Horse Power and Torque

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mopar74

mopar74

FABO Gold Member
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Good afternoon all,
I have never posted a thread as this before so here goes, I'm putting my car on a chassis dyno at the local college I work at (Palomar College Welding Instructor). Any how I'll get two pulls for forty dollars and a chance to do a bit of tuning if needed. Car is a 1974 Challenger (in my sig.) not an A body I know but a mopar anyhow. Plus this site gets a lot more traffic than E bodies only. So what do you think it will make for HP and Torque at the wheels as this is a chassis dyno. Specs to follow and I'll post results tomorrow.
Engine: 1975 360 .030 over
Pistons: KB107's not sure on the true compression ratio but I have between 180 and 185 cranking compression all plugs removed and the carb wide open for the test.
Cam: Comp cam XE268 installed as per cam card recommendation of 106 I think it came in at 105.5 if I recall
Heads: J heads with 2.02 intake and 1.60 exhaust valves with a bit of port work done to them years ago. They were milled .050 back in the 90's to raise compression on another 360 I had.
Ignition: stock electronic with initial set at 20 and total limited to 33 with a FBO plate. When I don't put race fuel in it I can not set total above 29. This is all in at about 3000 RPM any faster and with more total it detonates.
Fuel: 1/2 tank of our wonderful 91 octane (CA.) and 5 gals of 110 octane leaded gas. (this is for the dyno pulls only) when I fill back up it will be back to 91 and 29 degrees total timing.
Intake and carb: LD340 with a 670 street avenger.
Exhaust: Stock Jeep Grand Cherokee manifold on the passenger side and an RT Dakota on the Drivers side. These are the bigger outlet manifold of between 2.125 and 2.25 opening.
Exhaust piping: true duals no crossover with 2.25 size and flowmaster 40 series mufflers to include 2.25 tail pipes to stock style tips I made back in 98, opened up the inlet to 2.25 and made stainless steel tips to match the old chrome tips.
Not sure if it matters but the Trans is a 727 with a 2800 stall. Rear-end 8 and 3/4 with 3.55 sure grip and the car weighs approximately 3900 with me in the drivers seat. I know heavy car but what do you expect for a 1974.
I'll post results tomorrow night. I'm hoping for at least 275-300 at the wheels for HP and 350 to 375 for torque. What do you all think.
Kevin
PS I won't be disappointed if I'm totally off base with the HP and Torque as it is a daily driver and not a race car. Super fun to drive, will light the tires up at will and I've had it 20 years now.
 
When was the last refresh/rebuild of the motor?
Approximate mileage on the motor since the refresh/rebuild?

Thanks.
 
rebuilt in the spring with start up and cam break-in in April. Its probably got all of 2000 miles on it give or take a couple of hundred.
 
Ok....must have pictures!
And E-Body are always welcome here! !!!!

Jeff
 
Will Do on the pictures. Thanks I have been a member of this forum for a long time and I do have an A body also 69 valiant with a fairly warmed up 318, 727,3500 stall converter and 3.91 gear. It is a work in progress and is not registered for the street as of yet should be road worthy in early January.
Pictures to follow.
 
Rear wheel HP and Torque, 272 hp @ 4500 359 tq @ 3500
 
Just for giggles, know this: There is no such thing as horsepower. HP is a mathematical product of a formula from torque and RPM. All you really need for a basic dyno is a device to load the engine and a means to measure that torque, and something to measure shaft speed, IE RPM
 
Something isn't right if it's pinging at more than 29* total. That should likely take 33-35 total pretty easily. ]]

What you might try is slowing the curve with heavier springs and back out some initial. With that cranking compression, it should be good at about 16 initial. Once it starts detonating, it's tough to get it to stop on a pull.
 
Thanks Rob I did put a heavier spring on the dist. slowed it down from all in at 2200 to 3000. Now when I was having the detonation issues it was back in August and Sept when we were have the 100 degree days and the clutch fan and radiator were giving me issues. I have since replaced both and installed an aluminum radiator. The car now runs at 170-180 no matter what the outside temp is. So today I put total back up to 33 in anticipation for tomorrows pulls. So we shall see. If it likes it there I'll recurve the dist. back to 16 initial and 33-34 total.
PS I still haven't installed the headlight relay kit I received from you but it is on my list as soon as the semester ends at school and I have a bit more time. Can't rush these things when you get to be my age lol.
 
The issue is the heads with the camshaft IMO. 180-185 is about the limit for pump gas with no other design elements to help put off ping or detonation. Your tuning needs to be perfect. If you have to adjust the timing, I'll toss out that the carb may not be optimized because it "should" be ok with the convertor and car it's in, with mid 30s timing and high initial. Good on slowing the rate of centrifugal, now get deeper into tuning the carb. Look at the jetting and more importantly the power valve(s).
In terms of power - I think it will slightly down from where you want it, because of what I would call tuning issues.
 
Well bad news, good news and more bad news. On my way to college this morning (where I work and where the chassis dyno was going to be) I jumped on the car hard about a mile from the college, it pulled hard thru first, second and than a loud bang. I lost power steering so I figured I tossed a belt to the steering pump. As I was pulling in the lot the car shot up to 220 degrees so maybe I tossed the water pump belt also. Boy was I wrong, the water pump fan and pulley snout broke, which in turn put the fan into my maybe 3 month old aluminum radiator. The good news is I was able to get my stock radiator (which I changed in favor of an aluminum radiator do to this one needing a bit of work) from my house, a used flex fan which I despise and a new water pump to get the car up and running again. The bad news again was I was not able to put the car up on the dyno. I finished at about 2:30 but he had about 5 cars plus a motorcycle ahead of me and he was shutting the dyno down a 4:00. So there is always the end of next semester when he will be back and I'll give it ago then. I have never seen a water pump break the way this one did, maybe bad casting who knows it was only about 5 months old. But at least I was able to drive it back home this evening with minimal out of pocket cost. Time to get on the internet and find a 7 blade fan and purchase a new radiator.
Kevin

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yes yes it does. But that's what we get when we play with these old cars. It's what keeps us young
 
I have to say, I've seen a water pump shaft break, but not the whole housing.
 
Probably more likely some sort of harmonic vibration, either a fan out of balance, or an odd belt situation causing vibration. "Back in the 70's" when I swapped a 340 into my old 70 440-6 RR, I eventually adapted the "hang on" AC onto the SB. I ended up with "just the right" (wrong) belt situation on the AC that at about 3 RPM points that thing would vibrate like you just cannot believe

I was even more ignorant back then than I am now, and it took me a couple-three months to realize that all I had to do was flip the eccentric belt adjuster and that would change the belt length.
 
I have never run it, but maybe a water. Or water methanol injection system would cure the detonation situation? I see there are also detonation gauges available, but I don't know the cost. We have 93 pumpgas here in MN, but I am pushing it with 10.1 compression and iron heads So I am curious about this myself.
 
was that the older style pump with the smaller (1/2" I think) shaft , or the better 5/8" later style
 
I have a nice 7 blade fan Clutch style if you need. Aluminum mopar.
 
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