Engine Rebuild Part 3 (the finale)
#181
Nordschleife Master
Join Date: Oct 2004
Location: Vacuuming Cal Speedway
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FWIW I think you're choked up. The stock mufflers are extremely heavy and congested. An after market system, perhaps Fabspeed's, would expand your new motor's ability to breathe. Stay with the stock air box but switch to a better element, I use BMC.
4th gear is where most stock geared Porsches dyno. Mine have always been in 4th....
Here's my latest dyno sheet on a Dyno Dynamics machine. They produce considerably lower results than a Dynojet, many say 10% less. I'll have to get on a Dynojet if I want to race with NASA this year. I'll probably go to a 2.5 TB and hopefully get the WHP down to 270 or so.
Our motors are significantly different, you use the larger Nikies cylinders to get to 3.6, I used the 3.6 crank and rods with decked 3.4 heads, cams, and a 5 angle valve grind. I also have 3.8 manifolds to straight pipes, FVD's slightly enlarged throttle body, and GIAC's street flash. YMMV....
![](http://img585.imageshack.us/img585/3429/dyno1e.jpg)
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4th gear is where most stock geared Porsches dyno. Mine have always been in 4th....
Here's my latest dyno sheet on a Dyno Dynamics machine. They produce considerably lower results than a Dynojet, many say 10% less. I'll have to get on a Dynojet if I want to race with NASA this year. I'll probably go to a 2.5 TB and hopefully get the WHP down to 270 or so.
Our motors are significantly different, you use the larger Nikies cylinders to get to 3.6, I used the 3.6 crank and rods with decked 3.4 heads, cams, and a 5 angle valve grind. I also have 3.8 manifolds to straight pipes, FVD's slightly enlarged throttle body, and GIAC's street flash. YMMV....
![](http://img585.imageshack.us/img585/3429/dyno1e.jpg)
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#182
Three Wheelin'
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My T/B is stock cable op at 74.8 mm. Are you sure yours isn't 76.4mm? I don't remember a 74mm for the 996 (1998-2001), except maybe on a smaller Boxster engine. I'll send you a PM.
I would be open to throwing it on and taking it to the dyno again, which I'm starting to get the itch a little to see what was up with those torque figures.
I'm just not sure how much it could help without complimentary intake and exhaust porting. Heh maybe I could get out the dremel like speed rII did.
![Wink](https://rennlist.com/forums/images/smilies/wink.gif)
To my knowledge, cars should be dynoed on the gear that is closest to 1 ratio. On 996 it's 5th gear... I bet that you would gain some hp if you dyno the car again with 5th gear. Wheelspeed is high, about 240km/h. If the dyno allows thesekind of speed's I would do new pull's ![Wink](https://rennlist.com/forums/images/smilies/wink.gif)
![Wink](https://rennlist.com/forums/images/smilies/wink.gif)
http://www.dynojet.com/automotive_dy...o/default.aspx
Our motors are significantly different, you use the larger Nikies cylinders to get to 3.6, I used the 3.6 crank and rods with decked 3.4 heads, cams, and a 5 angle valve grind. I also have 3.8 manifolds to straight pipes, FVD's slightly enlarged throttle body, and GIAC's street flash. YMMV....
No doubt your other mods are exploiting your upgrades, the straight pipes and the throttle body. My valves also had a grind FWIW...
#183
Three Wheelin'
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I nearly forgot about plugs too... geez the snowball certainly gets bigger once it starts rolling down hill.
Last edited by logray; 03-31-2012 at 02:31 PM.
#185
Three Wheelin'
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PM sent on the larger T/B. Yes FVD goes to 76.4mm.
I tried looking for the 3.6L throttle body specs but couldn't find them.
For sure I think this might help, if the stock 3.4L head ports can handle the extra volume. Considering I've got the 3.6L mufflers and aftermarket headers, I am thinking this would help including the K&N w/ the stock air box.
I don't want to go crazy with mods nor tear into the engine again at this point, but I wouldn't mind giving this a go and maybe putting her back on the dyno to see if it can breathe easier.
Anyone out there know off the top what the 3.6L T/B measures out at (or would like to measure)?
I tried looking for the 3.6L throttle body specs but couldn't find them.
For sure I think this might help, if the stock 3.4L head ports can handle the extra volume. Considering I've got the 3.6L mufflers and aftermarket headers, I am thinking this would help including the K&N w/ the stock air box.
I don't want to go crazy with mods nor tear into the engine again at this point, but I wouldn't mind giving this a go and maybe putting her back on the dyno to see if it can breathe easier.
Anyone out there know off the top what the 3.6L T/B measures out at (or would like to measure)?
