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Author Topic:   What Might have caused this.....
RC Racing
Member
posted August 05, 2003 12:22 AM
New motor with maybe 120 laps. Been kinda snake bit though so far.

76cc heads, 1.94/1.50 valves; Stock dia. single w/damper springs; 130# seat max allowed; guide plates; 450 lift cam; 4v flat cast piston; etc etc

1st Race: bad carb. Replaced with loaner carb.

2nd race: ran fine in heat, but heard noise. Skipped feature. Turns out cam went flat (4E). Must note, used cam (only about 10 races on it though) with NEW lifters. Replaced cam & lifters.

3rd race: No noticable problems.

4th Race: New carb (gave back loaner). Ran fine in heat, but experienced high rpm miss. Saw 7000+ at end of straight a few times (yes I was suprised to see those numbers. About 600 to 700 revs greater than I expected. And I'm geared properly). So we checked valve spring seat pressure. They seemed like they were already going away.

5th race: No noticable problems. Didn't hit the high revs either though.

Between 5th & 6th race, toonk nreak to start shimming valve springs.

Now here's my problem. So far, I 've only gone through 2 cylinders. Notice 3 out of 4 push rods bent (slight bow): 1E & 1I, 3I bent.

Any ideas what may be causing this? What to look for?

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gerald berry jr
Member
posted August 05, 2003 08:38 AM
valve springs binding


jammin
Administrator
posted August 05, 2003 09:28 AM
yup, too much lift for the springs...

jammin


Raz_900
Member
posted August 05, 2003 10:39 AM
Yup.. havta agree with the spring problem. Get Crane spring 99846 I think is the number you want. Stock dia, stock installed height, much higher pressure and can take .575" lift and will last forever on a .450" cam.

For future reference, never NEVEREVEREVEREVER reuse a flat tappet cam with new lifters. Or used lifters on a new cam for that matter. Doesn't matter if it was run for 20 minutes, new lifters on a broke in cam WILL wear at a much accelerated rate. The only way to ever reuse a cam is if the lifters were marked as the cam was pulled out so each matching lobe/lifter is reinstalled in the same way.

Rollers can be swapped and reused, but flat tappets can't, period.

prostock15
Member
posted August 05, 2003 09:11 PM
Thanks for the replies guys. Let me add a couple of points and then request an explanation from y'all.

Forgot to point out that I'm using 1.5 ratio stock appearing rockers. Also, the engine was built top to bottom by the same shop (from oil pan to intake, balancing rotating assembly, building the heads, ....). All I had to do was bolt on the fan & pulley, stab the distributor, and mount carb.

What I'm trying to say is, because the engine was put together by a reputable shop (that I've dealt with in the past), I would like to believe that components were matched (heads to cam to springs to etc) and clearances properly established (and no, I don't believe in Santa Claus)

Now on to my request for an explanation: I'm trying to understand how weak springs could bend a pushrod. The cam has an established lift that does not change, the pushrods a length that does not change, etc. So how can weak spings bend a pushrod?

Understand, I'm not questioning the fact that the springs may be the culprit (needed new springs and rods anyway, so I bought new ones today, thanks for the tip on the Cranes Raz). I'm just trying to understand the reasoning.

Thanks in advance for the replies

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Raz_900
Member
posted August 07, 2003 09:09 AM
quote:
Originally posted by RC Racing:
Thanks for the replies guys. Let me add a couple of points and then request an explanation from y'all.

Forgot to point out that I'm using 1.5 ratio stock appearing rockers. Also, the engine was built top to bottom by the same shop (from oil pan to intake, balancing rotating assembly, building the heads, ....). All I had to do was bolt on the fan & pulley, stab the distributor, and mount carb.

What I'm trying to say is, because the engine was put together by a reputable shop (that I've dealt with in the past), I would like to believe that components were matched (heads to cam to springs to etc) and clearances properly established (and no, I don't believe in Santa Claus)

Now on to my request for an explanation: I'm trying to understand how weak springs could bend a pushrod. The cam has an established lift that does not change, the pushrods a length that does not change, etc. So how can weak spings bend a pushrod?

