350 drill hole for mech. fuel pump?

acex008

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I bought a 1995 Chaparral with Merc 350 that the previous owner didn't winterize so I'm replacing the engine. My neighbor has a newer Vortec 350 and since it's from a truck it had an electric fuel pump. It does have the plate covering the hole where the mech fuel pump would go but I haven't pulled it off yet. I called my local machine shop and asked if they could drill out the hole for the rod that goes up to the cam but they said they can only do it if the hole was "started" or some sort of indication on the block as to where the hole would be. They have a jig for a 4.3L but not the 5.7L... They say the drill bit for both is the same, but without the jig they need some sort of indication as to where to drill the new hole.

I'm assuming GM wouldn't have punched the block or even started a pilot hole since they weren't using mech fuel pumps in the late 90's but they did keep the plate...

I'm curious if others that have drilled the rod hole have seen a punch or pilot hole where the rod to the cam goes... Or know some way of drilling this hole without a proper jig.
 
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acex008

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Or should I just get a Carter P4389 and be done with it? At only ~$100 with an oil pressure switch it may just make the most sense...
 

Rick Stephens

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Go electric. Airtex E11003. You'll need a oil pressure switch and a solenoid to power it properly.
 

thumpar

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Go as Rick said. I don't know if they did away with the mechanical fuel pump lobe at some point so if they did drilling wouldn't help.
 

acex008

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Any threads comparing the two pumps? I like the Carter since it has a mounting bracket and its ~$25 cheaper.
 

funk6294

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First things first, pop the cover and see what you have first. If there is a hole great!, your ready to go. If not then it's time to decide if you really want a mechanical pump (Motor disassembly). Or just add an electric pump, oil switch and a relay.
 

Rick Stephens

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Nice part with the OEM Airtex is you can get the Mercruiser pump mounting hardware and factory stainless fuel line.
 

flipbro

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If theres a plate theres a hole. On the down side the roller cam does not have the lobe to run a mechanical pump. But a nice upgrade to that engine is a ram jet cam. It has the lobe..
 

NHGuy

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If you DO end up doing the electric pump you need a place for the oil switch too. '
What I did was get some MIP tube at Lowes and a tee. MIP & NPT are the same.
I also was a little unsure of the wiring til I asked on here and then looked up the Mercruiser, Airtex and Holly diagrams.
I bought a Sierra oil switch from iboats. It had no instructions, so as I inspected It I found there were three terminals; I, S and P, So I wired them to the Ignition, the Starter, and the Pump.
To make it as OE as possible i used marine tinned purple wire, and I bought some yellow shrink wrap markers that I put on the purple wire from the starter to the switch to the pump. That's the color system that Mercruiser uses. I put a waterproof solenoid between the oil switch and the pump to unload the circuit of pump voltage. Then I put a fuse in the line between the solenoid and the pump.
Soldered my connectors and shrink wrapped them.
The oil pressure switch allows power to the pump when there is oil pressure or when the starter is running. Conversely it cuts power when the engine isn't running. That's important so that if there's ever a stall the fuel pump stops.
 

acex008

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Thank you all for the information. I'll be popping off the cover this weekend to see if the hole is drilled already or not. I've heard that the boss is there to mount the pump but the hole for the pushrod isn't always there. If there's not hole I'm going electric. If there is, I will reuse the cam from the marine engine which obviously has the lobe needed to run the fuel pump.
 

acex008

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So alas, there's a the boss for mounting the mech. pump but the hole wasn't drilled. So I'm going electric. I'm leaning towards the Carter P4389.
 
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