I'm going to ask why was the cam installed 4 degrees retarded? I made that mistake on a 500ci, put the cam in 4 degrees retarded, my own fault, wasn't paying attention. Wondered why it wasn't running like it should. Checked the cam, and put the cam back in 2 degrees advanced, it was like night and day.

made two pulls at 108 ,moved the cam -4 just to see what would happen we picked up from 763 to 772. when I get the car to the track i certainly will consider cam position during test tune session! love that Jesel belt! . performance will be the judge!! it may have been a little lean I ran the carb just the way it was.put away. I have the smallest .030 air bleed and 96 jet! thats exactly what the carb ran last season! that also will get changed to a 98.

So am I understanding this cam position right?
Cam LSA 112
original pulls with intake lobe centerline 108 ATC,
Then retarded the cam 4 degrees to 112 ATC ?

yes correct

BFSC is way low?

Am I seeing -4” to -4.5” of intake manifold vacuum? If so Something’s restricting the intake flow big time.
Doug

There are different parameters one can look at to evaluate the effectiveness of an engine combo.

On the dyno I’ve used for the past 26 years, the “better” combos, running on gasoline with a single carb........ have one of those parameters falling into a pretty narrow range most of the time.

For sure, all of the top BB Mopars I’ve tested that were built along the lines of the OP’s combo fall into that narrow range.

The results on Bob’s dyno sheet have that parameter pretty far outside what I would consider the “normal” range........ without there being any reason(in my mind) why it would be that much better.

AndyF’s 572 example, along with Jeff’s 563....... also fall right into what I consider the normal range.

That parameter?
TQ/CI

Bob’s 529 is showing 1.465/ci........ which on the dyno here is extremely rare for a single carb on gas.
The normal range for typical bracket race builds?
Well, here they are normally in the 1.30-1.35 range.

I see nothing in Bob’s build that would indicate it would fall outside that window....... on the high side

So, this also falls into the “racing dynos” theme, which is why I stipulated that the numbers would look quite a bit different if the engine were tested here, with my dyno headers......... in the same way all the other “better” combos belted out 1.30-1.35 TQ/CI.
Perhaps seeing 1.45+ TQ/CI isn’t that odd of an occurrence where Bob tested.
But no single carb BBM has ever really gotten close to that on the dyno here.

If the TQ/CI number for Bobs 529 ended up at 1.35 here, the peak TQ number would be about 715 instead of in the 770’s.

Looking thru a pile of old dyno sheets, I only see one single carb BBM build that exceeded 1.35, which is a 14:1 572 with 440-1 cnc345’s on it...... and that one went 1.37.
There are also quite a few sheets from pretty nice running combos, making what I feel is decent power....... that didn’t quite make it to 1.30.

Sure........”never say never”, but in my mind the chances of Bobs combo making 1.465 TQ/CI on the dyno here is solidly under 1%.

OK yes but the peaks and there corresponding RPM to me makes me consider the cam is not what it was advertised. And the headers being so small they could compound that to help explain the RPM AND the unusually high torq value as well.

Sean, in my mind it’s a dyno/facility thing in this case.

I’ve had my own motor show over a 60hp spread between two different dynos, along with quite a few other engines I’ve tested, that had been tested somewhere else, where the sheets looked different enough you wouldn’t even guess it’s the same engine.

What I’m saying is, in my 33 years of dyno testing....... I’ve seen drastically different numbers, gleaned from different dynos, often enough to acknowledge it’s a real thing.

I still say the right course of action for Bob is to just put the motor back in the car and let the timeslip be the judge of whether the motor picked up with the new cam.
It’s just a new cam, not a new “combo”.

Yes ok and thank you. I just am having a rough time getting around the RPM issues.

I have to say in a side note after talking to Bob some time ago on the phone he is a pleasant/likeable guy and I hope this iteration refresh gets him to his goal...Good luck Bob!

Here’s another thought I had in mulling the results over........
On this combo.......13:1 529” bracket race build....... is the best cam installed position going to be the same if you’re testing with 1-3/4 to 1-7/8 x 3.5 headers vs 2-1/8 x 4 headers?

Fortunately the engine has a jesel belt on it so moving the cam is pretty easy.

Indeed!
One of the nicest people you’ll ever meet.

The wrong headers can certainly cost some power. The Mopar fender well headers are famous for killing 50+ hp when compared to a dyno header. I'd have to see the headers used to guess how much they cost you. Passenger car headers always cost power over a good dyno header. We use custom built Stahl headers on the dyno here. They've worked well for 20 years and make really good power.

Let me add my 2 cents, using a 1 7/8 header on a 529 that you plan on using 2 1/8 exhaust on, gave you a lot of useless info. The HP/TQ will be down, the A/f will be off, the timing won’t be right. The good news is the oil pressure, the vacuum shouldn’t change, and you got to see if it leaked. I ran a 512 with that same cam and when I shorten the 2 1/8 headers from a 32” primary to a 28, I pick up 18hp. My advice is put the cam back at 108, put it in the car and go have some fun.


Joe

Andyf: does that oil pan have a big window in the side?

Yes. That engine had windows everywhere. Valve covers, valley plate, oil pan, etc. That was a dyno mule that we used to test parts.

next post will be the first outing ! I'll do a rental in the spring ! this will have to be "To BE CONTINUED "like the old Adam West Batman week to week episode! thanks for all the discussion!