Removal of MEFI 4 system from 6.2L V8

[BigChris]

Anyone?

 

[BigChris]

So wiring harness is in, only had to modify the water temp sending unit lead and the "alarm" leads.

Once fuel system primed, she came right to life.

Here is what I observed when setting the base timing.
I started at 1000 rpm. Inserted the bypass harness and connected + 12v power to the flying lead. Engine rpm dropped to about 650-700rpm. Hit it with the timing light to see where I was at by pointing the rotor at the #1 terminal on the distributor cap with cylinder #1 at TDC when I set the distributor in place. I was at 5?ATDC. I set timing to 10?BTDC at 650-700rpm. Disconnected the harness. Engine rpm increased to about 1200 rpm. I turned the idle back down to 750-800 rpm. I verified ignition timing. I was surprised to see timing at 800 rpm was 15? BTDC. So I rechecked, inserted the bypass harness, and yep back to 10? BTDC. Then I revved the engine to 5000rpms several times to see what total advance was. It stopped just short of 30?.

Didn't put it in the drink over the weekend for several reasons. Firstly given the weather here, it was sure to be crowded. Secondly given the fact it would be busy, if I did run into a mechanical, it would be sketchy because of the launch being busy, I'd end up being "that guy". And lastly, I want to do some high speed runs to take a plug reading, and want to wait for calmer water to do that. I'm thinking Wednesday evening after work might be good.

 

[BigChris]

So I've gotten a chance to do some tuning this week. The lake wasn't so busy and the water was calm.

Carb is a 1410 in stock marine trim. .113" primaries, .107" secondaries. .071" x .047" Metering Rods, and orange step up springs.

All tests were done from idle to WOT. Idle set at 800ish rpm.

Started tuning tonight with the typical Edelbrock bog when you punch it, but it was pretty bad, I felt like it would almost stall....

So first step was change the step up spring which controls the metering rod. The orange spring was baseline. Replaced with the pink, bog was still present, but engine response was better.

Then I changed the step up spring to the silver spring, much better. Bog still present. Tried getting closer to top speed, also has lean feel climbing past 3500

Increased secondaries from .107" to .110". Bog still present, lean feel past 3500 better but still there.

Changed Metering Rod from .071" x .047" (stock) to .070" x .042" MUCH Better, Bog almost gone.

Changed Metering Rod from .070 x .042 to .070 x .037 Bog completely gone, accelerates with AUTHORITY.

Still has a slight "flat" spot climbing past 3500-4000, it's not terrible, I can hear the engine ( I wear ear muffs when I do this to get rid of the wind noise) , no pinging. But it's also not perfect. I ran out of parts and daylight.

I think tonight I'll try changing the secondaries from .110 to .113. See if I can get rid of the flat spot climbing past 3500

I may also try going back to the pink springs just to see.

Hot restarts in the water is solid. But I can smell she's just a tad rich at idle. (That's why I want to go back and retry the pink springs)

 

[alldodge]

Nice work, thanks for the process info

 

[HT32BSX115]

Howdy,


NICE JOB!! I have just one question though......and I apologize for being so late in the game!

Earlier you said

The original engine was 5.0L with the MEFI 4 system. So off to the junkyard I went, and grabbed a couple 5.7 liter small blocks. I bought the Eagle racing 383 kit from summit, and built a properly clearanced marine engine. .003" piston to cylinder wall with hypereutectic, .030" top ring gap, .035" second ring gap, 9.8:1 compression ratio. Valve train is designed to handle 6500 rpm, though it'll never see it.

Those rotating assy kits don't appear to come with a cam. Your mention of a valve train being capable of 6500 and

But here's my problem...........top speed run (WOT, flat water, perfect trim) she's tulipped the intake valve on #3 cylinder twice on me now.

makes me think of the "wrong" cam being in there.......... although I don't think the wrong cam would cause a valve failure it could result in some reversion......I just throw this out there because you didn't mention what camshaft you did use. if you used the original EFI cam, that might be a different issue.......

