Big Cam=Poor choice= poor result.
Thread Starter
Teching In
Joined: Mar 2007
Posts: 41
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From: West Australia
Big Cam=Poor choice= poor result. I Have just got my 383 back from the tuner has PP stage 2 LS6 heads Fast90/NW90 and a comp 242/244 on 110+4.
Car laid down 431rwhp on a dyno dynamics dyno and under 2000rpm its undriveable, just bucks and surges.
Above 2000 rpm the thing takes off like a rocket ship and it sounds like a warzone at idle but the amount of overlap caused too much reversion in the intake and no amount of tuning could overcome it, plus it left a pretty hefty hole in the lower end of the torque curve.
Im going to do some more homework now and drop back to a 230ish something cam depending on what I can decide on.
Hopefully with the 10 degree drop the torque curve should come up to a respectable amount and the bucking and surging should disappear.
If anyone has any suggestions I'd be happy to hear it and hope my mistake can help some others along the way.
Car laid down 431rwhp on a dyno dynamics dyno and under 2000rpm its undriveable, just bucks and surges.
Above 2000 rpm the thing takes off like a rocket ship and it sounds like a warzone at idle but the amount of overlap caused too much reversion in the intake and no amount of tuning could overcome it, plus it left a pretty hefty hole in the lower end of the torque curve.
Im going to do some more homework now and drop back to a 230ish something cam depending on what I can decide on.
Hopefully with the 10 degree drop the torque curve should come up to a respectable amount and the bucking and surging should disappear.
If anyone has any suggestions I'd be happy to hear it and hope my mistake can help some others along the way.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
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From: BFE
Yeah, if you have the $$ buckaroos, get a Harrop ITB setup, it will idle like a kitten and scream like an eagle.
But 23* overlap shouldn't be a problem with that size motor.
Could you give us a beakdown of your combo, compression etc...
If it all jives well, then might want another tuner
But 23* overlap shouldn't be a problem with that size motor.
Could you give us a beakdown of your combo, compression etc...
If it all jives well, then might want another tuner
Thread Starter
Teching In
Joined: Mar 2007
Posts: 41
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From: West Australia
Yeah, if you have the $$ buckaroos, get a Harrop ITB setup, it will idle like a kitten and scream like an eagle.
But 23* overlap shouldn't be a problem with that size motor.
Could you give us a beakdown of your combo, compression etc...
If it all jives well, then might want another tuner
But 23* overlap shouldn't be a problem with that size motor.
Could you give us a beakdown of your combo, compression etc...
If it all jives well, then might want another tuner
The harrop intake is a bit out of budget and the loss of driveabilty annoyed me the most, more HP would be nice though. Im all ears Predator if you have any ideas on a new cam.
Last edited by R32WA; Mar 20, 2008 at 07:40 AM.
Driveability, for the most part is all in the tune.
A good tuner will mess with the lower tables to get you ball parked, then from there its all in the datalogging and driving, THEN go back for a readjustment, thats whats going to give you the lower rpm driveability.
Question, What transmission and rear end gear ratio? Also stock sized tire, or something taller?
A good tuner will mess with the lower tables to get you ball parked, then from there its all in the datalogging and driving, THEN go back for a readjustment, thats whats going to give you the lower rpm driveability.
Question, What transmission and rear end gear ratio? Also stock sized tire, or something taller?
Thread Starter
Teching In
Joined: Mar 2007
Posts: 41
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From: West Australia
6 speed 3.91 rear end stock tires, the tuner that did it is one of the best in the country and from what it was to what it is is a world apart it was more my poor choice on the cam for what i expected really
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Thread Starter
Teching In
Joined: Mar 2007
Posts: 41
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From: West Australia
I know the dyno dynamics used here read a lot different to the dynos used in the US, how much exactly Im not sure but they do read lower.
That is pretty odd. My TRex/stock bottom end cruises pretty well at about 16-1700 rpms. I don't think there's anything wrong with your cam choice. Do you have a dyno graph?
Thread Starter
Teching In
Joined: Mar 2007
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From: West Australia
I do I'll scan it and post it up tomorrow. I didnt think this cam would be too big for the 383 , I tried to up the compression and advance the cam to try counter act some of its bad traits, the moment it drops under 2k it starts to stumble, I have to drive everywhere in 4th to keep it smooth but that attracts too much attention because its loud. At this stage it looks like I'll be going for a comp XER281HR cam 232/234 .595/.598 on 112 unless I can find something else not sure if something on LSK lobes would be better yet.
232/234 .595/.598 on 112
****...that's not much different than what i have in my 346.....and it runs reasonable smooth down low...on a crappy tune.
i can cruise at 1200-1800 no problem....only a little surge here and there.
something else is wrong
****...that's not much different than what i have in my 346.....and it runs reasonable smooth down low...on a crappy tune.
i can cruise at 1200-1800 no problem....only a little surge here and there.
something else is wrong
Okay, to all the people who say that driveablity is all in the tune, I have to disagree. I would say "the proper tune can make a cam more driveable than if the tune is not spot on"
At some point a huge cam is just going to be unruly on the street - end of story. And he's running a pretty big cam for stock displacement.
At some point a huge cam is just going to be unruly on the street - end of story. And he's running a pretty big cam for stock displacement.
I have a larger cam than that in a 347 and it's perfectly drivable. ...and it makes 433RWHP, something is not right here. I'd guess it's the tune. ...if not...
...I'd go back to the basics. Compression and leakdown tests, make sure you have fire on all 8, make sure you're getting fuel in all 8, etc.
Any codes? Vaccum leaks?
...I'd go back to the basics. Compression and leakdown tests, make sure you have fire on all 8, make sure you're getting fuel in all 8, etc.
Any codes? Vaccum leaks?
Thats a healthy cam for sure, but I vote for a tune problem. YYZ28 said is best... go back to basics.. make sure it is mechanically sound, then if everything is cool, bust open that tuning software and start logging. Post your tune or a log to the PCM section (or here) if you want someone to look at it.
For comparison; my 383 stroker has a much smaller cam than that and it put 492hp to the wheels through a 4.11 geared Ford 9".
For comparison; my 383 stroker has a much smaller cam than that and it put 492hp to the wheels through a 4.11 geared Ford 9".
Last edited by Goldfinger911; Mar 21, 2008 at 01:53 AM.
well i would look at the tune because i had the same problem with my t-rex. also dyno dynamics always read low. take it to the track and look at your mph to see the real horsepower.