prostock85

My current boat has newly built (standard) 330's. Now, I have my old but still good roller rockers from two TRS 400 motors. Is there any benefit to putting the rockers and push rods from the 400 in the 330? Will they fit or it the rocker stud different sizes. Thanks

bcarpman

They may fit, but will probably also require new studs, and guide plates (depending on engine year and pushrod size), and will be a waste of your time. Sorry. The only reason to run roller rockers is if you are running a high lift cam with high spring pressures. With the stock 330 cam you will gain nothing.

You'll have to modify your valve covers, and even then they may not fit depending on the pushrod lengths, and how high they end up sitting on the studs

The only factor that may (Repeat MAY) gain a small bit of performance is from the fact that some stamped rockers aren't "true" 1.7 ratio, so you could possibly end up with slightly more lift, but I've never seen any tests that actually show this to be the case.

The only reason everyone puts them on their motors is because its a mod that virtually everyone can do, and doesn't require an engine teardown.

If you plan on doing a rebuild with a better cam, hang onto them.

prostock85

Thanks a lot, I appreciate your response. I saved all the old stuff because it all had less than 200 hours on it. I still have the whole motors minus the SHOT heads (rust). Guess I'll be building spares with all forged internals.

bcarpman

Yeah, now that's a good idea!! Although if it was me, I'm not sure how long they'd remain "spares" after the rebuild

prostock85

I've been thinking the same thing!!!

KAAMA

iTrader: (1)

Unless things have changed, the 330's use a 5/16" diameter push rod whereas the 400 Merc uses a 7/16" dia push rod. You'd be experiencing a little bit of the domino effect with part mods as previously mentioned. I was always told something like 5-10hp gain going from a stock stamped steel rocker arm to a roller. Roller rockers will help kill some of the oil temp heat created by stock rocker arms too. All said and done it's not much of a gain anywhere, but they are much better than a stock rocker arm. This is just me, but if I had a stock pair of 330's, then changing out the stock rocker arms for some rollers would be one of the first things I would do....along with swapping out some other external items----but that's another story.

Back in the 1980's we used the Crane Golds on a pair of stock 330's, but we changed the ARP studs, went to 3/8" push rods, and went to some taller valve covers. We did things little by little as our wallets would permit over a couple of years until we had some 330's on roids......after market cams, ported heads, larger valves, forged pistons, ARP rod bolts.....blah, blah, blah. We learned a lot and had some fun...those were some good ol' days back then.

BadDog

Would it help with valve guide wear?

bcarpman

No it doesn't. It's been proven over and over that the roller tip doesn't actually roll, it slides just like the stock rocker. In fact most of the current high performance production stuff that uses high lift cams (that require roller rockers) use roller fulcrums with conventional tips.

You should never have issues with stock rockers and stock cam that rollers will fix. In fact I would say the opposite is true. If your engine is running well, your valvetrain is fine. If you take it apart and put in rockers with MANY more moving parts, you are just risking a failure.

Now this is not true with a roller cam and lifters. That will fix many possible issues and is a no compromise HP adddition (other than $$$).

As an aside, back in my engine lab days, I did some testing on various aluminum roller rockers. They not only deformed under load MORE than the stock rockers, but they had higher inertia, leading to a lower valvetrain limiting speed. This was not true of the high buck stuff (Jessel, etc.) but most of the stud mounted rockers just didn't do anything good until the spring loads became high enough to make them a requirement.

I did use them on my current 330 on roids project, but only because my spring rates were getting a little high. I could have probably gotten away with the stock rockers, but with a .55 lift cam I didn't want to take chances. It did necessitate changing pushrods, guideplates, studs, and modification to the valve covers. A lot of work and expense if you don't need them.

As long as the loads are low enough that the layer of oil between the rocker and the ball is not breaking down, the stock rockers have virtualy the same friction as rollers, HOWEVER, as soon as the loads increase JUST enough to allow metal to metal contact...BAM bad things start happening quickly!!! The problem is that as soon as you put a bigger stick in, without extensive (and expensive) laboratory testing, you don't know when you've exceeded that point.

KAAMA

iTrader: (1)

bcarpman, It sounds like you have done some extensive and interesting research on rocker arms----can't argue with that. I am not trying to be/sound dogmatic---I respect your input. I guess I have always been taught that a roller rocker arm is better than a stock, stamped steel rocker arm, but didn't know some of the finer details of such as you have found/described in your testing and is interesting to me.

At this time I am using the Jesel shaft mounts rockers on my engines which are not stock---which I know are better than a stud mount roller rocker arm system---well, who knows---maybe someone else might come in and say something in fine detail about those that I didn't know about. I'm only a weekend warrior and I've had to learn a lot the hard way through our trial/error experiences with the Merc 330's since the early 80's some 25+ years ago and try to pass them on here. Anyway, as far the Merc 330 is concerned, do you remember if the stock rocker arms of a Merc 330 has the grooved fulcrum balls or not? I was always told the non-grooved balls were an issue with heat/friction. I suppose they could be replaced with the grooved ones. (???)

bcarpman

Jessels rule! You really can't go wrong with that setup. I've never heard of or tested any better way to do rockers. Very distinctly different than tossing a set of Cranes on stock studs.

I know my 330 didn't have the groved balls. I'm only guessing, but I think i recall the groves not working as intended. They just reduce surface area, which lessens load capacity. But don't take my word on that as fact. I'm just going off what I think I remember others telling me.