1996 4.3LX options

[Shadow91]

Took a gamble on a 1996 Glastron with a non running engine. Previous owner couldn't get it started and sold it as a needing an engine. I know the automotive engine is interchangeable for the most part but looks like i have a specific year range i can use. The engine is a 1996 4.3 Gen + with Thunderbolt 5 ignition, which from my understanding has balance shafts and different heads, intake and the works, and just trying to get a concrete answer on what truck engines i can use. I have searched and either read conflicting answers or all gen2 and older info and just want to be absolute before buying.

I believe my serial # is M339517 and the engine has an enclosed cooling system if that matters/helps

Thank you!

 

[Rick Stephens]

So, before you jump on replacing it, what is the condition of the current motor? Compression test? Ignition functioning and you got spark? Carburetor and fuel filters clean? Oil look good? Oil smell good? Does the starter crank it over correctly?

 

[Shadow91]

Hi Rick, I am currently in the process of diagnosing the engine. It currently has spark going into the cap but very little coming out. I am starting with fresh plugs, cap/rotor and dist. Sensor. I will do a compression test while I replace the plugs as well. The oil is clean and clear. The previous owner said he got it started once and it had a knock but he was also very uneducated with engines in general and was waiting on a friend to check it out. Friend never had time so he put it up for sell.

From doing my research online it seems possible that it may be the tick/knock from the balance shaft or anything else. My first goal is to get it started.

And im looking at a ‘drop in’ truck engine (as close to that as it can be) if I find a crack or the engine isn’t rebuildable. Trying to figure out a ‘worse case’ scenario if you will.

Im an Automotive tech by trade, with a few years working for GM, so this should be a fairy straight forward engine.

 

[QBhoy]

Maybe a tick from the flappers ? Usually really noticeable at just over tick over. Initially sounds like an engine noise. If it goes away at higher rpms...usually this is the problem ?

 

[Scott Danforth]

first, prior to spending money, do the compression test

then pressure test the cooling water jacket

then check the flappers, etc.



then if you want to replace the motor, you need a 1996 or newer

if you go with a TRUCK motor, long before you can "drop it in", you need to strip it down, replace the head gaskets with marine, the core plugs with brass or stainless. that is right, you will only use the long block

then bolt on the marine intake/carb, accessories, water circulating pump, starter, alternator, ignition, etc. from your current marine motor.

 

[Shadow91]

Well got her started finally. Engine started nice and quiet and with a random tick that would come and go. Would knock real loud, then silent, then loud, then silent. Seemed to not be with the rotation of the engine at first. After i started recording it seemed to get more consistent but a secondary knock is there that comes and goes. At first i didn't think it was going to be a bad engine but at the end it does sound internal. RPMS were also jumping between idle and 2000rpms whenever it wanted and would sometimes run great, sometimes couldnt hardly get started. Now time to start digging into her

https://youtu.be/WDlX9I70SIE

 

[Scott Danforth]

Pull the drive to see if knocking goes away, may be ujoints

 

[Shadow91]

So I’ll be honest, I’ve never ran an engine without valve covers on. I would assume I should have oil spraying the top end? I could see the rear cylinder spray oil for a second then it stopped. Am I correct in this? Maybe bad oil pump?

https://youtu.be/iumWleDrDwM

Scott i will move the the drive next

 

[havoc_squad]

So I’ll be honest, I’ve never ran an engine without valve covers on. I would assume I should have oil spraying the top end? I could see the rear cylinder spray oil for a second then it stopped. Am I correct in this? Maybe bad oil pump?

https://youtu.be/iumWleDrDwM

Scott i will move the the drive next

Is that oil milkshake I am seeing on those valve rockers or is that the video lighting causing problems?

If that's milkshake (oil & water), I think a compression test and water system pressure test is in order first before going any further.

 

[Shadow91]

Both valve covers had a pretty significant amount of condensation in them. And then it looks like it’s not circulating at all.. the oil in the pan is clean and clear and slight brown, but not cloudy at all

left my compression tester and cooling system pressure tester at work earlier, so that’ll be tomorrow

 

[Scott06]

Saw a video of engine making a similar noise where head gasket was blown leaking water into combustion chamber. Does look like there is more than just condensation in the oil. You're on right path with compression and coiling system pressure checks

 

[Rick Stephens]

If you are determining possible water in your oil based on dipstick signs, that don't usually work. As you pull the dipstick, the clean oil at the top of the dipstick tube will flush the heavier watery oil off and the stick comes out clean. Fastest, easiest, surest method is to drop a suction tube down the dipstick tube and pull a little oil off the bottom of the pan. That way you get a true measure of what's sitting at the bottom.

 

[Shadow91]

Okay, got her running half way smooth and for S&Gs and to really test the outdrive I took her to the lake with a buddy in another boat on standby.

First off, holy hell, this thing rips. And is so smooth in the water.

But, I definitely have a crack somewhere. Now the oil on the dipstick is very full and milky. BUT I have no coolant loss or oil in my heat exchanger.

Haven’t ran to my work yet to get the coolant system tester and haven’t done compression yet.

Going to see the new avengers movie now, then I’ll head to work to grab tools. Going to do a quick oil change with some cheap oil to flush the engine. Then will pressure check and compression check the engine.

