Another Guess the HP thread - 428 Street Motor

[FElony]

OK, fastf67 and Dougie. You guys are the shizznit. Your guesses are not guesses, they are the epitome of careful, logical, wondrous mental calculations. The rest of humanity would be so much more tuned and ethereal if only they could achieve a fraction of your talent and modesty. Personally, I stand in awe. Or, I would stand if only my entire blood reservoir wasn't 80 proof right now. Neverthelesssss, the rest of America is beholden unto you.

I would really like to hear an FE at 9 grand, but it ain't to be seen in anybody's lifetime.

And, if Jay actually had t-shirts, he wouldn't have to rely on me to supply accolades. Get with the proggy, froggy.

[FElony]

And let's have a meaningful discussion about the two torque curves. We all know that hp ain't jack; it's tq that moves the car.

[cjshaker]

The only thing that sorta surprised me is the 400 rpm difference in torque peak between race and premium fuel, with premium  winning at +2 @ 400 rpm lower. I guess the slightly slower burn rate couldn't compete at that low of an rpm on what is basically a pump fuel street engine, even with advanced timing?

FElony, Shady and I have been very close on almost every guess. Him and Harley Jack almost nailed the HP guess. I don't know about Shady, but I have a pretty simple rule I follow. Seems to work pretty good most of the time.

[My427stang]

Jay, which beehives and retainers did you use and at what installed height?

[jayb]

Comp 26120 springs and the matching steel retainers, setup up at 1.88" installed height.  They measured just about as specified for seat pressure, 150-155 pounds.

[Joe-JDC]

I would think that the 230* camshaft duration @ .050" might be the reason the engine noses over instead of lifter issues.  That is a lot of seat pressure for only 5300 rpm or so.  Still, great information, and glad you posted it for us.   Joe-JDC

[blykins]

I think that hyd setup did exactly what it should have done.  A .030” over 428 with unported edelbrock heads and a short duration cam with no duration split won’t be a high rpm engine.

I’ve done several 428CJs here with similar specs (but more exhaust duration) and about 5500 is about all they can do.

Spring pressures are fine for 5500, and the dyno sheets didn’t show any valve float, it just simply ran out of camshaft.  I think if you would have had more duration though, the lobe design would have needed to be different or it would certainly not have lived up to expectation.  Those Xtreme Energy lobes are not easy on stuff.

Ok, so I was a little off on my guess......

I do think with some more tuning that the engine vacuum could be improved upon.  11 inches seems low for 62 deg of overlap.

[fastf67]

Very nice torque #s. I knew it would come in pretty quick and hold awhile, but not expecting to see it hit 500+. That will hold you in your seat with a smile.
       P.S.
             Your tire dealer will love you. Lol

[plovett]

Interesting.  My Eboks like 36-37 degrees total timing on high octane pump gas.

Nice engine!

[jayb]

I think that hyd setup did exactly what it should have done.  A .030” over 428 with unported edelbrock heads and a short duration cam with no duration split won’t be a high rpm engine.

I’ve done several 428CJs here with similar specs (but more exhaust duration) and about 5500 is about all they can do.

Spring pressures are fine for 5500, and the dyno sheets didn’t show any valve float, it just simply ran out of camshaft.  I think if you would have had more duration though, the lobe design would have needed to be different or it would certainly not have lived up to expectation.  Those Xtreme Energy lobes are not easy on stuff.

Ok, so I was a little off on my guess......

I do think with some more tuning that the engine vacuum could be improved upon.  11 inches seems low for 62 deg of overlap.

I don't agree that the dyno sheets didn't show any valve float, the early ones certainly did.  The one graph I showed with the green tangent lines on it show a clear discontinuity in the horsepower curve.  I've dynoed enough engines to know that isn't normal; a discontinuity like that is a dead giveaway to valvetrain issues.  However, the issue seemed to go away as the oil temp rose and the dyno session went on.  Also, I do agree that the peak HP RPM was about where it should be; any valvetrain issue in the early pulls didn't really affect peak HP production.  What surprised me the most was the high RPM where the engine made peak torque on race gas; I was figuring 3600-3700 RPM for the peak torque value, and that's where it landed on the pump fuel, but the race gas was higher.  Go figure...

Brent, I'm curious about how you think idle vacuum can be improved.  Are you suggesting different carb tuning?  The idle vacuum seemed pretty much in line with what I was expecting, but if there's something I could do to make it better, I'd give it a try.

[cjshaker]

What surprised me the most was the high RPM where the engine made peak torque on race gas; I was figuring 3600-3700 RPM for the peak torque value, and that's where it landed on the pump fuel, but the race gas was higher.  Go figure...

I mentioned that in my post. If I recall correctly, doesn't race gas have a slightly slower burn rate? That would probably affect torque output, especially at lower rpms. You'd think that the advanced timing might overcome that, and this is just a guess, but I think it just wasn't optimal for the engines operating parameters. The faster burn rate and retarded timing just seemed to be the optimal point for the engine. Knowing that, if I was going to race it, I'd probably just run premium with the backed off timing (also safer), and maybe just toss a gallon or 2 of race gas in if I were worried about detonation.

All the above are just guesses though.

[shady]

FElony, Shady and I have been very close on almost every guess. Him and Harley Jack almost nailed the HP guess. I don't know about Shady, but I have a pretty simple rule I follow. Seems to work pretty good most of the time.

Well, I figure what I think the engine should do & then I take 10% off  for being overly optimistic. 

[blykins]

I usually see loss of valvetrain control (or float) as an up/down in hp within several hundred rpm.  I'll have to go back and look at your charts, but it looks like it was just done and just fell off.   This one is in that black/white area of not being able to really see what the real underlying issue is.....if it's done without valvetrain control issues, then the cam was too short.  If it was done because of valvetrain control issues, then it was an aggressive lobe coupled with heavy valves. 

I will say this, if the cam had been made to the numbers in the lobe catalog, I think it for sure would have been easier on things.  I typically try to aim for around 55° major intensity (delta between advertised and .006" duration on a hydraulic cam) because I've found that to be a sweet spot in terms of noise, power, and ability to rpm.   I think those Xtreme Energy lobes are nice for SBF's/SBC's with 11/32" stemmed 2.02/1.6 valves and polylock adjusters, but once you introduce a big FE valve and a rocker arm with the adjuster hanging off the hindend, the weight combined with the lobe aggression start to be too much.

Those Comp beehive springs setup as advertised (155-160 seat, 385-390 open) will let an FE hang on to 6500 with non-adjustable rockers, 11/32" stemmed 2.150/1.625 valves, and the correct lobes. 

As for tuning, what did you have the initial timing set at?  I'd be tempted to try it at 18-20 initial and then try to close the butterflies a little more for increased vacuum.  I was pretty shocked to see only 11" of vacuum with that little cam. 

[blykins]

Jay, your graph from this dyno is what I generally associate with valve float:

http://fepower.net/simplemachinesforum/index.php?topic=2675.0

The horsepower starts to go up, then dip, then come back up. 

Now, it could be that the lifters were giving up and not able to hold the valve spring pressure, but I only see that on aggressive cam lobes and it's audible on the dyno.  The last time I heard it was with a 230/236 Xtreme Energy cam that the customer supplied, in combination with 3/8" stem 2.09/1.65" valves and Comp Cams lifters. 

[blykins]

Jay, are the timestamps on the dyno sheets when you did a snapshot, or when the pull was?