Disappointing Dyno Numbers -- I need advice please! I think something isn't right.

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Larry, I've used the one on Wallace racing and this one and they both come out with similar ratios.
https://www.uempistons.com/index.ph...e=comp&zenid=5f3f439d841bbe5fcf9c3cc5f039ebd1
Cylinder Head Volume 68(cc) Cylinder Head Vol (cubic in.) 4.148
Piston Head Volume 21(cc) Piston Head Vol (cubic in.) 1.281
Gasket Thickness .039(in.) Swept Volume (cubic in.) 56.966
Gasket Bore 4.4(in.) T.D.C. Volume (cubic in.) 6.635
Cylinder Bore Diameter 4.3125(in.) Gasket Volume (cubic in.) 0.593
Deck Clearance .042(in.)
Note: Neg. number above deck, Pos. number below deck Deck Volume (cubic in.) 0.613
Stroke 3.9(in.) STATIC COMPRESSION RATIO 9.586
OPTIONAL DATA
Rod Length 6.385(in.) Adjusted Stroke (in.) 3.152
Intake Closing Point 60(degrees) ABDC @ 0.050 lift plus 15 degrees DYNAMIC EFFECTIVE COMPRESSION RATIO 7.939

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Wrong rod?

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Those DCR calculators that use 0.050" cam timing are pretty much useless. The IVC is so much further away from the advertised number as to make them inaccurate. They assume a duration difference between 50 and adv, and every cam is different. They also do not take into account an assymetric lobe profile. Use advertised numbers, much more close to the actual valve event. The Pat Kelley calculator uses it.

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Yes, I am using a BBB. I've played around on the calc quite a bit and it stores your previous entry in thos fields so I must have clicked on one where I was playing around with a SBB.
It still comes out to 7.922 DCR using 6.608

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

As stated, double check that it isn't using .050" events. They might not be accurate.
It's kind of a toss up anyways being that restrictive heads and induction will reduce the amount of atmosphere that can be trapped.

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

This shouldn't make a ton of power differance. But I found it odd, and maybe I misread something. But I thought you said a machine shop built the motor. But the motor is still at standard bore size 4.3125.....no over bore but they rebuilt it?. Also being about .042 in the whole is where the factory stuff tends to run, did they not even do a clean up cut on the decks?

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Larry is correct. I don't want to detract from Ed's discussion. I just thought since we are using the same cam and similar builds (subjective) it was worth a mention.

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Yes I noticed that and appreciate it. That is one hella motor!

another thing I thought of is that a 350 is 77% the displacement of a 455. Why then cannot a 350 be built to generate 77% of what your 455 can. That would be still a lot. 388 feet of torque at 2800 and 451 tq at 4900. and 462hp at 5500. Shoudnt that be enough power to send my lead land barge the distance in under 14? Its just a matter of scale isnt it?

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Doesn't quite work that way, 425hp 350 isnt hard to do but the TQ will climb up pretty high in the range and that means more gear and converter to work well

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

455 has bore and stroke 4.31 x 3.90
350 is 3.8 x 3.85

the 350 has nearly the same stroke as a 455 so wouldnt the torque actually be lower in the rpm range? I realize it wont be as much torque. 77% less which is stil a lot. But with its long stroke it should be lower rpm no? I just think nobody cares about the 350 and nobody has ever tried to build it optimally for what it geometrically would be good at, low rpm torque. Am I wrong?

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

It is very reasonable to assume a certain output based on displacement.
A roughly 9:1 engine should be capable of 1 tq per cube.
The rpm peak torque is at has more to do with the airspeed through the induction tract, with peak # rpm's brought down by restrictions such as camshaft events or exhaust restrictions.
Peak hp happens as the port or induction begins to choke out.
So, basically the port's airspeed and how it relates to the cylinder supports peak power and tq.
You can get a certain amount of torque from the cubes.
A 350 has pretty good head flow for it's size, so the hp potential is there...just at a slightly higher rpm.

Another aspect of the questions on rpm and testing is illustrated nicely with the OP's and Larry's dyno sheets.
My previous post (#60) explains the dyno's limitations.
They require more rpm to brake better, kind of like a propeller in the water...it can idle in gear without much load as it easily slips.
OP's peak torque shows relation of the induction to the cubes.
It might make too much torque down low for the dyno to hold well enough to get a stable measurement.
It's also really tough on the engine to full load it at low rpm.
It isn't good for business to beat up an engine prior to shipping, or the dyno.

Larry's posted sheet shows peak torque at a higher rpm....because of the induction (and of course the camshaft intended to compliment it)
It still makes great torque well below that due to the cubes and overall efficiency of the build.
The OP's engine will make for axle-twisting torque just off idle.

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

what about stroke/bore ratio? Doesnt that determine what rpm range the engine has the most mechanical advantage for torque and hp? The 350 has the same stroke as a 455. Is that meaningful in some way?

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Stroke and rod ratio have more to do with avg. piston speed, otherwise that's a close and reasonable assumption.
Our posts crossed.
Cubes = Torque
Higher piston speed via stroke wakes up the induction system by drawing harder on the intake.
The peaks are still dictated by a certain airspeed through the port, with A LITTLE influence from bore/stroke ratio

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

When I have a engine dyno'ed always have a someone or you have a hand held weather meter. Take a reading then plug that in the dyno. There is your first data for that type of day. Too many factors a dyno can not do. Talking with some very high end prostock engine builders they taught me a lot. You can mill cast iron head down pretty far. But you'll have to order custom push rods then. I would call someone like TA , Tri-Shield , Scott Brown, or the alike to have them pick a cam for you. They can calculate your compression static and dynamic just by knowing your build. Believe me, I burnt enough bridges in here to know. A lot of guys in here know there stuff. First thing you should do though is tell them your price limit. From there, they can build around that and you'll be surprised on what these guys can pull out of a top hat. Being a exmachinist, I liked when a customer asked nine thousand question and then asked is there anything I missed? That's where you'll find out how good the machine shop is.

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Sorry Russ, I just noticed your post.

I think your question has already been answered by Larry re: DCR.

I am looking forward to having a look at your results when you are ready. That will be great!

After I get the engine in the car with the headers installed, cam degreed, and distributor adjusted I will put her on a chassis dyno here in NZ.

As you said Larry, the engine is basically sound and it seems that the consensus is that it is making the expected power given the build. I have grown weary of 6 am Skype conversations with the machine shop...........I am going to toss it in, run it and have fun!

Aluminum heads will come a bit further down the track. Next up is finishing a little bit of body work, installing the interior (I have already done the seats), and painting. I am doing these things myself..........I may get a pro to do the headliner though. I am a little intimidated there.

I am a few months away from the finish line yet. Stay tuned!