Rebuilding a 1998 Mercruiser 4.3L Need advice please.

[RSBJ]

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

Thanks again Tail_Gunner, here is some news. It appears as though MEFI Burn's site is down. I hope it's not permanent, or I will have to find a used one or an alternative. Also, the 2" bore of my TBI is used on engines making much more power than I ever hope to with this engine, so the carb is out. I found a guy in Indiana who slightly mods the TBI's for a little more flow. He should be calling me tomorrow so I can ask him some questions about the mods, though I don't think I'm going to change them in the end. As far as the manifold, the only question I need to answer is Edelbrock 3713, or 2114 with the adapter plate. I will call Edelbrock tomorrow, but I'm pretty sure I already know the answer to my question; what will make more power in the mid and top? It should be the 2114 with a TBI plate.

On the exhaust side, we are so limited with these 4.3's. I think I'm just going to call Extrudehone here in Pittsburgh and see if there's anything cost-effective they can do with the stock ones. I won't be expecting any miracles regardless.

In the next few weeks, I should have my heads done, block bored and finished and all of my parts ready to bolt on.

 

[Tail_Gunner]

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

MEfI site is back up i doubt there going any place soon. What i was trying to illuminate your existing manifold will work just fine...adding a two inch spacer will increase plenium volume and will aid it. If you must do a manifold the 2114 would be the choice.. Modding the tbi just a opinion here it is so over built for the 4.3 why.... Here is the informative place you will ever find for tbi tech TBI - Third Generation F-Body Message Boards

There is someting called the Ultimate tbi mod's..one step is to raise the injector pod off the body a bit. Makes for better velocity..does it work..dunno dont have the room to lift anymore under the sunpad. Looking back Volvo and Merc really overbuilt the 4.3 if thats the thought...They sure made it upgradeable with little effort as to exhasut....:sleeping: little to be gained the heads simply dy at 5200... fall on there face... run out of steam etc etc etc..

However you want to run 10/1 that's scary stuff for marine and very scary for the 4.3. Dunno why but most builds stay at 9 something with that motor and i have a pdf file that shows they retard the timing on the 4.3 compared to the 5.7..and the heads are the same. Pistons of first choice would be these...they would aid in a high CR motor...wait and see if Bondo or John S respond

http://www.summitracing.com/parts/uem-kb142-060/applications

http://www.boatfix.com/merc/Techbk/95/95HGB4.PDF
Timing tables for marine motors

 

[Bondo]

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

See the two head bolt holes, go straight up to the water passage. That web in the passage has the crack, but I didn't know it at the time so I didn't scrape off the remnants of the head gasket and you can't see it. When I go back down to the shop I'll take another pic.

Ayuh,... Repairin' a block as common as the 4.3l,..?? I donno, but I'd just find another,...
'course, I can't see the cracks, 'n donno what yer Machinist has in mind either...

TG is right 'bout the pistons,... Goin' to a D-dish gives the best bang for the buck, with Vortec heads, 'n a tight quench,...
A quench of .040/ ,o45" is 'bout ideal, if ya keep the comp. ratio to 9.5:1, or less, you'll have No problems...

Hopefully, John will be along,... He's 1 Sharp motorman....

 

[RSBJ]

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

Again, thanks you two. My machinist, who's owned his fairly big business for 30 years, only lives a few houses over. I know where to find him so-to-speak. He's done work for me on other projects in the past, so I don't think he's going to screw me. If he says the cracks are harmless, I believe it. I will get a pic to share though.

In fact, he's too conservative for me. I wanted .030" quench, and he said not to go below .035 even though one guy built a SBC at .024 quench and ran it to 7000 rpm without any mashing of metal, so we are meeting in the middle at .032 for my engine. Same with piston-to-wall clearances of .002875". I will be getting forged, flat-top, two valve relief, .030 over pistons that specify .003 PTW. I wanted .00275, and he of course wanted the manufactures spec of .003", so we met in the middle. Of course he can't measure that fine, but we understand each other and always have a laugh at my absurd specs.

I know you are leery of my 10.5 compression, but that's with a 210/215 cam, 93 octane, 1250 foot elevation, and mild temperatures of 88 or cooler. If I run a 206/210 cam, then the compression will sit around 10.3. I mentioned a figure as high as 10.75 in my first post, but that was with a 215/220 cam that I don't think will be a good match now that I'm staying with the stock TBI and manifold so I've adjusted it down.

