3900 Info

[Joseph Upson]

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.

[Superdave]

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

[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..

[Joseph Upson]

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.

[Nightingale]

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

[Nightingale]

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

[Joseph Upson]

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]

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.

[SappySE107]

This thread sucks with all the missing pictures

[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.

[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!!

[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.

[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.

[zinX11]

got to agree, would lots of good info and pictures... should be easier to find.

Mike

[CNCguy]

I have been wanting to replace the pictures but my problem is a lack of time. I will try to squeeze some time in for this.