Rebuilding a 1998 Mercruiser 4.3L Need advice please.

Well, this is only to start. I'm looking to up the horsepower on my general purpose (cruising and water skiing) Regal 2100LSR to 260-270 through 10.75:1 compression, a Edelbrock 1409 carb, and a mild Comp cam and I was wondering a few things.

I wouldn't mind taking a little weight out of the engine, any ideas sans aluminum heads? There doesn't seem to be much margin in the crankshaft, how about a slightly lighter flywheel? The exhaust manifolds are crazy heavy, and the aftermarket doesn't cater the the V6's much, but that seems like an easy target.

How many rpms can the stock rods reliably turn? What should I use to get 5250-5500 rpm?

If I put in a Comp 266AHR or 270HR, how can I get the ignition curve to compensate, especially on the low end where the bigger cam's lower vacuum could cause erroneous readings?

Do any of you have good or bad experience with any of the aftermarket pistons? I need to order those soon to keep my machinist busy.

When I measured the ring gaps, I was getting around .024 top, .030 second. That doesn't seem very worn to me, is it? I was getting 22-37% leakdown and 115-125 psi compression on the cylinders, hence the rebuild.

I've only rebuilt Japanese 4 bangers up to now, mostly motorcycles. I'm impressed with the overall design of the Chevy, which is something I never thought I would say!

Thank you to all who reply with constructive feedback.

Rick

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

RSBJ said:

Well, this is only to start. I'm looking to up the horsepower on my general purpose (cruising and water skiing) Regal 2100LSR to 260-270 through 10.75:1 compression, a Edelbrock 1409 carb, and a mild Comp cam and I was wondering a few things.

I wouldn't mind taking a little weight out of the engine, any ideas sans aluminum heads? There doesn't seem to be much margin in the crankshaft, how about a slightly lighter flywheel? The exhaust manifolds are crazy heavy, and the aftermarket doesn't cater the the V6's much, but that seems like an easy target.

How many rpms can the stock rods reliably turn? What should I use to get 5250-5500 rpm?

If I put in a Comp 266AHR or 270HR, how can I get the ignition curve to compensate, especially on the low end where the bigger cam's lower vacuum could cause erroneous readings?

Do any of you have good or bad experience with any of the aftermarket pistons? I need to order those soon to keep my machinist busy.

When I measured the ring gaps, I was getting around .024 top, .030 second. That doesn't seem very worn to me, is it? I was getting 22-37% leakdown and 115-125 psi compression on the cylinders, hence the rebuild.

I've only rebuilt Japanese 4 bangers up to now, mostly motorcycles. I'm impressed with the overall design of the Chevy, which is something I never thought I would say!

Thank you to all who reply with constructive feedback.

Rick

Click to expand...

Ayuh,.... Yer headed in the Wrong direction,....

Yer Hot Rod ideas won't work with a boat,...
Yer horsepower expectations are too high, as well as the expected rpms, 'n the cam is Way to big...
Compression ratios much over 9:1 will lead to detonation, 'n yer motor will become an anchor in minutes...

Ya need to think Truck motor, torque, built down low, aka: idle to 4800 rpms...

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

^^^^ +1

An automotive performance cam would not be good for a boat (Google "reversion"). Marine cams typically have less overlap and not as much lift.

Your $$$$ may do better with a bigger block and the power will be where you need it - in the low to mid-range.

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

You can throw all the money into carbs/heads and machining, but it'll be wasted. Boat engines require high torque on low end, and they run for hours at steady redline rpm's. They're more like an industrial engine.

It sounds as if you need to sell your current boat and buy one with more horsepower. You'd come out much better.

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

You expect any significant performance increase by removing a few pounds of weight from a boat that weighs a ton and a half?

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

RSBJ said:

I'm impressed with the overall design of the Chevy, which is something I never thought I would say!
Rick

Click to expand...

What did ya think? It was gunna be held together with wing nuts, and bailing wire?

