Duke, Sorry for the delay....

[George J.]

Duke,
Sorry it took so long to post these. The first two, where the peak power is about 293hp, are with the side exhaust and the last one is with the dyno exhaust. Both use the stock exhaust manifolds. After getting the car home, I did some tuning such as 38 degrees total advance, adjusting of the power stop, etc. A little more power resulted, noticable by the seat of the pants, but these are good for comparison.

George

[Joe C.]

Re: Duke, Sorry for the delay....

George,

Great comparison.
Also notice that the mixture went lean with the lower restriction dyno mufflers. A mixture adjustment would have made the comparison even MORE dramatic.

[Duke W.]

Re: Duke, Sorry for the delay....

Thanks for posting the data. I need the answer to a few questions in order to understand the full context, so I can compare it with other test data.

I assume this data is from a lab dyno test. Is that correct?

The highest power sheet says 1 5/8" headers and 3" mufflers. You said manifolds. Which is correct? Also, where the dyno mufflers straight through or reverse flow type?

The torque and power columns indicate the data is corrected. It is normal to correct lab dyno data to "standard temperature and pressure", which is standard scientific sea level conditions - 29.92", 59F, dry air. Is this the correction or was is "SAE correction" used, which is what is used to rate modern engines and is usually used for chassis dyno tests. SAE correction lowers the data values about 4.5 percent relative to STP correction.

What does "1.5 turn" mean after the bore-stoke data.

BTW, the A/F ratio data looks suspect.

Duke

[George J.]

Re: Duke, Sorry for the delay....

Thanks for posting the data. I need the answer to a few questions in order to understand the full context, so I can compare it with other test data.

I assume this data is from a lab dyno test. Is that correct?

The highest power sheet says 1 5/8" headers and 3" mufflers. You said manifolds. Which is correct? Also, where the dyno mufflers straight through or reverse flow type?

The torque and power columns indicate the data is corrected. It is normal to correct lab dyno data to "standard temperature and pressure", which is standard scientific sea level conditions - 29.92", 59F, dry air. Is this the correction or was is "SAE correction" used, which is what is used to rate modern engines and is usually used for chassis dyno tests. SAE correction lowers the data values about 4.5 percent relative to STP correction.

What does "1.5 turn" mean after the bore-stoke data.

BTW, the A/F ratio data looks suspect.

Duke

Duke,
yes it is the lab dyno sheet.
It had the stock exhaust manifolds for all tests. I don't know why they didn't change that. We did not spend hours on this, just a few runs. I knew that I was going to need to tune the car on my own, since the shop had NO idea how fuel injection units functioned. If I remember correctly the mufflers were the straight through, type. It was a few years ago.

I can't tell you what the corrections were. At the time, I was not aware that there are so many variables with dynos. I did know that comparing the data from two different dynos was not relevant, but that was about it.

I also do not know what "1.5 turn meant". It may have had to do with the previously tested engine. It may have had to do with the power stop of the fi unit, but I can't really remember.

I hope this helps.

George

[Duke W.]

Re: Duke, Sorry for the delay....

Okay, thanks. I printed out the pdf, annotated it, and added it to my engine test file.

One other thing. IIRC from the prior discussion this is a "stock rebuilt" (.060" overbore) '65 327/375FI - all OE or OE equivalent parts, no "head massaging" other than a standard rebuild valve grind. Correct?

I have another lab dyno test of the same configuration, .060" over with some head massaging. The tests were run with dyno headers and the results were STP corrected

365 lb-ft @ 4800
365 HP @ 6000

The head massaging gets close to the advertised gross HP and the headers improve torque above what the advertised 350 lf-ft, but contribute less to top end power. A "327 LT-1" (massaged heads, Crower rods, LT-1 cam, average measured CR 10.35:1 with the OE replacement pistons and a .026" head gasket) that started life as a '65 L-79 was lab dyno tested (STP correction) with both headers and manifolds showed eight percent better peak torque, but less than two percent better peak power with headers. With manifolds the best runs were:

338 lb-ft @ 4400
356 HP @ 6400

With headers:

358 lb-ft @ 4500
362 HP @ 6500

The vehicle exhaust system, especially side pipes, will negate much of the improvement seen with headers when there is little or no exhaust restriction.

