First drive with the updated 390, comparison to "old" 390

[Bolted to Floor]

Thanks for the ride.   

[My427stang]

Sounds GREAT for a 390 in a big car...wait until we get you bit by the 4.25 stroker bug

[chilly460]

Thanks for the feedback guys.  On reflection I think I was expecting a bit much from this.  Maybe the best testament to the combo is it never feels like it's in a "big" car.  I guess I've been driving trucks and other heavy vehicles so long, I don't even think of the Merc as being "big".  Anyway, light throttle, cruise, rolling throttle, WOT...it never feels like it's hooked to a 4400lb combo.  2000rpm in O/D, it pulls great, and now with the new combo it feels pretty good over 4500 where it used to flatten out.  Will get it on dyno and try to get it to the track to quantify things. 


Lol, already there, Ross.  I have a 428 block I bought from Jay, Blue Thunder 2x4, carbs on the way from Drew, and picked up some Mahle pistons for a 4.16 x 4.25 stroker I found at Carlisle for $150....all plans are in place to put a pretty nice 462" together.   Deciding if I want to run a set of Medium Risers I have on the shelf (after port work) or go with a set of TFS. 

[turbohunter]

Looks like fun. And yeah, sounds great. Congrats.

[Drew Pojedinec]

I have a 428 block I bought from Jay, Blue Thunder 2x4, carbs on the way from Drew

Two boxes should be knockin on your door tomorrow

IMG_0792 by Drew Pojedinec, on Flickr

Adding 70ci is going to make this feel like a different animal for sure.

[chilly460]

The Ass-o-meter calibration was pretty good.  I thought it was around 30hp better, it was 34hp stronger this time around with best gains over 4500, but better through the whole curve, smoother curve up top, made 334rwhp at 5500 and 386ftlbs at 3400.  Nice tow truck motor. 

 Overall a good day, started with 32* and it was up 10hp at 34* then down 5hp at 36*.  Not apples to apples, being run on a different day, 99* in the shop and water was at 205* for the pulls so it’ll like cool weather.  Just a tiny bit fat in the midrange but perfect otherwise so I’ll leave jets as is, they’ll be perfect in cooler weather

https://youtu.be/lwjz56WuBe0

https://youtu.be/YVq0iSd8Pmc

[blykins]

Pretty healthy bump for no increase in peak horsepower RPM.

[chilly460]

Yep, after thinking on it a bit, happy to pick up a good chunk of power along with actually helping low rpm power as well

[gdaddy01]

very nice , I will have to save this one , thanks for sharing .   

[Barry_R]

A 10-12 percent gain with no negative sounds about perfect for this type of deal.  Never tested that particular swap, but based on other ones I have compared I imagine that the cam is probably 50% of the gain here.  I normally try & spec hydraulic rollers to peak somewhere between 5500 and 6000 depending on the build and vehicle (weight, power requirements, compression, O.D. trans is a big one because of cruise RPM...).  That particular cam has become a "go to" for use in big cars and you have the reason "why" right there - no downside at lower RPM and still works well further up the curve.

[chilly460]

Barry, I'm definitely happy with the cam.  As stated, it's helped the lowend, and helped it pull 4500+ and flattened the curve up top.  It pulls O/D cleanly at 1600rpm, and is "on the cam" at 2000rpm, can easily roll into the throttle at 60mph cruise and zip up to 80mph without a downshift.  In the video I took of the Dynojet display, you can see he ran it to 6000, it would never get there with the old combo, it ran clean but was flat over 5200rpm or so and would labor over 5500, absolutely no reason to run it up beyond there previously. 

 

[BigBlueIron]

Chilly,

Having never been on a wheel dyno give me an idea of what you have for a trans and what gear the pull is made in. I assume close 1:1 as possible.

And I'm curious how gear ratio and tire size plays into the outcome.

[chilly460]

TKO 500 trans in 4th gear, which is 1:1, 4.10 rear, 28" tire. 

I assume they run it in 1:1 to reduce variables caused by the trans gear adding additional leverage, and it bypasses the cluster gear so .  As for rear gear, I've read up a bit on it and there's a rule of thumb that for every change of 1.00 in the rear ratio - 15-20hp I've seen thrown around.  No idea if it's true, but did find quite a few references to the lower gears being down on power so I'm guessing there's some credence to it.  Whether it's due to increased friction or with how it calculates inertia into power figures, nobody seems to really know. 

My thoughts are a lot of the myths/guesses/rules of thumb from chassis dynos stem from guys trying to justify why their car didn't pull as much HP as they thought it would.  God help the high stall convertor auto guys, their chassis dyno numbers are all over the place. 

In the end, any attempt to calculate actual flywheel HP from a chassis dyno number usually is fruitless.  Always boils down to what it will do at the track.  I had a '93 Lightning, basically stock with a supercharger pushing 7psi with a tired engine that pulled 300rwhp but ran 13.01 at 103mph at the track and surprised me.