Another Guess the HP thread - 428 Street Motor

[jayb]

The time stamps are when I created and copied the charts, not when the pull was.

Brent, if you've got a copy of my book, look on page 228 to see an example of a solid vs. a hydraulic in a similar engine to the 428 in this thread.  The hydraulic cam HP trace looks just like the one from this engine with the green lines drawn in, even tips over at the same engine speed.  If you don't have a copy of my book, you should 

I have seen traces like the one you posted too, but those curves were on a solid lifter engine, not a hydraulic lifter engine.  Also based on your comments I don't think any loss of valvetrain control was due to the springs.  I think what is happening at the higher engine speeds is that the lifters are pumping up, and holding the intake valves off the seats when the lifter is on the heel of the cam, resulting in the power loss.  With hotter oil, the lifters can bleed down faster, and the problem starts to go away.  Also thinner oil; the problem would have been worse with 10W40, but may have been better with 5W20. 

On the timing, there was 24 degrees built into the Unilite distributor, and I had no way of changing that without also changing total timing.  I always tune for total timing on the dyno, to protect the engine at high speeds.  Based on the 24 degrees in the distributor, the engine probably only had 8-10 degrees of initial.  It makes sense that vacuum would improve with more initial timing, and I will suggest a distributor mod to the owner of the engine.  If he had 18 degrees in the distributor the initial would be 14-16, and I'll bet that you are correct that it would improve the vacuum.

[blykins]

Jay, I've used those very lifters up to 6500 rpm, with 10W30 and usually colder oil temps, with spring pressures up to 400 lbs open, and preload set at .060".   I really don't think yours were pumping up.   IMO, it was the cam giving out, or it was a combination of aggressive lobe with heavy valvetrain. 

Here's a dyno sheet of the 390 with TFS heads.  It used pretty much the same parts that you have, including the same beehive springs, standard Morel lifters, 10W30 oil, and pretty cold oil.  Cam lobes were lazier than yours and used 2.190/1.625, 11/32" valves.  We pulled it to 6500 and as you can see, it had only lost 1 hp between 6250 and 6500 rpm. 



Please know that I'm not being argumentative, I'm just trying to put a finger on exactly what was causing the drop off. 

[jayb]

I'm not trying to be argumentative either, and I think you hit the nail on the head with the cam lobe.  If this is a rather aggressive lobe, maybe it is causing the lifters to pump up, when the oil is thicker.  You have more experience with these lifters than I do, but its pretty clear that something is going on, and its not the springs.  So, combination of the lobe and the hydraulic lifters, and oil temps below 200?  That discontinuity in the HP curve is caused by something...

[My427stang]

Jay, if you think it’s got float throw a set of .050 keepers in there and see what happens. It will raise pressure by 18 lbs or so and you are still a mile from coil bind with that cam. If it is valvetrain related it should move up little before it loses control.

[jayb]

I don't think its valve float, Ross, I think the lifters are pumping up and leaving the valves open by some small amount, so the combustion chamber isn't perfectly sealed when the spark plug fires, causing the power loss.  Hotter oil is thinner, and the pressure is down, so that improves the lifter pump-up situation.  A more radical cam lobe makes it worse, because the closing ramp is faster, and would make it easier for the lifter to accept more oil and pump up while the valve was closing.  Just a theory of course, but my observations on this engine were an observed discontinuity in the power curve around 5300 RPM until the oil temperature got to over 200 degrees, and Brent's confidence in the valvesprings being capable of running to 6500 RPM with the right combination of parts.  If the issue is not the valvesprings, and is dependent on oil temperature, can you think of another explanation?

The test I thought about running is to put zero pre-load on the lifters and see if that changes the power curve when the oil is cold.  If that eliminates the discontinuity in the power curve, then I think it has to be a lifter issue.  But if it doesn't, that also doesn't necessarily mean its NOT a lifter issue.  Regardless, its not my engine to play games with, so I'm not going to run that test.  Maybe next time... 

[My427stang]

Well Brent knows how to make those Morels work, I would follow his lead.  One question I have is on the lobe, is it 288 adv or 282? The lobe number is 288 at .006 in the catalog, but lift didn’t seem to match up to anything with a 1.76 or 1.73 ratio either.

