I finally got the short block assembled. I encountered several delays due to parts preparation and clearances. The LS1 rings turned out to be file fit I discovered at the last moment. The connecting rods were not exactly fully preped requiring a little more clearance on the pin end.
GM runs a .006" top ring gap stock and that's what I measured. I installed the LS1 slugs at the recommended ~.016"
The connecting rod bearing clearance range is pretty tight also with a minimum of .0007". Optimum according to tests is .0024" but I opted for .0015" so I had to search out .001 under bearings as .0024" is the upper limit spec and I didn't want to start at that. According to my research the tighter clearance will add about 18 deg more heat to the bearing temperature but raise the oil pressure a bit by reducing the oil flow past the bearing by about 1 gal/min.
I encountered interference from the 7x crank trigger wheel with the bottom side of pistons 3 and 4 which had to be clearanced. For anyone considering this path in the future 6" rods would be the way to go to avoid this.
Although the specs are pretty much the same for the non VVT motors I discovered something very important for those tempted to use the earlier engine main bearings instead of the late design. In the picture below is a year 2000 bearing on the right next to the stock bearing from the engine. Note the groove in the stock bearing goes 180 degrees while the older bearing tapers off pretty early. That can have a considerable effect on oil pressure duration on the bearings. It may seem like a simple upgrade but when you take into account the cam module which continuously bleeds oil pressure and then the oil squirters I'm curious as to whether or not the change is a necessity as it provides continuous pressure to the crank port for more than 180 degrees as the oil passage eclipses the groove before 0 degrees and beyond 180 degrees of the upper bearing. So it maybe an upgrade for the older engines but essential for the 3900. Only one part store lists the older bearings for the 3900, I believe it's Advance, NAPA lists only the newer bearings for it and they run a little over $100 for the set.
Last edited by Joseph Upson; 11-03-2010 at 11:10 PM.
good note on the bearing clearances. This may explain why one of my engines died of what seemed like chronic internal oil bleeding.
I guess ill be pulling the pan off and checking again before putting this new engine into the fiero. Im pretty sure I was following what was in the FSM
good note on the bearing clearances. This may explain why one of my engines died of what seemed like chronic internal oil bleeding.
I guess ill be pulling the pan off and checking again before putting this new engine into the fiero. Im pretty sure I was following what was in the FSM
I had trouble posting pics of the outcome of this motor a while back but I damaged it, discovering after I learned you can extend the history tables in TP5 to show all of the boosted area kpa and rpm. Had I known that before hand I could have discovered the motor was extremely lean (18 in some areas) under boost. I eventually burnt the rings in cylinder #5 as it was the only one reading below 245 psi at 150. I could feel it thumping lightly due to it's weak compression. The engine still did 33 mpg hwy on the way back to Florida for "surgery".
On tear down I discovered the low oil pressure at idle was partly due to the oil squirters having the short arms knocked off by piston contact I did not detect on assembly because it didn't appear to be happening then. My bar graph afr gauge worked fine but I must have missed those moments it was reading extremely lean and had no idea it was happening.
My timing advance was far too high at some point also looking at the upper bearing.
Mean while, the stock motor I started with was reinstalled for the time being and it's doing well as you can see in the history table. I still have to energize the VVT module to see if retarding the cam will give up more power.
Last edited by Joseph Upson; 10-15-2011 at 09:40 PM.
Not necessarily. Wasn't lack of knowledge but lack of appropriate information. The AFR table was setup for 100 kpa matching the VE table so I never suspected it was possible to extend the table beyond that and I never read any suggestions indicating it was possible. I discovered the ability while experimenting with the adx file. If I had taken a moment to look at the monitor which I didn't appreciate at the time it would have shown there despite the limited table range. The engine just needs new rings and a light cross hatch as far as the major work is concerned. I have another set of heads if any of the valves are leaking.
I was curious to what you had found after tear down. Good update .
You may or may not know 10 times what i do.
ASE Master certified. Just means I can take tests. GM ASEP Graduate.
95' Z26, ported/cammed 3400/3500, OBD2, 282. Slowly emptying my boxes..
I'm having a little trouble operating the picture posts. The only picture relating to the forged motor is the one with the high afr numbers under boost. The other three are from the motor in the car now.
You can see the AFR averages under boost of the HO motor vs the stock motor in the car now for an idea of how bad it was. I've since improved the stock motor ratios but still have some dipping in to the 9s. It's almost as if some tables have more adjustment range numerically than they can actually adjust for as at the moment lowering the VE vs RPM adder in the range above 4000 rpm has not made much of a difference.
The HO motor injested a large quantity of oil from an extra oil drain hose to the oil pan being vented to the air filter for added crankcase pressure relief after the injury adding further insult. That's why there is a layer of crust on the piston and combustion chamber. I'm not sure what kind of stretching went on for the pistons to damage the oil squirters.
As you can see the stock motor is hitting near 14 psi. How's that for high compression and boost when the afr is not in the ceiling range. I have the meth injection setup but it isn't necessary except for long boost loads when the inlet temps climb very high, so far 309 degrees. I have an air to water intercooler planned for it.
Not necessarily. Wasn't lack of knowledge but lack of appropriate information. The AFR table was setup for 100 kpa matching the VE table so I never suspected it was possible to extend the table beyond that and I never read any suggestions indicating it was possible. I discovered the ability while experimenting with the adx file. If I had taken a moment to look at the monitor which I didn't appreciate at the time it would have shown there despite the limited table range. The engine just needs new rings and a light cross hatch as far as the major work is concerned. I have another set of heads if any of the valves are leaking.
I was implying that you learned from mistakes, not that you didn't have enough knowledge starting the endeavor.
Originally Posted by GPXSS
.
Posting Permissions
Reply With Quote
