Building up a Vortec 4.3
 

Anyone every build up a Vortec 4.3?

hopefully someone has... great topic..

Well what can be done with a 350 can be done to a 4.3..Its the avaibilty of vortec heads to the v6 that sets it all up..But v6 parts are limited and expensive..

Now with that said you can supercharge or turbo them very cost effectively...They can reliably take 18-25Lbs of boost ..thats 300-350hp..mabye 2000....

Then again you can buy a 350 crate engine for 2500 doing 300

GM performance parts has tons of stuff for them....now cost ?? 350-383 easy swap !

is it a balance shaft engine?

Brodix makes a real nice aluminum cylinder head in a big and smaller port version. it has a non vortec intake flange, so you can use a Edelbrock intake.

build it, build it. great motor to build. just do one without balance shaft. is it a m block or s block

The motor is a 1997 Volvo. It is out of a 19’ Scarab Jet. I have pulled the motor and it goes to the machine shop tomorrow so they can check to see what damage has been done.
I believe the motor is a balance shaft motor. Not sure about the “s” or “m”.
I purchased the boat as a project boat. The motor had no intake or carb. And one of the heads (along with a lot of parts) in a basket. Looks like it had blew a head gasket. Anyone know if these motors have a rev limiter? With it being a jet I would guess that it could be easy to cavitate and over rev the motor.

with the Brodix heads, a mild hydraulic roller cam (212*/218* @ .050), Performer intake and 4bbl it will make 325 hp.

This has been covered before. You are limited on your cam choices. The v6 is more prone to reversion unless you used dry exhaust. Also there are more aftermarket parts available for for SBC/BBC. Cost is not much different than building a SBC. I am sure you will hear many opinions for and against building one.

Hi Guys,

Thanks for the info. The brothers that own the machine shop had the same to say about the motor. Sounds like it can be done but will be costly and that reversion thing…… dose not sound like fun. Think I’m going to keep it close to stock and use it to move to a larger boat next spring.
Thanks,
Speed.

Anyone know the stock cam specs??

my brother is building one now for a customer, hang tight till tomorrow will get you all info.

Ok guys,
Looks like it’s coming down to up grading the cam or keeping the stock one. Here is what I have so far.
1997 4.3 vortec , (started life as a 225HP motor, not sure if that maters) pistons are now 60 over, Edelbrock Performer Intake and marine series 600 CFM Carb. Would adding a mild cam over the stock cam make much of a difference without the heads and valve work I keep reading about?

Thanks,
Speed

you could go to 1.6 Pro Magnum rockers and use the stock cam.. I don't think many cam companies stock 6 cyl blanks, unless Bullet or Crane have them.. you can get COMP to custom grind one from their blanks if you know the lobe profiles you want.. the Brodix heads would really wake it up..

the heads would be great, but trying to do this without putting much $$ into it. i have to add the intake and carb (previous owner lost them??) but the more i look around is sound like the cam alone will not do much so I may stick with the stock one.

Thanks,
Speed

let's see what fkboatman comes back with.... :)

in your case just the intake, carb, IMCO exhaust, and 1.6 rockers would be it.. make sure you get the non guide plate rockers...

Do not change the cam without first getting aftermarket exhaust with long risers. Reversion will kill it real quick.

Even the stock ones have reversion issues. They are a tough little engine though.

I have onlt seen one company that makes exhaust for the 4.3...
http://www.imcomarine.com/ca_store/i...roducts_id=805

I looked into this same thing 6-8 years ago and found it way to expensive to get any real gains from it. You will be much better off getting a used 350 or even a 454 and keep those stock and still have more HP than you could ever get out of a 4.3.

Comp Cam
1.Behive springs...allows for 1.6 lift with no head work
2.Compcam 266 cam or the 270...lsa is 112 should not casue reversion
3. eldobrock intake...Only game int town for a 4.3
4. 600 cfm carb..You will have to rejet..

About 1800 if self installed...You should net about 280-300 hp...You will more than probably have to change your drive gears to 1.5 or 1.66 depending on drive type.

After market exhuast wont help

Not sure if any could help you in the marine world but look up parts for a 91 syclone or 92/93 typhoon. I had a 93 ty with stock turbo, chipped and was probably around 300+ hp and 400 tq.

http://en.wikipedia.org/wiki/GMC_Typhoon

i installed the elderbrock intake and carb. the boat will only go to 4,000 rpm. it still has 1/4 tthrottle left but the rpm, speed, engine does not change in the last 1/4 of the throttle?? this is with the carb set up from elderbrock. when i try to re-jet it i get a miss around 2000 rpm?? any thoughts?