I’m just trying to check every avenue before dropping in another engine

 

[Scott06]

Intake valley under the heads is tyoical cracking spot , may get lucky if it's just under the thermostat . Likely block is roached

below is photos from a 4.3 I bought same symptoms as yours

 

[Shadow91]

Pressure test system yesterday and lost about 7psi over an hour. No obvious leaks and nothing external. I’m at a point between the known knocking and milky oil I’m just going with a used engine.

Bought a used engine with 90k miles on it for $150 today out of a 2000 Blazer. From my understanding this SHOULD work.

Plan on tearing it down to the short block and using all new marine gaskets and resealing the entire engine. So far I can only find prevortec engine reseal kits or head gasket kits only for vortec engines. Does anyone have a good part number or link to a site I can get either a felpro or Sierra marine overhaul kit?

As far as the core plugs, since I’m running an enclosed system with coolant and not raw water, can I leave the steel ones in without issue? How important is brass in this scenario?

Any other part part of the engine possible to let water into the oil or pay special attention to while I’m disassembling and rebuilding?

So so far my plan of attack is to disassemble the engine down to the short block to remove and inspect for point if failure.

Then
Complete engine reseal with all new marine gaskets
carb rebuild/replace
new water pump
new cap/rotor
new plugs
new serp belt
New raw water pump

I really want this engine to just be turn key ready and just fire and run without issue. Thinking of reinstalling the short block and putting heads and intake on in boat to ease the process, but hoping some of you seasoned guys can tell me if that’s a good use or not.

Obviously the bellows, gimbal bearing and ujoint will be inspected while the drive is removed and replaced as needed. Luckily already have the alignment tool from doing the bearing on my old Bayliner.

I have about $2k budgeted to get this back in the water, doing labor myself. So crossing my fingers I can manage that haha

 

[Rick Stephens]

I'd be plastiguaging the bearings and checking the end gap on the rings on the new old motor. Also, hook up a starter to the new motor and pull compression numbers off it. That'll tell you a lot. Closed cooling can use steel core plugs. If no one else grabs it, I'll dig you up a FelPro number when I get back to a computer this evening.

 

[Shadow91]

Thank you Rick. I had planned on checking compression before removing the heads to get a baseline on the engine. Also planned to check cylinder condition while the heads were off. Figured if it needed a hone i would likely rering it and throw a set of bearings in while its apart, but honestly im trying to cheap out on hope the rotating assembly is okay. I was able to see a running video fo the engine from a week ago, hoping the seller is honest however.

Called the local dealer and got the part number for a OE gasket kit, but at nearly $750 im really hoping to go Sierra or Fel-Pro but am too stupid to cross reference the numbers apparently.

Part number has changed twice, 27-824326A96 -> 27-824326A01 -> 27-824326A02 being the latest from MerCruiser

 

[Scott06]

If you are running closed cooling no need to change freeze plugs or the head gaskets. IMHO run his engine on the ground and take compression and oil pressure reading before you tear it apart. At 90 k if it has been reasonably taken care of you may be fine.

If you swap your marine externals marine intake, exhaust, ignition, harness etc you can easily run it on a pallet or on the ground.

One small issue you may may run into is block casting number 090m will have metric starter bellhousing and side motor mount bolts. The blazer engine may be us size. I ran into this when swapping a 4.3 for a 5.0, 4.3 was metric on those parts of the block, 5.0 was US on all bolts. Overall a trip to hardware store and new starter bolts got it done. Oddly front accessory bolts were all us between both blocks and heads

 

[achris]

Even with closed cooling, I would change to brass or stainless. Sea water corrosion doesn't just come from the inside. The engine is in an enclosed space, in a bilge, likely with seawater sloshing around in it. That's enough for all the little salts to look for a party space, and steel core plugs will be where they'll head. You're pulling the block down to a short motor anyway, why not just the extra step and drop new, non corroding, core plugs in? Even in my normal car engines I put stainless core plugs in.

As a side note, I was on a bus in New Zealand many years ago. We were going up a hill, and the driver pulled over and shutdown the engine. He said it was overheating, and when we looked at the engine, a core plug in the head had corroded through and all the coolant was on the road. We were many miles from any saltwater, and the bus wasn't that old.... Just saying....

Chris...........

 

[Shadow91]

Well I don’t believe it. Checked over the whole engine and externally it looked good. Figured wth I’ve got nothing to loose.

Put a can of BG hot oil flush in the engine and took it to the lake. Ran great for 20 minutes or so while progressively getting quieter. Serpentine belt broke but luckily I was right next to the launch when that happened.

Took her home, changed the oil and coolant. All fresh with BG cooling system conditioner and BG MOA. Checked comp and put new plugs in and fired it up! She ran quieter then ever, no ticks, no knocks. Adjusted my idle screw and ran it for 2 hours on muffs at idle.

No issue. None.

So today I’m at the lake. Been here for 4 hours. Have put the engine through it’s tests, max rpm speed is about 4800 rpms. Shits and gets and is like riding in a Cadillac compared to my old bayliner Capri

Holy **** lol this was a $1000 boat