Thread: Broke Comp Cam promagmun rocker

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Most of my BBC experance is with marine builds. Most of the time number 7 cyl fails, next most often is number 8 cyl. So this was in the back of my mind, was one of these cylinders were it failed. Usally a valve hits a piston with little evidence as to why. Have my thoughts about it.

High load conditions with a solid roller is an issue initself as many of the valve train componets need checked and replaced more often.

Originally Posted by turbo2256b

Most of my BBC experance is with marine builds. Most of the time number 7 cyl fails, next most often is number 8 cyl. So this was in the back of my mind, was one of these cylinders were it failed. Usally a valve hits a piston with little evidence as to why. Have my thoughts about it.

High load conditions with a solid roller is an issue initself as many of the valve train componets need checked and replaced more often.

well yes and no i not trying to get in a pissing contest with you. as i do not know who you are so i give you the benefit of the doubt. in that i do not know how many offsore engine you built . i built some marine blower engines and built many carb marine engines. i was a dealer in hi rent off shore used bbc big chief parts.blocks other parts. and the hi HP merc stuff many HD cranes ,and t&D .jesel stuff has past threw my hand over the years .along with many delwest valves. crower Hippo liftes. jesel bowtie all were soild roller engines with very good hold out not many if any number 8 rockers that i ever seen fail they were very good about number them. i been building engine and machining engines for many years. had many bbc with 700+. sold rollers that been street/strip. blower and turbo bbc Nos. been doing then for over 30 years .the hold out on parts as very good .. lifters so/so at low RPM no oil . but that was before hippo.old comp roller rocker and lifters were not very good for that use . as for 7 hole that is was with a 4/7 swap cam ? to say that 7an 8 fails it is common for the rod bearings to fail on some guys engines .but over the years just when you think you seen a pattern to failure . i seen just as many in other location as well .i seen fail. if you have any spin-tron testing or if you can tell me its harmonics. i like to see the test .like spring rate what spring . what cam lobe number.core size .base circle.fire order of cam .belt or chain timing set or gear if so 3 gear or 4 . valve alloy stain less . titanium. inconel ? many years ago i was told by one of the bigger builders of race off shore boat engine to never use steel body roller rocker arms in boat engines

Not saying necessarly the rockers failed on 7 or 8 but was most often failers in those cylinders for no apperant reasons. Result was pistons and valves hitting. They were engines I didnt build. Some I redid heads on after the fact. Didnt get to see all the dammage. Speaking with Kirt Urban years ago on his advice began installing 3/8" coolant lines from the rear of the intake to the front crossover or in boat ran the lines out the transom sometimes. He stated lost many engies on the dyno without there addition. I had been doing it on SBFs for years. Also gasket matched coolant hole between the head and the block. One in the front right and one in the left rear. I do know this evened up temps between the cylinders based on plug readings and valve coloring. Sometimes thinking was the rear cylinders higher temps weakened the springs while the others still held fast allowing the 7 or 8 cylinders to float to a valve.

Personally I have truset Crane for the most part as they had done R&D for the big three as well as many other venues such as Mercury Marine. I also discuss cams with Engle for the most part speaking to them your speaking wit ha cam grinder not a computer jocky or program.

urban worked at wheel to wheel ? why they hit back were. i think it,s whined up when the engine RPM fee wheel then when the prop lands back it the water. blower engine it alot harder on the crank. blower on one end prop on the other.i have no proof but talked about this with other engine builders . as for crane stuff there rockers and wide bodys they made for merc are good and they made all the copper coated roller cams core .when they closed down there others now that build better core like JC cores . for springs on race stuff it.s pac. psi .isky . i have my customs grinds done by Erson or Horwards .and use moral lifters

Thats another thought but seemed anything could fail winging the throttle coming out of the water. I have retired at this point. Have a few projects to finish up. Paint a 14" Exciter, rerig and sell. Install turbos on my SBCs in my offshore. Work on my cars and trucks sell off some of them. Hit some open track days. help a few friends with car builds.

friend of jon best ran two bbcs in off shore boat that had turbos on it jon k. i did a 540 twin turbo about 6 years go was at mike m. in the big D when they lost the clutch .and blew up the 5 speed lenco guy drives it on the street in ohio did some work on the buick v6 turbo stuff a friend made the heads intake blocks vavle cover .the 540 bbc is in photos in my gallery

I posted a picture of the broken rocker on Comp Cams Facebook page. They contacted me right away and asked me to send in my rockers. They might give me a new set of their redesigned Ultra promagnums. The new ones look like they are made tougher and they are black. My old ones were stainless silver. Hopefully they are better. I was very lucky I caught it right after it broke.

Originally Posted by BigBlockBird

I posted a picture of the broken rocker on Comp Cams Facebook page. They contacted me right away and asked me to send in my rockers. They might give me a new set of their redesigned Ultra promagnums. The new ones look like they are made tougher and they are black. My old ones were stainless silver. Hopefully they are better. I was very lucky I caught it right after it broke.

that.s great . even if it .s half off on a new set that is a good deal . the new rockers are by far much better i have used them. i like them and will used them again

Comp Cams replaced all my rockers with the new style. No questions asked. This is great.