Understand, I'm not questioning the fact that the springs may be the culprit (needed new springs and rods anyway, so I bought new ones today, thanks for the tip on the Cranes Raz). I'm just trying to understand the reasoning.

Thanks in advance for the replies


It's not only the pressure of the springs that matter, it's the solid height or coil bind height. If the spring only has say .480"-.500" clearance to CB when it's installed, it would be ok at normal engine speeds with your .450" lift cam. However, when you saw 7000rpm, it's very possible that the spring wouldn't be strong enough to hold everything in line. So, the lifter will 'jump' off the tip of the cam lobe and actually go higher than that .450" lift. But, the springs don't have enough room to go any higher so they go solid and the weakest link bends. Usually it's a pushrod but sometimes valves will bend too. That's the bad part of 'floating out the valves'. Each time a spring gets smashed to binding, it looses tension and will float easier the next time.

A minimum spring clearance to CB is .060" at max lift. Preferably, .100" clearance should be given. Make sure to check your installed height before putting those springs in. They'll work with your lift at any 'standard' SBC height, but 1.750"-1.800" is preferred. Plus, I missed the 130# limit you have. From Crane's website, the 846 spring will have 125#@1.800" and 147#@1.750". Take into account the springs will 'break in' about 5%-10%, and you should be good around 1.750".

That's where I run mine with stock length valves, Crane retainers and .050" offset valve locks (for 1.75" installed heights) and .534" lift. The cam's survived for over a season so far and you'll never float out those springs.


RC Racing
Member
posted August 07, 2003 09:32 AM
Raz, appreciate the detailed reply.

I only had time to do one valve/spring last night (other committed duties), but here's what I recorded:

1) Measured height of valve (ie no spring) was 1.894.
2) Added (1) .060 & (1) .030 shim (Shooting for 1.800)
3) Measured height w/shims: 1.806
4) Spring tested, using Moroso tester: 140#s (assuming 10% loss after heat cycle: 140#-14# lost = 130#s, within rules allowance)

Crane list the coil bind at 1.100

So if I understand this stuff correctly, is the following correct:

measured height- lift - coil bind = clearance
1.806-.450-1.100 = 0.256

So as long as my retainers are less than 0.25, I should be ok?

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prostock15
Member
posted August 07, 2003 06:40 PM
Something I didnt see posted at max valve lift see if you can see the top of the valve guide and when you get the springs off look close at the top of the valve guides to see if they have been machined down properly after replacement...but this condition usualy causes keeper problems when the retainer contacts the valve guide at high rpm......Towman


Raz_900
Member
posted August 08, 2003 03:29 PM
quote:
Originally posted by towmandan:
Something I didnt see posted at max valve lift see if you can see the top of the valve guide and when you get the springs off look close at the top of the valve guides to see if they have been machined down properly after replacement...but this condition usualy causes keeper problems when the retainer contacts the valve guide at high rpm......Towman

Good point. The retainers hitting the guides could bend pushrods too. Although, stock heads should be able to handle .450".

As for the measuring thing, the installed height is the distance from the seat to the UNDER side of the retainer. I use a Proform thimball style micrometer. (Proform PN 66903 $50 at Summit Racing Summit PN Pro-66903) With one of these, you wind the thimball down, put the retained on, put the locks in and wind the thimball back up till it stops. That's your installed height. With that Proform piece, it's meant for 1.4"+ retainers and has a step in the top of it for 1.25" retainers. So, you have to take into account the step (that really makes the installed height lower than what the gauge says for 1.25" retainers). I believe it's a .150" step or sumthing. If you have one of these to look at it would make sense.

If you have stock length valves, stock retainers and stock locks it should be around 1.700" Aftermarket retainers and locks will affect installed heights. Plus, they sell locks that are +/- .050" to help get what you're shooting for.

Good luck.




RC Racing
Member
posted August 08, 2003 04:06 PM
Thanks guys. I've probably overcomplicated this, but I want to be sure of myself (I'm going into uncharted territory for me).

