Building an LN3 from spare parts plus a Supercharger

[DAVES89]

This a very interesting read, and yet I keep thinking when I was doing the engine rebuild/swap on the Red I wished you would have offered to do my engine work. I have to believe it would have turned out better.

[2seater]

2 hours ago, Ronnie said:

I wouldn't have thought about there being a passage way behind the knock sensor that needs to be plugged. Was that passageway used for another purpose during the machining process of the engine block at the factory?

Yes, that passage extends all the way to the camshaft where the two oil galleries are located that run the length of the engine. One of those things that allows for more complete flushing and cleaning. All the oil passages are drilled, not cast in.

[Padgett]

Two springs in oil pump kit are probably 40psi relief (softer) and 60 psi relief (harder). I'd probably use the 60 psi spring.

[Ronnie]

My engine must have a 60 psi relief spring. It goes past 50 psi when it's stone cold.

[2seater]

The rear main rubber seal came in this afternoon so I was able to install the crank, hopefully for the last time. Thrust end play was very nice at .0055”. I believe I will double check that tomorrow before installing the piston/rod assemblies. The end play is good but is a bit tighter than I usually see. I plan to loosen the thrust cap a bit and tap the crank back and forth again to be sure the thrust faces are lined up. Starting to look a little more like it should.

[DAVES89]

Lookin good! Just don't forget to tighten the cam pulley bolts!

[2seater]

Piston/rod assemblies went in today. No issues with the install using ATF to clean the bores and Marvel Mystery oil to wipe the bores and pistons for installation. The pistons are hypereutectic Silvolite’s for an Australian Holden, a little different design. In theory, the raised island in the center helps suppress detonation by softening the pressure rise. Who knows? In any case, the overall photo illustrates the firing order and waste spark pretty well. #1 and #4 are both at top dead center, one on compression and the other on exhaust, paired together on one coil. The pistons are slightly proud of the deck with a target compression ratio of 9:1. I can’t tell exactly yet since the ‘95 heads will be used and they have not been cleaned up, and cc’d yet.

[Ronnie]

Looking good. I've never saw a piston with a little bump in the center like that. Just wondering... have you ever ran a 3800 without the balance shaft gear so it doesn't turn?  I've read about some of the guys who hot rod their 4.3 Chevy engines doing that to cut down on rotational weight for better acceleration. I have a hard time thinking that would make a difference in acceleration but who knows? On the 4.3 engine you can't easily leave the balance shaft out because of oiling problems and I expect that would be true for the 3800 to.

[2seater]

As far as I know, there is no pressurized oiling to the roller bearings at the front and rear of the balance shaft. If that is an issue, on another type of engine, one of the drive gears could be eliminated. It is an interesting question I have for a different reason: I always have my engine mods rebalanced since piston weight usually has changed but the balance shaft is never included, hmmm 🤔 

 

I know the next item is something I keep harping on, which is the timing chain damper. I have gone through this exercise before, which is careful measurements of the damper clearance to the front cover, specifically, the oil pump cover. Since this is a bit of a Frankenstein engine of different years and parts, I did so again and came out with .050”, similar to others. I add a shim washer behind the mounting bolt to the front of the block. At that point the pivot pin for the damper shoe has zero clearance to the front cover. The gasket for the cover will supply the minimum clearance. I tried to get a good photo of where the damper rides on the chain and it just covers the entire width. The second photo I have posted before which is of the original damper from my 1990 engine at 90k miles. I tried to line them up to show the new style damper and the steel framework required for the design, makes the shoe narrower than it should be to fully contact the chain with a bit to spare. The original design does not require that frame and offers complete coverage. Another project with little hope of getting to will be a replacement Nylatron shoe in the new design that will overlap the frame and cure this issue🤞

[Padgett]

Key to checking the relief is to be at a warn idle and slowly raise the revs in park. When the relief opens you will see a blip in oil pressure. For a 3800 it will be either near 40 psi or near 60 psi.

[Ronnie]

I'll check to see where is opens the way you describe the next time I start my car. If I remember correctly is reads over 50 psi at idle when cold. I think if I blip the throttle it will be near 60 psi. What does your '88 read when cold? May not be comparing apples and oranges since you live in FL but it was in the low 60s here today.