[Barry_R]

Looks like valvetrain control issues to me.  The term "float" is something of a misnomer - - its more a matter of the combination of spring, cam, rocker, and valve weight simply being "unhappy".  I have had reasonably comparable packages RPM nicely beyond 6000, and others do what happened here.  The sharp nose over is a key indicator.

The lifters do not really "pump up" all the time.  Sometimes they are collapsing.  Not collapsing under spring loads, but collapsing because the oil has become aerated and thus compressible, unlike the solid fluid that should be filling them.  Different oil can help, different amounts of oil in the pan or various windage trays or deeper pans can help.  Sometimes you can make it much better by adjusting the lifter deep into it's travel - just off the bottom - which shortens the collapsible column within.

We normally crutch the problem with more spring because that is how we've been trained forever, and we use lighter weight parts because we "know" that it works most of the time.  Lacking a Spintron and a ton of development time sometimes the best thing to do is just try things - I have swapped springs and retainers on the fly just to see what happens.  Sometimes it gets way better.  Sometimes it does pretty much nothing.  Sometimes adding or removing a quart of oil makes a surprising difference - especially if you see pressure wiggle at the top of a pull RPM range.  And if you are running a rear sump shallow pan to clear a rack & pinion you will need to simply accept the fact that your oiling system is marginalized by the pan's proximity to the center of the crank.

[jayb]

Well Brent knows how to make those Morels work, I would follow his lead.  One question I have is on the lobe, is it 288 adv or 282? The lobe number is 288 at .006 in the catalog, but lift didn’t seem to match up to anything with a 1.76 or 1.73 ratio either.

The catalog says 288, but the cam card says 282.  Seems like just an out and out error in the catalog.  Lift says .555 on the cam card, catalog lists it at .544 at 1.7:1; with a 1.73:1 FE non-adjustable rocker, that is pretty close to .555.

[blykins]

Jay, do you have oil pressure data from an early and late pull? 

If the engine isn't gone, it may be easy to try some oil-related activities, as well as some preload adjustments.  I may be willing to work a deal on some other "adjustments" as well, for R&D purposes. 

I'm trying to find the dyno sheets from one particular 428CJ engine to see what it did at higher rpm.  It was basically a box-stock 428CJ with unported heads and just some good pistons and a hydraulic roller camshaft.  If I remember correctly, it made 425 hp @ 5500, but I'm trying to find the sheet to see what it did above that rpm. 

If it's not the camshaft nosing over because it's done, I think it almost has to be the lobe aggression.  I have tried 10 different hydraulic roller lobes from Comp (and a handfull from Crane and Bullet) in FE's and I have it narrowed down to about 3 that work and work very well.  What's interesting is that I can get away with a hair more aggressive lobes in my Windsor and Cleveland stuff and I attribute that to the smaller/lighter valves and polylock rockers. 

[Barry_R]

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?

Octane is resistance to spontaneous combustion.  Burn rate is independent of octane.  Its a different characteristic.  Its the difference between how hard it is to start the fire and how long it takes the wood to burn.  We do not have burn rate information.  In reality race gas will often be designed burn more quickly than pump gas - its optimized for high RPM where we do not have much time in each cycle.  We could also be looking at energy output variances between the fuels - pump gas may well have alcohol & oxygenators in it that will impact the amount of energy available from a complete burn.

That stated, the 4100 RPM data point almost looks like an anomaly - did that little spike repeat in subsequent pulls?

[blykins]

Here's a 511 cube engine with a set of Barry's CNC heads and a Comp hydraulic roller, 251/257 @ .050".  Comp beehives, 165/390 on spring pressures.  Morel lifters. 



Here's a 445 with Barry's heads and a Comp hydraulic roller, 235/241 @ .050", with Comp 930 valve springs, 145/360, Morel lifters. 



And here's the 428CJ with the same Morel lifters, Comp hydraulic roller, 227/233 @ .050", with Comp 914 springs, 150/360.  It had Ferrea 3/8" stem 2.09/1.65 valves.  As you can see, it made it to 5500, but dropped off quite a bit at the end.   Considering this engine used the same lobes that I use in a lot of my engines, same lifters, and same valve spring pressures, it's either the heavier valves that made it drop off, or it was just the head/cam combination. 

[My427stang]

Well Brent knows how to make those Morels work, I would follow his lead.  One question I have is on the lobe, is it 288 adv or 282? The lobe number is 288 at .006 in the catalog, but lift didn’t seem to match up to anything with a 1.76 or 1.73 ratio either.

