Here's Larry Widmers take:
There’s a lot that leads up to this, but here’s a quick and dirty of my first experience with dynomometers (other than for kart engines). Our BOSS 429 Mustang had run 10.0’s locally at two tracks, before we were heading up to our first really big drag racing event in Pennsylvania. Bunkie Knudsen (president of Ford Motor Company) had taken a liking to our project, as had VP of Special Vehicles Jacque Passino. We left several weeks before the race and stopped at Holman & Moody in Charlotte. H&M built every Ford factory race car, including NASCAR stock cars, the GT40MkII’s, etc, etc. There was nothing on the planet that rivaled their operation, as that’s where all Ford Racing parts were developed and produced. It was like racing heaven.
While our car was more than competitive, we still spend weeks on one of the H&M dynos, where their experts changed cams, carburetors, etc, etc….ultimately finding an additional 125HP more than we had on arrival. We couldn’t wait to get to the races, as the quickest car in the country had just run a 9.95 second ET, and with all the new-found HP, there was no doubt in our minds that we’d have him covered.
First run and the car bogged and then accelerated slowly up to 7000 rpm where it became a rocket….In an effort to fix the bog, we began increasing flywheel mass, which helped the leave, but slowed the engine more through the gears. Bottom line was that we were still damned near a second slower than when we left Fort Worth. Our ET’s were so poor that we couldn’t have qualified for the 32 car field, so we hastily took all of the H&M pieces off, rebuilt our old combination, and promptly qualified 7th. We did very well in the 3-days or round-robin racing, and knocked off a number of quicker cars in the process (due to our staggered wheelbase and early leaves).
The Ford Drag Racing office now loved us, and life was good, but the most important lesson was that engines that make big power on a dyno, do not necessarily get you down the track efficiently. Everything I did from that point forward was geared toward acceleration and nothing else.
I built a number of intake manifolds to help produce ball-busting power at the bottom of the gear and each improved ET’s. The manifolds included the first cast aluminum tunnel ram (Engineering project in school) which use d a Wieand BBC plenum, “the hairy one” which I made of fiberglass (NHRA refused to let me run it), and then once I was moving and shrinking the intake ports, my aluminum manifolds which were the first with a V plenum and semi-side-exit runners. This was all done to increase intake velocity.
The car responded to each of these combinations favorably, but I got to thinking about piston speed and its effect on the intake velocity. We were running the Ford Nascar rods, which with the engines short 3.59” stroke, netted a rod ratio of 1.93-1. I figured that if the piston speed (acceleration rate to and from TDC) was higher, it would increase acceleration. I had rods made that netted a 1.78-1 rod ratio, and finally found a manufactured who had piston blanks large enough to make the huge-bore 4.40”, pistons with the pin relocated. First run out of the box netted an ET that was .5 (yes .5) seconds quicker than ever.
A couple years later when Roger Penske had me do a pair of 351C heads for his NASCAR program, I left the cross-sections of those huge ports pretty much stock, but picked up a lot of flow with my unique asymmetric valve seat arrangement. On Penske’s dyno, the heads were deemed good, but not that much better than what they were running. I brought the heads back to Cowtown, and set about shrinking the ports. I made aluminum castings that displaced 30% of the intake port cross-section, another that went behind the valve guide so lessen the bowl volume, and finally cast iron castings that I brazed into the exhaust ports to increase their velocities. Next I went to Edelbrock where Vic and Jim McFarland allowed me to scrape some cores to reduce the Torker maniifolds’ runner cross-sections to match my little intake ports. Murray Jensen at Edelbrock built an 830cfm square bore Holley, and I was set for more testing. I should mention that these “crazy little” heads weren’t well received at Penske’s. All of the Fords were currently running the Bod Moore box manifolds with the huge 4500 Holley carbs.
After several pulls on the dyno, the head of R&D said once again….there’re about the same on power as what we have right now. They paid me for the heads, etc, and I returned to Ft Worth with the knowledge that I’d blown my chance at the big time.
Two months later, I received a call from Roger Penske. He asked me to do several more sets of heads. My response was “do you mean the heads that don’t work?” Roger went on to tell me that they were at Daytona, and the best their engine combinations could do was 182mph….middle of the pack at best. In desperation, he had those crazy little heads flown down, with which they went 188mph, picking up 2 mpg in the process.
When I went to work for Roger, I found that almost every time we found more power on the dyno, it did not transfer to better on-track performance. Re-thinking the situation, I concluded that we needed to use dyno for acceleration runs from the lowest rpm we anticipated seeing to the highest, and whatever gave us the quickest ET on the dyno, always translated to quicker lap times.
There’s a lot more to all of this, but this is what led me to using the phrase “transient response”, and to this day, every head and manifold I do is engineered to net the quickest acceleration from the bottom of the gear to the top…..and making big dyno numbers isn’t involved, nor is huge airflow in many instances.
Maybe Larry knows something......He's running 21 to 1 compression ratios in his Honda race engines.