Brodix makes a real nice aluminum cylinder head in a big and smaller port version. it has a non vortec intake flange, so you can use a Edelbrock intake.

__________________
watch movies online

whats your total timeing, i will look tommorow in my merc book and see what rods,springs, jets that merc usus in there carb. if that motor is brand new you need to let it break in and loosenn up some before running it wot.

Stock distributor, set it at 10 BTDC (thinking stock) I spoke to Edelbrock today and sounds like I need to try a richer metering rod or move to a 92 jet instead of the 89 that is in it. Think I will try the rod 1st and if that takes care of the missing around 2000 rpms i will take it to the lake and see where the RPMS end up at WOT. I have 6 or 7 hr on the motor. Only saw 4,000 for a min or two. I have varied the rpms for the first 5 hrs not taking it over 3500. Let me know what you find out

Thanks for info! :drink:
Speed

take it for a good run and shut her down pull a plug from each side of motor and look and see if they are reall light in color, grey or white is lean. light brown is perfect. have somone run the boat and close choke butterfly and see if motor cleans uo, if it does its lean.

merc shop manual sais as follows, 89 primary jet. yellow springs. 89 secondary jet or a optional 95 secondary jet. merc number for rod is 16-6857. now edlebrock 4.3 calibration is as follows. 89 primary. .068x.057 rod. pink spring. and 89 secondary jet. Merc sais there carb is a 600 cfm. I remember a couple years ago i had to up secondary jet to the 95 because of a lean condition on top end. let me know if you need anything else. Frank

Thanks fkboatman,
I currently have 89 primary and 89 secondary with a .69 x .47 rod and pink spring. My thought was to try a .63 x 47 rod 1st and see if that cleans up the miss around the 2,000 rpm range. If so, try it at the lake and see what happens with WOT. If not try a 92 primary.
I know just enough to get in trouble with Carbs…… so thank you for any info!!
I will be out of town and cannot try the changes until week after next . I will let you know how it goes.
Thanks again,
Speed

if you read the edlebrock book on carb. it clearly explains how to richen up or lean down carb in the idle power and wot section. how did you set your timming on the motor, we know you use a light. but is there a bypass on your dist. to set base timming?

you really need to get a timing light with a advance. and run motor to about 2500 0r 3000 rpm and see what you get for total timming. either your not getting enough total timming or your lean. and with it miss firing around 2k rpm. i would say its running lean. Do you have anyone locally can help you dial this thing in or even the guys at the machine shop shoukld know basic engine tunning set up like we bein talking about.

There ya go merc is a weber but same metering rods...Try two or three rods richer..Should be spot on..with 26 degrees total timing..

Edited to 26 degress 8 at the base

Just getting back in town and hope to try the new rods in the next day or so. I did use a timing light with advance. Also borrowed a bypass module that plugs into the distributer to set the timing to 10 BTDC. Can I now check the total timing by running the motor at 3000 rpm with the bypass module removed, correct?
I also found the ederbrock info helpful but the 600cmf marine carb info is based on the stock set up and using the 89 jets rod set up they recommend with a 4.3 is off the chart shown in the book. You can see what they are doing and kind of guess what to do, so that’s where I came up the .63 x .47 rod to try next. The 68 x 57 rod they recommend for the 4.3 is worse than the 68 x 47 rod that came in the carb stock. So I’m hoping the 63 x 47 rod does the trick.
I will let you know how it goes

Thanks again for all the help!
Speed

correct about timming set up. i would pull the 89 secondary jets and change to min. 92 like you said early. but definately change out the rods. rods control mid rpm range.

Hi Guys,

I did get a chance to run the boat this past weekend however not enough time to check everything. The mid rpm runs fine with the 89 primary jets, pink springs and 63 x 47 rods. I also changed the secondary jets to the 92s ,however I still have an issue with wot, it tops out at around 3,900 to 4,000 with 1/8 or so throttle to go (throttle seems to be a little closer to the wide open position than before?, but still not right). Actually when you go to wot and back off to the point that rpm matches the throttle position you gain 50 to 100 rpm??? Unfortunately another problem surfaced when testing the boat…. A bearing is going out of the jet drive and before I take the boat out again it must be fixed. i think soon I will be able to take the scarab back to the factory and have it titled as a 2010!! :eek:

Thanks for all the info.
Speed

you really need to find out what your total timming is.

It does not like the Edelbrock Carb at first. Stay with it though, you can do it. I got it on my second round. I would still like a smaller carb but it was an easy option.

I did the heads, cam, carb, intake and IMCO exhaust on my father's 4.3. It really woke it up. It needs boost now.