In the auto world, the engine you have planned would be very respectable, and would probably give most V8's a good challenge.
But... As others have said, you can't get away with what you intend on doing in a marine environment. Too much constant heavy load on a high compression engine leads to detonation. Plus you need the low end grunt to get the boat out of the hole (no stall converters, or clutch dumping here). You are limited to around 5K rpm (+/-) by the drive.

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

Your on the right track but a 88 block is not a good place to start. See if you can find a 2000 and up block to start with with vortec 113 head casting's those heads already have screw in studs and are a improved casting. the the XM 270@112 lsa has 6 Degree's of overlap @.050 not enough to cause vacum loss maybe reversion if your boat sits low in the water.

Static line :Marine Engines- Water in Crankcase on a 2000-4.3-V6-Merc

The static line is a measurement of the true water line on the engine to the top of the riser.(example half way up the exhaust manifold.)The way you find the static line is to take a one inch clear hose that's about 15 feet long. You take one end and put in in the water the other end you fill with water and bring it in to the boat. You make a loop in it and hold it up against the engine with the top of the hose above the engine with the loop below the engine with water still in the hose. What you end up with is the level in the hose is the true water line. You then make a mark on the engine usally on the exhaust manifold and you measure to the top of the riser. This is the static line. The water line to the top of the riser. Since the roller cam being used in the marine engine it has made the static line be increased because of the duration of the cam being used.The positive pull on the exhaust on the compression stroke. All engine manufactures are fighting this problem. (Water reversation) The manufactures have redesigned there exhaust requirements when installing the roller cam engine. There have been extentions made that go in between the manifold and risers. New style exhaust flappers. Mercruiser has made a resignator and Volvo has done some redesign on there risers they have tried pulse tubes. Now they have new guide lines for there exhaust requirements. Now they require so much drop with 90 degree turns on each turn.

Now you may want to just turn to a 350 already built it probably would be less expesenvie and more power. Another problem would be all the risers not sure they would bolt up..and a 88 is a old block could be a terror to retro fit to a new cam and lifter's and spring's...in other word's by the time your done you could have a fresh 350. Good luck.

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

How predictable, one person out of six actually tries to answer my questions, while everyone else says do this, don't do that. Is it too much to ask? Guess I came to the wrong place. By the way, I studied reversion and wrote a paper on it.....in 1987.

Thanks Tail_Gunner,
Rick

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

RSBJ said:

How predictable, one person out of six actually tries to answer my questions, while everyone else says do this, don't do that. Is it too much to ask? Guess I came to the wrong place. By the way, I studied reversion and wrote a paper on it.....in 1987.

Thanks Tail_Gunner,
Rick

Click to expand...

Hey dont run off....:lol: There are plenty of people here that can support your project. Just layout your build ideal's i will give you this a 2000 yr roller block will save you money but if you want to do a 88 yr model so be it. I-boats tends to run on the side of caution...

:blue: hmm its a 98... that makes things much eaiser


Well, this is only to start. I'm looking to up the horsepower on my general purpose (cruising and water skiing) Regal 2100LSR to 260-270 through 10.75:1 compression, a Edelbrock 1409 carb, and a mild Comp cam and I was wondering a few things.

So if you use alum heads yes higher compression ratio's are acceptable...but keep in mind boat engines run under high stress all the time. If you ran a injected motor you would have knock sensors and could program in your own timeing curves.

If I put in a Comp 266AHR or 270HR, how can I get the ignition curve to compensate, especially on the low end where the bigger cam's lower vacuum could cause erroneous readings?

The cam comp cam's has a XM series (marine) very high ramp angle's well suited for you app. You can use any grind you wish for that series..The XM 270 is a v8 cam just have them grind the cam for the 6..and the 270 is very mild in the cam world no idle issue what so ever..

Do any of you have good or bad experience with any of the aftermarket pistons? I need to order those soon to keep my machinist busy.

Use a deep dished piston for quench and high compression


When I measured the ring gaps, I was getting around .024 top, .030 second. That doesn't seem very worn to me, is it? I was getting 22-37% leakdown and 115-125 psi compression on the cylinders, hence the rebuild.