Raz (and others), I AM using the proform gauge. I've measured a seat height average of about 1.875 (with retainer & locks in gauge).

So if I understand you correctly, you're saying the ACTUAL height is really about .150" less than that (1.725 for example)?

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RC Racing
Member
posted August 08, 2003 11:04 PM
Well now it's really getting ridiculous!! Pulled the passenger side valve cover.

Rockers 2I & 2E are burnt. The pushrod had impaled the 4I rocker and the 4E pushrod had 2 45 degree bends in it.

Anyone have any idea as to what the he!! is going on??

Looking back on the driver's side pushrods and comparing them to brand new ones, the old ones were barely bent. So I don't know what the heck is going on.

HELP!!

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iowa_dirt_track_girl
Member
posted August 09, 2003 12:11 AM
i have ran into this many times, and the problem that i have found was that if you are using an aftermarket pushrod the clearance is to tight in the guide where the pushrod goes through and your miss could be in your distributor. do you have a good module in it and coil??
are you running a hydralic cam or solid?if you are running a hydralic cam you might have to tight of clearance on your lash. on a race motor with hydralic cam you should have about 2 to 3 thou clearance on your lash.
one more thing did you check your piston to valve clearance? you might be hitting the top of your piston just thinking the burned valves would mean that ethier your way to lean or your timeing is off or the valve is staying open to long during or after the power stroke which means that your cam is not degreed right or valve setting is way off
hope that this helps you

Bachs racing engines

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you never know how fast you are going when your in the lead, until you blow the announcers hat off!!!


RC Racing
Member
posted August 09, 2003 01:24 AM
Thanks for all the help. And depending on what I find when I start tearing her down ....well this might be the last straw. I got into this to race, not turn wrenches 99% of the time and race 1%

Anyway, Ms Iowa:
1) Hydraulic
2) Will check on lash clearances (but optinions are many on this subject, as to which it should be...)
3) Good HEI package (I guess, only about 15 races old. How could I check for sure?)
4) Will have o ask builder about clearances
5) Don't think I'm lean. Good burn on plugs. And it's a new carb, and the carb buil;der was at the track for initial carb run to do any required tuning
6) We degreed cam after we installed new one
7) The pushrods are/were SealPRo thick walls. Pushrods holes were opened up. I've got guideplates.

Think I've addressed everything you asked for.

Will post more after tear down. (oh boy!!)

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DEEDDUDE
Member
posted August 09, 2003 08:29 AM
Robert,

I guess this is why I havenít seen you at the track in a while. Did you assemble the heads or the engine builder? I canít remember who you told me was going to do the work. Chris? I would be on the phone with him. I had a similar problem when I installed some new heads. The pushrods would hit where they go thru the head, had to grind this area out; kind of like porting the pushrod holes.
I also had a problem with the poly locks backing off, this could have been me not having enough torque on them, but I donít think so. Could have been the clearances of the pushrods when setting the lash making me think that I had it correct, but the pushrod was in a bind and once it got heated up the problem appeared. It would run fine in the shop, but at the track under a load and 7000 rpm it would start throwing lifters from the bores.
Good Luck.


RC Racing
Member
posted August 09, 2003 11:14 AM
Still trying to figure out what the problem is. And I don't know why I didn't snap to this earlier. As noted above, my cam went flat (on 4E) after about 30 laps. Replaced the cam and lifters. And now, I've got a severly bent pushod on 4E. Plus, when I pulled the intake, the snapring in the top of the 4E lifter had popped out of the lifter.

So what I'm trying to say is I've experienced two failures related to the 4E position. Any ideas as to what to look for? What to check?

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DEEDDUDE
Member
posted August 10, 2003 08:05 AM
Robert,

Did the lifter snap ring pop out or get knocked out by the push rod? Sound like the same problem I've had with the dart paperweights.