Now having said all that, as detailed and meticulous as you have been with the induction system........I suspect you have the cam covered too and just didn't mention it!:thumb:


Cheers,


Rick

 

[BigChris]

Hey Rick,

Cam is comp cam 08-466-8, installed right at 109?ILC, it has a LSA of 113?. I pull 16 inches of vacuum at 750 rpm idle.

https://youtu.be/Fld5DCM9GlQ

Intake valve on #3 "tuliped" twice. The valve got longer overall, so a true tulip. After doing more research mostly at the Offshore Only, too much timing in the Vortec heads will tulip intake valves. As you know, turning the distributor on the MEFI4 system doesn't change timing, it changes a parameter called cam-retard. It was set with a Rinda scan tool (mine) to 45-47?.

AZSM was made well aware of the cam intended to be used, as well as my heads. I just had it with not being able to tune the thing myself without further investing in software. (and not having any confidence in the guy tuning it)

She's now a solid 60 mph boat. It turns a volvo DP with F7 props to about 5100 rpm. I burned about 50 gallons of fuel this weekend at the Chesapeake I romped on her pretty hard. Harassed a 26-28' Donzi with a NA 454 in it and out pulled him by about 2-3 mph on top end. I'm confident my problem is behind me. I can tell I'm pushing the design limits of the hull.

In the previous post, I mentioned I was still chasing perfection with jetting, I did change the secondaries to .113 and she liked it. Did a WOT run for about 40 secs and pulled the plugs, look good. This has moved me 2 "stages" richer in the "power mode staging" and 2 sizes richer in the secondaries. Jetting is real close now, real strong out of the hole, but still a tiny flat spot climbing through 3500.

I think the flat spot is once the accel pump shot is over and right before the secondaries come into full play. I may try one more size up in the power mode staging circuit. I'm thinking a .116 primary jet with a .075 x .042 metering rod. This should yield 1.33% increase in surface area with rods down, and 10.72% increase when the rods up compared to stock jetting of the 1410. (With a .113 jet and .070 x .037 metering rod I'm at 1.82% richer rods down, and 7.95% rods up compared to base)

I'm confident my problem is licked. However realizing how much richer the carb settings are from baseline, the more it makes me think the stock manifold and injectors had no chance to keep up.

I've been using this chart to contemplate jetting changes.

Jet	Primary Jet Area	Rod dia down	Area rod down	Rod dia up	Area rodup	Jet area rod down	% change from stock	Jet area rod up	% change from stock
0.113	0.01003	0.071	0.00396	0.047	0.00173	0.00607	0	0.00829	0	Stock Calibration
0.113	0.01003	0.070	0.00385	0.042	0.00139	0.00618	1.82%	0.00864	4.21%	Option #2
0.113	0.01003	0.070	0.00385	0.037	0.00108	0.00618	1.82%	0.00895	7.95%	Option #3
0.116	0.01057	0.073	0.00419	0.042	0.00139	0.00638	5.16%	0.00918	10.72%	Option #4
0.116	0.01057	0.073	0.00419	0.037	0.00108	0.00638	5.16%	0.00949	14.46%
0.116	0.01057	0.075	0.00442	0.042	0.00139	0.00615	1.33%	0.00918	10.72%
0.116	0.01057	0.075	0.00442	0.037	0.00108	0.00615	1.33%	0.00949	14.46%
0.116	0.01057	0.073	0.00419	0.047	0.00173	0.00638	5.16%	0.00883	6.51%	Option #10
0.116	0.01057	0.075	0.00442	0.042	0.00139	0.00615	1.33%	0.00918	10.72%
0.116	0.01057	0.075	0.00442	0.042	0.00139	0.00615	1.33%	0.00918	10.72%
Secondary jet change
0.107	0.008992
0.11	0.009503	5.69%
0.113	0.010029	11.53%

 

[HT32BSX115]

Wow! Going from a 5.0L "sleeper" to a 383 in that boat would be a huge increase in performance! Your strong holeshot is primarily due to the Duoprop though. I had a 460 King Kobra in my FourWinns 211 Liberator and it was a real dog out of the hole. With the Merc 454(same hp) + Bravo III the difference even now still amazes me!!

Looks like the duration of your 08-466-8 is nearly identical to the "Extreme Marine" 08-417-8 [7] cam. more pictures!

You have really done your homework!!

 

[BigChris]

Your strong holeshot is primarily due to the Duoprop though.

No doubt, and my wife loves the way it backs up compared to the Alpha 1 gen 2 we had on our last boat. She usually drives it on and off the trailer. You can actually steer it in reverse. And it does get tons more "bite".

