4.3 V6 Edelbrock & MSD for performance?

[loco]

Hi all,
I have a 4.3 V6 Vortec with 4bbl carb. I'm looking for a bit more torque and pickup without swapping to a V8.

I'm thinking an edelbrock inlet manifold to replace the gm12550460 manifold I have already.

Also, it has a Delco EST ignition. I'm wondering if the MSD 6M-2L ignition unit could be used - it has some features such as a capacitive discharge, and produces multiple sparks for the first 20 degrees of rotation below 3000 RPM, which should improve performance. I'm not sure if it's compatible with that ignition, though, so am digging around for wiring diagrams. I've got a sneaky suspicion that the ignition module is housed in the dizzy cap on the delco, so possibly couldn't work without swapping out the distributor as part of it.

Would there actually be any significant benefits in performance with these add-ons?

Ultimately, I'd like to go one pitch longer when I next change my aluminium props, possibly going for stainless whilst I'm at it, so I can cruise at a fractionally lower RPM, without sacrificing accelleration onto the plane too too much.


Any thoughts very welcome!

 

[Lou C]

The Edelbrock will not work on the OMC/Volvo rigged engine because of the high mounted alternator. On the Edelbrock the water outlet for the thermostat is shifted to the port side so it would interfere with the alt mounting. Look it up on the Michigan Motorz website. Unless you can re-mount the alt Mercrusier style with the low mount it won't work. I don't think there would be a big power difference and the Edelbrock is aluminum vs cast iron of the OE style. Not sure on the ignition question. Which carb do you have, Holley 4160?

 

[Bondo]

Would there actually be any significant benefits in performance with these add-ons?

Nope,... It'll be 'bout the same,....

 

[Scott Danforth]

Hi all,
I have a 4.3 V6 Vortec with 4bbl carb. I'm looking for a bit more torque and pickup without swapping to a V8.

...... thoughts very welcome!

the V6's are already near their limit naturally aspirated, so without adding a supercharger you wont get much. then at that point the crank will most likely let loose.

cam change will get you a bit, however not enough for the cost and effort.

you really need 2 more pistons or drop down in pitch on the prop for a better hole shot

 

[jimmbo]

As mentioned the intake will make little or no difference, in fact the difference would probably be a drop in performance. As for the ignition system, I doubt any difference that would be noticeable. The only thing multiple sparks do is wear the spark plugs, rotor, and distributor cap out sooner.
As for propping, you choose your prop so the engine will run in the WOT rpm range for your engine. Most people try to get it into the upper half of that range. Propping it for a higher cruising speed at a given rpm may lower the WOT rpm below the low point of the range, not good.
Careful selection of props may help, the Mercury Enertia prop can offer improved acceleration and still yield a good top speed. But it is one of the more expensive props. In the end a bigger engine is often the only real performance boost.
In the mean time, leave the wife, kids, and the mother in law, especially the mother in law, on shore. Mistresses and girlfriends can remain aboard

 

[loco]

Thanks for the responses!
I've got the low-mounted alternator, so I suspect it would be Ok, but if there's little benefit to be had, then not much point.

So, a bit of background on the boat: it used to have an AQ205a, which was the non-vortec volvo v6, with a twin barrel carb. When that needed a load of work done to it and was an 'engine out' job, it made more sense to swap it out for a new long engine, which was the GM 4.3m but with vortec heads and 4bbl holley 4160 carb. Some of the anciliaries came across from the old engine.

So, she's pushing an extra ~20HP over what was in there previously, and we've since dumped a whole load of weight such as the hot water tank which was an easy 60Kg of legionnaires disease kicking around in the engine bay that we didn't need.

The dp290 leg and props are unchanged, and on good cruising days, she runs pretty high in the RPMs - around 4300 - 4500. I'm tempted to go up one pitch with the props next time I replace them but it's an expensive gamble, and if it runs like a dog with the new props, then I'll have some expensive paperwights to deal with. Slightly lower RPM might give me some slightly improved fuel economy too, though not much point trying to gain MPG from a boat.

That's why I wanted to put in a couple of mods to up the torque/power just a bit more so I could be sure about going up a pitch. Other thoughts included larger trim tabs, or converting to fresh water cooling, but ultimately, it sounds like there's not much to be had out that engine.

 

[Scott Danforth]

Here is the funny thing about fuel economy in a boat....your fuel burn rate is directly related to how much power you command. 0.4 #/hp/hr is the BSFC for internal combustion spartk-ignited marine motors.

what is your WOT speed? can the motor hit 4800? what is your drive ratio?

which props do you have on the drive now?

jumping to the next prop set will lower your RPM's by about 400. if your motor can not hit top RPM, then you will be lugging it, and kill it quickly. a motor spinning away at 4400 RPM that is lightly loaded will burn less fuel than a over-propped and lugged motor spinning away at 4000 RPM

regarding fresh water cooling. if the boat has ever been in salt water, forget about it. the time to switch was the time you were wrenching on the new motor and prior to dropping it in water.

 

[QBhoy]

Hi
How did you manage to get an extra 20hp over the already pretty powerful and maxed AQ205 ? That has the big 4 barrel quadrajet. The MPI only has about 220hp five or take.

 

[jimmbo]

A 20hp increase amounts to about a 4 mph increase

 

[loco]

Hi
Just had the boat out the water this weekend, and a bit of an update. To respond to the above, the original engine was an AQ205a which had a 2bbl carb on it. The new engine has the vortec heads and 4bbl holley carb, which I believe comes in at around 220HP.

It currently has B5 props on it and I believe a 2:30:1 ratio box.

Looking at the props today, I've got horrendous cavitation corrosion on the rear face of the front prop. It's so deep, it goes all the way through the prop in a couple of areas! So I'm looking into the causes of the cavitation.

Reading up on the props on the below site, it shows that the B5 with my leg is good for 32kts, though the boat can hit 34 on a good day - max ever speed is 36Kts. Could they be over speeding, or is it more likely to just be a pitted prop that's caused the cavitation? They're about 4 years old now. I'm not convinced my tacho is that accurate, so can't be too sure on engine RPM. Maybe need to invest in a shop tacho.

Prop document:
http://www.pentamarine.co.th/pdf/propellers.pdf

cheers all

 

[Maclin]

Regarding the cavitation, you might look at how the props are clocked. Try to get install them with one blade down and two up on one, and one blade up and the other 2 down. If they are not close to that then you should try this method. You only need to remove the rear prop to get this done. There are articles and posts about the 290DP and DP-A/B/C drives that if the props leave an open area at the anti-cav plate that cavitaion can result, burns the edges of the props, and maybe worse.

Here is a link to some discussion so this...
https://forums.iboats.com/forum/gen...s/10045470-indexing-v-p-duoprops#post10045470