As to compression, what I don't get is how the stock 9.4:1 engine can run fine on 87, yet everyone, my machinist included, huff and puff when they hear 10.5 on 93? With the tight quench, bigger cam, and 93 octane, I would think 11.25 would be safe but there has been such an outcry I've had to meet in the middle.....again. I have a history of overdoing compression (15.4 in my R1 motorcycle, 10.4 in my Tecumseh 5hp mower, 9.5 in my Briggs snow blower) so I need some restraint I guess.

 

[Tail_Gunner]

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

Those are odd duration's..11.25 CR im afraid your building a moby ****...aka thar she blow's...Just kidding.....ummm no dont think so.

 

[RSBJ]

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

The injectors are already held up by a 1/4" black spacer, and can't be raised any further without fuel spraying out of the venturi. Funny, as that was a question I had as soon as I saw how close the injectors were to the mouth of the inlet.

Here is the 266HR camshaft data: 56-450-8 - Magnum The 210/215 numbers I mentioned earlier are the .050 duration numbers.

Advertised: Intake opens 25 BTDC, closes 61 ABDC. Exhaust opens 71 BBDC, closes 19 ATDC. .500" lift In/Ex. Lobe separation 112, intake centerline 108. Rpm range 1800-5000.

Can anyone backup their claims I am going to run into detonation? Again 9.4:1 on 87, but imminent danger at 10.5 on 93 with internal mods that should allow a half point higher alone? 87 to 93 should allow a 15% increase, and the tight quench, and longer duration cam another .3-.5. I should say one of the bigger benefits of a tight quench is more turbulence on the compression stroke, which speeds up the combustion process. So I plan on retarding the ignition 2-3 degrees to make up for the faster burn. I will experiment on what advance gives the best power/speed, but 2 degrees retarded from the base is probably where I'll end up.

 

[Tail_Gunner]

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

Thats the pod spacer never went that far but there it is... The 266 has 4 less degree's of overlap than the 270 and less lift in the end its is your decison and what you feel comfortable with..The xm 270 is a v8 grind and can be ground for the v6 at the same price call comp cams and talk to them.. High compression...if your boat is heavy or you load it down...not good but again if you know how to build it to survive..merc's racing doesnt run in the 10.s

The 270 does not revert or show's signs of reversion in my volvo v6 but the exhaust has flared elbow's and the riser's have some kind reversion valve..advance the timing at idle..with the mefi..this may all had something to do with it...Remeber reversion take's place below 1200 rpm (exhasut reversion) and i dont put around..1500 rpm gets me below the no wake zone.

I just took mine to the edge prepared for thru the hull exhasut..it just didnt need it so far...better look at my exhaust again for water trace's..:lol:

Below is a link on how to modify your heads for the increased lift without machining.

http://www.s10planet.com/forum/showthread.php?t=14790&

http://www.carcraft.com/techarticles/vortec_valve_spring_upgrade/

http://www.pacificp.com/forum/viewt...&start=0&sid=72a2f10f8cac040856d21288c9eebedd Great thread

As to high Compression raito's have a good read: http://forum.grumpysperformance.com/viewtopic.php?f=52&t=727&hilit=compression+ratio

 

[RSBJ]

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

Just wanted to post an update on my "V8 power with V6 weight and V7 fuel burn" engine build. Block is bored and honed, I am bringing it home to do the measurements to set the deck height tomorrow. I have run hundreds of simulations with my parts and specs, and I feel pretty confident that the engine should be making around 275hp at 5300 rpm with a 300 rpm overrun capability. Please look at the one chart I have made based on those simulations. The red line shows what the engine should be producing, along with the stocker in blue, and a green line representing my worn stocker. I am looking to extend the RPM range up by 800 ticks or so from the stock 4.3; this will let me run one size smaller prop, while still increasing my top speed from 49.5 to 56. It should take around 33% more power, which I will have, to go 13% faster, but I could be off a little one way or another. A lot depends on what I want to do that day, but if you look at the chart I have made and included here, it looks like a 19 inch for a medium load, and 17 for a heavy load will put the engine at it's peak for a cruise.
One picture is of the piston cutouts resting on the cylinder head. See how the squish pad doesn't match either set of pistons I have! I am frustrated that you can't buy pistons that match the shape of the chamber without spending $1000 and having to run .0045" PTW.
Another picture is of the pushrod pinch in the intake port. Casting thickness is around .185", allowing me to open them .100".

