rocker arm stud diflection
 

How much is normal? I am running good roller rockers with the 641 hyd roller cam. aftermarket oversize push rods with ARP studs.
I am running the stock valve covers with the oil drippers removed and noticed a bump in the cover next to the oil fill hole. removed the cover and all of the rockers seam to be properly adjusted with out tearing into it. There is a rub mark on the bottom of the cover that shows that the lock nut is moving more than 1/4 inch. I find this hard to believe that it could flex that much without breaking. I have snapped cheaper studs on other motors in the past.

Do you Have the rocker corner ground away? I believe #1 and #8 intake. I didn't grind mine enough and it was deflecting my valve cover a bit. Might not be your problem just throwing thoughts out there.

i don,t think it could flex that far without breaking.

[ATTACH=CONFIG]540044[/ATTACH]


[ATTACH=CONFIG]540045[/ATTACH]

These are not the rocker arms that you need to grind the corners.
You can see the mark on the underside of the cover.

There are marks from other nuts on the underside of the cover but none of them show this sign of movement.

This is the engine that has been in the Daytona for the last year. It runs perfect with NO strange noises.

Sounds like the stud may be loose in the head? If it moves 1/4 inch (which I think it would snap) you are diminishing lift/duration. check every one close.

Do you think that at one time it did snap one off and that is the the prior damage? If you put the cover back on does it spot off on the nut? When my rockers were touching my covers I could hear a distinct hollow noise. Throwing ideas out.

Before the motor goes back into the boat it WILL be checked out.
I am in the process of stripping the boat ao it can go to the gel coat repair guy to have everything fixed that the previous owner did. I am also adding an extension box so some of the holes on the transom need to be filled. AND I am raising said box 1 inch and going from a standard deck to a tall deck block that will raise and spread the exhaust ports. And reworking the dash.

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That rocker is on the base circle of the cam and nothing seems to be loose. I will check it out before it goes back into the boat.
The broken rocker arm stud was a few engines ago.

Or permanent deflection.

That is a lot of deflection, if it really is bending the rocker arm stud. Did you say that this was not there before? Another possibility is the the threads on the nut are jacked, the nut could be cracked. inspect or broken parts 1st bed threads in the head. If nothing is found. Clay the gap between the nut and cover, pull off and check distance. Clay again but roll the motor over a couple of times. See if the clay smears. It the nut is touching the cover try bluing the cover and bolt cover down to see the interference pattern. Blue the cover again and roll motor over and check. If you don't have bluing dye I have used permanent black marker.

i noticed that the intake rockers are not the same as the exhaust rockers.is there a reason for that?

1.7 and 1.8 ratio. one set is SS the other is chrome molly.
Just thinking here. The cover is dented at the rub point. I wonder if the stud or the lock nut are bad and the cover is holding the nut on the stud when the lobe lifts the valve. Will have to turn it over without the cover on or see if the cover moves with it on but not bolted down.

Are those pro 1 heads?

Possible the mark is from when the valve cover flexed/dented during install....and not rocker nut/stud flexing?

Yes they are Dart Pro 1's

Are you sure there isn't an issue with the rocker bosses. Those heads are notorious for that.

If memory serves me the studs had longer threads on the head side to counter that. BUT I will check for a loose stud in the boss. If it deflected that much I would think that it would have ran off the head of the valve stem.

i have used a lot of pro1 heads through the years and never had a problem with the stud bosses.if the geomitry is wrong or the valve train is unstable you can damage any brand of head.

The head has issues. It's not a myth. When you use a rocker arm the geometry is always wrong that's why there is a pattern/ sweep. What's your point? You walk on water. Have a magic wand you can wave over a valve train and it becomes perfect. Not sure what you are getting at. I on the other hand was simply trying to give the OP I different idea than what was posted by others as what to look for.

my point is simple,as i said i have never had a problem with a pro 1 head.i dont walk on water or have a magic wand,but i do pay attention to detail,maybe that,s why i don,t have the problems you have.no need for you to be a smart azz.for you to make a statement that the pro1 head has issues is completly false.maybe you have issues,just sayin.you are famous for posting up incorrect information,but carry on,it is the internet!

and just fyi,the op probibally does not need you to tell him his,and all pro1 heads have issues!

I have seen a broken boss as stated by Black Baja on a Pro1 head. This head had the wrong rocker studs in the head. The PRO1's need the longer stud that protrudes past the boss and into the head. ARP has a special part# for Pro1 heads.

