There was just no room above either.

I'll post some pics and stats when I finally get it on the water.

turbo2256
01-28-2004, 08:46 AM
Have the heads ported to increase air flow at low lift figures make shure the intake dosent step on the flow. You will see more power this way than the cam change.