L-72 Dyno Test

[Chevy454]

I was just thumbing thru my MCR and noticed the dyno test they did on one of Peter Simpson's COPO engines...what are everyone's thoughts on the outcome?

I was surprised to see that changing the valve lash changed the torque amount the way that it did. That is one of the things that I have began to mess with more and more in the past year or so, and according to that article, my "lashing" is justified!

[Belair62]

I was surprised to see the engine needed carb spacers to get close to the advertised HP figure. I think they wound up with a 2inch spacer.

[COPO]

That surprised me too and was a bit disappointing. The LS-6 they tested came right in at the factory rating of 450 hp, so I expected the same from the L-72.

I can tell "seat of the pants" that the valve lash makes a difference, I too was surprised it was that large.

[JoeC]

The article states that they experimented with total timing from 36 deg to 44 deg and the dyno numbers did not change significantly. I would think that an 8 deg change in total timing would have shown some differance.

[Keith Tedford]

I was surprised that the engine made advertised horsepower with the stock exhaust manifolds. These pieces were a bottle neck. The value of fine tuning was also quite obvious. It would be interesting to see a run on the engine with headers. You aren't going to be driving on 112 octane gas all the time so how would the engine run on 92? As for the 2" spacer, it is not going to fit under a stock '69 Chevelle hood. The breather almost touches now.

[Edited by Keith Tedford (02-27-2001 at 04:53 PM).]

[COPO PETE]

Sorry to drag up an old thread but I found some of the comments very interesting on this topic. The motor did make 420 honest horse without any spacers and before fooling with the lash. All dyno's are different, they are not calibrated like scales and federally watched. When my engine builder asked what dyno I wanted to use, he asked if I wanted to use a happy dyno or a sad dyno. The happy one would show 20 more horse he said. We chose the sad dyno because like he said, "when you have 420 horse, you know it's a true 420 horse. Depending on altitide, temp, and dyno, your results can be + or - 15 horse. The dyno is simply a tool for measuring changes which it does well. So while the paper out of the dyno is very interesting, the piece of paper that matters is the one at the end of the return road. That piece of paper said 12.69 @ 110 which was on F70-14 polyglas with a stock GM converter, and a single cross flow muffler. Also no spacer was used. The 454 MCR dyno'd did not have a stock GM cam and was run with 2" headers not manifolds. Have a great day and sorry to bring up an old thread but I'm new around here.