Engine Swap

[520SC]

Originally Posted by olddog

Well the cost verses benefit on the roller cam is a personal choice.

At least in theory, the roller lifters allow a steeper ramp at both ends, thus the valve can be opened quicker and held open longer (because it can be close quicker). So a roller cam is the solution to your problem. It would act like a bigger cam, without sacrificing manifold vacuum. Again you have so many cid to make power with, you may not need or want it.

I haven't a clue what gearing and tires you are running, but I'm surprised you can hook that monster to the ground.

Originally Posted by cycleguy55

Fully agree. Plus, of course, the roller cam allows you freedom to select the motor oil of your choice without worrying about low ZDDP and/or wiping out a lobe.

That was the thought I had, when I saw "I did a couple of full throttle pulls up to 4500 rpm in 2nd gear yesterday." I would think 'full throttle pulls' in 2nd gear would break the tires loose unless running wide, super-sticky rubber, perhaps even then.

The added cost for a roller cam would have been a bit over $1000, about 13% more than I paid in total for the long block (plus shipping) from Texas to Hawaii. ATK recommended against a roller cam because they felt that the power increase wouldn’t justify the added expense. I once watched a YouTube video (https://www.youtube.com/watch?v=8VjFZMKvEwY) produced by Engine Masters, which compared dyno results for two Isky cams, identical in duration with 244 degrees and identical LSAs of 108 degrees, but one was hydraulic flat tappet with .505” lift, and one was a hydraulic roller with .558” lift. The roller cam provided +21.4 hp and +6.4 ft-lbs over the flat tappet cam. So, in their case, with an added expense of $900, they gained 0.024 hp per dollar using the roller cam. Here’s the graph. I was surprised at the result. http://imgbox.com/EyzjA0Yf

Agree about the need for cam lobe protection. I'll have to use a ZDDP additive with every oil change until I convert over to Royal Purple synthetic in about 4000 miles.

As for the full throttle pulls, I started them at 2800 rpm and brought the throttle in gently, so as not to break the tires loose. My rear tires are Firestone Firehawk Indy 265/60R15s, so they'd go up in smoke if I were to suddenly floor it.