hi,as the title states im somewhat confused.my truck is a 94 f250xlt 7.5l.its main purpose in life is to pull my 4000# tt.torque numbers are around 395 on a good day,which isnt alot when pulling a steep grade.thats a lot of c.u for only 395 when my 71 merc with a 429 is rated at 460 ft.lbs.the merc does have 10to1 compression so my question is does the comp.ratio explain the difference in torque numbers or is something else going on.its about time to think about a rebuild and if there are things that can be done to bring the torque numbers up to around 460 without making the engine way bigger i would appreciate someone clueing me in.thanks

 

71 was rated by the old gross power numbers influenced by marketing considerations. 460 is rated at net power, with the mufflers and air cleaner and ps / water pumps etc. Compression impacts torque also. More later.

 

This goes into the Wayback Machine and gives eye-glazing detail about the change from gross to net.

https://ateupwithmotor.com/terms-tec...et-horsepower/

Look at this blast from the past. A 390, in 3 different configurations, makes 427 lb/ft in each one. A pillow barge 428 as seen in T birds and Galaxies is rated 345HP. Add some performance parts and it is now shown to be 335HP. "Marketing considerations". You can't sell something your customer can't insure for example.

FE Series Engine Specification Chart

 

A fellow traveler. There is no free lunch:

Headers vs. Stock manifolds - 460 Ford Forum

 

And curious that the Boss 302 and the Chevy 302 had the same HP rating. I had Werby run the numbers on the stroker 454 I built out of a lowriser 427 back in the 80's. Same stock comp ratio, only difference being the HM310 cam (.515 gross lift, 294* advertised duration 108 LSA) which isn't all that different from the stock cam in these engines. he came up with 460 HP at 5500 rpm. with the stock 2x4 intake and carbs.

 

Producing torque is easier for a larger engine at lower speeds, but it's also highly dependent on how the engine is set up. If you look at the current 5.0 liter Coyote engine, its torque peak is 400 lbs-ft in the truck version, and 410 for the Mustang version. And horsepower is close to 400 for the truck and 460 for the Mustang. These numbers are all SAE net at the flywheel. This engine has small block displacement, but producing big block power and torque. mostly from very sophisticated air flow management that consists of fancy plumbing on top of the DOHC heads and really complicated computer control.

 

Mostly due to variable valve timing.

 

Yes, the VVT is part of the air flow management I was referring to, and it's making the engine very versatile.

I know Ford is using TiVCT to implement passive EGR, but I'm not sure if it has enough range to run the engine in Atkinson cycle to improve efficiency.

 

apples to oranges to banana's..... 50 plus years of technology..

major changes in testing.... type of testing... computers vers analog...

where is my Sunoco 260 fuel .... Amoco White Gas...( not the camping stove white gas)
Sunoco "Blue",,,, Cam II..... etc.
love the smell of 112 octane gas.

 

That was the Cancer causing Benzene you were sniffing...………………………….

 

between motor oil and axle grease in my hair... and brake shoe Dust up my nose.... I got to die from something....

66 years and counting... motorcycle riding for 49 years.. and Still Here.
50 years as an auto mechanic.. and still have all 10 fingers...

for many years.. I used gasoline in my cigarette lighter...

 

What ? I use it and still do to wash parts ! How many times have I had the stuff in my mouth trying to get a siphon started ?

 

I use a tired electric in-tank fuel pump.... and 30 feet of wire

I am not fond of flammable spit...

 

To the OP.

Apologies for the DERAILMENT

2 smashed rail cars.. broken building... no words for the overhead Wiring.

If I had done a better JOB of derailment.. I would have dug out the Steam Locomotive derailments .....

 

Boss 302 and Z-28 are prime examples of HP selected with marketing in mind. Keeping them under 300 HP, they kept the insurance man from excessively surcharging these cars. Not sure the links work here anymore, but the Ford made 372 and the Chev 356 when HRM got into their Wayback machine:

https://www.ford-trucks.com/forums/9...omparison.html