Take a close look at your heads...valves springs a little weak?

http://forums.iboats.com/non-repair...-go-my-383-stroker-winter-project-524489.html

Here is a 270 in action valve train a little out of wack but no huffing and puffing at all.


Here are some link's for valve train mods

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

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

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

Thanks again Tail_Gunner. I like that cam in the 383; not too much if the idle quality is being used as a measure. (Note to all you nay-sayers, I know that the 262 will act/idle as if it has a bigger cam in it vis-a-vis a 383 V8, so keep your comments to yourself).

Yea, I've read that about the exhaust reversion pulling in water, but my manifold has those huge risers with the 135* bend in them. That has to be pretty effective at keeping the water out at the expense of back-pressure. I'll check my water line anyway, good idea.

Also, I forgot to say that I was pleasantly surprised that my heads are the good Vortec's (kidney bean chamber, no center intake bolt) as I was expecting the older, slower burning type. They will be sent off to an older gent who's been porting these things since Carter was president. Strict instructions not to overdo it, just better flow for my setup.

Last thing, I do plan on running knock sensors. So that, coupled with my 1500' elevation, should allow my planned 10.5-10.75 compression to run reliably on our 93 octane. Compression isn't nailed down yet because I don't have my pistons picked out.

Thanks again!

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

The nay sayer's arnt really nay sayer's...there just siding on the side of caution. Take it easy...your misinterpting them imagine if you will a novice to boating reads a thread... see's the hot cam and drop's one in with little if any experience...and his motor hydraulic's with in months...Not cool.

Keep up the build post pic's there is very little info on 4.3's being built. Not to much support from aftermarket mfg's, you will find it is the induction system that realy holds back the 4.3 in the end. Here's a pic of the 4.3 zz4 270hp stk gm engine .....what is glaring to you...

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

I have bult a 4.3 with with the same idea, dident last to long and was still slow. And that was in an s-10, in a boat it would be a waste of money. get a good big block.

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

What happened..fresh build..old motor new cam.

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

I see quite a few threads on various Internet forums about the same sort of thing . . . Going the high performance route with a 4.3 and talking about camshaft upgrades, etc. Tail Gunner, you had one on hotrodder back in 2009.

These threads would be great resources, except of all the ones that have been started, I did not see any that were taken to fruition, so there is no telling how it all worked out.

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

Mine worked out quite well, there was a big break in continuity due to the fact the engine is a efi model and at that time there was little that could be done to reprogram a mefi ecu. It actually took me well over a year to find and reprogram the mefi. Eventually i ran into this program MEFI Scan & Tune, MEFIburn, MEFI tuning, Ramjet it will take care of any alteration's one would choose to do in a engine....today they have expanded there tuning to remote tuning...OBD Diagnostics, Inc. - Custom MEFI Tuning on the fly done by one of the best in the indrusty.

If you dig deep you will find that the 4.3 truly is a 5.7 aside from crank design and oil gallery's..conterblanced also. Due to the nature of hot rodding biggger is better so why even start with a 4.3 and that is a good question..why. Becasue you can and it is a adventure..ive never really posted the build due to the fact there was so much involved some of it marine based and some not..as to the results i have a little 19' bow rider that does over 60 with ease..ive never dynoed the result's due to the fact of money and time. The motor was a fresh engine it was only head's cam's and a retune. I would have had to pull the engine build a crate and then pay the expense for a dyno and that is out of the question.

Volvo's 4.3 gi came from the factory to be hotrodded...454 tbi...single plane intake...113 heads...fantastic fuel cell setup...a exhasut system designed to prevent reversion. It was a simple as new cam..new spring's..keeper's and retainer's...little mod of the intake..2 inch spacer for the intake. The below pic..think that's a dual plane intake..



http://www.crankshaftcoalition.com/wiki/V6_Chevy_90_degree_engines

In the end a person of influece and quite of bit of marine insight stated i was tinkering...he was right. It was very intresting to build the engine..it actually inspired...Stickly a opinion your milage may vary.