 

[Tail_Gunner]

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

I'am confused ... The velocity's in the chamber under compression stroke are huge...the squish band is for flame propagration.. what would lineing up have to do with anything. That piston is ramming home the charge...Or is your concern with the induction stroke...check the timing of the intake valve at opening.. the piston does not come into play...other than just drawing in the charge.

 

[RSBJ]

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

Knowing that the point of highest combustion pressure for most piston engines should occur around 15 degrees ATDC for best power/economy, and the flame continues to burn at the farther reaches from the plug till some time after that, I think it is safe to assume the flame front has not reached the squish band at TDC. I could be wrong, and I willing to learn if I am, but the tighter squish bands more forcefully eject the unburned mixture towards the flame front or spark plug; creating more turbulence and a faster burn. Look at the picture I included, it clearly shows that the pointy part of the squish pad is aimed dead on towards the plug. This is not a coincidence, it is designed that way. It's a shame that pistons are built without this in mind, I assume to accomodate the lowest common denominator in engine rebuilding or to somehow reduce manufacturing costs by some miniscule amount. I realize that the 99% doesn't care; well I am not one of those. To me, no detail is too small.
Again "racing" pistons from JE have the design I want, but their recommended piston-to-wall is .0045" or even more depending on the application.

 

[Tail_Gunner]

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

GrumpysPerformance.com • View topic - FLAT,DOMED OR POP-UP PISTONS DESIGN

So the keith black piston's dont align correctly as illustrated..That is crazy????

Actually this is above my paygrade if i am reading this right..Go post over there with the question...i will be watching. Are you trying to build a engine like a circle track engine??? Makes good sense but i have not been able to find any good info on that subject..but those guys make some crazy big reliable power with v6's.

 

[Tail_Gunner]

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

As to big power look at the timing curves on a v6 very weak page 12

http://www.boatfix.com/merc/Techbk/95/95HGB4.PDF

Another big speed bump is the intake manifold..i posted a pic of a truck it was the 4.3 zz. That engine was 270 from the factory..It has a Ramjet intake. Get by those two speed bumps and 300 is pretty easy today.

 

[RSBJ]

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

I am sorry Tail_Gunner, I should have said I can't find forged pistons with the proper shape. I did look at those hypers, but I really need forged ones as they will withstand light detonation whereas hypers will not. The KB forged are still considered racing pistons and require the bigger ptw clearance. At 10.5:1, forged they will have to be, but Speed Pros as they require a more normal .0015" clearance.
Thanks for the links, they will come in very handy soon!
As to the intake, I am going to go with the Edelbrock 2114. I thought about keeping the stock marine one, as it is known to be a pretty good performer but it's quite rusted (and heavy). It looks like the TBI will bolt right on without an adapter plate.
What are your thoughts on the stock 454 TBI and the Ed 2114? I may have to look into that Ramjet intake, 300hp will get me awfully close to burying the speedo!!!
I'm not familiar with circle track engines, so I'll do some reading to see what parallels I have with those engines.
Thanks again,
Rick

 

[Tail_Gunner]

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

2000 CHEVROLET 4.3L/262 ICON Premium Forged Pistons - SummitRacing.com
That should work give KB a call.

The marine intake and the 2114 are the only game in town so what are you going to do..Find a 1 or 2" spacer to open the plenum up. You want the engine to see both injectors a dual plane will split them up.As to the Ramjet intake there are none. GM never released the 4.3 zz engine and only made one...But you could cut up a 5.7 and weld it back together....:laugh: It's actually been done.

Your clearance issue is intresting..Now i would really take that to grumpy's and post a thread. Marine blocks are colder than automotive and the piston is literally bathed in fuel and again cooler oil..very rich afr's.Hmm you literally want to squezze this little v6 dont you.

