4.3 - sbc another couple questions....

[wca_tim]

In terms of swapping out my 4.3 for a small block. I have a good sense of what I can use off the set-up I have now and what I need to pick up if I go with a reman longblock or the like and then dress it. Thanks to a few of you and your many helpful posts I've read (bondo, Don S. 180 shabah, lots of others) THANKS!!!), I think I've got some feel for the motormounts, manifolds, freeze plugs, carb, distributer and drive-gear ratio stuff, and just went through all the general cam, carb, intake, compression ratio, etc... considerations when getting the current engine together. I've measured and am pretty sure I have plenty of room and am considering GLM powder coated aluminum manifolds and risers to put the weight in about the same spot to my current set-up. Anyone have any real / recent experience with these manifolds?

The thing I'm the most uncertain about is flywheels and couplers bellhousings and enging blocks if I build the engine or pick up a solid 4 bolt main shortblock and put the right freeze plugs, etc, in it. The boat is a 1988, ca. 18 feet, and the current engine was a reman drop in on an older-style non balance shaft block reman that I had fitted with vortec heads, roller cam, intake, etc... How do I know on a given small block chevy block, whether the current flywheel and coupler will work? Isn't there a difference based on the rear main seal? If I get the "wrong one" what else would I have to change? How about the bell housing? is there a potential compatibility issue there? Thanks in advance for any input!

Oh, and yea, I realize that I may fog, drain and pull the v-6, replace it with a small block, hate the new set-up or trash the outdrive, then finally heed the wise advice of some and put the 4.3 back in... but hey, what's the point being an adult living in a "free" society if ya can't do silly **** once in a while just because it makes ya grin

 

[Bondo]

Re: 4.3 - sbc another couple questions....

How do I know on a given small block chevy block, whether the current flywheel and coupler will work?

Ayuh,........
Basically,..... Your current Flywheel is engine Specfic,.... you'll need 1 Specfic to your New motor.......
Their Balancing is Different.........
And,.....
The Coupler will be Specfic to the Flywheel you choose......

Do you have the 2pc. rear main, or the 1pc. ,..??....
The Crankshaft mounted Coupler,.. or the Flywheel mounted Coupler,..??....

How about the bell housing?

It's a Chevy,........ They're All the Same,.... 2.5l to the BBChevies, All the Same.......

Anyone have any real / recent experience with these manifolds?

As a matter of Fact,...... I'm dealing with a Flaw in a set of Cast Iron GLMs I've got for my V6,......
It seems I was having a Water Intrusion Issue this last summer, 1st season with these manifolds,......
I think I've found the Issue,....
Hopefully,... I'll be posting a thread with pictures as soon as I can find the time to get back to the project,....
What I found is the Inner exhaust passage Gasket Sealing Surface is Lower than the Outer Gasket Sealing Surface, causing there to be less clamping force on the Inner surface,+ consequently,.....
A Water Leak into my motor.......
I'm hoping I can cut them down a few thousandths,+ get a Full Sealing Surface out of them,......
Either That,....... Or Toss'em........

 

[TilliamWe]

Re: 4.3 - sbc another couple questions....

The sbc went to a one piece rear main seal in or around 1987. It uses a different flywheel than the older motors. Something like 154 teeth now versus 168 in the old ones. Or maybe I have that backwards. Whatever, they are different.
The engine coupler will have to match the flywheel you end up with as Bond-o says. Good thing for you, Mercruiser sells each kind new. The starter is also "flywheel" specific.

If it was me, I would find a complete take out small block on e-bay or somewhere else. Since you seem to be handy with engine building, it could even be broken. What ever it takes to get all the attached marine parts. Even if you don't use those manifolds, you'd still be able to test fit the entire engine package in the boat. And you'd get a correct starter and the front of the engine accessories.
Although, if you aren't afraid of a lot of work, you accessories should work too. But it's hard to tell what starter you have, since the 4.3 id "new".

 

[wca_tim]

Re: 4.3 - sbc another couple questions....

Ayuh,........
Basically,..... Your current Flywheel is engine Specfic,.... you'll need 1 Specfic to your New motor.......
Their Balancing is Different.........
And,.....
The Coupler will be Specfic to the Flywheel you choose......

