Missed Shift = Bent Valves?
07-11-2012, 01:48 PM
#17
Former Vendor
Join Date: May 2012
Location: Petaluma CA
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+1 on this. I have seen this multiple times and always after a spin. Check the bottom plenum hoses on each cylinder inlet where the plenum mates to the intake adapter.
07-11-2012, 03:44 PM
#18
Race Car
I didn't put 2 and 2 together that this is the ex-Serge 4.0L car we're talking about here. Hopefully it's just the Pleanum hose and no harm was done to that awesome motor.
Did you ever dyno the car after final tuning was done?
Did you ever dyno the car after final tuning was done?
07-11-2012, 05:07 PM
#19
Hey guys. Thanks again for all the replies! And sorry for not getting the video of the spin up last night...I got distracted with the car....
So I was probably an hour's worth of work away from dropping the motor yesterday but with all the responses pointing to a blown hose at either the plenum or intake manifold, I figured I better go take a look before proceeding any further with dropping the motor. Well low and behold, the driver's side hose between the plenum and "intake distributor" as the PET calls it (what connects the plenum to the intake manifolds), was indeed blown off! I couldn't believe it. So rather than upload video of the spin, I worked into the wee hours of the morning to reattach the hose and button her all back up so I could fire her up in the morning (cup exhaust at 4 AM is not appreciated by the neighbors
). I only had about 5 mins this morning before heading into the office but thought I might as well give her a go. She started right up and idled normally with no popping, etc. However, I'm still trying to discern whether or not there is now more valve train noise than before. For some reason I think there is. I only let it run for about 30 secs as I didn't have time to really listen and play with it, but hopefully tonight. With all that said, I am still concerned with the leakdown results on number 3. But when I tested it was cold so I will definitely be doing another leakdown with the engine warm.
One thing I noticed though, is that there appeared to be a lot of room b/w the plenum and intake distributors, so much so that I had to position the plenum just right in b/w the intake distributors to get the rubber sleeves to "be on" on all sides. Basically I wasn't able to get the sleeve's fully seated against both sides of the plenum and intake distributors. Not sure if this is easy to follow but it seemed like the intake distributors need to be "squeezed" together another inch. Anyone have any experience with this on their cars? Or even get what I'm saying?
Audion19s - yes, this is indeed Serge's car with the awesome motor in it. You can bet that if any internal damage was done it will be fixed ASAP and the motor will be just as awesome or even more awesome than before. The only upside to pulling the motor is that I can swap in some new cams as it's currently running the stock 996 cams which is one of the items really limiting the output of the motor (along with intake and headers). I did get it tuned and dyno'd down at 911Design and she put out about 370hp to the wheels and just over 300 ft-lbs on a Dynapack dyno (7-10% lower than a Dynojet from what I've read). Overall power was a bit lower than expected but the powerband was quite nice though and the torque comes in very low which makes it quite fun on the street. Talking with Loren at 911Design, he thinks that depending on which cams I go with, I could see anywhere from 20-50hp at the wheels. And that could be even more with a 997 cup intake but unfortunately that is a pain w/o switching the oil cooler housing and other parts. A set nice set of headers (currently have stock 997 GT3) could probably add another 10-15hp to that number. Bear in mind all these numbers are estimates and I am in no way making claims that these numbers would actually be realized
And IIRC, Loren was saying that the highest HP he's seen on his dyno from a 4.0 cup motor with vacuum pressurized oil system, etc was 475-500hp (I can't remember what exactly he said).
So I was probably an hour's worth of work away from dropping the motor yesterday but with all the responses pointing to a blown hose at either the plenum or intake manifold, I figured I better go take a look before proceeding any further with dropping the motor. Well low and behold, the driver's side hose between the plenum and "intake distributor" as the PET calls it (what connects the plenum to the intake manifolds), was indeed blown off! I couldn't believe it. So rather than upload video of the spin, I worked into the wee hours of the morning to reattach the hose and button her all back up so I could fire her up in the morning (cup exhaust at 4 AM is not appreciated by the neighbors
). I only had about 5 mins this morning before heading into the office but thought I might as well give her a go. She started right up and idled normally with no popping, etc. However, I'm still trying to discern whether or not there is now more valve train noise than before. For some reason I think there is. I only let it run for about 30 secs as I didn't have time to really listen and play with it, but hopefully tonight. With all that said, I am still concerned with the leakdown results on number 3. But when I tested it was cold so I will definitely be doing another leakdown with the engine warm. One thing I noticed though, is that there appeared to be a lot of room b/w the plenum and intake distributors, so much so that I had to position the plenum just right in b/w the intake distributors to get the rubber sleeves to "be on" on all sides. Basically I wasn't able to get the sleeve's fully seated against both sides of the plenum and intake distributors. Not sure if this is easy to follow but it seemed like the intake distributors need to be "squeezed" together another inch. Anyone have any experience with this on their cars? Or even get what I'm saying?
