Hi 78, thanks for the response, it's a lot more than I expected. I agree with your analysis, something's amiss. I know this engine is capable of more than 100. The only conclusion I can come to is that the header is too restrictive above ~4000 and I'm in the process of building a 1 5/8" header now. The dyno'd header has some 37" of 1 1/2" primary whereas the "Hot Rod" article used 26" I believe. Guess where the Helmholtz calculations place the torque peaks for the two headers: yup, 3000 and 4000, respectively. I tried the Darcy gas flow calculations but without accurate EGTs it's an academic excercise, at best. Anyway, I thought I'd put the conclusion at the top of the paragraph instead of burying it at the bottom. Here's some feed back to your specifics:
I looked at your Dyno graphs and noticed something interesing on the Torque graph. You seem to have a small dip between about 3250 and about 3750 on the output from both dynos and a smaller dip in the HP lines. Any idea what is happening here?
You know how both the intake and exhaust are affected by reflected waves? For instance if a reflected high pressure wave arrives at the intake valve at the correct time cylinder filling is enhanced. I believe that dip is indicating an odd harmonic: Either a high pressure wave at the exhaust or conversely a low pressure wave at the intake. Maybe cross-talk from the collector or intake plenum??? I'm hesitant to question the ignition/fuel mapping because it's such a localized dip. Natch, the HP dip is just the torque dip displayed a different way.
*Edit* I see the same dip in Brantley's dyno curve, so I wonder if it's an intake signature?
Its kind of hard to compare the engine dyno results in the old "Hot Rod" article with your chassis dyno results...but I tried.
-Your torque peak was at ~2800 RPM vs. about 3750 for the old stock 2.3L carbed engine. You were up about 5 ft. lbs. Both are good.
-Your HP peak is very similar to the stock older engine. Not so good.
Yup. I came to the same conclusions.
I wonder why Racer Walsh's roller cam doesn't have more lift?
Yeah, you know, this is a Crane cam and every time they add lift (.420",.450", .480") they increase the duration (226*,232*, 240*), so I wonder if they're keying off of ramp rates and valve float? FWIW, when I queried my Dyno2000 simulation to find the "BEST HP" cam for this combination it came back with this cam, retarded quite a lot, and with more lift. SIC ~9:1 compression.
So what are we missing?
Your A/F ratio seems to drop off quite a bit over 4000 RPM.
Yeah......<scratches head>
Is there any evidence of pre-ignition above 3000 RPM? Does your ignition system retard the ignition when ping is detected?
No evidence of pre-ignition or ping, and it doesn't have a knock sensor.
What grade of fuel were you running on the dyno?
87 consistently, no funny additive business. K.I.S.S.
Can your ignition be advanced manually?
Sad to say, no.
Can your fuel pressure be raised more?
Sure......But......it's aleady pretty rich at ~12:1.....???
FWIW, here are some other checks:
I looked for a dead hole but compression checks out OK around ~155 psi.
TPS checks out: 4.8V at WOT.
Oil pressure is excellent (~35 at idle up to ~60 at redline).
Transmission losses? The Trac-Loc is still tight up to the limits of my torque wrench, 100 ft-lbs. Could be a slipping clutch but the olfactory alarm isn't going off. Oh. Duh. Torque is torque. It transmitted ~126 ft-lbs OK at ~2800. OK, eliminate that question mark.
The back pressure test shows the exhaust isn't a restriction aft of the header.
Check out what happened when I disconnected a coil pack.
I never flow benched the ported head; it might not flow as well as we would expect, perhaps even worse than stock
Anyway, thanks for the response and hopefully you're getting some benefit, too....? What not to try?
*Edit* 350-390 CFM seem like a lot of carburetor, you're not worried about throttle response? That's the equivalent of 966 CFM for a 350ci (!) I mean, you only need to fill one cylinder at a time with the four cylinder.