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Author Topic:   Breaking rocker arms?????
sideways
Dirt Forum Champ
Total posts: 715
posted June 19, 2005 06:33 PM  
I am running a 383 with long slot 1.5 ratio rockers stamp steel(per rules).I have used Pioneer and Renagade(midwestmotorsports).I have the #8 Midwest cam and Manley hardened push rods.The geometry is right and the spring pressure is 100lbs on the seat.Single 1.25 springs with dampaners.And the push rods are breaking up through the rockers.#3(just one the first time both the second time) has done it twice and #6 once(both)#8(both).They are not burnt like lack of oil but broke.Has not bent a push rod.I have turned a max. rpm of 6000. Help?????

kracker
Dirt Newbie

Total posts: 1
posted June 19, 2005 06:48 PM  
THAT HAPPEND TO MY 406 ONCE TOOK ME AWHILE TO FIND THE PROBLEM COMT TO FIND OUT IT WAS THE LIFTERS AFTER THEY WAS REPLACED IT HASENT DID IT SINCE

sc1 racing
Dirt Freak

Total posts: 419
posted June 19, 2005 06:53 PM  
may want to double check your valve lash. bet they are to tight, and cam is probably starting to flaten out..im guessing this is a solid lift

Raz_900
Dirt Forum Champ
Total posts: 635
posted June 19, 2005 07:52 PM  
Coilbinding. Either springs are going solid or the retainer is hitting the guide.

Occasionally, this will happen even if everything's right with stock type rockers. But not more than once a year.

Only solution is Crane 'nitro' rockers. They're made from stronger material but are stock appearing. They're about double the price, but won't break as easily.

sideways
Dirt Forum Champ
Total posts: 715
posted June 19, 2005 08:10 PM  
Valves have been adjusted at least 3 times.i get one full night out of them then 2 cyl. go bad.Checked valve lash on a few tonight it was ok.I will check for coil bind and hitting the guide.Were to buy nitro rockers??Are they stamp steel?Thanks for the replies.

[This message has been edited by sideways (edited June 19, 2005).]

sideways
Dirt Forum Champ
Total posts: 715
posted June 19, 2005 08:26 PM  
I found them.thanks I will check all of the above.Then if all else fails order a new set of nitros.

rrrrick
Dirt Maniac

Total posts: 192
posted June 20, 2005 10:37 AM  
The only time I ran into problems breaking Rockers or studs was incorrect geometry ( new cam old length push rods)

sideways
Dirt Forum Champ
Total posts: 715
posted June 20, 2005 12:07 PM  
I checked it with my little blue tool.The length is correct. thanks for the reply

waltonjr1
Dirt Forum Champ
Total posts: 516
posted June 20, 2005 12:43 PM  
I would lean towards the valve springs. That is some fairly weak springs for that cam. Likley coil bind.


eenfield
Dirt Maniac

Total posts: 116
posted June 20, 2005 01:44 PM  
what method are you using to adjust the lash?

sideways
Dirt Forum Champ
Total posts: 715
posted June 20, 2005 02:08 PM  
The one in the "TOOL BOX"in the upper left corner.Always worked before.? I was givine some thought to doing it with both valves on compresion on that stroke??Good idea or not???

[This message has been edited by sideways (edited June 20, 2005).]

crazyhorse
Dirt Roller

Total posts: 15
posted June 20, 2005 08:32 PM  
sometimes the hardened pushrods cause that problem.been there,done that.

sc1 racing
Dirt Freak

Total posts: 419
posted June 20, 2005 11:39 PM  
ive been running solid lift cams for 6 years now and i still dont trust but 1 way to set the lash.

i have a friend that has pushed 4 push rods through the rocker arms, and he finnally brought it to me i checked sprig pressures, i checked all clearances, check the geomatry, and found only thing wrong was lash set to tight. it is to easy to flatten a solid lift cam so i double check and then check 1 more time before i button it up. he hasnt broken or pushed a push rod through since i adjusted the valve for him

sideways
Dirt Forum Champ
Total posts: 715
posted June 21, 2005 10:00 AM  
I go over it twice.But please share your way of adjusting lash.I would like to solve the problem and am willing to try multiple things to fix the problem.So how do you adj them.The cam card says .016.What method do you use?

rico 08
Dirt Forum Champ
Total posts: 1139
posted June 21, 2005 11:53 AM  
You need .600 lift springs for that cam,even "good" z-28 springs (120 lbs)will barely handle .550,i'd get some good .600 lift springs and some .050 offset keepers and try that.

