Thanks Dwayne, I just tried it and we'll see with the two pics I'm gonna post.

Yesterday was a bit of a struggle--I fired the Hemi on the dyno after spending the entire day and then some hooking it up on the dyno. It fired unbelievably quickly and I start running through all of my usual checks --terrified of of oil leaks especially the rear main on the B/RB's and all seems to be going well. My carb guy Guillaume Bordeau shows up as he went through the brand new carbs a month or so ago and we proceed to attempt a pull. I set the rpm too low @ 3500 and when I load it it blows through the absorber and just hangs at 5500 rpm. The torque doesn't look right at 651 ft/lbs so I know something is up with the dyno. Long story short I spent most of today (Sat) replacing the absorber mechanical seal and we get back into business by about 1:30 p.m. First test from 5000 rpm-5500 rpm is a success and we do bunch of other stuff like a plug change (was running the old plugs)--fool around with the widebands, etc....

Long story longer the engine runs really really nice--doesn't leak a drop of anything and I'm impressed with the cam the previous builder used. It makes almost 17" of vac @1100-1150 rpm (solid roller) We ended the day with 710-715 tq (probably 750 at peak) and 708 hp with awesome manners and consistency. I'd like to load it at a lower rpm and capture the actual peak torque but I don't think I will be able. The graph shows the before and after differences nicely. J.Rob

Couldn’t pull it lower after the seal change?

No lower than 4900 rpm. Any ideas Dwayne? I know you have an SF. I have the 871 absorber, it was far better but something is still off. I think it may be the inlet assembly valve not allowing suction. J.Rob

Does yours not have the low rpm/high load “boost” line?

Not that you should need it for that combo, but using it would answer the question as to whether or not it was an inlet volume issue.

Servo valve has full range of motion?

I wonder if a pair of shear plates would help with the power any. I wish I could try it on my 572. Glad you are happy with your build. Tim

That's a nice improvement. I'm sure the owner will be much happier w/ it now!

Really nice looking engine J, that should really make your customer happy.

One question, what are the cam specs?

I'd sure like to see it pull lower as others mentioned, but glad for any info at all.

Thanks

Impressive!👍

So I've been working on it since Monday. Yesterday I machined a coil bracket, lashed the valves, re-torqued the heads, compression test all cylinders while plugs were out--205psi across the board-150 psi first crank,hooked up electric chokes to +12v, removed the electric water pump, installed the serpentine drive kit and installed the MSD 6Al2 programmable. Warmed it up and made a couple of tests--its much stronger with an ignition curve in it--It is now about 20ft/lbs stronger and making 735hp and climbing. Going to disassemble the absorber today and try and figure out what is going on. I spoke with Superflow yesterday and they weren't a whole lot of help although they said my dyno should hold 800-900 ft/lbs @ 3000 rpm--which I have NEVER been able to do. I'm starting to wonder if this absorber had tight enough tolerances to begin with--we bought it new in June 2009. All I have for cam specs is a photo the customer supplied we with. Thanks, J.Rob

How is your water supply to the absorber?

My builder had to upgrade his pump and supply line to his Stuska to hold the GP Hydroplane engines he's building. The absorber is supposed to be capable. 15 hp pump with a 3" supply line. Also had to add air supply capacity to the tune of 8000 cfm.

Supercharged 468 on Methanol.

Should be loud...

Kevin

I wonder if you won't see even more power once the dyno is figured out. Seems odd it would essentially peak at 5500 and flatline from there.

Nice progress!

Jesse....... does your dyno have the boost valve?(I think all 902’s have it)

Does it not make any difference?

I haven’t dynoed a high torque/low rpm combo in a long time, but I don’t think the one here would hold 800ft/lbs@3000 without it being open.

Thanks!
That helps quite a bit, with the inevitable comparisons that come to mind.

