BBC Reverse Rotation Cams

It seems there has been a shroud of mystery surrounding the BBC Reverse Rotation cams here... and I *think* I finally have uncovered what there is to know. Greg (BuffaloBFN) was the first to start documenting these oddballs in his engine rebuild. All the RR instances Ive found utilize a gear on gear set up, and spin the opposite direction as the crank. This allows RR 454's to use standard rotation distributor gears. Of course, though they spin the same direction as a LH engine, these are not LH cams- the firing order is reversed. Because of the gear on gear timing set, the RR blanks also have a different snout on the front- so the blanks (LH and RH) are not related. In his quest to go roller, Greg discovered that this would be an expensive route... to the tune of $2500 for a custom blank and grind. In my searches, I have found minimal references to factory RR rollers- and I have my doubts any ever existed at all. If such an animal ever existed, I wouldnt know where to find one. I also confirmed the astronomical pricetag on a custom blank.

But there is good news.

Flat tappet reverse rotation blanks DO exist, at least for the near term. Thanks to a knowledgable tech at Comp (who demanded that I send my original cam to them for verification), you can still get a custom ground cam. If you call the 1-800 number and cant find someone who knows what theyre talking about, ask to speak with Mike Mclaughlin in the tech dept, and he'll set you straight. He did allude to the fact that there arent that many blanks left though- and whether more will be made available or not remains to be seen. Luckily, Lunati also has a few blanks remaining as well. I ordered a custom cam from Comp (and pony'd up for the nitriding service to boot), but hedged my bet by picking up a few "spares". Everything lines up with the original, so these are legit.



While our original cam was at Comp, we had them measure it up to see what we were working with. It turns out our '79 330hp OMC cam was pretty consistent with another 330hp Mercruiser part number I found... and this thing is tiny: its on the order of .460/.480 of lift (at the valve, with the stock 1.7 rocker ratio). That seems to support the rumor that the 330hp marine longblocks were really only good for 280-290hp on the dyno. It seems that unlocking the power from these behemoths isnt going to be all that hard... but Ill save that discussion for when we get the motor bolted back together. Just wanted to share the good news for now!

Hey Tim,
Yesterday I was talking to my buddy, he turned me on to a web site called "off shore only" I surfed it a little. Anyway lots of those big boats have twin BB Chevys that counter rotate. Check out the forums there.

Eric, I called Melling about that cam and got the specs. Like you said, its basically a stock replacement- in the ballpark of .500/.500 of lift. There are tons of guys, on the street and the water, running hot cams in their big blocks, even with flat tappets. Im talking well over .600 of lift. My upgraded cam will be pretty tame in comparison, but nowhere near stock. The stock BBC cam is significantly smaller than the warmed up cam I have in my small block Ford!

Andy, Ive spent a lot of time over on Offshoreonly. Ive also spent some time reading about general BBC stuff on Hotrodders.com. Performanceboats.com is another good source for info- mainly classic jets and v-drives. Unfortunately, basically no one runs reverse rotation engines anymore. Only old school twin screw inboards- which are rarely built for performance. Any outdrive built in the last 20-30 years has had the ability to spin in either direction- so basically all twin engine applications are running automotive rotation stuff exclusively.

If you call Linati cams and ask for harold,he can help with custom grinds. old harold set me up for my 71 stang and did a great job. jeff