3900 Forged Turbo build

[FallenZ24]

Damn that's a shitty deal. Ha $50 discount.... I would have laughed in his face. More like you're replacing a crank and reduing the machine work. The world would be a better place without stupid people.

What's the guys Business contact information? I think we should all call him and give him shit. Spread the word around town and ruin his reputation. That would cost him more than owning up to his own dumbass mistake.

I'm really eager to see what this build will do. Hopefully you don't run into any more problems.

[Joseph Upson]

I'm planning another trip home shortly to hopefully finish this thing once and for all. After thinking it over, researching and thinking it over somemore, I decided I should stick with my original plan for high compression and boost and not use the 3.43" crank. If I'm only able to muster 7 psi out of it the overall benefit of high compression on pump gas with the 6 speed should make it worth it, especially if fuel economy breaks into the solid 30+ mpg range. I picked up another 3900 for a great deal as a crank donor and had the crank offset correctly so far this time, 3.555". I did a mock up of the stock piston in the bore and measured .040 deck clearance which suggests stock is .035 since I couldn't get the full 3.560 offset.

At the moment it appears my compression is going to be slightly higher than 11.5:1 but I plan to cut valve reliefs which should take my 9cc LS1 pistons to an estimated 11 cc. I'm working on polishing the chambers and opening up the bowls a little. The fuel injectors spray a good portion of the fuel directly on top of the intake valve in this engine and I plan to run the Deka 60 lb/hr injectors at 60 psi static for atomization benefits, they are rated for a max of 85 lb/hr @ 87 psi. The rail mount bosses have to be shortened about 1/4" for them to seal properly in the ports as they're shorter than stock.

I'm pretty confident that with past performance in a poor state of tune I should be able to accomplish the goal of at least 7 psi with the intended compression and not be running on edge and without the alcohol injection. If I'm wrong I can always purchase a thicker headgasket.

[Joseph Upson]

I'm taking my time like my father suggested. The little things add up. I had to notch the pistons today. The stock pistons would have been no problem but the LS1 pistons were cutting it extremely close with the intake valve having maybe .015 clearance with the cam at proper install angle. I used the phaser from the stock motor that I used spacers to help limit but now realize since I installed it 1 gear tooth retarded to help, It will have to be modified again to eliminate all advance and retard function because defeated its ability to start in the locked position and this will allow the cam to retard a little until oil pressure builds to force it forward. If that happens and it moves far enough the exhaust valve may hit the piston. As it stands the exhaust valve has more than .100" clearance.

I accidently posted info intended for this thread under the swap thread. The bearing info and #3 and 4 piston contact with the 7x ring should have been here.

I used an extra head and gasket along with a lockable collar to accomplish the piston notch. I purchased 40 grit adhesive back sanding discs and cut them out slightly larger in diameter than the intake valve. In order to incorporate additional radius I did not use the head gasket which causes contact to occur a little further out towards the perimeter. I did an initial light mark with the gasket installed first.

I've read of clearances of .045" being used for the intake valve but very strong springs were used and these guys had to be careful not to float the valves. My intake clearances should be at least .070" although I measured .080.

[GPXSS]

im no expert, but I wouldnt feel comfortable with those sharp edges on the pistons like that.

[IsaacHayes]

I agree. I'd chamfer the stuff and smooth it out. Sharp edges to me would mean hot spots, and spots for stress cracks to form, but looks like the stock valve reliefs are left sharp too, so who knows.

[Joseph Upson]

I agree. I'd chamfer the stuff and smooth it out. Sharp edges to me would mean hot spots, and spots for stress cracks to form, but looks like the stock valve reliefs are left sharp too, so who knows.

Yes the stock relief edges are pretty sharp and I did chase the new reliefs with my dremel tool although it's not visible in the picture. There's another area of interference that I need to mention and that involves pistons #3 and 4 and the 7x ring. I had to clearance them on one side below the wrist pin. I'm hoping I clearanced enough as now I'm a little paranoid about how close combustion and the sudden stop at bottom dead center is going to close the gap. I'll rev the engin gradually so that if a little contact occurs it can gradually rub the high spot away.

Those wanting to perform this upgrade in the future should use 6" rods or an external crank trigger to avoid it. The highest cylinder pressure reached with oil is 255 psi, with the lowest being 220, the pressures should stabilize as the engine is broken in. I tested about half the cylinders before I realized I still had paper in the intake ports to keep stuff from falling in them.

1. 220
2. 230
3. 220
4. 255
5. 240
6. 250

[Joseph Upson]

I forgot to update this thread. The engine is running and to date gave its best performance while runing on the Turbo Grand Prix 8F code since that was the closest thing I had to a running tune and needed my Wideband O2 controller in order to do anything with code59 which it is running now though the controller arrived later than what I would have liked. Unfortunately I ran out of time before reaching a good enough tune to take video of. I do know that it launches quicker now with no boost than the previous engine did with boost and amazingly it feels as fast if not faster than the previous engine did with 7 psi. No doubt the result of cam being degreed in along with the extra stroke and compression. So basically I'm pretty much at the boosted performance level naturally aspirated. I removed the 4 psi wastegate spring and will run the engine this way until it is tuned enough to start adding boost.