Audion19s - yes, this is indeed Serge's car with the awesome motor in it. You can bet that if any internal damage was done it will be fixed ASAP and the motor will be just as awesome or even more awesome than before. The only upside to pulling the motor is that I can swap in some new cams as it's currently running the stock 996 cams which is one of the items really limiting the output of the motor (along with intake and headers). I did get it tuned and dyno'd down at 911Design and she put out about 370hp to the wheels and just over 300 ft-lbs on a Dynapack dyno (7-10% lower than a Dynojet from what I've read). Overall power was a bit lower than expected but the powerband was quite nice though and the torque comes in very low which makes it quite fun on the street. Talking with Loren at 911Design, he thinks that depending on which cams I go with, I could see anywhere from 20-50hp at the wheels. And that could be even more with a 997 cup intake but unfortunately that is a pain w/o switching the oil cooler housing and other parts. A set nice set of headers (currently have stock 997 GT3) could probably add another 10-15hp to that number. Bear in mind all these numbers are estimates and I am in no way making claims that these numbers would actually be realized
And IIRC, Loren was saying that the highest HP he's seen on his dyno from a 4.0 cup motor with vacuum pressurized oil system, etc was 475-500hp (I can't remember what exactly he said).
07-11-2012, 05:50 PM
#20
Rennlist Member
In a nutshell, peak power slides in right between a factory 3.8 and RS 3.8. Power up to 5500rpm or so (aka Torque) ANNIHILATES the RS 3.8 and is also slightly better than the factory 4.0. The 996 cams really do limit peak power output, as was expected. Though, I was anticipating another 20 or so peak hp.
I'm very selfishly hoping that this engine does get some 997 intake cams and higher flowing cats.
I'm very selfishly hoping that this engine does get some 997 intake cams and higher flowing cats.
07-11-2012, 06:13 PM
#21
In a nutshell, peak power slides in right between a factory 3.8 and RS 3.8. Power up to 5500rpm or so (aka Torque) ANNIHILATES the RS 3.8 and is also slightly better than the factory 4.0. The 996 cams really do limit peak power output, as was expected. Though, I was anticipating another 20 or so peak hp.
I'm very selfishly hoping that this engine does get some 997 intake cams and higher flowing cats.
I'm very selfishly hoping that this engine does get some 997 intake cams and higher flowing cats.
And it doesn't help that there is a full catless RSR exhaust as well as a set of GMG headers in the classifieds right now!
07-11-2012, 06:48 PM
#22
Race Car
With regard to the plenum not seating into the rubber sleeves/ tubes that far, I also made that observation when I split all of that apart to get my coolant fittings off to be welded....or when I was putting it back together actually. That's probably why they come apart easily when you spin
Glad to hear its back up and running.
Glad to hear its back up and running.
07-11-2012, 06:50 PM
#23
Nordschleife Master
If tire lock up you are usually good
If not cluth / pp go boom
if they hold up you have a bent valve, if a valve is bent the car sounds like a popcorn popper
If not cluth / pp go boom
if they hold up you have a bent valve, if a valve is bent the car sounds like a popcorn popper
07-12-2012, 12:25 AM
#24
Well guys here is the video of the spin. Figured I'd throw an extra lap in at the beginning so the spin is right at the end of this clip. I was just getting into the groove too...
Off to go play with the car...
Off to go play with the car...
07-12-2012, 12:54 AM
#25
Rennlist Member
Looks like you were in 2nd and tried to go to 3rd but ended up on 1. That's not all that bad. We're you provided a leakdown test prior to buying car? I was far worse then u in the misshift category but since engine is upsized I don't know how tite the tolerances are for over revs. Mike
07-12-2012, 11:30 AM
#26
Rennlist Member
I would doubt you were in 1st when you spun. Looked at previous shots when in 3rd and the gear lever position seems the same as in the shot when you're about to spin. Also it looks as if you have engaged the specific gear completely. If you were to engage 1st, i think you would have heard a 9.000 + Revs kind of noise. Couldn't this be just a simple rear wheel lock by lifting the clutch too abrupt ?
07-12-2012, 11:52 AM
#27
Rennlist Member
To make an intake plenum blow takes more then a spin. Clutch is in gear and usually the wrong one so engine is heavily loaded and going backwards. That is a pretty instantaneous snap. Mike
07-12-2012, 02:12 PM
#28
Race Car
