What to expect from 1.6 rockers on a '509 cam 440?

[Kern Dog]

I hate cam swaps. It is almost always guaranteed that something causes the engine to NOT start right away and I stress about the possibility of a destroyed lifter or lobe... or 2 or 3... Roller cam? Too much $$$ for my tastes....
Yes, my cam is a relic. A dinosaur. It makes decent power, but I'm curious if anyone knows the effects of adding the 1.6 ratio rocker arms? For some time, the Mopar Performance 440 based 500 CI crate motors used the '509 cam with 1.6 rockers and 9 to 1 pistons. They claimed that with a 750 carb and headers, the motor was a 500 HP mill. Thts great, but I have no idea how many HP are the result of the ratio bump.
Has anyone here made this change and do you have anything to report?
Thanks, Greg

 

[lewtot184]

going from a true 1.5 rocker to a true 1.6 rocker will net about 6 degrees duration at above .200 lobe lift at the valve, and gain about .030-.035" gross valve lift. power gains aren't great, maybe 5-7hp with the rocker ratio change.

 

[Hemirunner]

Depending upon how the heads are setup and what valve reliefs may or may not be in the pistons, the most likely outcome is destroying that engine. You need to put up more info on the combo and let us know what heads are on it and how they're set up. If it's stock junk, you most likely don't have clearance between the valve seal and the bottom of the retainer. You'll need good springs as the added ratio will increase valve acceleration off the seat. Are the springs on it even good enough for the 1.5 rockers? Most guys don't even check.

 

[lewtot184]

Depending upon how the heads are setup and what valve reliefs may or may not be in the pistons, the most likely outcome is destroying that engine. You need to put up more info on the combo and let us know what heads are on it and how they're set up. If it's stock junk, you most likely don't have clearance between the valve seal and the bottom of the retainer. You'll need good springs as the added ratio will increase valve acceleration off the seat. Are the springs on it even good enough for the 1.5 rockers? Most guys don't even check.

good advice. stock heads don't like much over .480 lift, .500+ lift with stock retainer to guide clearance is cruising for a bruising. most people don't know how to tune for these big hydraulic cams and should avoid them.

 

[Meep-Meep]

Also the higher ratio puts more strain on the valve train, and if that causes significant deflection, then you may not be getting what you think you are at the valve. I'd just keep the 1.5's. If you want more lift then change the cam. Personally the .509" with enough compression should run like a bat out of hell.

 

[Kern Dog]

Personally the .509" with enough compression should run like a bat out of hell.

The car has more power now than the tires can handle. I was thinking that the additional ratio might help increase idle vacuum.

 

[lewtot184]

The car has more power now than the tires can handle. I was thinking that the additional ratio might help increase idle vacuum.

the added ratio may decrease idle vacuum. the added ratio has the effect of adding more cam.

 

[Garys1969RR]

I put a .509 cam in my 77-440 8 to one compression. It runs pretty good, but the power brakes wouldn't work so I went to manual. You just change the firewall plate, push rod, and master cyl. I am much happier with this brake set up. So now putting in a 451 stroker, with 11.5 to 1 compression ratio. Will use the same cam, so will see how well a compression bump up works with the cam. Will be also using the 906 heads off the 440.