HaxbySpeed

Just thought I'd share some info on a line of hydraulic roller cams that work very well for marine engines. In this day and age, there are no big secrets to building BBC marine engines. No secret oil pans, magic cylinder heads, or special cams that are going to set the world on fire. You can find out everything you need by reading, and asking people who know what they're talking about. If someone won't give you an answer, it probably means they don't know. Anyway, back to cams. Going back a few years, I was having lots of valve train related issues from using custom cams. Needing to use fancy $800 lifters for a fairly basic engine, breaking rockers, all the Morel lifter failures, etc. I had a few take out zz502 cams on the shelf, so I swapped one in on a low rpm jet boat deal in place of the custom cam that was causing lifter issues. I figured it had to have a pretty stable lobe because it could run so much less spring pressure, and I was willing to give up some power from the greatly reduced lift. Surprise, it made more torque, and seven more hp. The next couple builds I tried an off the shelf Erson, it made very respectable power, but closed the valves a little harder then I was comfortable with, so the search continued. I had a customer who had purchased some custom cams for himself, and was on his second set of lifters, had multiple broken snap rings on his rockers, one trunion broken in half, and had damaged a valve stem from the lifter bleeding down at higher rpm, this was after about 25 or 30 hours. I had had excellent results with Lunati solid rollers in the past, so I picked up their catalog to check out their hyd rollers. I chose a cam with almost identical duration as the custom cam, but opened the exhaust valve just a little later, and a fair bit less lift. That probably will give up a bit of power on a computer simulator, but in reality, especially in a blown application it can help parts stay alive. We dyno'd the engine with the custom cam, and experimented a bit to see what was going on with the lifters. We pulled the cam on the dyno, and swapped in the Lunati. It made 90hp more, egts were better, it idled cleaner, lifters were quiet, etc. Same day, same dyno, same lifters. It confirmed a lot of my suspicions. On the second motor we tried some Johnson lifters in place of the Morels. They worked well, but gave up a few hundred rpm earlier then the Morels did. I'm currently running one set of morels and one set of Johnsons in the same boat to do some long term testing, and use both regularly as I've never had another Morel lifter failure since I switched to using off the shelf cams. Every Lunati cam that I have used, and other builders too, has made more power then the custom cam it was replacing, and improved performance in the boat. So.., long winded way of recommending Lunati EFI Compatible Cams. They're available in genVI, and retro, and work well for NA or low boost blown deals, carb and efi. No reversion issues. I've used almost every cam in that series and they all work great. If you want something bigger, or something custom, the Lunati Voodoo marine lobes are killer. I could right a novel about the amount of time I've spent screwing around on the dyno with custom cam issues, having to switch to solid lifters, changing springs, etc. Suffice it to say, talk to several reputable builders when you're doing your homework for your next build. When I get time I'll try and post some builds with dyno sheets and specs in case it will help any one in the future.

Jason3603

Hey Alex thanks for the added info. Unfortunately I had to learn that the custom cam super whammy space shuttle $h!t is a recipe for disaster. I was having intake valve failure where the head of the valve would snap clean off. I was told by the person that spec'd my cam that it was a valve train instability issue. So out with the wallet and several thousands of dollars later I had the shaft rockers, heavier push rods, better lifters and much more. Dyno'd the engine and they made respectable power. Unfortunately 10 hours of engine time in the boat another valve failure. 2 valve failures in 2 years, bummer right? So after 2 years of no boating and grasping at straws on what to do I decided to replace everything cylinder head related including the valve train and related parts, due to the fact there is so many opinions that are unfortunately just opinions with no fact.

I appreciate that out of all the professional engine builders that you provide honest straight forward factual information.

Thanks again!

mike tkach

iTrader: (3)

i must say some of your post suprised me,some did not.i have had some morell,s fail within minutes of start up even with 5w30 oil but only a few.they colapsed so that part of your post is no suprise.i understand the effects of fast open-fast close ramps and how that can shorten the lifter,spring and valve life so again no suprise.the part that got my attention was the increase in power with off the shelf camshafts.i am curious if you have discussed this with the person i believe you got a lot of custom cams from.if you don,t respond to my post that won,t suprise me.

HaxbySpeed

No Mike, it was easier just to swap the cam and move on. Discussions of spalling, damaged wheels, lifters, etc. didn't really go anywhere, and when there was an issue on the dyno it would just turn into swapping and upgrading parts until it worked; no real search for the root cause. To call back and say "I swapped the cam and made more power", probably wouldn't have helped any. I just sent a lunati efi cam to another builder who tried two different custom cams in the same engine, and ultimately made more power in the rpm range he wanted with the Lunati. I believe he did tell Bob about his results. Last summer during a quick freshen up I replaced a custom cam spec'd by a well known builder, and ground by a smaller cam company. I didn't build the engine originally but did dyno it, and it made good power for the combo. I noticed some valve train issues, so I put in a Lunati efi cam with almost identical duration. It picked up 1.5mph, reusing every original part other then rings and bearings.. The specs on the original were pretty good, but proven, engineered lobes, make power.

mike tkach

iTrader: (3)

thanks for that info alex.now i will try to process it .that,s not always easy with my little brain!

ICDEDPPL

iTrader: (1)

Joe and I agreed on a nice Lunati marine grind for my build that i would have loved to use ,250/255 .646/.664 on a 112 if I recall right.
They also have the same cam with .630 lift. .... showed some really nice improvements on the sym program (45+hp) I would have went that route if my cams sold but 2 new cams not in the budget right now


btw, Alex I`m sending you this:
(hopefully it reaches you in time!!)

Full Force

iTrader: (5)

Following....

mike tkach

iTrader: (3)

are you sure that the camshaft was the root cause of the intake valve failure?was piston to valve clearance correct?was valve spring pressure correct?i ask these questions because sometimes things get blamed for causing a failure when in fact it was something completly different that caused the failure.

Jason3603

You have great points Mike. It is very critical that the engine build is set up to the proper specs in their entirety, not missing or overlooking anything. Over the years I have learned a lot, one of the most valuable lessons I have learned is that everyone that assembles engines has an opinion on what proper specs are. One thing I know with absolute certainty is that I am not using these specific cams ever again, probably end up using them as table legs. You are more than welcome to put them in a set of your engines to prove me wrong or you can take my word for it. Are you willing to take the risk? Please don't take this out of context, I am not trying to be abrasive or rude.

This thread is not really about my build, if you would like to discuss my build in detail feel free to contact me. I was trying to bring out my thoughts on how I will seek an off the shelf cam before I go after a magic bump stick.

horsepower1

Great post Alex.