I wonder where John S. is at..and a few other's...YOOO JOHN

KB Performance Pistons-Engine Building with KB Pistons

KB Performance Pistons-Bench Racing

Not being critical but your pushing a v6 pretty hard...GrumpysPerformance.com • View topic - piston to bore clearance

Finally found that old intake mod

Photo and image hosting, free photo galleries, photo editing

And remebered why i didnt use a 2114 its a dual plane and they split the engine or the carb tbi etc and could cause fuel distribution problem's. Now its been done in cars...a lean burn in a car can be tolerated not a good ideal in a marine engine. The marine intake for the v6 is actually a single plane with a divider...now why would they do that when a dual plane does provide more low tourqe. The only thing i can think of is fuel distrubiton. And may have a advantage with tbi...tbi does not rely on a signal like a carb nor atomization. it couold be very possible that it would provide the same low tourqe as a dual and the added benefit of higher flow rates.....I can turn my v6 to 5500 and it pulls hard all the way there.

 

[RSBJ]

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

Thanks for the info regarding the intake. I may look into a 2114 but cut the divider down some or add the spacer. How much to cut down? Who knows, but I would keep it very close to the dimensions of the marine intake that came off of it.

I am two months from being on the water, but what do you think is the biggest prop the boat can reach plane with? I am looking to break-in the engine with the highest cylinder pressure possible, which would be WOT, at 3800-4000 rpm. I was thinking a 22 or 23, maybe 24 but I have doubts about the 24. Again, a 1998 Regal 2100LSR that's 2,900 pounds empty with a stock power curve at planing rpm (2200-2400). Figure 400 pounds of fuel, equipment, and me, so 3,300 pounds. I'll error to the smaller prop, as I can always add weight with fuel or ballast.

Thoughts?

 

[Tail_Gunner]

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

What cam are you using, even a marine cam will turn a engine to 4800....4000 wot and you will badly lug a high compression motor

 

[RSBJ]

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

Tail_Gunner, I am trying to "lug" the engine for break-in. In short, when my dad owned a flight-school in the 90's I was in charge of flying the engines the first 25 hours and adhering to a strick set of guidelines printed in a booklet by Avco-Lycoming, the manufacturer. Now I realize an air-cooled aircraft engine and a Chevy are very different in application, but the process of breaking in rings is mostly the same. Our leak-down readings were always around 5% post break-in. To summarize what the guidelines were, run the engine with high cylinder pressures, to include staying at or below 7000' (don't hit anything!) while keeping the mixture knob full-rich. The rich mixture keeps combustion temps low, which helps prevent coking the oil. Tiny oil-coked particles will bury themself in the cross-hatch of the walls making it smoother, preventing break-in.

As for the cam, I have not settled on the profiles yet but it should be this week. I'm trying to get Comp to make me a set of custom lobes, but I don't think they will. If not, I'll probably use an aggressive ramp-rate 268In/272Ex profile with the LSA at either 112.5 or 113 and the ISL at 110.5.

I'm going to vary the RPM of course on each run, but here is my outline for the break-in after the 20 minutes at 2000 rpm thing for the cam. I'll mix 10% Sunoco 112 octane fuel to make the tank around 95 octane.

2 minutes 17" prop. Vary rpm and load peaking at 4750 rpm.
5 minutes 19" prop, same.
15 minutes 21" prop, same
Pull a plug and borescope, checking for piston-to head issues before going to a higher rpm.
Repeat 1,2 and 3, peaking at 5600rpm on 1, maybe 2 (that would be around 60mph).
1 hour, 21" prop, 5 minutes WOT, vary load for 30 seconds, repeat.
2.5 hours, 23" prop, repeat.
15 minutes, 17" prop, vary load to 5600rpm.
5 hours, 23" prop, as much sustained WOT as possible varying rpm only for a few seconds.
Reprogram the fuel map to take out the excess, cooling fuel.

Thanks for listening to my rant,
Rick

 

[Tail_Gunner]

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

You wrote a paper on reversion and selected that cam??? Uh uh, if you say so. Seroiusly, it's your boat, build and run anything you like, none of here have ever had any experiance at it...

Many things come into play with reversion. Bubba what degree of overlap occur's @ .050. the static line is important this is not a heavy cruiser squatt'n down with a dangerous high level of water in the y-pipe or above. Google the xm270hr@112 lsa its been used extensively for year's in marine engine's...But with that said that is a agressive cam for marine but quite mild in automotive i need to play around a bit here..

