Rebuilding a 1998 Mercruiser 4.3L Need advice please.

[Tail_Gunner]

Re: Rebuilding a 1998 Mercruiser 4.3L Need advice please.

And the 276 which i now wish i used....oh well that may have been the straw that broke the camel's back.............NOT. 55 degree's a bit hot huh.

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http://www.mefiburn.com/sc/details.asp?item=mefitune


Give them a call explain with great detail your build and the type of work done to the heads, very good tuner's id say the best around but that invite's critism...They just tuned a run of Camaro's for GM using mefi 5 module's...they can handle the boat...

 

[RSBJ]

Re: Rebuilding a 1998 Mercruiser 4.3L Need advice please.

Tail_Gunner, I will say that the dyno software software I ran till I was sick of making changes was quite different than those Comp Cams charts they have on their website. Obviously lots of differences in basic engine set-up and parts, but I would guess the CC charts are old, with outdated heads. The dyno simulations, which are supposed to be very accurate show the same bottom end, but start to diverge past 3500rpm. If you have Vortec heads, or something that flows around 230In/160Ex, I'd be willing to bet your torque peak is around 4000-4150rpm and Hp is around 5400-5500 with 10-15 more of each.

My cam lift looks like it's going to end up right around .530" regardless of what lobe/rocker ratio combination I choose. The Vortec intake ports actually start to stall past .450" on a flow bench but flow only goes down a few percent by .550. I'm going above .5" for three reasons. 1). If I want an aggressive lobe, I can't go any lower than .500. 2). I have made some significant changes to the Vortec ports (even when I said I wouldn't!) that should delay the stall to .500". 3). By far the biggest reason; I want the lobes opened to .400" as fast as possible to get the ports flowing as soon as possible. The valve will spend so little time at stall lift, that the benefit of getting them opened to good-flowing lifts quickly will pay dividends at all rpm's. So.....the 56-450-8 with a 1.6 rocker (.533). A lobe out of their master lobe catalog I've been eyeing, .534. Or one of my design, .520".

Funny, I spoke with a Bob at MEFI Burn 5 weeks ago and we chatted about what I was doing. Nice guy, and I like that the programmer will come with maps pretty close to where I should end up.

 

[Tail_Gunner]

Re: Rebuilding a 1998 Mercruiser 4.3L Need advice please.

Here's a link to vortec heads more than probably the bible of the design. Its a very long read but there is a lot of info buried in there and mush. but in the first page or two its very intresting

Vortec Cylinder Heads: The Definitive Guide - NastyZ28.com

Part 4: Gary talks about the HP potential and airflow of Vortecs. That topic lay's it all out.


How are you going to approach the increased lift issue...using comp's spring's and retainer's or machine the heads?

Your estimate of my power band is very close. the engine runs out of steam at 52-5300..that up from a 4700 peak..but from 3000 to 5000 its two stroke time that is it feels like a two stroke.

Those cam graphs and link's yes there 350 with stock heads...not 4.3..:laugh: There is no reference data for a 4.3 so ive used 5.7 info...probably not the best ideal but you have to use something..and a 5.7 is almost identical less a few cylinder's. Really its all centered around the induction system and what you can get away with reliably. The great thing small blocks are easy to build big blocks it requires head changes and cam's now once that done then its forged internal's to support the top end and that's money.

 

[RSBJ]

Re: Rebuilding a 1998 Mercruiser 4.3L Need advice please.

Quick update. The engine is being put together over the next week. Piston to head clearance is .030, ring end-gaps are .014 first and .020 second. Piston to wall is .001, but should quickly become .0016 after some of the wear coating........... well, wears. Compression is 10.55:1.

I spent 4 hours measuring camshaft timing last night, here is the seat timing allowing for the .006" lash Comp designs in:
IO 22 B, IC 63A (only 265 when it should be 268, so my best effort still had some inaccuracies despite hours of fine-tuning)
EO 71B, EC 20.5 (same as intake, my measurements came up around 2-3 degrees short as it's supposed to be 274, but came out 271.5)
ICL 109.3. Speaking of that, check out the picture of my measurements. 6 times I came up with 109.25 (I wrote down the first 5). The only noteworth thing is the chain is pretty tight and I expect it to stretch and stabilize around 110 pretty quickly.
LSA is 113.
Cut guides, Comp beehives, 1.5 aluminum rockers, and new pushrods round out the top end.