Do you have the 2pc. rear main, or the 1pc. ,..??....
The Crankshaft mounted Coupler,.. or the Flywheel mounted Coupler,..??....

It's a Chevy,........ They're All the Same,.... 2.5l to the BBChevies, All the Same.......

I have the 1 piece rear main, but will need to double check coupler on this one. It's whatever came stock with an 88 4.3 / alpha 1; flywheel mounted coupler if memory serves me correctly. I broke shoulder and colar bone last summer and had someone else actually put the engine in the boat...

So if I get a motor with a two piece rear main, I'll need to find the right flywheel and get a new coupler (planned to do that anyhow, didn't change the one in there when put the 4.3 in and seems like better to get a new one then to have to change it after the fact...). How difficult would it be to find one or is there anything else that could make it a real pain to deal with?

I'm asking specifically about this because tomrrow I'm going to check out a stroker engine built for a friend by a reputable local machine shop for one of his street toys. He had it in for a little while and just decided he needed more cubes / big block. Since it's coming out of a "muscle car", I'm assuming it'll be the 2-piece main seal. It has a forged steel, balanced rotating assembly, good, reworked performance heads, forged pistons with a compression ratio to run on street gas, full roller cam / valve / lifters/ rockers assembly etc... If I can buy it for what it sounds like he wants (x-mas toys money for the kiddos), I can easily afford to change the freeze plugs, swap cams for a 1000-5500 rpm marine appropriate, power band cam (assuming I need to - don't know cam specs yet, but since the engine was designed to run up to 7500 rpm, assuming I will want to change out cam, intake and obviously carb) and then pick up the other items, distributor, starter, manifolds and carb... flywheel and coupler if needed, I could probably put together a really strong / durable set-up with gobs of torque and horsepower on a very reasonable budget all things considered... Will have to see on this one i particular. If doesn't feel right, I'll keep looking or eventually buy a 383 short block or long block reman and go from there. I'm not in a huge hurry, I'm on the water with the 4.3 until the new set-up is ready to drop in... If all goes well, plan to take a few days in jan / feb or sprig break and swap everything out.

Sorry to hear about the GLM manifolds!!! That's kinda (ok a lot) scary! maybe I would be better off waiting until I can find a set of stainless steel headers at a decent price.... or just going with cast manifolds. In reviewing how much weight I have been carrying, I realized that the tool box I've been carrying in the engine compartment weights 90 pounds... had no idea... add a bunch of other stuff, and I can easily get weight down to where the 4.3 set-up is now I think... I'll be intersted to read when you resolve the situation.

Thanks again for the assistance / advice! I wouldn't feel comfortable deviating this far from the service manual / typical set-up without the input I've gotten from folks on here.

have a great one!

 

[Bondo]

Re: 4.3 - sbc another couple questions....

I'm going to check out a stroker engine built for a friend by a reputable local machine shop for one of his street toys.

Ayuh,.......

My Guess is,..... Once you figure out What components were used in this build,......
There'll be Little more than the Block,+ Possibly the rotating assembley that'll work for a Marine Motor..........
Building HP at 7500rpms takes Way Different components than a motor making HP at 5000rpms,+ Under........

When looking for Blocks,......Make Sure that it's drilled,+ tapped for the Staggered Bolt pattern Starter.......
If it's drilled for Only the Straight Accross pattern,...... You'll have to use the 12" Flywheel,+ that'll bring up abunch of other fitment Issues.....

I have the 1 piece rear main,

If So,....... Stick with it,... It'll save abunch of misery......

Btw,......
The Flywheel of Choice in this build will be the 14" 1 that fits the crankshaft of whatever you build,.....
It doesn't have to be Marine, 'cause a Standard Transmission Flywheel drilled for the 12" Clutch is the Same drilling pattern as for the Merc. 3 point bolt on Coupler........
Which is the 1 you'd rather have.......

 

[wca_tim]

Re: 4.3 - sbc another couple questions....

Thanks, good advice... two-piece rear main seal, wrong bolt pattern, etc... wm going to look for a 383 stroker in relatively mild form with right cam, etc... go from there...

 

[TilliamWe]

Re: 4.3 - sbc another couple questions....

You know you can but a 383MPI directly from Mercruiser, right? It's a remanned engine, but the manifolds and everything else are brand new. Marine Power Service has them advertised at $6895 with 325 horsepower.