But if the MCM makes a difference on a stock bore motor (it does from my experience) because of superior valve timing if should make a difference regardless of displacement.

 

EXACTLY !! The MCM unleashes superior TRQ(therefore HP) over stock timings - this means the engine is able to "Breath" in a way that is superior to stock timings - so stock timings rob you of power.. Certainly (IMO) a big bore would be robbed worse than a stock bore as it is trying to pass more volume in and out of the same valves and ports as a stock bore, making better cam phasing even MORE important (IMO)..

When done right, the intake "GRAWL" (that is so offensive to the ears when the airbox lid is removed) GOES AWAY.. Those that report otherwise simply did not do the mod correctly, and somehow got away with not destroying their engine.The TRQ ramps up strongly from 4K and holds until the exhaust system/airbox lid/snorkels/lean main jets all combine to kill the top end power..

 

We need hard data - and we don't have it.. Just a lot of unsubstantiated dribble.. All we have is that Jhoffy22 did the MCM and 351 all at once. Loved it. Blew the engine 100 miles later..

 

What was the cause of the motor failure?

 

Well, those posts have been removed. I did see most of them when I first joined. The reason they were removed, IIRC, is because they cast a shadow on the MCM + 351 that was unwarranted and unfair as there was no proof the MCM had anything to do with the failure.. He did ride it for, IIRC, 100 miles or more before the failure.. IMO, MCM would have done its' damage immediately if there was a valve-to-piston problem.. I've PM'd Jhoffy22, asking him to "weigh in" on this subject.. Since he did the MCM and 351 at the same time, all he can verify is that his bike ran fine afterward - for some amount of time - but not an assessment of MCM's additional power to the 351..

 

I just PMed him and hopefully he responds. If no one else has done the MCM for any length of time with the 351 I will be going back to stock. I have to much invested to chance the timing change.

 

Perfectly understandable.. Jhoffy22 was an early adopter of the MCM. IIRC, his engine failure stopped all other 351 owners from doing the MCM out of the same fear that maybe, somehow, the MCM played a part in his failure...

 

As I said before, Jhoffy admitted to essentially flogging the bike hard. Also as KLXter says, if it was the cam timing causing valves to hit it would have happened long before 100 miles based on the description of the run in.

I don't remember if valves hit or piston seized. I'd think it would take more than 100 miles to run in a new top end decently. Plus flogging can easily cause a serious over-rev that could float valves.

I do not question your skill or knowledge with cams and timing Zombie, all I ask is for the information on what should happen with the stock 110°timing versus his personal evaluation of 106° versus Marcelino's roughly 100°. What causes the radical change in tone? I did find where you said 10° likely wouldn't cause any valve contact issues - the implication based on where/when the comment was placed - and Joe Minton's comment on the Nighthawk S that a couple degrees one way or the other wasn't highly critical either for performance, but that the extreme for the Nighthawk - which was huge at 133° versus Minton's 108°. Fine tuning is fine tuning. Sure it may not be huge for everyone, but when it's free and apparently does work - WHY NOT DO IT?

It's also a chance to get that unneeded compression release disabled or removed.

 

Funny that this topic is being revisited this many years later. Back when I purchased this bike in 2011, I was an immature 20 year old with a shoot first, ask questions later attitude. I jumped in and did all of the performance mods at once. When I installed the 351 big bore kit, I did the MCM at the same time. I had never experienced either independently, so I cannot comment on any additional power gains from the MCM on top of the 351 big bore kit.

After my top end blew up, I called Bill Blue and spoke to him extensively about what had happened and even directed him to this thread. I don't want to misquote what he said out of respect for him and respect for accuracy - it was years ago, so I don't really remember. I do recall him saying that it was foolish to do what I did. Beyond that, I don't remember many details. If you considering doing the MCM along with the 351 big bore kit, I think it's wise to talk with him first.

 

So, what are you doing now? Still riding, goofing around? I hope it didn't sour you on riding for sure.