Check out the picture of the block deck with #1 at TDC. My machinist was adamant about putting it 5 down, but I told him if he wanted paid, to put it as close to zero as absolutely possible. I haven't checked the other cylinders yet, but #1 is .0000"!! I am using a Cometic .030 gasket.

Lastly, my daughter took a pic of me. Now you can put a (ugly) face to the obsession.

 

[Tail_Gunner]

Re: Rebuilding a 1998 Mercruiser 4.3L Need advice please.

Yes obsession could be a way of looking at it. You used flat top's and your still planning for 10 plus compression? A question your PTW clearance is so tight it's seem's your going to run into problem's...Are you building for a cold block and hot piston's or is it just a discipline. What cam did you end up with and you went with 1.5 rocker's..why not 1.6 the cost would have been the same.

Do you plan to burn your own tune or are you going to have OBD do it...when your done if you could save the tune and maybe share it with me that would be very interesting.. watching your detail on the engine I am intrigued on how your going to tune the that thing.

John S is not around it would be interesting to get his take on how tight your building that engine..Kieep it going.

 

[RSBJ]

Re: Rebuilding a 1998 Mercruiser 4.3L Need advice please.

A few factors on the compression: 1.My altitude is 1000' ASL and the temps don't go above 90. 2.The marine thermostats are 140*, so that's about a half point right there. 3.Our pump gas is 93 and I don't mind mixing in a little unleaded 110 if I'm off by a little. 4. A big chunk of my compression increase is in a tighter piston to head clearance, which supposedly suppresses detonation.
It's been found that detonation is prevalent in the chamber where .050'' to .100'' of mixture lies. The SBC has squish right there, with mine measuring .069" around the narrow raised ring of the piston, and around .100" everywhere else. That's gone, down to .030" static/.008?" or so running at 5500 rpm.

The piston-to-wall clearance is as tight so the piston-to-head clearance doesn't change much as the piston rocks at TDC. These forgings measure .016 smaller than 4.03, so that must be the tightest Speedpro wants them. This engine will be broken in with full throttle, cool running; extra fuel I'll program in will keep it relatively cool. This engine's #1 and 3 cylinder spark plugs threads will be getting a workout as I plan on lots of bore scoping to keep tabs on what's going on with 4 things: 1 Piston to head clearance, 2 top ring end-gap issues, 3 piston to wall issues, 4 burn propagation.

Good question on the 1.5 vs 1.6 rockers. The lobes I chose have extremely aggressive ramp rates, and at .535", they are already well above Vortec intake stall lift of .450". I don't mind being above stall lift, as the stall doesn't degrade cfm a lot, and the valves are opening to their sweet spot faster, but I don't think everything in the valve train is up to these lobes at 5500 rpm with 1.6's. The biggest doubt would be the Comp pushrods. As you've figured by now, I am extremely aggressive, but I held back here in part because I see aluminum heads and 1.6's in it's future. That's probably 2 years from now, but taking the heads off isn't that big of project.

I'm going to tune the TBI, but I'm told the MEFIBurn is going to need a little fuel before I go set sail and that should get me pretty close. AFR gauge should get me within 1-2% eventually after break-in.

Thanks for the encouragement, if we go back 5 months ago to my first post you'll remember that the intent of this log is to create a recipe for the next guy and save them the hundreds of hours of learning and research I've done. Maybe back off PTH, PTW, compression, and ring gap a little for larger margins, but that won't change the end result much and the fuel and ignition trial and error will be solved. In essence, "set aside $2,???, buy this and do that, and expect to spend ?? hours doing it". I've taken 8 gb of pictures and video if anyone needs a little coaching.

 

[Tail_Gunner]

Re: Rebuilding a 1998 Mercruiser 4.3L Need advice please.

Yes post what you have done Iboats luvs pics and a story. Start a new thread one with continuity this one is all over the place.

 

[RSBJ]

Re: Rebuilding a 1998 Mercruiser 4.3L Need advice please.

Well, I was hoping to update this thread with some numbers, but I can't even get as far as tuning the MEFI with the MefiBurn software! This software was written some time ago, and there isn't any instructions for an operating system of the last 5 years and MefiBurn's website is down.
Anyone here know how to program this thing, or how to get in contact with Bob or anyone else at MefiBurn? Very frustrating to say the least.
Thanks,
Rick

 

[Tail_Gunner]

Re: Rebuilding a 1998 Mercruiser 4.3L Need advice please.

