mpottorff

I just finished up the bottom end overhaul of my 502MAG GenVI motor...this is a roller motor. We used all stock Mercury parts (rings, bearings, gaskets, oil pump) for several reasons..but that is water under the bridge. I have the stock heads in the shop getting a good valve job and a little port work done.
My questions are this.
#1 Are roller rockers worth the cost? And if I use them should a guy install new push rods? And what kind of roller rockers have you guys had good luck with? My rockers now are non adjustable so I'll also need an installion kit to install roller rockers? Should a guys use 1.7 ratio or 1.8 ratio rockers...I know the 1.7 is stock.
#2 Valve springs have about 500hrs on them but test in the OK range. What kind of valve spring pressures should these used valve spings test at? Or should I just replace them with new ones and forget about it. If new ones are the best bet any suggestions on the ones to use?
Thanks,
Mike

MILD THUNDER

iTrader: (3)

For the cost of springs, I would replace them for cheap insurance. I dont believe you need special pushrods for roller rockers. Just going to roller 1.7 rockers might not gain any perf, but going to 1.8 rollers may. Im sure some guys will chime in on this with better opinions.

Pat McPherson

I agree with Mild...
At 500 hours I rebuilt my 502MagMPI with parts from GM High Performance and gaskets from Merc.
Replace the lifters and springs for sure.
I would going to 1.8 roller rockers; don't bother with 1.7 rollers on the such a small cam.

Griff

Unless you plan on a remap of the ecm, just go with 1.7's.

New pushrods are not needed. Just inspect them.

The only thing you need to convert to an adjustable valve train is the rockers studs-- ARP part # 135-7102.

If you use the newer style Crane Gold rockers, you will not have to grind the corners of them to clear the valve covers. You will have to grind off the drip tabs inside the stock valve covers.

Pat McPherson

I respectfully disagree that the ECM would need to be touched.
Going from 1.7 to 1.8 is only adding like 0.030" worth of lift.
A fuel pressure bump is likely all that would be required.

kennyo

I needed longer pushrods to correct geometry when I put GM performance roller rockers on. Check it !

satisfactionII

Change the valve springs for sure. With any BBC chevy over 500 HP 200 hours max on the valve springs.

nwimbush

Here you've established the level of performance increase> a little port work. To the benefit of the port work, you should look at increased flow and what you can do to leverage on that investment.

You could go to 1.8 to the benefit of the port work investment. The roller rockers don't offer up much performance increase at stock revs, but the reliability increase is available with the higher-end units.


YES - you should replace the springs with the recommended ones for the cam, in your case stock - you'll have to check the ones you have to ensure the compressed height will allow the use of the 1.8 rockers, but that would be the best bang for the buck.