BBC Reverse Rotation Cams
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=16845
Printed Date: October-06-2024 at 4:25pm
Topic: BBC Reverse Rotation Cams
Posted By: TRBenj
Subject: BBC Reverse Rotation Cams
Date Posted: March-19-2010 at 12:22am
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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! |
Replies:
Posted By: BuffaloBFN
Date Posted: March-19-2010 at 10:20am
Good research Tim. I bailed when I got the roller price and went back mostly stock...plus it was getting warmer.  ------------- http://correctcraftfan.com/diaries/details.asp?ID=2331&sort=&pagenum=12&yrstart=1986&yrend=1990" rel="nofollow - 1988 BFN-sold "It's a Livin' Thing...What a Terrible Thing to Lose" ELO |
Posted By: Waterdog
Date Posted: March-19-2010 at 10:21am
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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. ------------- - waterdog - http://www.correctcraftfan.com/diaries/details.asp?ID=3896&sort=&pagenum=2&yrstart=1978&yrend=1978" rel="nofollow - 78 Ski Tique |
Posted By: eric lavine
Date Posted: March-19-2010 at 10:42am
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I found a stock Melling, which i will install this week for 169.00 wo lifters, I almost fudged on the Piston install, rod tangs towards the outside of the block and the dots on the piston tops go opposite of a lefty, very important as confirmed by Greg and the service manual. staying stock because of reliabilty issues and its from a US towboat.
if any interest, I still have 3 biggies for sale, one is a righty 454 bottem and 427 heads, and 2 330"s long blocks lefty's, fired and ran with 135 compression ------------- "the things you own will start to own you" |
Posted By: TRBenj
Date Posted: March-19-2010 at 2:14pm
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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. ------------- |
Posted By: eric lavine
Date Posted: March-20-2010 at 12:01pm
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I find when I make them hot for a customer the phone starts a ringing, they start sending rods thru the bottem lol, more of a CYA thing for me.
I guy brought in a handful of busted roller rockers, and my guy at the shop is using guidance from his Big Brother who installs furnaces for his engine rebuild, I hand him a rocker and told him, where do you think those needles went? he is 24 and i try to convey to him pointers and he always ends up doing what his brother tells him to. he has 4k tied up in this thing, not stroked, big dollar heads, all the blsht, and he shows up with a ford 9", to put in the 95 transam, another 500 bucks, and im like what are you doing with that?? I dont want to blow a rear-end, more advice from bro, are you going to the strip? no are you putting slicks on it? no just a funny story, i thought ------------- "the things you own will start to own you" |
Posted By: connorssons
Date Posted: March-21-2010 at 12:03pm
| 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 |
Posted By: StuW
Date Posted: June-09-2018 at 1:52pm
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Yes, I know this is a very old thread!!!!!! If any 454 BFN owners are still looking for a RR camshaft, Camcraft Cams definately still has some reverse rotation flat tappet blanks on hand. I just bought one myself, $250. Ask for Hunter https://www.camcraftcams.com/" rel="nofollow - Camcraft Cams ------------- 1982 Barefoot Nautique PCM 454 |