Looking forward to the next installment

The water supply is way overkill in this case. I have a 20hp 3Ph centrifugal pump that I bypass a lot of water back to the 1550 Gallon reservoir to maintain 45 psi line pressure--I can and have cranked it up to 65psi+. It doesn't work that way with a Superflow anyways. The SF has a suction inlet which uses a little impeller to fill the absorber . You should be able to dunk this thing in a lake and have the absorber work properly. This particular model (871) absorber is rated for 2500 hp/2000lb/ft and so is the load cell. Thanks for the questions though Kevin. J.Rob

Oh yes of course I have the boost valve--I think all 901/902's have it because SF's crappy priming system never works all that well. So you fire and engine and have to run and open the boost valve and then close it. I've only ever had it prime a handful of times with out assistance. Oh and yes I've replaced the mechanical seal now 4 times in it's 11 years of use. The boost valve only seems to make a difference on smaller less powerful engines at least that I can notice. Oh and thinking back to EMC testing days--When the contest RPM was 2500-6500 I would always choose a smallblock and this dyno always struggled with 430+ tq @ 2450-2500 rpm.

Would you mind looking through some of your past tests of large cube combos and sharing your data and thoughts especially about the lower RPM end of the scale. I really think this unit should be capable of performing a pull from 3800-6000 rpm without any issue. I could be wrong though. I do remember being very impressed my first time at EMC (2009) with how easily the DTS could pull down our 471 TR to 2300-2400--and remember thinking "Our brandnew 902 couldn't do that I don't think" Thanks for the help guys. Maybe I should change the thread title to SF-902 Dyno Saga--since the engine has been flawless and the dyno has not. LOL J.Rob

The dyno here is a 1997 vintage 901.
When it was ordered then, the boost valve was an option.
The dyno shop I worked at in the early 90’s had a 1986 sf-901...... and that one didn’t have the boost valve.

The prime solenoid has a very small pathway through it, and gets clogged somewhat easily.

I don’t think it acted up on this one until it was about 12 years old.
I took it apart, cleaned it out..... and it worked fine for several more years.
I’ve done it once or twice more since then, and it needs to be done again.

Opening the boost valve on this dyno makes a very noticeable difference on how low you can pull the big tq/low rpm combos.

I almost never need to use it for the typical stuff I build.

I’ll see what we have for sheets with high tq/low-ish rpm.

The only thing I have handy is a mild 505 from a few years ago..... which was 592tq@3200....... and I didn’t use the boost for that motor.



I know we’d be able to do that here with that motor........ and likely without the boost.

As it turns out I do have a run here from a 572 wedge street motor with EZ 295’s on it, and about 10* more cam than your Hemi build........ from 3800-6100.
This run is with an ootb 337 intake and a Mighty Demon 850 carb, and my dyno headers.
Those are 2 - 2 1/8 x 4, so they’re not helping the numbers down near the bottom.
By 3800, the absorber is pretty happy...... so this is no problem at all.


The real high tq/lower rpm stuff would be something for a boat with a roots blower on it....... and I dont have any of those sheets here.
But I’ll see if I can dig something up.

One last thing....... and forgive the dumb question....... but I’m going to ask it anyway.......

You have adjusted the capacity valve...... right?

Well...... not necessarily.
The HP line is just math......... the TQ line is measured........ and the TQ curve is already dropping pretty steadily.
The only way the “dyno” could really be the cause of that is if the load isn’t being transmitted into the load cell correctly(which I suppose is possible).

That’s not to say the curve couldn’t be improved with “tuning” though.

Just seems odd to me it would have a nearly perfect flat HP "curve" over a 600rpm range (and possibly more if pulled higher)

Thanks for the help Dwayne that's awesome. That 57I2 of yours looks like Ron's.

Yes I had the capacity valve backed out all the way. Good news though toward all apart started over found the servo was indexed incorrectly and made a couple other changes. Dyno is working awesome now. Thanks for all the help. J.Rob

Glad you got it figured out.

Power numbers seem good....... with a vastly improved curve compared to the “before” combo.

The fuel flow dropping off at the top end seems a little odd though.
(Fuel cell running low?)
It was using a way more fuel on the first sheet you posted.

Let’s give this a try......