Well, I was hoping to update this thread with some numbers, but I can't even get as far as tuning the MEFI with the MefiBurn software! This software was written some time ago, and there isn't any instructions for an operating system of the last 5 years and MefiBurn's website is down.
Anyone here know how to program this thing, or how to get in contact with Bob or anyone else at MefiBurn? Very frustrating to say the least.
Thanks,
Rick

Hey long time no see...Dont stress this out there are only two tables that you really need to worry about. Timing at idle a little advance to soften the cam and from there its's as simple as adjusting the the pulse rate every few hundred rpm. So do this give bob a call 888- 469-3274 ask for bob...expalin your build and ask him to do a remote tune. All you need is a lap with internet. Once you see how he adjust's the table's it pretty much down hill just math calc's.

OBD Diagnostics, Inc. - Custom MEFI Tuning

Remote tuning

We can tune your controller remotely, anywhere in the world, if you have purchased our MEFIburnTM software and you have a high speed internet connection while connected to the vehicle you want tuned. You will be able to watch your laptop's screen as the MEFI calibration parameters are changed and saved. Clear descriptions of what is being done will be explained as it is happening. Our price for remote tuning is $250. Call or email us for details.

The above is very simple old tech he has just updated making custom tuning on the water very affordable

 

[RSBJ]

Re: Rebuilding a 1998 Mercruiser 4.3L Need advice please.

Reached Bob, and I have put a first-time best guess fuel and ignition map in.
I can't say enough about how much better this engine runs compared to the stocker, it's an absolute blast to drive!! It idles at 600 rpm, with the very slightest hint of a lope, and runs on top like I never thought a 4.3 could. I had an aluminum 21" prop on it, so very big for a 21' boat that weighed 3700 pounds with people and a full tank of gas, and it went 55mph, still 500 rpm and 18hp below it's power peak of ~5100. Again, just a rough guess at fuel and ignition, so hopefully more to be had there. This boat last year went 48mph on a 17" prop when I had the weight around 3250# (Me, my wife, and around 10 gallons of fuel) and with nearly the same temperature and baro. I'm hoping to max the speedo at 60 in a few weeks by getting the weight back down to 3250 and after the engine is broken in and can sustain 5250 rpm without the tight top rings butting. At equal weight, my boat should be around 11-12mph faster than last year. Keep in mind my boat has that rough coating on the bottom that prevents crud from sticking to it, but apparently also costs it around 2mph on top.

If 12mph was all there was to report, I wouldn't be smiling ear to ear like I am. The real payoff I found was cruising on the 21" around 3000 rpm and 36mph and nailing it. The tach immediately went to 4000 rpm, making a sort of growl past 3500, and continued to climb to 4650 as the speed of the boat caught up to the prop slippage. It was so fun, I kept doing it over and over under the auspices of breaking in the engine when my wife questioned me. Last year, I didn't know what prop cavitation was, but a few days ago, I got to know the feel and sound of it quite well as my engine had plenty of power to do it.

The intent of this thread was to create an outline of do's and don'ts on how to get V8 power out of our V6's and I have to say I think I've accomplished that. Others my want to back off my compression ratio of 10.55, or piston to head clearance of .030" or alter the cam by a few degrees here and there, but I believe the basic outline is there. Hopefully in a few weeks I'll have experimented with the fuel and ignition timing enough to have some numbers I can trust publishing and finish the outline.

Speaking of, I did end up going the Edelbrock 2114 route. As you may know, this isn't made for EFI, but I made it work by grinding out some of the inlet. See the picture of one side modified, and the other as-is out of the box.

 

[Tail_Gunner]

Re: Rebuilding a 1998 Mercruiser 4.3L Need advice please.

Very glad to hear the report...reading your performance description does the word two stroke come to mind and from a 4.3. In regard's to high CR ive never seen nor heard of such tight tolerance's until now and i am glad to see it is working out.Bob at OBD is a very talented person and very generous with his time and knowledge...Did you advance the intial timing 3 degree's to smooth out the cam?? And the cam you used the 266 hr did you not?

I believe you will find adding a 2-4" spacer will sharpen the overall response...the more plenium volume the better that 4.3 will breathe...until you lose velocity that is. So did you calculate your own curve's or did Bob set you up

 

[RSBJ]

Re: Rebuilding a 1998 Mercruiser 4.3L Need advice please.

