Oil pump help
 

Im rebuilding my mark IV 454 (330hp block) and am going to replace the oil pump as it ingested some water...
The rebuild is going to be higher compression (~9.5:1) forged pistons, same cam as before Crane H-296-2, Edelbrock 6155 heads (prev) on motor... stock crank/rods

That said Im having a hard time finding/deciding on an oil pump! Probably going to get a Melling
Should I use a standard volume or go with a high volume?? part # if anyone can recommend one!

Also, does anyone have part # for the pick up tube??

Thanks in advance!!
Chris

EDIT: Worth mentioning this is with the standard 8qt oil pan

My engine builder suggests using a high pressure, standard volume pump. His reasoning is that a boat engine is held at constant RPM's as apposed to a car that has changes in RPM's.

M77HV melling and a good drive shaft for the pump. It will be plenty good.

You have a similar set up as I once did on a pair of 454/330's. Bought a 92 28' challenger new and had the engines out within a month. I ended up using stock pumps. They performed well however as 14 Apache mentioned the m77hv's would be a good choice. Same ones I put on a pair of freshly rebuilt 496's. They performed great on the Dino anyway. Old school rule of thumb use to be 10 pds per 1k rpms's. Assuming your bearing clearances are set up to spec you'll be fine. Btw as mentioned above I had very similar builds. I used the 502/465 hp cams. Dyno'd at a very solid 485 hp.

Clearances will determine pump more then anything.... what are they??

Are you going to use your stock/original pan? You can reuse your stock pick up tube but it's a good idea to tac/braze weld it back in place. Just ck before you remove to keep the same depth in your pan. If I'm not mistaking it's around 1/2"". But again just ck your old pump for correct depth, etc. Also not a bad idea is to use some clay putty btwn your pick up screen and pan and dry fit to make sure your at the correct height. Just add gasket thickness to squish. Not a bad idea to measure old and new pump from bottom machined surface (mounting side) to both inside and end of pump shaft. They should be the same but always good to confirm proper dist hieght. I've seen this happen only a couple times however only takes 5 minutes.

i just rebuilt my 340 horse 454s.i used mellings 10778 pumps,they are high volume,high pressure.they may be a little overkill but i don,t plan on rebuilding them again for another 1600 hrs.

The M77HV is my main runner right now... My stock pump is def out of equation, lol


I will check with the machine shop once the short block is back together... not there yet. Appreciate the advice and will definitely ask them about the M77HV vs an even higher volume or possibly pressure if the clearances need such!



Thanks, getrdunn... I am using stock pan, so Ill def measure it and test fit with putty as suggested!! Same goes with tack welding the pickup!! Thanks sir!

Thank Mike... Ill look into the 10778 pump as well... esp if my machinist says I need a HVHP

If you didn't have any problems with the old setup and doing a basic rebuild only using new Pistons, rings and bearings. Why not use the same part number pump (new) over again. If the engine gave you a bunch of trouble free hours and no bearing issues I would go with what was in it previously...

Solid point BB.... Ill have to see if there are any markings on the pump. The motor had been rebuilt in the past so Im sure its not the original...

On my rebuild this winter, I went with the Melling M-77 std replacement pump and replaced the spring with the optional one.

I went with the melling HVHP deal. I've also got a 14qt pan and HV pickup. My machinist told me it's better to run more Clarence and use a bigger pump so that we can keep plenty of cool oil flowing through the bearings. Running a higher volume of thicker, cooler oil through looser Clarence's is better than less, thinner hotter oil in my opinion. He wouldn't set my Clarence's until he knew exactly what weight oil, and what pump we were going with.

I like the sound of the way your machine shop works

Its pretty simple, IF you are running tight clearances (like .001 to .0025) on mains and rods use a std volume pump with optional spring, IF your clearances are closer to .003+/- use a high volume one. FWIW I have my mains and rods at .003-.0035 and used the melling high volume that has the extended pins etc and boat still has 100 lbs of oil pressure cold, even with extra rod side clearance and lifter bore clearance. IF you try to run something like that and your crank/rods are tight you will have problems, IE bypass opening all the time,oil foaming from internal relief opening all the time, blowing filter apart or seal out, accelerated wear on cam gear and distributer gear.

