1970 -vs- 1974 440

[Jireh Customs]

What were the changes made to the 440 from 1970 to 1974 that caused such a drop in hp? Building a 1974 440 to between 400 and 124 hp, what are the best streetable upgrades?

 

[greenmonsta79]

Compression mainly, pre-72 were steel crank, camshaft grind.

 

[63RedFury]

intake,carb,headers,cam,windage tray,and atleast 9:5 pistons would be the best upgrades.

 

[Jireh Customs]

What was the biggest contributor to the lost compression? Pistons or heads or both?

 

[greenmonsta79]

The heads were a closed combustion chamber on the 906's and that's what the 70 would have had which increases compression over a later open style combustion chamber plus I do believe the pistons were a bit different plus the Camshaft from a 375HP is different vs. the standard 440 cam.

 

[WileE]

Sorry, the 906 are open-combustion heads, as are all except the 67 915's. The main differences are lower compression, intake port design, camshaft, carb & ignition tuning for emissions.

 

[dbowperson]

You can take any 440 block and make it into what you want. It's based on what you put on/in it. People even take the old motor home 440 blocks and make them into ground pounders. Just due your due diligence in picking the right parts. The biggest thing will be using the right heads and cam, though. Either use a set of 69/70 era heads, or any of the new aluminum heads.

 

[WileE]

intake,carb,headers,cam,windage tray,and atleast 9:5 pistons would be the best upgrades.

Precisely, although the windage tray won't make much of a difference on the street. I'd also consider to do intake work on the heads, you probably have 902 heads with hardened valve seats. You can also richen & tune the thermoquad to work, as well.

 

[Cranky]

If you buy new pistons, which you should as the stock 74 pistons will be about .100 down in the hole, buy according to compression height and not 'advertised' compression. A 6 pack piston has a compression height of 2.062 and are around .015-.020 in the hole. With a composition head gasket and open chamber heads, you still won't have any quench working for ya....

 

[MustangAndy]

What were the changes made to the 440 from 1970 to 1974 that caused such a drop in hp?

Gross power ratings vs. real world Net.

From what I've seen manufacturers started to rate the power output based on what you'd see on a chassis dyno (wheel horsepower) instead of the older way of what the car was making at the crank.

 

[racedodge]

Gross power ratings vs. real world Net.

From what I've seen manufacturers started to rate the power output based on what you'd see on a chassis dyno (wheel horsepower) instead of the older way of what the car was making at the crank.

andy nailed it.. they did this due to the insurance pressure of the early 70's as well as to address newer emission standards.

 

[bigjimmyl]

plus the switch from net to sae hp ratings

 

[dbowperson]

Plus significant compression drops.

 

[Meep-Meep]

The best thing to shoot for is about 9-9.5:1 CR for the street with 91 gas and if you do it with a closed chamber head better yet. If you use aluminum heads I think you want to add about .5 point of static CR to compensate for the heat loss from the chamber. Then build the engine around the calculated compression by picking a cam that wont decimate your cylinder pressure. Shoot for about 175-180 PSI.

I'm running a 77 440 with zero deck pistons and closed chamber heads and I have 10.1:1 CR and 190 PSI. Car runs like a bat out of hell for what it is but needs a splash of 110 race gas to keep it happy.

 

[Randy73]

Gross power ratings vs. real world Net.

From what I've seen manufacturers started to rate the power output based on what you'd see on a chassis dyno (wheel horsepower) instead of the older way of what the car was making at the crank.

Not quite true, 1970 hp was raw HP at the crank, w/no accessories and 1974 would be HP at the crank with all accessories (alt, PS, A/C, etc..) hooked up.