But when I'm talking about holeshot, I've been doing a bunch of jetting changes. And I'm talking about throttle response right off idle when you immediately punch it. My throttle only has two positions. Combine the huge torque numbers of a 383 with the grip of the duo prop and it's a recipe for pure boating bliss.

As for the jetting changes, I know the carb is a bit "big" (750cfm) for the application and because of that it doesn't have as strong a signal to the jets as a 600cfm would. So I knew it'd take a little time to dial it in. However I felt the ability to throw all the air at it I could at WOT would offset the challenge of dialing it in. The bottle neck in the equation now is the exhaust.

I build dirt oval karting engines, and have a water brake dyno, jetting for a restrictor plate is much the same, you need to go richer because of the reduction in velocity in the venturi. This is me: www.rperacing.com

"Looks like the duration of your 08-466-8 is nearly identical to the "Extreme Marine" 08-417-8 [7] cam."

Yes except with an ILC of 109? instead of 110?, the cam I chose favors slightly more torque, it also has higher lift numbers.

"Going from a 5.0L "sleeper" to a 383 in that boat would be a huge increase in performance!"

Yes it's massive. nthego:

"You have really done your homework!!"

Thank you.

 

[Silvertip]

As for plug numbering on the distributor cap, it makes no difference which terminal you use as long as the firing order is adhered to. You then index the distributor properly (rotor at #1) and crank at TDC on compression stroke when you drop it in.

 

[BigChris]

As for plug numbering on the distributor cap, it makes no difference which terminal you use as long as the firing order is adhered to. You then index the distributor properly (rotor at #1) and crank at TDC on compression stroke when you drop it in.

um.................yeah, thanks for the input. Great stuff there.


Anyway, back to performance testing.

Talked to the folks at Marine Engine Depot about the short comings of the AC Delco Voyager system. Seems as though at 750 rpm, it's already begun it advance curve. They were nice enough to take it back as a return. I mean if you had yourself a complete stock 350 this system might be adequate as it would nicely interface with the factory harness and is a descent upgrade from the Thunderbolt setup. It's also mild enough to really prevent you from hurting the engine in most DIY situations, and not really a strong performer in a performance built engine.

But this wasnt what I was looking for. So I pulled the trigger on the MSD system.

Here are my initial thoughts:
The quality of components: superior to the Voyager hands down.
The cost of the system: about $200 more than the voyager
Performance: Hands down better let me explain.

What I did:
Determined through observation that with this cam and these heads it likes to idle best at about 15? of initial timing. You can simply hear/feel that is smoothest, fastest idle. You then tune idle mixture to achieve maximum manifold vacuum at idle. (google and read on a hot-rod forum, so much easier than the tach method) I get about 16-17 inches of vacuum at idle.
Once I had that dialed, I knew I really didnt want to go over 30? BTDC for total advance. ( I know I started not wanting to go over 28? but she's handled that so well, I felt like....what the hell. )

I then custom machined an advance limiter bushing to .390" O.D. and a .195" I.D. and about .180" tall. This gives me 14-15? of advance.

This leaves me with a total timing of just a smidge shy of 30? BTDC.

All that done, I put her in the lake and romped on here pretty hard. The stiffest advance springs sucked. Went to one light silver spring and one heavy silver spring , (mid range) much better. Then went to one light silver and one heavy silver. This was real nice. That flat spot I mentioned in post #26, that was distributor, because it's gone.

So to summarize:
Idle in neutral 750 rpm
Idle in gear 600rpm
Base timing 15? BTDC
Manifold vacuum at Idle 16-17"
Advance 14?
Total advance 29? and all in by 2000 rpm.
Edelbrock 1410 750 cfm carb
Choke disabled. (adjusted so it never closes)
.113 primaries
silver power mode staging springs (Strongest)
.070 x .037 metering rods (2 stages richer)
.116 secondaries (2 stages richer)
Hot restarts require less than one engine revolution.
Cold starts require 3 pumps of the throttle to prime with the accelerator pump.

60mph top speed
set you in your seat out of the hole acceleration
Fuel consumption is slightly less than the space shuttle.

 

[HT32BSX115]

pulled the trigger on the MSD system.