Static line http://www.perfprotech.com/blog/articles/marine-exhaust-riser-height#

Opps i have a 270 in a v6...You would think it's a two stroke not a 4

His engine is also has more flexibility built into to it..it's tbi which does not need as much vacum to tune and he can advance his timing below 1200 rpm effectively calming the reversion pulse's....there is no need for power below 1200 rpm and reversion should not occur above 1200.The mefi system can reprogrammed to adjust both fuel and timing curves.

Seat to seat that cam is only 44 degree's below is a chart of cam grinds

10*-35*: trucks and RV's that require low-end torque and where gas mileage is a concern.
30*-55*: cars and trucks where idle quality, low-rpm performance, good street manners and strong off-idle throttle response are desired.
50*-75*: high performance cars where performance is the primary goal with reasonable street manners.
70*-95*: roundy round, open road race and strip engines that consistently operate at high rpm's
90*-115*: all-out drag-race engines.

Many will tell you the need for low end tourqe on a boat is much like a truck....That is a very bad anaolgy boat's do not even begin to hook up 1/1 like a auto they slip badly..aka prop but here's a pic i took of a common 19' boat at 6mph..no wake speed@ 1500 rpm it hasnt even begun to build a pressure wave that did occur until 1800 rpm. The next time anyone's out there tooling around watch the tach speed relationship and where the boat idles at 5mph and then climbs out of the hole. Now if one was to drop a clutch @1500 on a truck or car yes the motor would flat out stop on a boat who cares. Now with all that said marine reversion is a very bad thing for a boat engine so why gamble....Like anything else it's a risk but it can be a educated risk to.

http://www.michel-christen.com/ExhaustElbows.pdf

Marine Engines Water Ingestion/Intrusion - Background and Checking | Performance Product Technologies

 

[RSBJ]

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

You wrote a paper on reversion and selected that cam??? Uh uh, if you say so. Seroiusly, it's your boat, build and run anything you like, none of here have ever had any experiance at it...

I realize I sounded very stand-offish in the beginning, and I apologize for that. What I didn't say was that my paper was for intake reversion, not exhaust. I didn't say so because it really doesn't matter, what matters is that when the piston reverses direction with the corresponding valve still open, gases get pumped where you don't want them. My point 26 years ago was that, if strong enough, the reversion could cause a carb to meter fuel three times to that reversionary air. One in, one out, and one in again.

I wishfully agree with Tail_Gunner though, and that is that this is a very mild cam by almost any measure. A stock truck/marine grind is around 248 seat-to-seat degrees intake, and if a real hot-rod is 300+, then my 268 doesn't seem so bad. I figured this is about as big as I could go keeping a fairly smooth 700rpm idle. Please also reference my post a couple of weeks ago where I posted a picture of my new power curve overlaid on the stock one, and my worn stock one. You will see I am not giving up any power at planing rpm, which for my boat, is 2200-2500 rpm.

If you think I am overlooking something, please say so. Tail_Gunner has given me some great links to parts (MEFI Burn) and said I should measure the water line; two things I would not have known about as I am new to boating. His input, along with my machinist, was also instrumental in my lowering compression .25.

 

[Tail_Gunner]

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

It has been so many year's since i have built a engine it's beyond me to make any kind of build ideal's that are current or releavant. But what is now apparent or seems to be is your approach to building is very similar to motor cycle or avaition tech....the high ptw really bug's me..the metallurgy in airplane and bike engine's has to be different (expansion rate's). i know imports are built differntlly so be it... but remeber when KB suggest's a spec for marine it one that should be followed..Wtih that said trust me im all ears here im about to play with a 454 from the bottom up. You have taken in account marine black are very cold with respect to auto or air cooled engine's yet higher piston temp's

As to break in every engine ive had and there have been many was much different, Low loads high rpm until the rings seated..aka i wanted to make sure everything strectched propery before the components began seating....I can tell you many times i have taken a american v8 with a hundred miles on it and ran to the redline for minutes in a low gear just to stretch it all out. Sound crazy its not if you knew how many engine's ive broken in it would amaze you..(Indrustry perk) Your protocols for break are very thourgh myself i would just run up and dwon just the same as you but with just one prop.

That cam is a old grind and seem's to be used in mopar a lot, Does it lift over 500 do not count that our you want lift...lift is much the same as increasing valve size and still retaining velocity...that's the voretc true strength. Looking back i was a bit intimidated by all of the cam talk and went size to small i think..

The 270 wich i used..