Engine dyno and chassis dyno.
After x pipe....
- Thread starter Mopar Tim
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moper
Well-Known Member
I don't care if he's Jesus. It's wrong. The X pipe made it go leaner, which is exactly what it is supposed to do. That's why the power it's making at idle changed, and as a result the idle changed. But like I said if you're at 1100-1200. the carb's not on the idle circuit entirely. So it's going to be harder to tune trying to use the idle mixture screws. You need to set the timing curve, lower the idle rpm, then re-tune the mixture screws to the highest vacuum reading at your final idle speed.
Sorry, I wasn't questioning his or your expertise. I just know that things are different on the street than they are in a dyno cell. I was just trying to help you suss out your minor inconvenience. I'm thinking your idle is a bit much for a stroker with that cam. When I last had my 416 running, it was idling about 750 - 800 with a bigger bumpstick and a Thermoquad.
I'm just suggesting that there might be more tuning needed now that you have changed your backpressure.
Cool beans. Post up on this thread when you get her going.Thank you both^^^ Good info.I never liked not having a PCV so im adding one, and will work out the tune when I get that installed. Thanks again^^^
I think the overlap makes it a little rough at Idle more than the lift or duration. But I will be the first to admit I am not really up on all the aspects of how a cam makes power. .
I will......Again
Both
Lustle
Well-Known Member
I just wanna check something. Are you sure that cam card is correct?
Cause I'm seeing a cam with a 102 lobe separation. 247/250 duration at 50. That is a serious cam for a small block. Even a 408 cube small block. Power with a cam like that wouldn't come on until at least 3,000 rpm. Maybe higher? What is this in? I'm also surprised at his recommended stall...
If the cam card is correct then I also have to disagree with moper. A 1000-1200 rpm idle seems in place for a cam like this. Looks a lot like a circle track cam.
That is what it is! you are correct and that card is correct. A 408 stroker 411 gears 69 Dart .
Lustle
Well-Known Member
Street dart? Or drag car?
That would be a heck of a cam on the street. And I'm still surprised at his recommended converter. I mean if I had a cam like that I would think I'd be running a 5k stall converter. Hmm.
But yes. An idle of 1000-1200 sounds right for that lobe separation/duration. That thing must sound nasty. What exhaust did it have before? Just dual? What's it's idle in park, before and after? 1200? And it drops to 1000 in gear? With a large drop like that and that tight converter that would explain the hard engagement. It's a sudden load on the driveline. If the drop was less rpm or the converter looser you wouldn't notice it as much. As for why it idles different now. As others have mentioned it's probably leaner with the new exhaust. The x-pipe is not only more efficient. But also more "spacious", the exhaust gas now has more places to go. Have to talked to the builder and asked him his recommendation?
Yes a street Dart. It does sound nasty. Had duel before, just added the X pipe to get a smoother sounding idle. park 1200 RPM, Goes down to 1000 in drive. I am calling him Monday morning. It is a quick little Dart!
He told me that cam would act like a big cam without the problems of a big cam on the street. His own grind design.
Lustle
Well-Known Member
Yeah the 200 rpm drop is what's causing the hard engagement. It's the load on the driveline that is doing that. So it idled at 1200 in and out of gear before that?
Yes it did. Maybe a 50RPM drop.
Lustle
Well-Known Member
Ahh ok. Yeah I imagine it's just the more efficient exhaust. Just have to retune for the x pipe.
Thanks for your input. I came up against a 69 396 Malibu yesterday, poor guy never had a chance!
that engine is in this.
And the Converter is a custom built unit for the engine build. He told me it was on the conservative side for "street" use. Stall being 3000RPM. Talked to the builder this morning.
seabee
Well-Known Member
What throttle/kickdown linkage is that? Beautiful ride!
Thanks. It has a reverse pattern manual valve body. No linkage. Not needed, and every Mopar I own from now on will have this as well. That setup from Mopar is a pain.
Well how did the PCV valve work out? I'll let you tell me weather it's worth the money.
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