sideways
Dirt Forum Champ
Total posts: 715
posted June 21, 2005 12:32 PM  
Should be here tommorrow.I already have .050 retainers on.I am going to get a spring checker and do the coil bind,clearence check and seat,open pressure deal hopefully this week.I will measure installed height and set accordingly and check for retainer to valve guide clearence as well.If my bad back gets better.If not then I wont need it til next week anyhow.Thanks for the reply.Also going to use different method for setting valves.

merlinmech2
Dirt Maniac

Total posts: 131
posted June 22, 2005 07:19 AM  
All I saw in the tool box was for hyd. cams. For solid turn eng over til ex. starts to open and adj. intake. Turn over til int. just closes and adjust ex. I'm running the exact same thing you are and never had a proplem. Hope it helps.

sc1 racing
Dirt Freak

Total posts: 419
posted June 22, 2005 11:07 AM  
sorry i forgot about this thread merline does the same way i do that is the only way to find the true flat spot on your solid cam.

.016 sounds kind of tight to me is that the specs on your cam card.

you can adjust them with both valves closed but you never know how far the lifter is on the lobe. you may get a few right but its not worth the results just do 1 valve at a time and double check. still doesnt take 15-20 miniutes and you know its done right..

sideways
Dirt Forum Champ
Total posts: 715
posted June 22, 2005 11:29 AM  
Ok thanks,yes .016 is right I thought it was tight myself but read cam card on both cams(both #8 midwest)And thats what it said.All I saw in the tool box is small block chevy valve adj.order.Didnt specify hyd.solid.? Turn it over by hand or by bumping it?Or eaither? thanks
[This message has been edited by sideways (edited June 22, 2005).]

[This message has been edited by sideways (edited June 22, 2005).]

sideways
Dirt Forum Champ
Total posts: 715
posted June 22, 2005 06:48 PM  
Here is what I did tonight.Checked(on one that had broken rocker) installed height 1.780 115lbs on the seat,exhaust lift .543 over the nose pressure 340 lbs(@1.237)Coil bind 1.120.Checked valve lash at #1 like described above and got a tight .024 cold(loose according to cam card).I am afraid to take out the .050 offset retainers and install stock that would put seat pressure around 100lbs.And afraid to drop a valve.I been setting lash .016 hot thought I would try.022 cold.?????The retainers are not hitting the guide bosses cause the valve seals are still on there.Could it be too little spring pressure?? thanks for the help If the piston was hitting the valve looks to me like it would bend a valve.?I checked that during pre assembly.Took a 1.6 rocker no head gasket and 0 lash and the engine rotated freely.

[This message has been edited by sideways (edited June 22, 2005).]

fastrack1
Dirt Maniac

Total posts: 145
posted June 22, 2005 07:52 PM  
Had some screw in studs that was not centered up , no problem on rollers .On long slots it caused problems .Use a straight edge and make sure its not leaning to the center of the engine

eenfield
Dirt Maniac

Total posts: 116
posted June 22, 2005 08:09 PM  
Have you checked the valves in the offending cylinder(s) Take your spring off and run it through the guide by hand.

Try going to GM and getting (or at least comparing prices to those nitro's) a set of stamped rockers. I read somewhere that the material used in a lot of aftermarket stamped rockers are not as good as the factory stuff.

Otherwise it seems as if you have done most everything right.

BTW, are your pushrods straight? .022" is too wide cold... If your cam card calls for .016" hot then start with .018" cold if you motor is an iron block/head setup. Iron block/aluminum head would be .019" and alum/alum would be .020"

sideways
Dirt Forum Champ
Total posts: 715
posted June 23, 2005 08:38 AM  
I have checked the valves they are smooth and bind free.I have checked the push rods on plate glass after throughly cleaning them and wipeing clean.I will try .018.As far as the studs I will check that today good thought.This set up has never caused me any pain before so I am baffled.The only thing I changed was the short block. thanks for all your time and replies please keep them coming.

sideways
Dirt Forum Champ
Total posts: 715
posted June 23, 2005 01:41 PM  
Checked geometry again with the tool and calipers.I came up with needing a push rod .280 longer than stock.I have 8.050 in there.Also looks as if the rocker wear mark,were the valve "rubs"goes out to the end of the machined area of some of the rockers.Should I order push rods in a 8.100 to correct this????Going to take rockers with me sat. and check and or change after each run.??????I hate to spend $130 on new pushrods if I really dont need them. I mean man this cant be that hard a deal I am pulling my hair out. thanks

[This message has been edited by sideways (edited June 23, 2005).]

