Hmmmmm, purdy <img src="/forums/images/graemlins/smile.gif" alt="" />

Kevin, I remember your interest in a set of these rods for your next build, so this one's for you.

Tonight, I installed each rod/piston assembly in the #1 bore to check rod length/piston deck height.... ran them to the piston stop, zeroed the dial indicator, removed the stop and rechecked maximum lift above the deck:


You should be able to read my marks on the rods:


IMO, these rods are very high quality machine work - balanced right out of the box, the pin-fit was excellent and consistent from rod-to-rod. Apparently the length is very consistent - all showed .014" height above the deck except one at .013" and for all I know, that could be in the piston. It would be interesting to swap pistons on that rod, but I'm not curious enough to remove the pin locks to do it.

It's looking like I have a tall deck, thankfully - it's .007" better on that cylinder than I was afraid it might be..... and depending on the other rod throws, I might dodge the shim fairy.

Tomorrow night or Sunday, I'll check the crankshaft throw distances and then I'll see what I have...... so far, so good.

Frank

The pistons are in:




Rings were filed to:

.010" - oil rails
.020" - 2nd ring
.018" - top ring

With the rings centering up the pistons in the bores, I saw a beneficial difference in the head clearance. I also found some looseness in the dial indicator, so I took out the 3rd leg and got some even better readings on head clearance. The crankshaft throws are typical of what I've seen from Mitsubishi - around a .002" variance:

#1 = .009"
#2 = .010"
#3 = .008"
#4 = .010"
#5 = .009"
#6 = .009"

With the stock rods, some select fitting can be done to give equal head clearance, but not so with custom rods, so I'll live with it. I surely don't want to have the crankshaft indexed, ground and rebalanced. I'll just use the .010" clearance for figuring CR. That'll certainly help lower the odds on head shims.

Rod big end side clearance is tight, but right at the lower end of the range at .004-.005".

I measured the piston head volume..... it's a shade over 10ccs, as I specified (probably should have asked for an 11cc dish)

I want to wait until I measure the old head gaskets on the other engine that have been torqued down with head studs before I make a final decision on head shims, but based on today's work, the guesstimate is for 9.04 Static CR and 7.494 Dynamic CR. I've been shooting for 7.5 DCR, so I just might get lucky yet.

Today's measurement of deck clearance suggests one of several possibilities:

1) the last Diamante block that showed .017" clearance with a supposed .002 skim cut on the decks had been rebuilt before I got it (don't think so)
2) the other machinist lied to me about how much he removed
3) 3SX rods are shorter than OE (I actually measured them at .002" longer than OE spec, but it's a tough thing to measure accurately)
4) Mitsubishi blocks have a large variance in deck height

Perhaps some day I'll find the answer to that question.

Frank

Looks great Frank <img src="/forums/images/graemlins/kewl.gif" alt="" /> What kind of oil do you use on the bores to prevent them from rusting? <img src="/forums/images/graemlins/cheers.gif" alt="" />

Looking nice.

I would expect you are using quickseal in the cylinder bores but they look a bit shiny for that process.

How is the edge finish on your 3SX rods? The one set I had needed to be polished.

After washing the block, I sprayed them with WD-40, then they always get a little assembly lube that drips into them during the crankshaft installation - I wiped out the bores with a paper towel, but that lube residue sorta fills the honing marks. After I install the rings on the pistons, I dip the piston tops into a coffee can of 10W-30 (up to the rings) to help with ring compression and lubrication.... then install the pistons and leave the extra oil that you see in the bores. It'll all burn off on the first couple of revolutions after it fires. The bores aren't really as shiny as the oil and light make them appear.

Charlie, I didn't see anything wrong with the edge finish, but maybe I'm missing something. There were no burrs or flashing, if that's what you meant.

Frank

Thanks Frank. Getting ready to rebuild my first engine (twin B&S <img src="/forums/images/graemlins/lol.gif" alt="" /> Seems like a good place to start) and so I'm gathering tips and tricks <img src="/forums/images/graemlins/cheers.gif" alt="" />

You can never be too careful building an engine. I just caught myself and the machinist speeding.

My mistake #1:

#1 and #2 pistons were on the wrong side of the engine. I suppose I would have found that when I tried to degree the cams, but dang! I've replaced the pictures in the prior post - I'm surprised nobody saw the error (including me for a while).

My mistake #2:

I forgot that my piston stop has a slight bow in it - nothing of concern so long as isn't installed the wrong way. Of course, I had been using it with the wrong side up and had to go back and recheck everything.

Machinist's mistake:

Funny readings on piston/deck clearance caused me to swap the piston stop to the opposite diagonal on a couple of bores and I found the cause...... not enough chamfer at the top of the cylinder in a couple of spots to completely remove the honing edge.... which gave a false deck height.

I also swapped a couple of rod/pistons and the final readings (rounded to the nearest .0005") look great:

#1 = .0115"
#2 = .0110"
#3 = .0115"
#4 = .0110"
#5 = .0115"
#6 = .0115"

Those numbers are terrific for power balance, but will move the CR up a little bit.

Frank

This may set a new level for redneck valve spring testing at installed height, but it works well enough for my use:





These heads saw some heat when the last engine spun the bearings and seized, so I thought it wise to check the valve springs for damage. I only had to check the springs on one head to see that all of them need to be replaced. They're all shorter than the free length spec limit and at installed height show from 60-70 lbs. The spec load is 74 and 5 out of 6 on one head were more than 10% low.

I've never been a believer that there was much to gain by replacing valve springs on a N/A engine that doesn't turn high rpms, but on a forced induction engine, boosted intake pressure will further reduce valve seat pressure, so these should be replaced.

I can't find any higher rate replacement springs to fit, so I'll have to use a stock replacement. There may be a little headroom to shim for more pressure, but I probably won't do it.

Frank

My FYI on springs... The springiness (modulus of elasticity) of the steel never significantly changes regardless of heat treat or alloy.

What does change is the yield point (the point of permanent deformation).

Over time the springs take a set reducing preload. The steel itself still has the same "spring". Heat allows them to relax as does cycling them for a lot of miles.

Short story? As long as the springs are the correct design all you need to measure is the free length.

Kevin