#187
Pro
#188
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HOWEVER... (getting tired of howevers)
There is still a third related problem, once the car heats up, it still runs great, and idles great EXCEPT on a hot re-start it idles very poorly randomly, barely able to hold 680 RPM idle with no loads (stumbles a little as it dips lower) and then the ECU changes timing/adds fuel etc and gets the idle up and holds it steady and smooth for a long time, but will occasionally lose the 680 or 720 rpm and stumble again. In fact, it actually stalled on me at a stop light once. Once there is a load (A/C, fans, etc) it immediately smooths out again and can hold it indefinitely. No codes, of course, I'm dying for a code but the DME doesn't want to offer me any help.![Wink](https://rennlist.com/forums/images/smilies/wink.gif)
There is still a third related problem, once the car heats up, it still runs great, and idles great EXCEPT on a hot re-start it idles very poorly randomly, barely able to hold 680 RPM idle with no loads (stumbles a little as it dips lower) and then the ECU changes timing/adds fuel etc and gets the idle up and holds it steady and smooth for a long time, but will occasionally lose the 680 or 720 rpm and stumble again. In fact, it actually stalled on me at a stop light once. Once there is a load (A/C, fans, etc) it immediately smooths out again and can hold it indefinitely. No codes, of course, I'm dying for a code but the DME doesn't want to offer me any help.
![Wink](https://rennlist.com/forums/images/smilies/wink.gif)
What is driving me bonkers though is the idle.
![order](https://rennlist.com/forums/graemlins/order.gif)
#189
Three Wheelin'
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#190
Three Wheelin'
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Did you ever get this resolved? I've done the exact same thing that you did, with the exact same build, (threw a rod twice on the track, so two rebuilds) and I couldn't be happier!! What a machine it is now! (I actually did a bit more, single mass flywheel, Accusump, Oil crap, Tranny work, etc.) --- BTW, Love your head bolt idea, will do that next time I tear it apart.
What is driving me bonkers though is the idle.
Since the car mostly plays on the track, it's not too bad of a problem, but I still have the original stock seats, and would like to drive it on the street more.
What is driving me bonkers though is the idle.
![order](https://rennlist.com/forums/graemlins/order.gif)
It was a combo problem. My IACV was toast, the open winding was only providing half the resistance (this was the biggest contributor). But other things that were contributing: I didn't upgrade the injectors when I upgraded the displacenent (leading to a computer induced rich condition, and even though I had swapped the injectors for larger ones the computer hadn't learned yet, it needed a reset and was still dumping too much fuel), my MAF and CPS were also marginal. ALSO, make sure you don't have any vacuum leaks. I didn't, but did a very thorough check.
Now it PUUUURRRRRSSS at idle, but I don't spend much time there (I like the other end of the tachometer better).
![Wink](https://rennlist.com/forums/images/smilies/wink.gif)
![burnout](https://rennlist.com/forums/graemlins/burnout.gif)
Oh, forgot to mention those 3.6L cans I bought from a RL member, one of them has a broken baffle inside and squeaks/rattles all over the place, so this winter it will be off to Dr Fister D for repairs.
Last edited by logray; 10-16-2012 at 12:49 PM.
#192
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#193
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Logray - Thanks so much for undertaking this detailed writeup ! This is an Awesome and valuable thread to a guy like me: below is why....I am not sure my below warrants a new thread (I am not sure how forums work to well...I am kind of new)...but I am looking for 1) crank specs 2)feedback on my choices.
thanks
************************
I am rebuilding a 997.1 3.8L S motor (D-chunk crack cyl 5) into a 4.0. Likely failure was a gel slug behind the water pump (wrong coolant added?)....Oil was chocolate milk mixture. (bought it this way as a project with 100K miles on it); could be gel slug was from coolant added after Dchunk failure and low coolant showed....I will never know.
Cases are coming back next week from LN Eng with nickies and JE pistons. IMS solution also being installed in the rebuild.
This will be built for street...no plan to ever race...so following decisions were made (I am open to hearing advisement if you disagree on any decision or have opinions)
1) stock rods will be reused (new bearings)
2) Using NEW OEM bolts everywhere (connecting rods, head bolts,crankcase carrier bolts etc.....I was advised if not racing..then ARP would not be needed...only really needed for the high RPM abuse of racing)
3) replacing water pump
4) Undecided on LN eng billet timing chain guide ($330) vs stock ($40) since not racing...might do it anyway for "insurance"...since it is deep in the motor)
5) all new chains and guides
6) heads were inspected at a shop..they stated guides were good...just changing the seals and resurfaced them
7) all new oil separators
8) reusing oil/coolant heat exchanger (they seem to be a suspect part from what I read even when bought new they are no always good...so if it aint broke on that one I dont want to take a chance on replacement)
9) Bought wrist pin insertion tool..plan to grind wrist pin hook away (I read this is the flat six approach) on cyl 4-6
10) will weight and match all opposing pistons+rods+rings+bolts+pins+clips for best balancing
11) Undecided but probably will send crank and all parts to shop for professional matching(to confirm my work) and crank balancing/magnaflux (This is not where this motor had a problem..so I suspect magnaflux is not needed...but insurance again comes to mind))
...lots of other smaller decisions made...but above are the bigger ones or not fully decided ones to give folks a flavor of the project
REAL question for why I am writing...I cant for the life of me find specs for 3.8L crankshaft! Info is not in the WSM. Trying to confirm Journals are in spec for standard main bearings or not so I can make my big parts buy for the rebuild.