I agree with that theory. While some guys get their panties in a bunch about oil film strength, tight clearances being the modern magic trick, and so on, I personally like the idea of a little looser clearance, cooler running bearings, in a offshore marine engine that sees extended high rpm high load usage. Esp when you start pushing the envelope on power. Just my opinion.

That's my theory also and how mine is set up....

i have to disagree with some of this post,all oil pumps have the bypass valve open most of the time,a standard gear pump can make 200+ lbs of pressure if you don,t allow the bypass to open.i also disagree that a high volume pump will prematurely wear dist gear,if the correct gear is used for the camshaft in the engine and is set up properly you won,t have a wear problem.and if your oil filter is not blowing up with 100 lbs in a loosley set up engine why will 100 lbs blow it out in a tighter set up engine?

who is clarence,lol.

Ha! Stupid phone auto correct!! That's who Clarence is lol

Mike, have you ever seen a motor with tight clearances running a high volume oil pump show 120+ psi of oil pressure, I have and have seen where filters blew orings, were sorta swedged etc. When I start up my boat I run it real easy until the oil warms up and pressure drops to something more reasonable as I dont want to twist off the pump drive or blow anything apart. The biggest problem and its came out in the tech section several times here is a guy bolts in a high volume oil pump on a motor that doesnt need it, there is so much excess oil that the factory block bypass valves open and oil does NOT go to the filter and cooler and things go down hill from there. The factory oil system on most stock mercs has fittings with inside dia as small as 3/8 inch, cant push 8-10 gpm thru it real well, fwiw.

i rebuilt both of the engines from my searay 35 footer.340 horse 454s.i installed mellings 10778 pumps and am useing 15w40 shell rotella oil.i ran both of them on the run stand ,they idled at 80 and after the oil warmed up they idled at 60.rod bearing clearance .0022,mains .0026 to .0029.0032 on rear main.after the oil warmed up a little i set the total timing at around 4000 rpm.oil pressure was at 75 lbs.these are 1990 mark4 engines that came from merc with the 8 qt aluminum pans.in a different deal i helped another oso brother sell a sbc that sat for a number of years,i hooked up my 120 lb oil gauge and it berried it while priming with the drill,i thought that was strange but did not pay much attention to it.i then put it on the run stand and started it,within 5 seconds i had to shut it off because it blew a ton of oil past the rear main seal and it berried the oil pressure gauge.i took it off the run stand,put it on an engine stand and removed the pan,pump&rear main cap.i tested the pump on my pump dyno and it berried the 200 lb gauge.long story short the oil that was laying in the bypass valve turned to gunky crap and caused the bypass to stick in the closed position,i took the bypass spool out,cleaned it and the bore it rides in reassembled&retested and it made 77 lbs pressure.i then replaced the rear main seal,cap and bearing,and oil pump then reinstalled the pan,refilled the oil[15w40 rotella and reinstalled the engine on the run stand and ran the engine.80 lbs cold and 70 hot at 4000 rpm.this experiment prooved to me the pressure potential of a gear pump and what can happen if the bypass valve gets stuck shut.this is my experiance and why i made my post.on another note i must be lucky because almost every engine i build gets a mellings 10778 pump and i have never had a dist gear or cam gear go bad.now that i said that the next one will no doubt take a chit.

I'm with you Mike. I put the 10778 in my one engine that I rebuilt because I wanted to make sure there was enough oil pressure at the turbos. I also liked that the 10778 gears are supported in the bottom cap. In a car the standard HV and HP oil pumps work fine, but my thinking is that in a boat with the high RPM's that if you want higher pressure wouldn't you want the gears to be supported on the top and bottom?