3900 Info

[ericjon262]

I know the thread is almost six years old, but I feel it needed a bit of a bump. any chance some of these missing pics will ever come back?

I think we should probably sticky this thread too, lots of useful info in here.

[Superdave]

iirc they needed to be modified slightly to seal right but i've had gen2 covers on my 3500.. i took them off to finish polishing them but never put them back on due to laziness.

[IsaacHayes]

That's just crazy how the gen2 covers fit the gen4 engines!! LOL

Can't wait for the results!!!!! You have the cam locked in place? What about the crank trigger? External or internal replacement?

Us FWD'er need to get on the ball and use this engine!!

[CNCguy]

Yeah..... They were misplaced when our server crashed. I will see if I can find and replace them. Anything in particular that you were looking for?

On a side note, I had a little time this past week trying to get this engine ready for dyno tuning. The headers are mostly finished with the exception of adding bungs for O2 and EGT sensors. These were made for use on the engine dyno and have 1.62" diameter unequal length (23.5"~27") primaries to roughly replicate what will fit in the Chevette or a MGB. The the merge is 6" long into a 6" long 2.5" collector. I have also started working on the Megasquirt wiring harness that will be controlling it.

This is a stock LZ9 with Comp Cam springs and retainers, TCE spring seats, Manley Teflon valve seals, modified 1393 cam from WOT-Tech and a 75mm 5.3 TB.

Tuning will be done on a Superflow engine dyno at Kammr & Kammer. They specialize in Mopars but work with most other engines and have experience with Megasquirt. They will be doing two tunes, one for max power and one for everyday driving/economy. Should be interesting to see the results.

http://www.kammerracing.com/kmr/pages/superflowengine.htm

There are several things left to do before it goes to dyno. Injectors need to be cleaned or replaced and final engine assembly. I also will be building an engine test stand to fire it up to be sure everything is working correctly and to set the idle A/F using the wideband. At $100/hour, I want to minimize dyno time and don't want to risk a wire or some other little thing not being right.

[SappySE107]

This thread sucks with all the missing pictures

[Nightingale]

Nice find on the Mahle pistons. I need to go check the cylinder bores and see if my block needs cleaned up or not, but I doubt it with only 4200 miles on it. Maybe a light hone even though there are still crosshatch marks visable.

nevermind I found it on the specs page... For some reason I passed it up a half dozen times lol.

So that means all that's necessary to use these forged pistons for much cheaper than custom;

http://www.jegs.com/i/Mahle/644/LS1340898F01/10002/-1

is a possible valve relief and proper size wrist pin busching and maybe balancing depending on the weight difference. That's less than $60 a piston complete with rings.

[Nightingale]

nevermind I found it on the specs page... For some reason I passed it up a half dozen times lol.

[Nightingale]

Anyone know for sure if the 3.9L shares the same deck height (8.818") as the previous 3x00 engines?

earlier in this thread, it was stated that the timing cover would bolt up but it has the wrong size holes. Is it possible that the old 2.8/3.1 timing covers would bolt up also? As someone stated that they used a 2.8 timing cover but redrilled some of the holes to use it on a 3100 or 3400 in their fiero..

Depends on how the 3900 timing cover differs from the 3400. I enlarged three holes in the 2.8 cover to make it work on the 3400. The problem aside from that is the coolant exit from the end of the cylinder head on the 3900, so as far as putting this engine in the Fiero there is no benefit to putting the 2.8 cover on it because you can't mount anything by way of assesories to the cylinder head which for added hassle are left and right pieces.

[bbeck]

earlier in this thread, it was stated that the timing cover would bolt up but it has the wrong size holes. Is it possible that the old 2.8/3.1 timing covers would bolt up also? As someone stated that they used a 2.8 timing cover but redrilled some of the holes to use it on a 3100 or 3400 in their fiero..

[Superdave]

here is the card from my 3500 cam (just to compare)...

