On the internet, i dont remember were. But i found that the Mavericks of all engine sizes seemed to be unbelievable lagging in power. My friend who is an outragious gear head, said that he read that the ratings back then were underrated because of the insurance or somthing like that. Is that true. I believe him because him and his dad have many beautiful cars. recently he has a 67 Fairlane GTA with a dyno tuned 289 at over 500 horse with no power adders
yeah ive herd the same thing , but i think that only applies to something like 68 mustang 428 cj or 69 429, super hipo cars like that , i dont think a grabber with little 302 they are goin to cut hp numbers, but i could be wrong JMO
no easier way put then this "ratings in the 1960's appear to be higher than today. This is true because before 1973-ish, the rating were SAE Gross, which means the engine on the dyno was set for max HP numbers, and not running through any real exhaust system, no alternators or other accessories were attached, and tuned for big numbers which is not necessarily the same it would be tuned leaving the factory. SAE net, which is what automakers publish today, net, which is still HP at the crank, but with all accessories attached as it would be in a car, as well as "normal" tune and exhaust. SAE NET has proven to be about 20-25% lower than the GROSS numbers, so an old 327HP Chevy 327cid would rate at about 260hp today (coincidentally the same as a 1995 Impala SS w/ a 350). "
Yes, they definitely changed the ratings in the early 70's because of the insurance companies. The cars did not have less power, just a different way it was rated
In the 60s and before, they would run an engine with no accessories at all, open exhaust, etc... Then they would flog it until it died. In the early 70s, they went to 'net'. They would not just rate the engine, but they had to rate it for the car. Therefore, they would add every accessory to the engine that was available on a Maverick, then they would use a full factory exhaust. The dyno sessions also became more engine friendly... not just measure it til it blows. Dave
Yeah I do agree with the 70s change in rating, but it says that a 327hp engine in 1970 for example would be rated at 270hp today. Yes that is true but there is also a fact that these cars also dynoed more at the real wheels than what they were rated at, which we all know that you lose 10-20%hp through the drivetrain. I have seen them dyno Hemi cudas that would do 500hp at the rear wheels when in 1970 they were rated at 425hp. Now the problem is knowing which ones they underrated for lower insurance prices. From what I have heard "most" of the underrated cars of the day were big blocks, and the "sports" cars of the day, if that was possible. In the end, I just wish I had a small underpowered 302:evilsmile.
SAE Net from 72 until whenever was measured at the back of the tranny with all accessories installed and running, so a 74 Comet/Mav with AC, power steering and alt all on, running under load was 138hp after running through the tranny. you can ditch about 20hp loss after turning everything off. I don't know how they do it now, but most Corvettes are putting at least advertised power to the ground, the 2000 Mustangs are 260 at the flywheel, about 20% less on the ground.
143hp is the worse case scenario assuming the engine is in tune and doesn't have any mechanical problems to cause lower power. A good guesstimate would be subtract 23% from a 70ish 302 numbers for drivetrain loss, I don't know how much power the compression would cost. Ballpark would be 160hp. I've heard of more than a few people that had their Comet/Mav dyno'ed and only had 120rwhp, but that is a 25+ year old original engine as well. I can tell you, mine has lost power since I got it in 97, time to rebuild.
The rating with insurance was for anything over "300"HP. A 1976 car listed as 143hp is probably real close to only 143hp. This insurance thing was used for motors like the BOSS 302 which was listed as 290HP (<300HP mark) but was supposed to be closer to 340hp.
You have to figure that you are going to have the AC off... That is 15 hp conservatively. Then if you remove everything that makes up the AC system, you will gain an effective 10 rwhp because of the weight loss. Then the PS is worth another 15 when removed, and probably close to 10 with the weight loss. So on a dyno, properly tuned, and not worn out, you would see: 143 +30 = 173 at the back of the tranny - 17 for the rear end and drive shaft (10% roughly) = 156 at the rear wheels Then when you accellerate without the weight of those 2 systems, you will accellerate like you have an additional 20 more rwhp than before. So your car's effective power stock =129 rwhp Your car feels like =176 rwhp after the 2 big power drains are gone. Some notes on my figures and some dyno facts: *10% assumed loss from auto tranny *10% assumed loss from drivetrain behind tranny (20% overall from crank is pretty standard for auto tranny) *100#s of weight lost = 10 rwhp effective gain OR 1 tenth off the quarter (tried and true formula) *Standard trannys don't lose the full 10% of autos, it is more like 4% to 7% depending on the exact tranny used. *Aluminum or CF driveshafts also cause less parasitic power loss *Aluminum rims lose less power than steel... a taller rim (ex 17" vs 15") will drain power because the larger rim is generally heavier than the larger tire. *Higher gear ratios dyno higher numbers than lower gear ratios, even though the car might be MUCH faster with lower gears. *Aluminum flywheels lose less power to the wheels, HOWEVER they can cause a torque loss just by having less rotating mass to act against the drivetrain.
