Thread: Torqueflite 727 (TF727) Questions

Well, well, I never would have thought of that. This is opposed to the low rev and high gearing setups that bigger engines tend to have.

What about all that lost horsepower from parasitic loss?

that glorious little motor

Nice to read something positive about these engines instead of the usual!

Originally Posted by Davo

Well, well, I never would have thought of that. This is opposed to the low rev and high gearing setups that bigger engines tend to have.

What about all that lost horsepower from parasitic loss?

Nice to read something positive about these engines instead of the usual!

I honestly have no recollection of a parasitic loss problem, as i said it was used very succesfully as a race vehicle, and others remarked at how well it went, they were very surprised it only had a 3.5, no EFI either!!

just to add to the revs vs fuel economy debate, higher revs but low load with SU type carbs equals relatively good fuel consumption. but work it hard towing etc and . The RR weighed in at 1650KG including the rollcage, ( a FISA spec cold drawn seemless low carbon steel structure), so the light weight would've helped a lot too. A 110 would suffer a bit in this area so it is the reason you don't hear too much about good 3.5 county experiences

And YES, that little 3.5 IS a great engine.


JC

Originally Posted by Davo

Well, well, I never would have thought of that. This is opposed to the low rev and high gearing setups that bigger engines tend to have.

What about all that lost horsepower from parasitic loss?

Nice to read something positive about these engines instead of the usual!

I honestly have no recollection of a parasitic loss problem, as i said it was used very succesfully as a race vehicle, and others remarked at how well it went, they were very surprised it only had a 3.5, no EFI either!!

just to add to the revs vs fuel economy debate, higher revs but low load with SU type carbs equals relatively good fuel consumption. but work it hard towing etc and . The RR weighed in at 1650KG including the rollcage, ( a FISA spec cold drawn seemless low carbon steel structure), so the light weight would've helped a lot too. A 110 would suffer a bit in this area so it is the reason you don't hear too much about good 3.5 county experiences

Carbs work a lot differently to efi, my cousin used to get 26Mpg from his 4 spd manual 308 4 barrel carb HZ K'wood on a long 100km/h run, it had a 3.36:1 diff and was just revving happily along with almost NO load. (But open those cavernous secondaries on the Quadrajet and that was the end of ANY economy run...)

And YES, that little 3.5 IS a great engine.


JC

To weigh in on this "parasitic loss" thingy, I have a dune buggy I built 25 years ago using a 727 Torqueflite/IH 4WD trans and transfer case on a 4.4 Leyland engine, I'm sure I would have noticed it if it really was 40hp. That thing went hard when I poked it. I'll give it a 10% power loss rate similar to any other 3 speed trans of the era, not more.





In mud rally trim

I drove a standard 2 door auto once in Saudi Arabia, (a loan car back in 1985 so it was almost new) and wish I hadn't.
It was the SLOWEST SLUG compared to my 81 manual that I ever drove.

I am sure there was 50BHP lost in the driveline. It took about 1/2 minute to actually start driving.

Regards Philip A

I think the problem with the 727 is not the trans eating the power but the engine unable to work properly due to carbies, vacuum advance and camshaft conspiring to prevent the engine reaching the stall point of the torque comverter and the power band at the same time.. The 727 has a very tall first gear (80km/h in first gear in a valiant). A decent tune and a higher stall converter may well have fixed the problem. As Justinc noted, once the revs are up its all go.

Originally Posted by bee utey

I think the problem with the 727 is not the trans eating the power but the engine unable to work properly due to carbies, vacuum advance and camshaft conspiring to prevent the engine reaching the stall point of the torque comverter and the power band at the same time.. The 727 has a very tall first gear (80km/h in first gear in a valiant). A decent tune and a higher stall converter may well have fixed the problem. As Justinc noted, once the revs are up its all go.

Hence the 1.222 high range, went really well IMO.

JC

Parasitic loss concerns the loss of HP ,not Torque , therefore in simple terms the Rate of Accelleration. (Rpm/second gain)Torque convertors often multiply Torque depending how they are set up.
Perhaps some defer 1.4s and a 3000 stally !
10% power loss ? Parastics are never a percentage .thats only for those who cant work it out .(Run down Decel test on a rolling road Dyno,-Diff parasitics . Best 3spd auto for Parasitics was the old Trimatic ,with also a substaintiqally lower first gear