Dart:
"ROCKER ARM STUDS
All Dart big block heads use an exhaust rocker arm stud with an increased thread length where it is installed in the cylinder head. It has a 1.300” thread length for the raised rocker arm boss. Do Not Use a Shorter Length. Part# Dart 27002204 exhaust stud Dart 27002223 intake stud ARP 235-7202 Kit"

https://www.google.com/url?sa=t&sour...iBCVp6GJwPbuHg

100% correct,the afr head also uses that stud.hardly a geomitry problem but a builder error.

that don't look like the rocker stud looks more like the cup side of the rocker hitting.

The mark IS from the lock nut. I will be going out in the garage soon to finish tearing apart the Daytona. I will check out the valve train.

I've seen several used dart heads, that have had incorrect rocker studs installed in them. Guys slap in a "general" set of 7/16 rocker studs, that typically have a threaded portion of .700, when they should have used the proper stud, that calls for 1.300 on the exhaust. I've seen that setup hold up ok in a low rpm, low spring pressure basic marine engine, but certainly doesnt hold up with higher spring pressure setups, esp with the amount of force needed to open the exhaust valve when its opening against cylinder pressure. Yes, the bosses can break when that happens.

I have many many friends running Dart Pro 1's, or race series heads. From mild 600hp marine engines, to 1000+hp blown marine engines, for years, that have not had any issues.

stud girdles anyone?

a stud girdle helps keep everything in place but it won,t fit under the stock merc 500 style valve cover.

If I was buying all new again I would just go with T&D or Jesel shaft system. After adding up new studs, new rockers, adjustable guide plates and girdles it's just a few $$ more. Granted, i'm not using girdles so that is a $315 savings.

I'm not going to point fingers but saying that pro 1 heads are notorious for a problem with out explaining what the root problem is is worthless on here. Our little community is built up of people who can relate personal experience and can tell of the solution to remedy the problem. I think we all appreciate everybody's opinion but mix some facts to back up your statement. Saying the pro 1 heads are notorious for problems: worthless. Saying that pro 1 heads need a longer stud that is 1.3" to prevent rocker stub breakage and that the stud protrudes past the boss into the head along with providing a part number specific for the application: priceless

is there a valve cover that clears stud girdles and clears marine exhausts?

The Dart pro 1 head was designed to be a light weight head. They come in around 29lbs each. There race series come in around 45lbs each. Where did all the weight go. Maybe someone used there magical wand combined with a sprinkle of pixie dust. I don't think advising the OP to take a look at the stud bosses is bad advice. If you feel as though it's not a good idea to pay attention to this area of a cylinder head then don't pay attention to it. I've seen problems with intake and exhaust bosses with these heads. Was it a geometry issue? There is always a geometry issue its the nature of the beast and BBC's have the worst of them all. I've even seen a few sets of Pro 1's where alot of extra effort was put into the stud bosses to try and combat issues before they happen.

The 598 is getting AFR 357 CNC heads with Jesel pro shaft rockers. And timing belt.

Lunch is over - back to tearing the Daytona apart.

ok, this seems like backwards land. the race series is 16 lbs heavier than the pro 1? why make it that much lighter if not to win races? when the race length is april to october and the winner is the one who spent the least time in the pits, one would think durability matters more than the boat being 32 lbs lighter.

Thanx for pointing that out Joe, something I would not have checked.

Correct stud on bottom for my Dart heads. Top is what the previous owner installed. "it`s fiiiiine"

http://33outlaw.zenfolio.com/img/s10...63852700-3.jpg

The dart race series, are a completely different casting, than the Pro 1's. The Race series weigh 37lbs, where the pro 1's , weight 29 lbs. Thats actually 8 lbs, not 16lbs. While AFR doesnt publish their heads weights, I believe if you put one on the scale, they are around 32 lbs..

There is nothing wrong with the pro 1 casting. They have been used by many many offshore engine builders, many other forms of motorsport builders, sold by hardin marine, keith eickert, cp, and many other marine shops, as well as thousands of shops across the country. If their was a flaw in that casting, it would have been corrected a long time ago. These are not procomp heads we are talking about.

Thank you for the correction. I was going off of memory. 8lbs of cast aluminum is alot of aluminum. If you go and put big roller springs on these heads the potential for failure goes up. There are also limits with the deck of the head but I don't think you will find it with pump gas and a blower.

i ran 355 cnc pro1 heads on a blown alcohol engine with 340 lbs on the seat,8500 every pass,guess what,never had a problem.as i said,ATTENTION TO DETAIL!black baja,care to tell us exactly what problems YOU have had with a pro1 head.