I went to the chassis dyno today for the first time since the rebuild. I put about 450 miles on the car to make sure the rings were properly seated. The motor made 335 horsepower and 465 ft.lbs. of torque at the rear wheels.The car has a TH400. I was happy with these numbers since I'm using the original Stage 1 heads (mild porting) and the cast iron intake as I want the engine bay to look as original as possible. The air/fuel ratio looked okay so I didn't make any carb adjustments. Now I need to get it out to the track to see how it will run.
I ran the car twice. The first pull was 332/462. I'm guessing there is about a 24% loss between the crank and the rear wheels through the TH400.
24%:eek2: That would give you some serious numbers at the crank. 465 x 1.24 is 577lb/ft of torque, possible but unlikely. 335 x 1.24 is 415hp, that one is a little more plausible. I have never heard anyone use 24% for driveline loss. The accepted numbers I have heard are 18-22% for auto trans cars. 20% gives you 402hp/558tq which sounds much more realistic to me given the minor changes you have made. At what rpm did the numbers peak? What type of dyno was it Mustang or DynoJet, they give very different results.
I had heard the same thing, about 20% as a rule of thumb. That is what they told me when I dyno'd my 87GN last spring. It was about 360 rwhp and 420 rwtq. Those Dyno's are cool, I need to get the big block up on it.
I'm not sure what the correct driveline loss is, but I was happy with the rear wheel horsepower. I put the car on a Dynojet. I'm going to try to post a copy of the dyno sheet with the before and after dyno runs on the same page. If there is a 20% loss, wouldn't that result in a crank number of 418 (335/.80=418)?
I must have been using "new math" sorry Looks like you came up over 100hp and 100lb/ft, that has to feel good! The chart is interesting. I was surprised to see how much the torque fell off with rpm. My dyno test, on a Superflow 901, not in the car, was a little different. I showed 500TQ staring at 3000rpm, peaking at 550 at 4000rpm and still at 500 at 5000rpm. I have to wonder what a full exhaust will do to those numbers? Hey Jim, when are you gonna install that Dynojet?:gt:
I ran the car with conventional 20w50. I think if I ran it with 10w30, I might be able to squeeze a few more horsepower out of it. Does anyone have an opinion about the torque drop off?
OH.. I would be putting in a SF 901 first, but the roller dyno would come in handy for testing complete cars this time of year. Since the primary reason those things exist is not to measure HP, but to work on driveablity stuff. We may chassis dyno Tim's Regal when we get it done, and if you do yours, we could have a couple of good comparisons, considering both of those motors have been on the engine dyno. JW