Hint: the next time you start climbing out of the hole and begin to climb the pressure wave noitce your tach's rpm....it will be well above 1500 rpm and your prop slip will be high making a very compelling argument for cam's that start to develop power at 1500 and quit around 5500....Reversion on the other hand is a very real event and not to be taken lightly.

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

Well I feel this thread is now going in the right direction, thanks you two. I couple of developments in the last two days, I am going to look into keeping the stock tbi, but reprogramming it will be a challenge. Those tbi ports look a little small, and I've heard the intake system in general is quite restrictive, so am I limiting myself by keeping it and not going the Edelbrock 2114/1409 route? Thanks for the link to the MEFI reprogrammer Tail_Gunner, though it costs a little more than I was hoping. I guess it all will cost a little more!

My machinist found four cracks; two in the block and two in the head. Three are repairable, but the one head is junk as it cracked between the two valves. The other three are webs in the water passages. If 3 out of 4 of mine cracked, I would think that would call for a redesign, no?! No biggie, he had a homeless Vortec head, also ending in 140, laying around and he says the block is an easy fix. Also, I think a lot of my leakdown/low compression was the valves and seats as they were pitted. I guess the salt-water from the first half of it's life took it's toll.

I need to figure out the intake soon, so please chime in with your thoughts. Oh, and I won't reply anymore before my first cup of coffee, sorry for being snippy. I don't want to alienate anyone who may have something positive to say.

I've taken a lot of picture of the tear-down, and plan on the same with the build-up. I won't abandon the thread when it's all together and running down the river. I'll keep you updated and maybe this can be a reference for others who want to do the same thing; avoiding my mistakes and copying what worked.

Thanks,
Rick

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

RSBJ said:

Well I feel this thread is now going in the right direction, thanks you two. I couple of developments in the last two days, I am going to look into keeping the stock tbi, but reprogramming it will be a challenge. Those tbi ports look a little small, and I've heard the intake system in general is quite restrictive, so am I limiting myself by keeping it and not going the Edelbrock 2114/1409 route? Thanks for the link to the MEFI reprogrammer Tail_Gunner, though it costs a little more than I was hoping. I guess it all will cost a little more!

My machinist found four cracks; two in the block and two in the head. Three are repairable, but the one head is junk as it cracked between the two valves. The other three are webs in the water passages. If 3 out of 4 of mine cracked, I would think that would call for a redesign, no?! No biggie, he had a homeless Vortec head, also ending in 140, laying around and he says the block is an easy fix. Also, I think a lot of my leakdown/low compression was the valves and seats as they were pitted. I guess the salt-water from the first half of it's life took it's toll.

I need to figure out the intake soon, so please chime in with your thoughts. Oh, and I won't reply anymore before my first cup of coffee, sorry for being snippy. I don't want to alienate anyone who may have something positive to say.

I've taken a lot of picture of the tear-down, and plan on the same with the build-up. I won't abandon the thread when it's all together and running down the river. I'll keep you updated and maybe this can be a reference for others who want to do the same thing; avoiding my mistakes and copying what worked.

Thanks,
Rick

Click to expand...

Ayuh,.... Where, Exactly are the cracks in the block,..??

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

Fuel injection is pretty cool stuff, you can program in your own timing curves and afr.Here's a thought with mefi you can advance your timing at idle a few degree's stronger than the stock setting...now your cam now look's smaller to the engine...less lope less chance for reversion.. and from 1200 rpm and above right back to power timing. And if you choose you can run rich afr's for low speed lean for midrange and rich for wot. Great stuff

That TB should be a 454 TB flowing more than enough air for the 4.3..I belive 600 cfm..TBI adapter plates are all over the place..

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.

