Assembling 8.1L 502
 

Time to reassemble.

Block is back from machine shop. Bored 30 over, cleaned, crank polished, did not recommend cam bearing change said “they look like new”. Decked 2 thousands.

New Wiseco Forged pistons and New Scat forged rods. Balanced and gapped.

https://cimg5.ibsrv.net/gimg/www.off...32933d7b8.jpeg

I assembled the pistons and rods. Broke one 2nd groove ring. Waiting till Monday until wish opens to hopefully get the one ring. Anyone have an extra set for one piston?

Cam was cleaned. I’ve slid it into its home.

New GM cast iron heads sent to Machine Shop and moved over the old with new keepers and 4 new intakes and 1 new exhaust valve.

https://cimg7.ibsrv.net/gimg/www.off...8fbf84e58.jpeg

Have a couple questions, the 3 plugs in front above the cam, had holes in them. Anyone have a source for these? Or can I get some iron plugs from the hardware store and drill a 1/16” hole and be good? Below is what it had that machine shop did not return. Most of the plugs were destroyed to remove.
https://cimg2.ibsrv.net/gimg/www.off...96aacce87.jpeg


For the plug thread sealant, is Permatex 80632 good for this purpose?
https://cimg9.ibsrv.net/gimg/www.off...3e4790b276.jpg

New head bolts came with sealant already. All the head bolts have sealant actually. Can I assume this is the correct sealant to seal from water jackets?

Once the main and rod bearings arrive, I’ll check for oil clearance.

First engine build. Being extra cautious and asking lots of questions along the way. Been turning my own wrenches for 35 years just never a full build.

Anything else I should think of or tips are appreciated.

Yes you can use iron plugs and drill them, but I would use brass, a little easier to drill and easier to go into the holes. I have seen 1 of the plugs drilled but not all three.
I would ask articfriends his opinion on that.
you already know but lube on everything, the good sticky stuff on the bearings, and a light lube on the piston walls and skirts.
when in doubt, just ask. Most of us on here have built engines.

Oil bypass valves. I'm reading the Volvo Penta Shop Manual and it says "install oil bypass valves (pleural). I never removed any out and only saw 1 bypass valve under the oil filter adapter prior to sending to machine shop. It seems there should be another one adjacent to it. Could there be a reason why I didn't have a second oil bypass valve? To clarify, a bit more, VP uses remote oil filter housing and an oil cooler.

https://cimg0.ibsrv.net/gimg/www.off...746546361.jpeg

There should be some allen style pipe threaded plugs available locally. Easiest would be to drill and tap a piece of metal and screw them in...to drill them in a drill press. Or in a vice pinched with 2 pieces of wood and a hand drill. Small drill bits break easily. You need high speed rpm.

I don't remember the hole size to drill...but should be ok here somewhere. I would do all 3...as per the original block.

Do you have a ring expanded to install the rings? Or are you doing the twist on by hand? They're about $10 to get a ring expanded. Far cheaper than solving a broken ring issue.

Oil bypass:

https://www.offshoreonly.com/forums/general-q/68024-gen-vi-v-bypass-valve-2-a.html

Great to see it coming together.

Couldn't find brass hex head plugs locally. Did find 1/4" iron male pipe plugs at Home Depot that may stick out too far for the cam gear. Instead, I ordered Brass hex female head (so like the original) head 1/4" plugs from Amazon. Will drill them with a 1/32 drill bit. All three above the cam.

I twisted on my had. Super quick and easy, no force really needed. Except one seemed stubborn. I think I was the stubborn one. Live and learn.

That thread was useless. lol. Too many difference answers. But I'll search more on here about that topic before I decide what to do. Seems many like to ether block the pad oil bypass all together.

I don't know for certain on a Volvo, but on a Mercury 496/8.1 they do have 2 oil bypass valves from the factory. The one in the center, and the one off center are utilized on a Merc. Be sure to use GM part number 25161284 as this is the 30psi valve.

Oil Pump:
Opened the oil pump. Held down with five 10mm bolts. The cap had a paper like gasket requiring a light tap with a ball pin hammer to separate. The inside of the cap had some scoring above both gears which my nail could catch on. Also, the the gears had many scoring marks which my nail could catch on along with some pitting or tiny pits. Will order a new oil pump.