Here are my initial thoughts:
The quality of components: superior to the Voyager hands down.
The cost of the system: about $200 more than the voyager
Performance: Hands down better

/////////////////////////
Idle in neutral 750 rpm
Idle in gear 600rpm
//////////////////////////
Choke disabled. (adjusted so it never closes)
//////////////////////////////
Cold starts require 3 pumps of the throttle to prime with the accelerator pump.

60mph top speed
set you in your seat out of the hole acceleration
Fuel consumption is slightly less than the space shuttle.

Outstanding!

Couple of points.

Thanks for the great review of the MSD ignition system. I want one for my project truck!

I wonder about your in-neutral idle speed possibly being a tad high............. (don't how well VP cone clutches handle higher RPM though)

I have operated my 454 for 10 years or so with the choke disabled and adjusted permanently open, and also experience 2 or 3 pumps cold and fairly quick starts when hot.:thumb::thumb:

Out of the hole acceleration

DOUBLE the number of blades in the water and the difference is amazing!

Get yourself a fuel flow indicator!

Your fuel consumption will STILL be a function of your "right hand" though and the amount of "Smile Factor"!! (watch for bugs in your teeth!!)

Cheers,

Rick

 

[BigChris]

I've tried getting idle a little lower, and it just hurts hot restarts.
I've had an alpha 1 gen 2 on the last rig, and the engagement of the duo is much smoother even with the idle at 750. It doesnt bang or thud.
When this system was fuelie, I had the idle at 650......

I think the other factor with the duo prop most overlook is the straighten-ing out of the trust, although true laminar flow is impossible here it is much improved compared to a single prop. With a single prop, you've got a rotational component to the thrust. Visualize a tornado on its side, with the slimmest part of the tornado closest to the prop. A duo doesnt do that.

However, while I think fuel consumption is less at lower speeds, I do think I'm giving up some speed up top.

Trailer boats did an interesting article before they went out of publication.
https://www.stingrayboats.com/produc...ws/tb05_11.pdf


What I really love about this rig is it's where sophisticated meets rowdy. Nobody expects this thing to fly. I really need to get a pic of her at 60 mph, you wouldn't believe how much of the hull is out of the water.

 

[HT32BSX115]

I
However, while I think fuel consumption is less at lower speeds, I do think I'm giving up some speed up top.

You'll absolutely use less fuel because of the lower "slip" (it's like going from a regular to a lockup torque convertor....well not quite but you get the idea!)

Everyone says you lose some top speed. With my previously installed King Kobra and OMG 460 it did about 60 at WOT. But that was around 5000 RPM. (1.43:1 ratio and 20p stainless)

The 7.4 + Bravo III (1.81:1, 26p) I have now will do 57mph at 4600 RPM. (but I am now rev limited at 4700 too.... I suppose if I could turn it at 5000 RPM, I would get it right back and more!)

So I didn't really 'lose' much top speed with the similar hp engine. And it definitely uses less fuel all the way around. For water skiing and wake boarding, the speed control and maneuverability at slow speed and reverse are just incredible!

 

[BigChris]

Y
So I didn't really 'lose' much top speed with the similar hp engine.

I think the article I pointed to in post #32 (which is about as close to a fair back to back comparison as we can hope for) indicates a nearly 4% loss in top speed w a counter rotating propeller configuration vs a single prop.

While the trade off is the increase fuel mileage at "normal" cruising speeds from the dual prop .

Pay attention to the table on page 37 of the article.

I can see you're a huge fan of the dual propeller drives, as am I, but don't let your enthusiasm skew the empirical data.

 

[HT32BSX115]

I think the article I pointed to in post #32 (which is about as close to a fair back to back comparison as we can hope for) indicates a nearly 4% loss in top speed w a counter rotating propeller configuration vs a single prop.

While the trade off is the increase fuel mileage at "normal" cruising speeds from the dual prop .

Pay attention to the table on page 37 of the article.

I can see you're a huge fan of the dual propeller drives, as am I, but don't let your enthusiasm skew the empirical data.

But that 4% is not the same from one boat to another (and in the TB comparison, it was 2.3 mph and actually 3.8% to be precise).
I mention the exact difference because 2.3 mph is not really enough difference to even be significant. It's also interesting that the difference at every 500rpm "test" point is approx 1mph difference (Bravo III slightly faster) and that 2.3 mph difference is only at 5000 RPM.