Below are my measurements:
Crank Main Journals: Average =62.992 +.0432 / -.0292 (Max=63.03518; Min= 62.96279)
Crank Rod Journals: Average = 52.98794 +0.018 / -0.0131 (Max=53.00599; Min=52.974875 if too many sig-figs please disregard. I measured in inches the converted in excel to metric..not sure why I didnt just do metric....I am just not used to metric.
Full Disclosure: I am mech eng...but this is my first engine rebuild..I will take a few deserved lumps on this not so smart choice to make a $20K porsche high performance motor my first build....I deserve that:-); restored various previous cars and done engine swaps...just never did an engine...but I am having loads of fun!
For everyones interest Pic of Gel slug and D-chunk crack are included here Since I havent seen many when I was looking. (I do videos talking to myself for future reference...not pictures...so sorry for quality)
![](https://forums.pelicanparts.com/uploads26/D_chunk_Crack1570338669.JPG)
thanks
************************
I am rebuilding a 997.1 3.8L S motor (D-chunk crack cyl 5) into a 4.0. Likely failure was a gel slug behind the water pump (wrong coolant added?)....Oil was chocolate milk mixture. (bought it this way as a project with 100K miles on it); could be gel slug was from coolant added after Dchunk failure and low coolant showed....I will never know.
Cases are coming back next week from LN Eng with nickies and JE pistons. IMS solution also being installed in the rebuild.
This will be built for street...no plan to ever race...so following decisions were made (I am open to hearing advisement if you disagree on any decision or have opinions)
1) stock rods will be reused (new bearings)
2) Using NEW OEM bolts everywhere (connecting rods, head bolts,crankcase carrier bolts etc.....I was advised if not racing..then ARP would not be needed...only really needed for the high RPM abuse of racing)
3) replacing water pump
4) Undecided on LN eng billet timing chain guide ($330) vs stock ($40) since not racing...might do it anyway for "insurance"...since it is deep in the motor)
5) all new chains and guides
6) heads were inspected at a shop..they stated guides were good...just changing the seals and resurfaced them
7) all new oil separators
8) reusing oil/coolant heat exchanger (they seem to be a suspect part from what I read even when bought new they are no always good...so if it aint broke on that one I dont want to take a chance on replacement)
9) Bought wrist pin insertion tool..plan to grind wrist pin hook away (I read this is the flat six approach) on cyl 4-6
10) will weight and match all opposing pistons+rods+rings+bolts+pins+clips for best balancing
11) Undecided but probably will send crank and all parts to shop for professional matching(to confirm my work) and crank balancing/magnaflux (This is not where this motor had a problem..so I suspect magnaflux is not needed...but insurance again comes to mind))
...lots of other smaller decisions made...but above are the bigger ones or not fully decided ones to give folks a flavor of the project
REAL question for why I am writing...I cant for the life of me find specs for 3.8L crankshaft! Info is not in the WSM. Trying to confirm Journals are in spec for standard main bearings or not so I can make my big parts buy for the rebuild.
Below are my measurements:
Crank Main Journals: Average =62.992 +.0432 / -.0292 (Max=63.03518; Min= 62.96279)
Crank Rod Journals: Average = 52.98794 +0.018 / -0.0131 (Max=53.00599; Min=52.974875 if too many sig-figs please disregard. I measured in inches the converted in excel to metric..not sure why I didnt just do metric....I am just not used to metric.
Full Disclosure: I am mech eng...but this is my first engine rebuild..I will take a few deserved lumps on this not so smart choice to make a $20K porsche high performance motor my first build....I deserve that:-); restored various previous cars and done engine swaps...just never did an engine...but I am having loads of fun!
For everyones interest Pic of Gel slug and D-chunk crack are included here Since I havent seen many when I was looking. (I do videos talking to myself for future reference...not pictures...so sorry for quality)
![](https://forums.pelicanparts.com/uploads26/Gel_Slug1570338917.jpg)