Funny, as I was going to describe it as a two stroke, but I didn't want the impression of a mushy bottom end, nor the peakiness.
I haven't touched the ignition timing below 2400 rpm.....yet. This was a quick and dirty reprogram as we were expecting rain all week, but the radar showed a window off opportunity when I was expecting it.
The cam I used was one I spec'd out of Comp's lobe catalog. I used their EFI lobes, which have extremely aggressive ramp rates. I decided on 268/272 .535" 112.5 LSA. It is installed at 109.25 ICL for now, though I'll probably retard it 3-4 degrees in due time.
I read an article about installing a 1" spacer and the benefits to the performance it brought, but it appeared to me that the 2114 had a significant spacer built in. It had to be somewhere around 1" compared to the marine intake that came off of it. Do you think there's a little more midrange/top end to be had with a spacer on top of that? 60 is going to be awfully tough,even at 3250 pounds and a stainless prop, I'll take any help I can get!

 

[Tail_Gunner]

Re: Rebuilding a 1998 Mercruiser 4.3L Need advice please.

Performance Intake Manifolds


Given the two-planes' apparent advantage at lower air speed, what about as things get moving faster at higher rpm? The first consideration is the basic runner layout itself. Since the two-plane connects cylinders firing 180 degrees apart--given the firing order inherent in a V-8 with a conventional two-plane crank--the runners have to cross over from side to side. This is physically accomplished by splitting the runner layout in two horizontal planes (thus the two-plane name), with runners from one side routed up high, and the other side of the manifold having runners passing underneath the upper runners. The compromise comes in because there is only so much height that can be practically engineered into the manifold if it's going to fit under the hood.The upper runners generally have a nice straight approach into the head's port, while the lower runners aren't usually as fortunate. Secondly, since the plenum is divided, the volume is necessarily halved, and plenum volume is an important resource for the engine to draw on as the rpm increases. By necessity of the design, there is a disparity of plenum volume, with the low plenum having more room for a more generous plenum with a better transition from the plenum into the runners. The high runners are hampered by a shorter, more abrupt plenum, typically compromising both the plenum volume and the transition into the runners on that side. Benefiting from the available height, the high side of the manifold features an advantage in an improved, more direct runner approach into the cylinder head, while the low side of the manifold is typically compromised by the available height in its runner configuration and approach angle to the head. Due to these constraints, the low runners of a dual-plane typically suffer a flow disadvantage in comparison to the high runners--often substantially so. Nevertheless, many of these potential pitfalls of the two-plane can be greatly overcome with increased manifold height, and well laid-out runner and plenum designs. Ever hear of "high-riser" intakes?

A final consideration with a two-plane concerns the very division in the plenum that defines this type of intake. Each side of a two-plane divided-plenum manifold has only half of the carb capacity to draw on (a primary and a secondary barrel), compared to a single-plane where the whole carb is wide open to whatever cylinder is drawing. The net effect on carb capacity requirements isn't as dramatic as it may appear, since with a single-plane, the carb is being drawn on by an induction pulse hitting the plenum every 90 degrees of crank rotation versus every 180 degrees with the divided plenum of a two-plane.



When GM hot-rodded a 4.3 first they supercharged it...quick bolt on and finally they added that ram intake both are improved induction. To bad they didn't produce some of those ram intake's but notice the volume it has....everything I have read and tried to implement was based off a old head porter's comment's on horsepower. ive lost the link and have never been able to find since but the essence of the tutorial was think of indcution as a channel that the river flow's in ...he wanted all the bend's and curves (Runners) to be smooth and swooping as to not create any turbulence which slows down the water or air. And looking at how he created a actual channel in the runner's it was very apparent to what he was talking about.

A large plenum or spacer is merely a reservoir of air the trick seems to be how much before it loses velocity when you cut the divieder down you doubled the plenum..Now the ramjet intakes have a lot of reservoir and GM did get 270 hp out of that engine same displacement..it had to be cam valves and intake in the end it just all tinkering but I don't believe you will hurt the engine with that power the old typhoons ran big boost number's with there 4.3's and they held together well. AT 109 that engine should be a bit peaky but there is little overlap so reversion should not be a problem...

http://image.popularhotrodding.com/f/9018552+w750+st0/0601phr_intake_05_z.jpg

Ohh as to prop's look at the stilleto or turbo line, what they do that other's seem to lack is provide a lot of lift overall lift. In other word's less wetted surface high speed's and they consistently provide lift until about 4500 lbs at that point they seem to become like the rest of the crop. Solas HR titan line will provide with a great prop in even pitches's if you find yourself at a 22 pitch..Give me a pm when your there i have some intresting info im sure will make you smile.