[Ronnie]

1 hour ago, 2seater said:

I know the next item is something I keep harping on, which is the timing chain damper.

Isn't it odd that there are so many alignment problems with the tensioners and chains on these motors since the have been refined for decades. I'm glad you are posting about it. I may never be inside the engine in my Reatta but if I am I will be very careful to watch carefully how the parts come apart so I can get the right timing chain parts and get them assembled correctly when it goes back together.

[2seater]

I don’t know why there is this issue but it didn’t seem to exist before the late style damper. I imagine the design was changed on a later model and became the standard for replacements too. I am pretty sure I posted that same problem existed on the ‘95 engine too, exactly the same off the edge wear pattern with the smaller pitch chain, so that doesn’t seem to be the solution either? 

[Padgett]

There is a reason the early 231/3.8 engines were known as "shaky".

BTW Mercedes copied the Buick offset crank in a V6 but also has a balance shaft.

[Ronnie]

I had a '91 S10 pickup with a 4.3 that didn't have the balance shaft and it had an annoyingly rough idle. Otherwise a great engine that went 200k miles with no problems. I've had a '99 S10 Blazer and now a 2001 GMC pickup with a 4.3 with a balance shaft and they idle smoothly. I doubt the guys that hot rod their 4.3 engines care about a smooth idle. They are after maximum acceleration and less rotating weight in an engine helps that. how much difference stopping the balance from turning makes is probably very small. 

[Padgett]

OK, here is the issue: an inline 6 cyl (or 12 cyl) is naturally balanced. A 60 degree V6 is pretty good. It is the 90 degree V6s that were designed to go down a V8 assembly line that have a problem. Offset crank (even fire) and a balance shaft take care of vibration (imbalance).

[2seater]

Slow couple of days. Worked on installing the lifters and the plastic guide assemblies from the ‘95 donor. It all goes together smoothly but I am having an issue with one lifter bore. One lifter is sticky at only one point in the travel. It seems  it is likely where the oil band of the lifter passes by the oil port from the supply gallery but nothing jumps out so far. The oil gallery is a drilled passage which just catches the side of all the lifter bores to make an opening for the oil feed. The edges of that hole are relatively thin so possibly running a wire brush through the gallery displaced the edge of the opening enough to cause this?

 

The 95 oil filter adapter will clear the LN3 oil pan but not by a lot especially a long filter. 

[Ronnie]

In one of your earlier photos of the block I was wondering if you overlooked running a bottle brush hone through the lifter bores before final cleaning. They looked a little corroded. Don't mean to be critical. Just an observation.

[2seater]

Good observation. Yes, there was some flash rust in some of those bores. They didn’t need a hone but were cleaned with an oiled patch for a shotgun🤔 The block was laid on its side to do so. I did trial fit lifters in a few of the bores but apparently not my problem child. 
 

I don’t believe rust is the issue as it is only in a small range. Fully installed on the cam base circle, the lifter is completely free but lift it 1/4” or so it won’t fall back under its own weight, but will if pushed lightly with a finger.

[2seater]

A small update on the lifter sticking issue. It had nothing to do with the oil feed into the lifter bore but was on the opposite side from the oil feed. It looks to be a tiny void that was exposed in the casting in the lifter bore, a tiny pit for want of a better term. I don't know if there was something lodged in the pit that was displaced or reoriented from cleaning or what? Even a 7/8" diameter stainless steel brush didn't cure the problem but scraping across it with a knife blade at 90deg to it must have picked it out. I couldn't get a good picture of it being located about 1.25" down the .825" lifter bore. Whatever the hang up was is gone now. The pit, maybe the size of the tip of a ballpoint pen, won't cause any issues. The lifter now follows the cam using gravity only. This block is an '88 with only 5500 miles on it as well as the lifters.

 

My new cam sprocket arrived today. I had a new GM chain but I had run out of sprockets. I searched my Buick bolt container but it looks like I don't have the 7/8" long cam sprocket bolts. I guess that is part of the game when assembling salvaged parts and maybe missing the small things. 

 

Another item I would like to find at some point is the special shoulder bolt used to retain the original style chain damper. I have two of the original style damper, and the springs, but not that bolt. It isn't even listed as a part on GM Parts Direct or similar. I don't have a photo of it but this is what it looks like installed.