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Did you see the graph at the end of the video. That was optiona 2 vs 3. Option 1 was slightly lower than 2 but didn't tha e open headers. I only did mid pipe testing to see what the car config numbers looked like.
If I read that chart right, about 40+ HP and 40+ lbs Torque at around 4500 RPM with the 265's over the 315's. And that advantage is noticeable through 5200, then the 315s play a bit of catch up, but still are down a bit. I would assume thats just airflow but would love to see that if you would have had a hat on it when testing. The other thing that would be interesting to know is air/fuel distribution per cylinder, that would have required separate sensors on each cyl. Just to see why the 265's are out performing the 315's on this engine even at higher RPMs. Was that just more air, or better more even distribution?

Also interesting, would be that the 265's dont fall off as hard at 6800? I am curious what the possible thoughts are there.

Anyway, Thanks for sharing. I love this kind of Dyno testing.
 

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The fresh rings and hone job could easily be worth 40hp.
"Ported" 265's would need to be quantified to be compared fairly to the 315's
The 315's would require a completely different cam to be taken full advantage of and operate in the same rpm range.
On a properly built 496 combination, the 265's are not going to out perform the 315's.
 

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The fresh rings and hone job could easily be worth 40hp.
"Ported" 265's would need to be quantified to be compared fairly to the 315's
The 315's would require a completely different cam to be taken full advantage of and operate in the same rpm range.
On a properly built 496 combination, the 265's are not going to out perform the 315's.
Ahh.... I assumed these tests were all done after the fresh hone and ring job, otherwise you are correct, hard to compare. He did state the cam was a CS and was for the 315s?

Also forgot the 265's are 112CC's and the 315s are 121CC so probably about .75 pt of compression ratio rise with the 265's as well. Do we know the flow rates on the 265's after porting?
 
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Discussion Starter #64
Interesting. Was it the diameter of the exhaust, the mufflers, or both?
Thanks
Mufflers mostly but ~25 inches of 3 inch mid pipe was worth 20-24 hp

The fresh rings and hone job could easily be worth 40hp.
"Ported" 265's would need to be quantified to be compared fairly to the 315's
The 315's would require a completely different cam to be taken full advantage of and operate in the same rpm range.
On a properly built 496 combination, the 265's are not going to out perform the 315's.
I think the cam is really good with either but was definitely spec'd for 315 heads.
Wouldn't rings show more improvement over time as well? The old rings despite the blow by look were seasoned. The 315s also didn't have the same ventilation as the v2 265s.
I have thought about running the 496 like this sending my 315s to you and getting a 532 or 540 build going.

Ahh.... I assumed these tests were all done after the fresh hone and ring job, otherwise you are correct, hard to compare. He did state the cam was a CS and was for the 315s?

Also forgot the 265's are 112CC's and the 315s are 121CC so probably about .75 pt of compression ratio rise with the 265's as well. Do we know the flow rates on the 265's after porting?
The heads were flow tested at different places. Neither had a 4.31 bore fixture. I'm sure most if the gains are compression related. I think the heads are nearly equal for this room range despite the smaller intake valves in the 265s.
 
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Mufflers mostly but ~25 inches of 3 inch mid pipe was worth 20-24 hp


I think the cam is really good with either but was definitely spec'd for 315 heads.
Wouldn't rings show more improvement over time as well? The old rings despite the blow by look were seasoned. The 315s also didn't have the same ventilation as the v2 265s.
I have thought about running the 496 like this sending my 315s to you and getting a 532 or 540 build going.


The heads were flow tested at different places. Neither had a 4.31 bore fixture. I'm sure most if the gains are compression related. I think the heads are nearly equal for this room range despite the smaller intake valves in the 265s.
You can't say "despite the blow by". Blow by was a definite indicator of the condition of the rings regardless of how much time was on them and no, if they weren't broken in properly or the hone was wrong, it wouldn't matter how much time was on them. Even so, there can be 30hp+ difference between hone jobs on brand new engines, side by side with no "visible" blow by.
A 532 or 540 would be a fun build. :thumbsup:
 

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Discussion Starter #66
Interesting. Was it the diameter of the exhaust, the mufflers, or both?
Thanks
Probably a little bit is diameter. Most was the mufflers. My collectors are 3.5" and drop to 3" for the rest. A section of mid pipe (what I call it) is about 22 inches long do my o2 sensor gets a good reading was a loss of 22 hp alone. On top of that the flowmasters lost another 50 hp compared to the ultra flo.
Check youtube for flowmaster vs ultra flo bbc for more details.
 

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That's a pretty good power gain from mufflers!

The Dynomax Ultra Flo is a perforated tube with packing around it, the flow is in and out. The Flowmaster has baffles which redirects the flow around them, I'll assume it sets up some power robbing flow revision.

I have a pair of long discontinued Edelbrock RPM series mufflers, 3" x 3". Similar to the current Dynomax Ultra Flo but it splits the flow into two tubes. I'll assume they have a similar performance to the Pro Flo's.
 

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