The catalog says 288, but the cam card says 282.  Seems like just an out and out error in the catalog.  Lift says .555 on the cam card, catalog lists it at .544 at 1.7:1; with a 1.73:1 FE non-adjustable rocker, that is pretty close to .555.

Well, let me first say I am not critiquing the motor, because other than a little wiggle at the peak of where I would expect from the cam anyway and maybe some timing curve work, it's a nice engine on a budget

Interesting on the cam lobe catalog vs cam card, LOTS of errors in the lobe catalog.  Incredible errors in some cases that force you to do the math yourself all over the document.  Did you get a chance to measure what the cam really was?  Needless to say if it was 282 it was more aggressive and with your rockers you had more lift, which compounded valve control

I think whoever told you the cam lobe got it right, I think it was Brent.  IMHO it's not a hydraulic lifter issue per se, it's likely the lobe.  If you compared the intensity measurements of your lobe 12.7 opening/13.2 closing with a Thumpr lobe, 14.7/15.0 you can see the valve is opening a lot quicker and closing a lot faster.  I don't think your opening rate is lofting, but your closing could be bouncing, or you could be having a little oscillation being so far from bind. 

The oscillation and bind comment is half opinion and half experience....I just checked coil bind on a set of those and they are mismarked on the box, they are about 1.19-1.20 coil bind, so you can do the math on your clearance, what is opinion is: that setting up to close to bind matters on a beehive...if it was a regular spring I'd say yes, but I don't have the experience of running beehives to say it matters like it would a regular spring

I do still think that what you have can be crutched on your engine with pressure though using Barry's terms.  There is "enough" spring pressure by most standards, sure, but heavy components, more aggressive cam, both add to the challenge and adding a little more seat and open should force the lifter to stay put a little longer up until the point it can't operate like a hydraulic lifter anymore.  It also moves the spring around if oscillation is an issue

Although ignition may not matter on the dyno, I still think a set of .050 keepers and a distributor recurve would be worth it to see how idle vacuum and power changes with a cheap action.  If you don't have a Mallory "key" I can post the measurements, they are very easily adjustable.

I am of course being selfish because I am trying to figure out reference points for my 461 CJ build that needs RPM and vacuum, and what you learn I will proudly pirate!

Last comment....the race fuel discussion to me could result in anything depending on the fuel, and even the pump gas has a wide range now.  To me, it clearly has different characteristics, but remember, change the brand, change the line within a brand, and characteristics change again.  It is cool to show that fuels do change behavior though and race fuel isn't always better

[Heo]

I dont know anything about gas but I had a Triumph Boneville in the
early 80s 11-1 comp some cam, dont remember. Run fine on pumpgas
whatever the highest rating we had then 99 i think.  One time i was out of
fuel and we filled a couple of litres race gas  just to get me home that night
it was running rough on that,  i could feel it in my whole body (solid mounted engine)
Almost like when the carbs was out of sync, and would not idle, considerly down o power.
Went away next day when i filled up on pumpgas

And one time with the Model -A, i filled up at a small gasstation with a local gasbrand
first thing i noticed was the smell of the gas, just like the gas you can buy for chainsaws
and lawnmower that suposed to leave healtier exhaust it smells like the gas smelled when i was a kid
next thing it started to snease throught the carb so i fattened the mixture, You just turn the choke knob
to adjust the mixture. And holly plugwires Batman, it picked up so much power and was running
so smoth on that gas increased the topspeed by almost 10 mph it was incredible. But it wanted a fatter mixture.
When you have 40 horses to begin with i guess you notice every horse gained

My dad bought a new Stihl chainsaw filled it up with that Aspen healtgas after one tank it would not run anny more
so he went to the guy who sold it. He said you have used Aspen gas right? Yes.. Thats the problem it is crap
he dumped the gas filled it with regular gas, fourth pull it started and have run since on regular gas

[TomP]

  And if you are running a rear sump shallow pan to clear a rack & pinion you will need to simply accept the fact that your oiling system is marginalized by the pan's proximity to the center of the crank.

I saw one of those Canton pans at the swap meet two weeks ago. My goodness that shallow flat area is much larger than in needs to be! Just a simple half round notch right where the rack is and the keeping the rest deeper would probably help a whole lot.