For the sake of getting this project done, I contemplated not opening this up thinking it should be ok since I never saw any oil pressure issues. Since I have plenty of time, waiting on parts, and working on other small projects on the boat, I opened it up. Glad I did. Question is, do I stick to the stock oil pump, or upgrade to the higher volume pump. Is there any downside to the high volume pump in an essentially stock engine. Yes its a marine engine that operates at a much higher load consistently vs in an "over the road" application. Is that enough to upgrade? Undecided on this topic and will research other sources. I'm leaning more toward a stock GM pump.

Oil Pump part number: 12555868

https://cimg8.ibsrv.net/gimg/www.off...2ed3816d1.jpeg
https://cimg9.ibsrv.net/gimg/www.off...206a9828e.jpeg
https://cimg0.ibsrv.net/gimg/www.off...4657b6344.jpeg

Never build a new engine with a used oil pump, they are cheap

High volume Melling is a nice replacement. MEL M77HV

Are there any downsides to a high volume. From my short "google university" search, not required for essentially stock engine. The high volume oil pump also takes MORE power to run and there is some potential for the oil pump shaft to shear??

Looking for AC Delco or GM unless there is another Brand (Melling?) thats is more recommended.

I recently rebuilt my 496 and used a high volume pump. I used an arp oil pump shaft to get rid of the plastic collar that holds the stock shaft on the oil pump. Just good insurance imo either pump option you go with

Imannyr,

Melling 10778 Melling Performance Oil Pumps | Summit Racing

This is the one I bought for my rebuild. for the record, we removed ALL bypass valves. All the oil goes through the filter and cooler. I see 40+lbs at idle and ~60lbs at nearly anything above idle.

Thanks. Brad.

Did you replace the bypass valves with plugs or leave them open?

Mr brad has a 496 8.1l. A gen vii. Not a v/vi 502 8.2l. Just pointing that out, i do not know the gen vii oiling system.

Im building out a 496/8.1 GEN 7. Bored 30 over…so 502 now?

SB,

I guess I assumed OP had just mistyped one or the other, since 8.1 is a 496 and 8.2 is a 502.

Thanks. Brad.

Imannyr,

Not a shameless plug at all, but….

BBC Oil Filter Blockoff Kit

Just to give you an idea what we did.

For the record, we took out the bypass in the center, and blocked off the side port. Not really sure how it all works as OEM, but this works great. To be honest, I don’t really see a need for the bypass, given how often we change our oil, compared to an automotive engine.

Thanks. Brad.

how much? I like it. I have 2 bypass valves though. So would need to block 2 ports of same size.

Imannyr,

You have to really consider how much modification you are going to do. When I rebuilt mine, we scrapped a LOT of what made it a Merc engine. My entire oil system is custom, with the filter mount on the transom.

All we did was remove the center bypass and plug the other one. We also blocked off the two NPT block ports that are next to the filter socket.

Thanks. Brad.

VP simply has a cap that screws onto the filter adapter covering the entire filter pad. The 2 side threaded ports next to the filter pad is what is used to filter and cool the oil.

Decided to put in two 30 pound bypass valves. I had to think about this but thought it was best to increase the bypass PSI verses completely blocking them off. I'm not worried about the filters since oil changes are done regularly. If the oil cooler gets clogged, then the engine is SOL. The flow is....Side port--->remote oil filter--->oil cooler--->return to the second side port.

A picture of the filter pad and side ports with the 2 bypass hoes (center and off center on filter pad) is on post #3.

Could be wrong too. i speed read and skip a bunch sometimes. :)

SB,

We've established it's a VP 8.1. And we all know that's a Merc 496 by another name.

Thanks. Brad.

Double checking there isn’t an o ring or gasket for the oil passage on the rear cap to block joint.

https://cimg6.ibsrv.net/gimg/www.off...6e3a99468.jpeg

can you post a pic of the rear main cap

https://cimg7.ibsrv.net/gimg/www.off...f74b05ce9.jpeg

Crankshaft Main Bearing oil clearance.

1- .002

2- .0015

3- .0015

4- .0014

5- .0019

All within spec

Both heads are on. Found 2 bent push rods from the old heads. Can I just replace the bent 2 or do I need to replace the whole set and more? Thanks

ha e you determined why the 2 bent?

You have rockers that are non-adjustable. The adjustment is in the pushrod length.

I would source a an adjustable length pushrod, and see what you need for optimal rocker contact on your valve stems.

Then buy the appropriate sized set of pushrods.

How did you measure the main bearing clearances? Very tight for a marine BBC.