Tail_Gunner said:

Fuel injection is pretty cool stuff, you can program in your own timing curves and afr.Here's a thought with mefi you can advance your timing at idle a few degree's stronger than the stock setting...now your cam now look's smaller to the engine...less lope less chance for reversion.. and from 1200 rpm and above right back to power timing. And if you choose you can run rich afr's for low speed lean for midrange and rich for wot. Great stuff

That TB should be a 454 TB flowing more than enough air for the 4.3..I belive 600 cfm..TBI adapter plates are all over the place..

Click to expand...

So I called Edelbrock and asked them for the diameter's on the underside of their 1409 carb. The primary's are 1.6875 and the secondaries are 1.4375 (1 7/16 & 11/16). Now I may have these backwards, but it doesn't matter, what I was looking to compare was the area of the two bores in the TBI, which are 2 inches on each and the area of the combined primaries and secondaries in the 1409.

So....the stock TBI has an area of 6.28 square inches and the 1409 600 cfm carb is 7.72 square inches for a difference of 22.9%. Complicating it, amoungst other things, is that the carb has a lot of crap in the way of the airflow with all the fuel nozzles and such. The TBI isn't competely clear of course, but after studying this for the better part of a day I have to conclude the 1409 has about 17-20% more surface area, putting the TBI in the 500 CFM neighborhood. Going from what I've learned from intake tuning, that difference should cost me somewhere around 5% in peak power, and benefit the bottom by roughly the same amount.

Considering the 1409 is thought by some to be a little too much carb for stock 4.3's (a quote from Edelbrock themselves: "Designed and calibrated for optimum marine performance in small-block V8 engines") perhaps the stock fuel injection isn't going to cost me but 5-10 horsepower. The bigger issue for me is $500 seems too steep for mapping software that may be quite a pain to calibrate. Perhaps I should just get Edelbrock's TBI intake manifold/cam/chip combo and call it a day!

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

A few thing's: HP limit for Vortec heads? Power band? - Third Generation F-Body Message Boards

STOCK vortec heads have a relatively small port size and 1.94" int/1.5" exhaust valves

valve lift figures over about .520 in mildly modifyed /clearanced heads or .450 in stock heads do little to increase flow, they were designed for massive torque in the 1000rpm-4500rpm range, minor mods easily increase flow to about the 4700rpm range, while EXCELLENT FLOWING HEADS FOR THIER PORT SIZE they are NOT RACING HEADS heres some combos useing vortec heads
from this sitehttp://www.ryanscarpage.50megs.com/combos1.html

Notice the 4700 rev limitation's or better said where they begin to fall off.

Taking your TBI setup to the next level... - Third Generation F-Body Message Boards

That thread goes into a lot of depth but what you will find is that a 454 tb is capable of producing 375 hp and the limiting factor is rpm and air...@ about 5500 rpm again above the vortec heads design One thing that is very important to understand is the tb does not meter flo like a carb.. it meter's air yes but it also mechanically inject's atomized fuel...a carb does meter air but its dependt on vacum velocity to draw and atomize fuel..that's a big difference.

Lots of info there one last tid bit...since a tb does not rely on vacum signal like a carb a single plane manifold can be used extending it's range into the lower rpm...and you have one on the boat now..it a single plane with a divider..again here. Made simple TB does not need a dual plane intake for low end grunt and the engine will benefit at higher rpm due to the single plane design.Or the dual plane if you choose as much the 4.3has very litttle choice here the eld 2114 is the only game in town.

https://www.google.com/#hl=en&tbo=d...b8b13d38ba68b9&bpcl=39967673&biw=1366&bih=673

Doing tbi with mefi burn will be cheaper than buying a new intake and carb..jets etc..Your mefi computer is now easy to recalibrate...you have a TB more than capable of delivering both the needed fuel and air. Mefi also allow's you to map your timing to maximn efficenys along with taming down that cam at low idle...

a efi discussion on mefi MEFIBURN http://www.offshoreonly.com/forums/general-q/265811-efi-everyone-6.html

http://www.youtube.com/watch?feature=player_detailpage&v=i2DvnoHWagk future reference