I received my reground camshaft from Delta and it's not the 220/220 I wanted but according to Scott the base duration for at least one of the specs was around 202 which makes the reground specs a considerable increase in duration. I told them to use their better judgement over what I requested. The first time I discussed this subject with them months ago the person I talked to did provide any recommendation leaving the cam specs up to me, I don't believe it was Scott who handle the regrind.

I entered the specs in Desktop Dyno with a comparison to the stock specs (as best they could be entered due to dynos limitations with the exh specs) and it showed almost the exact same performance installed straight up as the stock cam showed with 15 degrees of retard.

This also further adds to the question of why the measured stock cam specs here are different from what they measured, particularly since Dyno would not allow us to enter all of the exact cam specs measured by members on the forum. I didn't have a problem entering Delta's specs.

The new cam grind doesn't respond positively to retarding or advancing from 0 degrees Dyno, although Delta says it should increase power when retarded up to about 6-8 degrees. The increased duration of the regrind hasn't increased overall performance above stock either in Dyno which doesn't make sense which suggests either the stock specs are wrong and need to be reduced or the regrind will have an adverse effect. The LSA was changed from 112 to 113 and that would have an effect. I was told to expect about a 15% increase in performance.

I don't understand some entries on the spec sheet.

I just performed an experiment with the stock 3900 camshaft. I recall reading a thread on a different forum where one of the members and owner of a G6 3900 with 6 speed manual tranny had an incident with bent valves and suspected his transmission might have had something to do with it regarding shifting problems.

I used my extra modulator with return spring and cam lock removed so that I could rotate it by hand. With the crank at TDC for cylinder #1 I got intake valve to piston contact with the modulator rotate towards the full lock position which is where it would be on initial startup of the engine. Although it is possible and likely my hand manipulation without a degree wheel may have been off a little but not enough to ignore the fact that this is entirely too close for comfort.

Here is what I believe happened to the guy that ended up with the bent valves, he probably had a higher than normal rev occur during a moment where the cam would have normally been retarded for more clearance and somehow it wasn't, like during a fit of rage due to difficulty shifting gears a momentary high rev from stomping the accelerator in anger and not enough cam retard leaving the piston and valve at their closest achievable distance (0 degrees retard) and contact due to the higher piston speed enabling it to catch up to the valve movement just enough to make contact or even worse due to valve float. It could also have been a PCM hiccup allowing the wrong combination to occur.

I'm going to block my cam into 0 degrees advance and retard from there especially since the specs are now increased to 220/220 and .510 lift which is sure to see valve contact in the stock locked position.

That cam spec should also function like a normal high performance cam at that setting and still leave me with high end VVT benefit.

I haven't spent much time with the electronic control for the VVT function but the Zeitronix WBO2 unit I have for tuning has an auxillary terminal that I can program to energize at a certain rpm and other sensor reading so I'll set it to to turn on a relay that will supply power to the cam retard module at about 4000 rpm to give me top end performance while I work on programming the basic stamp to send pulses to do it gradually with rpm increase.

That's very interesting but I don't understand it. What year is your cam? I measured this cam several times because the large LSA seemed wrong. Wonder if this cam has a lobe that is out of position. If I can ever get some free time, I will measure some other cylinders to see if the numbers are the same.

My cam is from an 06 Pontiac G6 however, GM parts direct shows an 06 cam and an 06-07 cam for the 3500 and 3900 so I don't know what's going on there.

I have an 07 3900 from a Chevy Uplander and its cam is listed for the Terraza and Uplander on GM parts direct from 06-07 but that doesn't tell me anything as far as whether there are two cam grinds for the 3900. Since you mention the possibility of a lobe moving, I'm afraid of using the 3900 cam I just had reground, my engine has about 3000 miles on it and loosing it to a camshaft lobe would be devistating.

I was wondering why no one mentioned it before but realized it was because probably everyone that has a 3900 for a swap has one from a car like my first 3.9. I noted on the Uplander engine I picked up yesterday two hoses going to the oil filter base which turns out is a sandwhich style oil cooler that uses the radiator fluid to keep cool.