3900 swap into Fiero

[robertisaar]

this is such an exciting thread...

i look forward to referencing it if/when i ever get the 3900 Turbo/F40 for the Monte...

[pocket-rocket]

Looking good, Joseph

[Joseph Upson]

Thanks, I'm just realizing how much power is tied up in this engine with the numbers it posted at just over 4000 rpm. Although desktop dyno is grossly inaccurate in my scenario beyond 4000 rpm regarding the curve it generates with the cam fully advanced and fully retarded, it is not too far off when you take into account the GTech measures net performance and Desktop crankshaft performance, 233 hp 306 lb/ft @ 4000 rpm. Horsepower wise that would be right in order with my corrected 217 hp net. The torque was always on the high side in Desktop however, I can only enter 15 degrees advance max and not the full 20 degrees the cam was actually advanced. Hopefully the cam angle correction will move the rpm power peaks up near the 6000 rpm range where they belong.

[robertisaar]

you couold advance all of the cam specs 5* so that DD will read correctly... you'll have to remember that the center position is 5* retarded though.

[Joseph Upson]

Pre turbo water/meth injection nozzle in place.
Rotating assembly is balanced. Total weight loss ~ 1.75 lbs
Modified new pressure plate. Stock fiero PP ~1650 lb clamp pressure. This plate stock, 1957 lbs. modified to 2357 lbs. The plates left to right; 4 speed muncie new and old and Getrag. Notice the additional strap in the new plate for added strength. Compliments of Tampa Bay Clutch.
Modified 3.4L F-body flywheel modified and balanced to work with the F40 6 speed trans. Should cut rotating mass by about 10 lbs. maybe more.
Pistons and rods ready for install. Rings were file to fit and rods were on the tight side so the bushed end needed honing. I'm starting the build about 3 days late because of that and other last minute discoveries.

The current engine is still in the car and successfully ran under Code59. The T4 doesn't seem to howl as much as I thought it would with open exhaust but I'm listening from inside the car. The car is definately faster than it was with the twins, the cam is still advanced although about 4 degrees less than before so the test with proper install will have to wait for the forged motor. Otherwise it spins the tires fairly easy on take off without dropping the clutch or reving the engine.

I'll be picking up the rod bearings shortly and plastigaging which will be a pain because the rods have alignment sleeves and the caps will not separate without a fight so I'll have to measure the top side of the pin and use a rubber mallet on the bolts to separate.

Hope to have pics of the pistons in the bore by tomorrow.
Static compression: ~11.7:1, boost, we'll have to see, I have a 4 psi spring to swap out the 7 psi for to start with.

[Joseph Upson]

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.

Check out this article link on bearing clearance; http://www.chevyhiperformance.com/te...nfo/index.html

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.

[GPXSS]

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

[Joseph Upson]

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.

[ForcedFirebird]

Education is so expensive.

[Joseph Upson]

Education is so expensive.

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.

[Z26-T]

I was curious to what you had found after tear down. Good update .

[Joseph Upson]

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.

[ForcedFirebird]

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.

[Joseph Upson]

I was implying that you learned from mistakes, not that you didn't have enough knowledge starting the endeavor.

Understood, I'm just not sure I should take blame for it yet.