1998 4.3L Knocking
- Thread starter calypso's cruzr
- Start date
Mike-n-Jolie
New Member
Did you pinpoint the cause of the "knock"? I know you said the rings were siezed in the grooves on#1 but I but I can't see that causing a knock. Oil control problems-sure but,knocking-thats kinda questionable. Unless your skirt to bore clearance is enormous,or your bore taper is seriously out of spec. Maybe I'm wrong and a member can enlighten me.
douglee25
Well-Known Member
When the rings are seized in the piston grooves, there is nothing there to center the piston in the bore. When this happens, piston slap will occur and you will notice a knock.
Doug
Mike-n-Jolie
New Member
Yeah,I guess you're right but,the way he described it,it sounded much more catastrphic. I've heard piston slap before but,never to the point where I was thinking"OMG-its gonna blow"! I guess its one of those"you had to be there" things. As long as he gets it fixed its all good. Sounds like hes not wasting any time-thats for sure.
calypso's cruzr
New Member
Will a main gasket set from a '98 MPI/SFI Vortec that's in a vehicle work with my '98 Carbed Vortec? Are the intake gaskets the same? I can't see anything else being different. I also heard the earlier Vortecs didn't have the balance shaft, This one does, so as long as I have the gasket set for this type of block I should be good right?
Dirtguy
New Member
Yeah, the gaskets are the same. Or they should be.
The rings don't center the piston in the bore. They do stabilize it's travel by adding circumferential drag evenly. And the prevent the hot gas from scorching the skirt. The wrist pin is offset in the piston for the purpose of guiding the piston down the bore with one side loaded to minimize slap, or rocking. That's why there is a flywheel or front side marked on the crown.
dg
The rings don't center the piston in the bore. They do stabilize it's travel by adding circumferential drag evenly. And the prevent the hot gas from scorching the skirt. The wrist pin is offset in the piston for the purpose of guiding the piston down the bore with one side loaded to minimize slap, or rocking. That's why there is a flywheel or front side marked on the crown.
dg
douglee25
Well-Known Member
calypso's cruzr
New Member
Just honed the worst of the cylinders. It all came out, every last mark! The new rings will take up any slack from the honing. Now to find new pistons at $155 each and a gasket set that won't cost $550 from the Mercruiser dealer.
calypso's cruzr
New Member
I have been looking at replacement pistons for the 3 that are damaged. How do I tell if I am getting the right type? Are the stock pistons Cast, Forged or Hypereutectic? What about weight will the aftermarket types weigh the same as the factory?
douglee25
Well-Known Member
I'm pretty sure they are cast pistons.
Try this
http://www.ebasicpower.com/pc/FED640P/MER6U/Piston%2C+GM+4.3L+V6%2C+Flat+Top
I believe the part # for a '98, 4.3l, 262 is #735-835001T. Doug Russel has them for around $125.
Doug
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calypso's cruzr
New Member
I have been looking at replacement pistons for the 3 that are damaged. How do I tell if I am getting the right type? Are the stock pistons Cast, Forged or Hypereutectic? What about weight will the aftermarket types weigh the same as the factory? Most of the applications note state they are for VIN 'W'. Since my boat isn't a car and doesn't have that VIN code I'm not sure what to do here?
douglee25
Well-Known Member
calypso's cruzr
New Member
I'm not paying $155 for a piston that I can get for less. The internals of these engine are not special. They have the same parts as an engine in a truck/van. The parts houses are asking $35-85 for them. I can't see anyone paying 3-5X's the cost just because it came from a Mercruiser dealer. The dealer always tries to get you bent over a barrel.
calypso's cruzr
New Member
I just went to pick up the new pistons from O'Reilly's. They are not the same. The ring grooves aren't in the same position as the mine. Meaning they are farther down the side of the piston. The oil ring is very close to the pin and the pin is bigger. The P/N from O'Reilly's is H699P . Which is the same as Autozone and Parts America. Anyone have to get new pistons? Where did you get them from?
douglee25
Well-Known Member
I guess you're going to have to order them from Mercruiser directly.
Doug
Doug
- Oct 3, 2006
- 2,019
- Boat Info
- 04 SeaRay 185Sport, Smart Tabs, Mageln Meridian Gold GPS, Hbird Matrix 87 dept/ff/gps/cp, Uniden vhf
- Engines
- 4.3L 190HP, Alpha 1 1.81 ratio, 14 1/4X21 Turning Point Prop
You really need to get marine engine parts not car engine parts for a Marine Engine. Marine engines run under a lot more load and higher rpm than automotive parts. The composition of the marine parts is different to the automotive parts. Do some research before you buy car parts for a boat engine. I have been an automotive mechanic for 40 + years and I thought that the parts were the same at one time myself but they are not.
calypso's cruzr
New Member
I have found out that the parts that the part stores sell are the old style pistons. That is what I keep seeing. I have spoken to my engine builder and he stated the reason my piston is expensive is because they are metric, meaning they have metric size rings. The old style piston is a standard size ring. The pistons size are 350CID also and the engine by design is a 350CID with the front 2 pistons removed. That comes from Chevrolet. I can run the old style piston but I would have to get 3 more, balance the crank for these pistons weight and get the rings for them. Then have them put on the rods. I'm just wondering if all that can be done for less than the OEM pistons and the cost of the work to have them put back on the rods. What a dilemma.
calypso's cruzr
New Member
Just talked to my engine builder. He has found and received the correct pistons for $30 ea and he ordered 6. Now just gotta get him the rest of the pistons and rods and I'm back in bidnes. YEAH!
skibum
Well-Known Member
So... fill us in. Are they just a different automotive piston, or did your mechanic find the Merc ones for that price?
M~
M~
calypso's cruzr
New Member
They have a casting number of H699P on them but they have the metric size rings. Will find out more info from engine builder. Anyone know where I can get torque specs for this engine?
