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Changing out 250 I6 with 292

T

tuandabrainz

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"Fellas,
I searched all over

"Fellas,
I searched all over, and finally found a chevy 292 inline 6 to replace the 250 (mercruiser 165) I currently have in my 20ft Tiara. Herein lies the dilemma. The cam in the 292 is automotive, so i need to change it. The 250 marine cam will fit, but the mechanical fuel pump is on the opposite side of the engine on the 292. So, I need to get an electric fuel pump kit, or a marine cam for the 292 (which seems to be a little difficult to find). Any ideas where I can find the cam? or would I be better off just using the electric pump? Where can I find an inexpensive kit?"
 
Friend built one of those with

Friend built one of those with .030 over pistons and a hotter cam. Close to 300HP.You will need wet exaust hose for the riser connection. motor is about 2 inches taller.
 
"Great,so that means I can use

"Great,so that means I can use the 250 marine cam. I read the bad info about the pump online, I haven't picked up the engine yet so I wasn't able to verify it visually myself. Other than the longer exhaust wet hose, are there any other special changes I need to make to get this to work?"
 
"292 is a tall deck version of

"292 is a tall deck version of 250. Like Bt Doctor said, it is 2 inches taller. Do you have at least 2 inches clearance above your 250?"
 
"I think so, I won't be ab

"I think so, I won't be able to go check until this weekend, but even if i don't have two inches, I can cut a notch in the overhang in the transom to accomodate the exhaust elbow if I need to. I don't think that will be necessary though. And maybe build some spacers to lift up the engine bay cover, but nothing too terribly difficult. The engine bay was built with a v8 in mind, and can accomodate up to a 454 I think. How do they compare height wise?"
 
"Do NOT use the 250 CAM.. the

"Do NOT use the 250 CAM.. the CAMS are different !!! the fuel pump is in a different location on the 292 and 250, and the 250 wont have the needed lift & duration for proper performance and the 292 may not have the same boss(I'm looking at pics, but can't quite tell) on the front for the front engine mount ( typically mounted on the sides, like V6/V8 engines.) Else you would need a small adapter plate (like I have on my 250 auto engine) to adapt the front mount.

The intakes/exhaust manifolds are the same, you can get CAMS from either Clifford Performance and/or COMPCams !! ( call to special order )

The Cylinder head is the same, but you may want to check the year and if it has Hardended Exhaust Valve Seats else you'll need a Lead Additive in the fuel to help keep them cool.. OR have hardened seats put in, and you can bump up the INT/EXH valve size while your add it, 1.94I/1.50E ( i think ) You'll probably want to use a carb from a 4.3L V6 engine but you'll need a small 1/2"-1" spacer to clear ( the 200hp 292ci Mercs had 4bbl Carbs) and when you take off your carb you'll notice a small restricter plate for the #3-#4 shared intake port you may need this on the 292, ( I wasn't able to easily run a 4bbl on mine without it ).

I can get you a pic of the front mount adapter plate i have and use."
 
"BTW, there are different head

"BTW, there are different heads with different sized combustion chambers that will effect performance and drivability."
 
"[b]"The cam in the 292 is

""The cam in the 292 is automotive, so i need to change it."

Ayuh,... There's absolutely No reason to swap out a perfectly Good cam...
The cam in that motor is a Truck cam, which will work Just Fine in a boat...
Their the Same thing, with the Same power band...

292s were a Truck motor, Never used in a Car...."
 
"ps.. I just want to clarify,

"ps.. I just want to clarify, you could use the 250cam, but as Bondo mentioned the 292 is a truck engine, and it's best to use that cam. be sure to keep the lifters in the same order as they are removed or purchase new ones and dont forget lube when reinstalling. It's my understanding that NOT soaking them in OIl achieves a more accurate DRY ZERO + 3/4 turn lash setting."
 
"Oh, again, you shouldn't

"Oh, again, you shouldn't use the 250 cam because the fuel pump boss is in the wrong place.

I've been wanting to upgrade to the 292 for a few years, but settled for a nicely modified rebuilt 250.. you can still get 292's rebuilt for about $1700-2300$"
 
"antoine williams please let m

"antoine williams please let me know if I can help further and please let me know how you make out. I have had many thoughts about this for a couple years, got close to getting a 292 but became unemployed. I have done a bit of research on this subject, but is no match for Bondos experience."
 
antoine williams ? what do you

antoine williams ? what do you think you are going to do ? Are you going to go with the 292 ? or not ? Just wondering. Have a great day !!

please keep me updated I'd be interested in some info and pictures.

thanks
Brian
 
"what about the engine mounted

"what about the engine mounted water pump? That got to be brass vanes if boating in saltwater.

The boss in the right place?

I also wonder if you can close off the fuel pump hole with a plate and go with a electric fuel pump?

Would solve that problem.

The cam in the 292 if i remember right, is correct or so close as not to make a difference."
 
"The 250's go the same pum

"The 250's go the same pump right ? I think so..
yea.. the fuel pump can be blocked off, dont think there's any concern there. Cams are obtainable if needed."
 
"Sorry I haven't responded

"Sorry I haven't responded, Brian, I have been traveling with work. I am going to go ahead and leave the 292 cam in it, and try that out. I have a 4bbl carb that came off an omc engine, but I don't know if it is a good carb. I may have to take the 2bbl off the chevy 250 I removed from the boat. I am in the process now of getting a gasket set. After I change all the gaskets and get it running, I'll post some photos and let you know how its going otherwise. I am keeping the 292 head also, but using the intake/exhaust assembly off of the 250."
 
"No Problem.. hope work is goi

"No Problem.. hope work is going well for you !!
Good to hear about the cam.

What size engine is the 4bbl carb from ?

The 250 Carb will be a little small, you'd want to use the adapter from the 250 manifold, it will at least get you running. You will need an adapter/spacer for the 4bbl, and some way to kinda block the #3 & #4 share cylinders. (you'll see the diffuser under the 2bbl carb plate) I've been trying to find a Mercruiser 292 and see what the original plate looks like.. guess I'll have to restart my search. ( to use my 4bbl carb too)

The int/exh will mate up, you'll need to find a longer bellows to go from the elbow to the exhaust tube being a little higher. You may be able to warm it in an oven to soften it and stretch it too."
 
the carb is off another chevy

the carb is off another chevy 250 set up for OMC. I also realized working on the engine today that I will need a longer metal fuel line from the carb to the fuel pump.can you use a rubber fuel line if I can find the right fittings for either end?
 
"You can use rubber fuel line

"You can use rubber fuel line make sure you use "Fuel Hose" and if you have auto parts store near you they sell "Brake Line" metal lines, they are the same flare, and fitting, you'd just need to cut one end where it goes into the fuel pump (compression fitting) unless you dont have something like that, it could just use the same fitting on both ends. One end has longer threads, not a concern."
 
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