I am researching a solid roller cam for a 598" (4.6 X 4.5) big block. The motor plans will be for 10:1 compression ratio, fully hand ported or CNC'd aluminum heads, single plane Dart intake with a 1050 carb, CMI E-top exhaust, shaft rockers, etc. I would want the motor to turn 5500 to 6000 RPM at WOT. Here are some of the recommendations so far.

Ultradyne 270/280 @ .050" on a 112+4, .710" gross lift.
Note: My current cam in my high compression 498" motor is a Comp 272/280 @ .050" on a 112+4, .714" gross lift.

Erson 276/284 @ .050" on a 114+4, .731" gross lift.

Anyone else have a suggestion? Both Ultradyne and Erson said these cams are very gentile as far as valve opening and closing and the ramps are slow for a solid roller and are designed for endurance motors. I have no clue about my Comp, but it has 30 hrs with no problems.
Thanks for your replies.
Craig

Anyone ever run a 4/7 firing order swap on a marine motor? Ersons cam recommendation included a 18736542 firing order.
Thanks,
Craig

The ultra dyne with 20 more lift would be great or use 1.8 rockers
and yes the 4/7 order is a great idea

Thanks Bobby!!!

Has Ultradyne overcome their problems - ie. is Harold back in business or still in a holding pattern?

Harlod is back up and running again and making a great cam. I would say both Erson and Ultradyne are great. I would also try Cam Motion and see what they have they also make some great grinds.

Excellent. It was a shock when he had his problems at the begining of the month, I am glad that he was able to recover so quickly.

Harold is truly gifted when it comes to designing and manufacturing camshafts.

What does the firing order swap accomplish, and is it only for special cam applications?

This swap has a couple of benefits (depending on your package) and does not cost you much if you are replacing camshafts anyway.

The biggest benefit are as a result of not having cylinders 5 and 7 from firing next to each other. This can reduce cross fire, but more importantly removes a potential 'hot-spot' on the cylinder heat. The elimination of that heat (which has a detrimental effect to valve spring temper) results in longer valve spring life and reduces the potential for valve spring failure.

A secondary benefit which is most notable in single plane intake manifolds is the elimination of "competition" between cylinders 5 and 7 for airflow.

In competition engines, some manufacturers suggest a modest (~1%) increase in power. Until recently the core cost for the revised camshafts were cost prohibitive and the change was not considered "economical". Today there are off the shelf cams with the change and custom cams can be built with with a modest premium (~$25).

ADAIVAN IS dead on ! Its worth it Vette