That's spec? Seems tight to me, my rods aren't that tight.
I thought at least 0.001"/in

In another life I built a lot of engines. Sometime in the beginning had a problem with one in particular that was eating main bearings. After a couple of failures I finally figured out that the machine shop I was using at the time didn't know wtf they were doing. They managed to align hone the blocks so they were small at roughly 60 deg before & after vertical. Wasn't until I had my own align hone that I saw how easy it was for that to happen. Had never run into it before, always just measured vertically. That was a real wakeup.

So - here is what I came up with - all measurements with a dial bore gauge that can read tenths, same with the mike. Measure journal in 3 places (find smallest dimension) Record all and take an average.

Measure crank in at least 3 places, check for taper, out of round. On an engine with some hours on it this is somewhat normal. Record largest & smallest dimension and take an average.

Subtract largest crank measurement from smallest journal measurement. This is the one that will get you in trouble the fastest. Actually printed out a form and kept it each engines file.




https://cimg6.ibsrv.net/gimg/www.off...bd5796381d.png

My measurements were vertical. At the left and right 45 degrees there was on average 1-1.5 thousanths
more.

VP shop manual:
https://cimg5.ibsrv.net/gimg/www.off...a615c30ba.jpeg

It seems this engine ***may*** have been worked on before. Some things I saw that’s appears that way.

Anyhow, I did have some corrosion on some
valves from salt reversion. I’ll have to look at my notes for #1 and 2 valves to remember what they looked like.

Heads are brand new from GM (bare). The machine shop moved over all the springs, valves, etc…new keepers new seals. We replaced 4 exhaust and 1 intake valve.

As of now, I don’t know the exact cause of the bent push rods.

I’ll get an adjustable push rod and go from there.

Do I need new lifters too now or will the new push rods mate with the old lifters no problem?

Used a dial bore and micrometer.

Generally marine engines with proper oiling don't have a lot of pushrod tip wear. Look at the old tips. If they're grg...then the lifter sockets should be as well.

Roller lifter wear is mostly on the rollers. If they appear to be clean and smooth...no pitting of lines etc...you should be ok if they spec out in the tolerances, and the hydraulic guts are clean etc.

The cam lobes will also let you know how the lifters are doing. Cutting corners here will not be a benefit.

Darin Morgan Quote:

If you run your main/rod bearings too tight, everyone will know. If you run them a bit loose, no one will know.

Engine oil cools the bearings. High pressure low flow = less cooling. MED high pressure high flow= lots of cooling. Tighter bearings restrict oil flow.

BMW perf V8 engines are running 0.0015" as a max tolerance on their rod bearings. They're spinning bearings. Some guys have set up shop just to do rod bearings on these before they have an issue.

M67 fragmentation grenade has a 4.5sec fuse. The spec is 4-5sec.

If you run that tight, all the machining and tolerances of everything else need to be in spec. Tolerance stacking to failure is an issue.

All the pushrods were well rounded, smooth, and polished. The tips look new. The machine shop the cam was good, didn't even recommend a polish on it. Rollers were all good, smooth, no marks, pitting etc. Again...those looked new as well.

I did not open the the lifters... simply cleaned them with diesel, soaked them in oil, and installed. Should I open them?

It doesn't take much time to disassemble 16x lifters. Just some care to not lose the parts and keep them all together for each lifter.

Any debris that has bypassed the filter will potentially be in the lifters.

If I was re'using lifters, I would take the time to clean them out. Easy win.

I have questions:
your machine shop bored block .030 over and I assumed decked block BUT left the cam bearings in, never removed them? What did they wash the block out with, doesn't look hot tanked, personally I would NEVER have any machining done to a block and leave used cam bearings in while machining ( metal can get trapped in feeds).
Your main bearing clearances are very tight, you may very well be fine at those specs IF crank is perfectly round BUT do NOT consider running a high volume pump of ANY SORT with those clearances or you will have crazy high oil pressure.
as far as the two bypasses near filter adapter, the center one thats considered a "anti drain back" is a restriction and I NEVER put it back in, the outer one is necessary and needs to be a gm 30 psi, dont make mistake of using a standard one or hot, unfiltered oil will bypass your cooler and filter. I also would question how clean the oiling system was cleaned with the center bypass still in its hole after all the machine work and "cleaning" was done.

At the last bits….

Ordered spark plug wires for the standard truck application. Those obviously did not fit. Does anyone have a standard spark plug wire recommendation? I prefer something like AC Delco or equivalent.

lmannyr,

John Mosetti, BoatsUnlimited in Texas, sells a really nice set of spark plug wires.

Thanks. Brad.

Read whole thread:
https://www.offshoreonly.com/forums/...lug-wires.html