Code59 is very impressive I can't stress that enough in relation to the tuning aids; cell follower for datalogs, and autotune which is amazing. I didn't figure out how to manipulate the graphs in Tunerpro for tuning until just a moment ago believe it or not when I figured out you can rotate the table in 3 dimensions. If I had actually used it during the little tuning time I had I probably could have made leaps and bounds with the tuning process. I didn't reach a point where I was able to drive it on the interstate.

The engine is calling for a lot more fuel up top relative to the 3400 bin it was started with suggesting it breaths very well in the high rpm range.

I included a couple of pictures on how one can address the cam phaser for fixed cam install. The next screw size down from 8-32 with about a 3/4" length would probably be best.

[Jonpro03]

That's amazing! I don't suppose you took any more pictures of the build did you?

[Joseph Upson]

Previous air temps at just over 7 psi were around 214 deg so the 40 deg lower temps are likely the result of the combined preturbo water/meth injection and a little better compressor efficiency than the twin T3s. I'm not sure an intercooler is worth the trouble at this point since even if it were able to reduce air temps by 50-60 degrees it may not be enough to offset what I'd loose as a result of the restriction to airflow. There's also the added traditional benefit of the second meth injection nozzle placed just before the throttlebody which hasn't been installed yet.

The engine is being tuned on 89 octane to insure 91-93 octane is an absolutely safe all out grade fuel at my boost level. I purchased my 35mm wastegates a few years ago without researching based on the typical T3 size wastegate port. Low boost = large port, high boost = small port. I have a 4.5 psi wastegate spring installed but as you can see that didn't stop boost pressure from hitting an unintended 8 psi, so the wastegate is too small. The engine pulls strong so far but there's still a good bit more tuning to go and I'm having a terrible time sorting out the hunting closed loop idle and off throttle stall. It's fine in openloop but that's not acceptable with todays gas prices and how much around town driving I do.


Top to bottom: RPM, Boost pressure, Coolant temp, Manifold air temp and at the very bottom knock retard. Manifold temp moves toward the bottom of the screen as it increases.

[Jonpro03]

The engine is being tuned on 89 octane to insure 91-93 octane is an absolutely safe all out grade fuel at my boost level.

I'm stealing that idea.

Can't wait for a video!

[pocket-rocket]

Did you ever figure out why the TPS never saw 100%?

[Joseph Upson]

Did you ever figure out why the TPS never saw 100%?

I thought I posted about that here, my suspicion was correct, the TPS read correctly and the throttle was not openning 100% partly due to an interference and adjustment problem that wasn't obvious at a glance. Below are before and after correction pictures.

[pocket-rocket]

I didn't recall seeing that you had found the problem. So there was a bunch of untapped reserve left in that engine, because IIRC you were only getting around 50% TPS. That's sweet but sucks at the same time.

[Joseph Upson]

Finally got around to rebuilding the motor, I wanted to do everything in one session since the tranny needed to be replaced.
I got an excellent bargain from Sappy on pumped up heads, studs and thicker head gaskets which lowered compression to about 11:1.

"Brand new 3900 heads, with pocket porting and gasket matching on the intake ports, fitted with custom Manley race series valves, PAC 1518 spring, Manley retainers, and new valve stem seals."

I also upgraded to a 60 mm wastegate (didn't know it was as big as it turned out to be) and a 50 mm blow off valve. I installed 745 HN connecting rod bearings to better withstand the high compression boost and moly coated piston rings. It was necessary to clearance the oil squirters as the shorter rods brought the pistons into contact with them, bending them suttley before the install so that they appeared to be okay as I looked at the bottom end and then breaking them off afte the motor was installed and running.

My stock gaskets measured out at about .05 vs the cometics .07, I needed the studs because I was initially planning to stack two thin layers from old gaskets on my new stockers to get .07 until the ones Sappy had came available. I ended up using the same camshaft since Crower dropped the ball even after being given a second chance on getting the camshaft grind completed on schedule so I cancelled it. Turns out to have been a good move.

The motor is currently limited to 3 psi but with the camshaft installed as recommended it feels much stronger than the previous stock motor with an intermediate level reground cam fully advanced running much more boost pressure. This motor is definately stronger and pulls hard all the way through the rpm range. I'm going to leave it at 3 psi for a while, mostly because I'm scared something will go wrong it's doing so well if I increase boost pressure. I remember how strong it ran with 8 psi briefly before it was damaged and it shows all the signs of having that potential now. At 8 psi it ran so hard the car shook.

I plan to take it to the track next month. For now I have to replace a worn out noisy walbro pump that causes fuel pressure to fluctuate between 50 and 55 psi and a flaky alternator.

First build, second. Not sure about the first motor but the second motor compression test was performed dry & the block was prepped by a machine shop this time.
1. 220 218
2. 230 190
3. 220 195
4. 255 214
5. 240 174
6. 250 190

I removed the heat wrap from the manifolds because both showed signs of flange contraction which was putting shearing pressure on the end bolts. I had to cut one end off of both and weld them back on to relieve the stress. I also installed a signal port to measure exhaust back pressure.

The new exhaust system was mocked up on the old engine and trans and is 3" into dual 2.25" baffled turbo pacs to dual 2" outlet capped with baffled chrome dual exhaust tips. The drone is gone and the car sound great.

[NateD4]

That 174 number would concern me slightly. As would the nearly 20 PSI variance amongst the others.

What exactly happened on the first engine that caused it to fail?