Duke

[George J.]

Re: Duke, Sorry for the delay....

Okay, thanks. I printed out the pdf, annotated it, and added it to my engine test file.

One other thing. IIRC from the prior discussion this is a "stock rebuilt" (.060" overbore) '65 327/375FI - all OE or OE equivalent parts, no "head massaging" other than a standard rebuild valve grind. Correct?

I have another lab dyno test of the same configuration, .060" over with some head massaging. The tests were run with dyno headers and the results were STP corrected

365 lb-ft @ 4800
365 HP @ 6000

The head massaging gets close to the advertised gross HP and the headers improve torque above what the advertised 350 lf-ft, contribute less to top end power. A "327 LT-1" (massaged heads, Crower rods, LT-1 cam, average measured CR 10.35:1 with the OE replacement pistons and a .026" head gasket) that started life as a '65 L-79 was lab dyno tested (STP correction) with both headers and manifolds showed eight percent better peak torque, but less than two percent better peak power with headers. With manifolds the best runs were:

338 lb-ft @ 4400
356 HP @ 6400

With headers:

358 lb-ft @ 4500
362 HP @ 6500

The vehicle exhaust system, especially side pipes, will negate much of the improvement seen with headers when there is little or no exhaust restriction.

Duke

Duke,
You are correct. The only non-stock items were roller tip rockers. Everything else was stock type. I instructed them to unshoud the valves, if possible, but I think they said that there was not much they could do on that front. At the time, hardended valve seats were talked about everywhere and so I told them to put those in. What a mistake. There is not enough material and they ruined a head.
The compression ratio was a measured 10.2.
It is interesting that your results above have the 30-30 cam making its peak power at 6000 while the LT1 is peaking at 6500.

George

[Duke W.]

Re: Duke, Sorry for the delay....

Peak power and the high rev power characteristics are all about head flow, when the valve timing is similar (which is the case with the 30-30 and LT-1 cams - the actual timing numbers are not that different) which is why that "327 LT-1" made peak power at such high revs with a less efficient induction system than the Rochester FI. The heads flowed 236/203 CFM at 0.5" lift, 28" test depression. They were very nicely massaged!

As I've said so many times, all other things equal, the LT-1 cam makes about the same top end power as the 30-30, but with much better low end torque.

The "327 LT-1" 180 degree manifold also favors low end torque (at the expense of top end power relative to Rochester FI), but it doesn't make much less top end power (less than one percent) than the 375 FI with massaged heads, though I have no detail on how those heads flow.

The FI system has a much more efficient high rev manifold architecture, but with OE machined heads it doesn't help much. Once the head flow is improved the FI system should make more top end power - more than is actually shown here according to Engine Analyzer 3.0 simulations, but, again, without having specific head flow data...

What's interesting here is that we have a 327/375 FI with massaged heads and 30-30 cam vs. a "327 LT-1" with massaged heads, LT-1 cam and the 327 SHP manifold and carb. Both were built and tested (with dyno headers) completely independently, yet they are within about 0-2 percent from the torque peak to peak power. That's a range you would expect to see from the same engine tested multiple times on the same dyno and same day!

A greater difference would likely have been evident if test data was available at lower revs. The "327 LT-1 made 78 percent of peak torque at 1600, and I would be willing to bet that the the FI engines with 30-30 cams will have significantly less low end torque.

Head flow has nothing to do with bottom end torque. Down low it's all about valve timing and compression ratio, and though the LT-1 and 30-30 cam aren't that different, the less overlap of the LT-1 cam really makes a difference down low.

Duke