[Jazz]

Some Input...
How do you know if you should run the 1.65 rockers over the stock 1.50 ?
I'm running a 67 400 with the 670 heads. (fresh rebuilt)
A RA IV Cam with the 469 lift at 1.5. , 308 intake, 320 exhaust Adertised Duration.
Dropped the compresson down to 9.6.
Just wondering if she will run better with the 1.65 rollers..

Thank's...

[steve25]

You will gain about .040" more valve lift and 4 more degress duration over the nose of the cam.
This change will provide a tad more top end power and will let you hange on to that top end power longer.
This change will not effect your bottom end power, but things need to be checked to make this change.
1) valve spring coil bind due to added lift.
2) retainer to valve seal clearance due to added valve lift.
3) push rod to push rod hole clearance due to change in pust rod angle.
4) with amount of lift your rocker studs should be up greaded to the full 7/16" type, do not run the factory studs as they will snap off in time.

[dmac]

I have a similar engine and went with 1.60 instead of 1.65 and end up with about .510 lift. You have lower compression and I would guess that more lift, more duration might lower your compression more than that cam is designed for. 1.65 is 10% more lift than 1.50, so I think you would be at about .518 lift, so be ready for that, and make sure pushrod holes are elongated. My thinking in going with the 1.60s was that a little less lift was a little less strain on the valve train. I also went with the full roller rockers, not just the roller tip rockers. Very nice set from Butlers. Also that cam is already kind of a top end power cam, so you may not need more power up there especially if the rest of your combo doesn't match.

[Jazz]

Thank You All for the Input..
Some Very Good Points made by All.
It Is Appreciated ! !