sparky40
Dirt Roller

Total posts: 7
posted June 23, 2005 09:39 PM  
There is no way you should be running that long of pushrods with that cam,stock or 100 over would be more than enough.take a black marker and color the top of the valves install the stock pushrods and set the lash,turn the motor over by hand 2 times and check the ware pattern on the valve it should be around the center to slightly over center.them blue pushrod testers dont work.I run 650 lift roller with 100 over valves and only have 7900 pushrods.I also had the same problem earler this year breaking rockers,on no 5 cyl, it ended up that there was not enough closed spring pressure and at 7000 rpm the valve would float and the pushrod would come out of the hole and ride on the outside of rocker and coil bind would break the rocker.just a thought.


sideways
Dirt Forum Champ
Total posts: 715
posted June 24, 2005 08:12 AM  
Well that could be with the springs.The wear pattern on the rockers that survived is almost all the way to the tip of the machined area.I done the marker deal yesterday and used a stock length pushrod.Didnt look to me like it was even sitting on the valve right?When I did that and just set lash I could see the whole top of the valve stem peeking out under the rocker.?It was rideing on the back side(toward the center of engine)of the stem.?I only have turned a max of 6200 this year so far. Thanks for the help.do the adj. push rod length checkers work better?I am giving thought to buy some or making some.

sideways
Dirt Forum Champ
Total posts: 715
posted June 24, 2005 08:29 AM  
Sorry I misunderstood I read the post again(acctually a forth time).I will do marker trick and post my findings.Thanks for the help.

JohnG
Dirt Maniac

Total posts: 137
posted June 24, 2005 06:04 PM  
you can get a plastic pushrod lenght checker for 9 bucks from about anyplace. summit jr etc.

you put it on the stud and down to touch the valve and swap out pushrods or measure the distance from a stock one till it touches the pushrod end and the valve end.

you should be doing it on every motor, so far out of approx 18 race motors ive had only one has ever used stock lenght pushrods...


sideways
Dirt Forum Champ
Total posts: 715
posted June 24, 2005 06:50 PM  
quote:
Originally posted by JohnG:
you can get a plastic pushrod lenght checker for 9 bucks from about anyplace. summit jr etc.

you put it on the stud and down to touch the valve and swap out pushrods or measure the distance from a stock one till it touches the pushrod end and the valve end.

you should be doing it on every motor, so far out of approx 18 race motors ive had only one has ever used stock lenght pushrods...



Up farther in the post we went through that and it did not work.Have always done it that way with no problem no worries but this time well.I have measured with my little blue tool 4 times on assemble,right before rockers went on the first time,when it broke the first 3 and again last night..Always get the same thing .280 over stock length.These have ran before always done me good.???? thanks for the reply

JohnG
Dirt Maniac

Total posts: 137
posted June 26, 2005 05:47 PM  
sorry, I must have missed it.


I have had no luck with stamped steel rockers whatsoever.

my spring pressures are 115-130 and 350-380 open on my motors.

I am running some 4340 rockers that look just like comp cams but they are for self aligning only, and are 56 dollars a set of 16.

I get them from raceparts engineering i think, they are in calif, and on ebay.

I ground of the self aligning sides and use them with plates now but will just use them as is and pull my plates of from now on, it takes about an hour with a die grinder and a grinder to make them work.

I do think they are blems. my comp rockers if you measure from the pushrod oil hole to either end of the roller are equal, these are all off. I think they are CAT blems. but they are deffinitely as strong as comps, they actually have more metal in between the stud and roller tip than the 160 dollare comps.

I tossed out all my stamped steel stuff, i broke them in half, and pushed pushrods thru them.

heres raceparts number, the guy I talk to usually race IMCA mods in southern calif..
1 951 684 3814

sideways
Dirt Forum Champ
Total posts: 715
posted June 26, 2005 06:18 PM  
thanks JohnG.I got there #.

sideways
Dirt Forum Champ
Total posts: 715
posted June 26, 2005 06:23 PM  
quote:
Originally posted by sparky40:
There is no way you should be running that long of pushrods with that cam,stock or 100 over would be more than enough.take a black marker and color the top of the valves install the stock pushrods and set the lash,turn the motor over by hand 2 times and check the ware pattern on the valve it should be around the center to slightly over center.them blue pushrod testers dont work.I run 650 lift roller with 100 over valves and only have 7900 pushrods.I also had the same problem earler this year breaking rockers,on no 5 cyl, it ended up that there was not enough closed spring pressure and at 7000 rpm the valve would float and the pushrod would come out of the hole and ride on the outside of rocker and coil bind would break the rocker.just a thought.


Ok checked as you suggested.Got the following stock length push rod just baerly rubbed off the back side(toward the carb.)of the valve stem ,like only .030 or so.Done this on #1 exhaust only for now(so all test would be linear).Put 8.050 rod in and it rubbed off the whole valve top.So I was giving some thought to trying .150 overs??What you think?


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