Again, I think judicious trimming, tab adjustment, load adjustment might narrow that down even to even less. (and who cares anyway?)

Yeah. I am a " huge" fan of dual propeller drives to be sure. My boat weighs about 5200lbs with the engine/drive, 4 people + full fuel.

My empirical data is that it was a complete dog out of the hole with the single prop drive regardless of the drive trim and Bennett tabs at their optimum settings.......... With similar HP and the contra-rotating props, it was (HUGE) different story.

In view of the TB article (and I think they mentioned it) a boat that weighs roughly 2000lbs less (~3000lbs) might not get enough benefit from a Bravo III/VP DUO to make it worth the extra cost! (and extra prop cost etc)

And with that, I absolutely agree!

 

[BigChris]

But that 4% is not the same from one boat to another (and in the TB comparison, it was 2.3 mph and actually 3.8% to be precise).
I mention the exact difference because 2.3 mph is not really enough difference to even be significant. It's also interesting that the difference at every 500rpm "test" point is approx 1mph difference (Bravo III slightly faster) and that 2.3 mph difference is only at 5000 RPM.


Again, I think judicious trimming, tab adjustment, load adjustment might narrow that down even to even less. (and who cares anyway?)

Yeah. I am a " huge" fan of dual propeller drives to be sure. My boat weighs about 5200lbs with the engine/drive, 4 people + full fuel.

My empirical data is that it was a complete dog out of the hole with the single prop drive regardless of the drive trim and Bennett tabs at their optimum settings.......... With similar HP and the contra-rotating props, it was (HUGE) different story.

In view of the TB article (and I think they mentioned it) a boat that weighs roughly 2000lbs less (~3000lbs) might not get enough benefit from a Bravo III/VP DUO to make it worth the extra cost! (and extra prop cost etc)

And with that, I absolutely agree!

What exactly is your boat.

 

[HT32BSX115]

What exactly is your boat.

It's a 1987 Four Winns 211 Liberator. My brother bought it new with a 460 King Kobra installed, I bought it from him in 2005

The 460 KC was rated at 340hp (crankshaft) and the other option was a Mercruiser 454 + Alpha rated at 330hp (Crankshaft) ..........He of course wanted the additional HP (like it would make a difference ) so he bought the OMG460 model.

After I got it, I discovered that I couldn't buy exhaust manifolds, coupler and certain drive parts.................so I found a swinging deal on a complete 1997 454/Bravo III from a wind damaged 24ft Bayliner and swapped it all out.

 

[BigChris]

Did you redo the transom when you did the swap, that boats almost 30.

 

[Bondo]

Did you redo the transom when you did the swap, that boats almost 30.

Ayuh,..... Rick is into those darn New boats,.....

My tinbarge is a '74,....

The hull I'm still retro-fittin' is a '73,.....

The Newest hull I've got is an '85,....

The '74 I replaced the transom in, 'bout 20 years ago, when I yanked the 140/ MC-1 out, 'n dropped in a 4.3LX/ Alpha 1,....
The '73 is still original, 'n solid, through I'm still sorta rebuildin' it, as in had an ole stringer drive in it, gotta fill the big hole to make a little hole,....
The '85 had the deck replaced before I got it, the transom is still solid though,...

Just finishin' up a '69 Hi Liner for a local doctor now,....
Transplanted a '86/ '87 350/ Alpha into it, had an ole 302/ 188 drive,...
Transom appears original, donno if it's been replaced,....

 

[HT32BSX115]

Did you redo the transom when you did the swap, that boats almost 30.

Hey! It's a "young'n"!!.... It was only 18 years old when I got it!!! [I am thinking of moving up though....I've been looking at 2000-2003 Formula 330ss 's !!]

I was worried about the transom too! AND when I pulled the old stuff out there was water in the bottom of it when I removed the drain fitting but there was luckily no rot. I did do some reglassing and sealing of the engine compartment area though and had to re-do the engine mounts. 454 mounts are in a slightly different position. The bolt-pattern for the Cobra and Mercruiser transom mounts are the "same" layout, except The Mercruiser Bravo transom mount has 2 additional mounting studs.........So I needed to drill 2 additional holes in the transom. All in all, the installation was pretty easy.