When you find the problem put that engine in a boat, as much as it has rain this year I think the track is going to start some new classes. Limited pontoons, Stock bass boats, Modified bay boat, and supercharged pirogue.


rico 08
Member
posted August 10, 2003 09:26 AM
If it's standard type hyd lifters you have to run some preload,if not it will blow the top's out of the lifters.Zero lash can only be run on anti-pump up lifters.


prostock15
Member
posted August 10, 2003 01:37 PM
sounds like your valve guide clearance may be to tight causing your problem. seen it before and it took a while to figure out what it was.

luke

Raz_900
Member
posted August 11, 2003 11:15 AM
quote:
Originally posted by RC Racing:

Raz (and others), I AM using the proform gauge. I've measured a seat height average of about 1.875 (with retainer & locks in gauge).

So if I understand you correctly, you're saying the ACTUAL height is really about .150" less than that (1.725 for example)?


I'm assuming your Proform gauge has the same 'step' in the top that mine does right? Do you have a pair of dial calipers to check it? Basically, I ran mine to like 1.800" and measure it with the dials. Sure enough... 1.800" was to the TOP of the step like where a 1.43"-1.5" retainer (Ford spring) would hit. The Chevy 1.25" spring fit just perfectly down in the step of the gauge that I believe was .150" or .100" (I check it everytime I do a Chevy now).

And what you're seeing is exactly what I saw and how I learned about the gauge step. I thought I had 1.8sumthing installed heights and had shimmed the springs for 1.75". Well... ahhh.. 2 broken rocker studs, a pushrod jammed through a rocker arm and several blue/black rockers later I figured it out. Took .060"-.090" of shims out and it's been fine for a year now.

As for why it's #4? Same reason it was #6 everytime for me. That happens to be the one that was .005" tighter than the rest and broke first. Your miss was the bent pushrods and I'll bet those 2 springs are junk and maybe broken.

Fix the spring issue first and I'll bet all the troubles go away. Maybe they installed the springs with a Proform gauge? Just a thought. Do you have any idea what kinds of springs they were? If they were stock, that's the problem (floated). If they weren't stock, then they went solid or weren't strong enough and still floated. Double check the retainer to guide clearance too. The dial cal's come in handy for that too.

Good luck.
Steve


[This message has been edited by Raz_900 (edited August 11, 2003).]

RC Racing
Member
posted August 11, 2003 11:33 AM
Raz, I have the Proform 66902. And last Saturday, I did some checking just like you have done. Ran the Proform out to 1.750, and then measured it with a dial caliper. Caliper read 1.750 from "OUTSIDE" top edge to "OUTSIDE" bottom edge.

So this morning, I called Proform to found out what the step measurement was. They had no idea (I think the tech guy was either hungover or had a bad weekend racing, whatever), so they weren't much help.

Also, I failed to mention this in prior posts: there were NO shims installed when I received it from my builder.

I'm taking the head, along with the Proform gauge, to my engine builder Tuesday afternoon. Hope to accomplish a couple of things:
1) Figure out what the heck is causing the problem(s)
2) Use his method to measure the installed height. Measure with my Proform and note the difference (For future reference)

Iím leaning at this time towards the possibility that we (friend & I) didnít properly set the valve lash after we replaced the cam

Once again guys, and gal, thanks for all the replies and suggestions. Keep Ďem coming

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iowa_dirt_track_girl
Member
posted August 11, 2003 10:42 PM
you can run restrictors in a hyd motor but you MUST drill them out a little because if you dont you wont get the oiling that you need but i wouldnt recomend that if you run stock hyd but you can with anti pump up liftors


RC Racing
Member
posted August 12, 2003 02:46 PM
Head and defective parts (lifter, rockers, pushrods,...) are at the engine builder for evaluation.

While I'm waiting on word, any opinions on valve train oil deflectors? Builder said it might not hurt to put one in. He siad he has suggested on occasion on roller tip rocker assemblies.

Hopefully I'll get a definitive answer as to what is happening/failing.

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RC Racing
Member
posted August 14, 2003 10:23 AM
Just a couple of notes in case anyone's interested, or if the info in this posting may be benefit to someone ...

Builder went through head and gave it the thumbs up. No bent valves, no guide clearance issues, nothing out of whack.

And while the head was there, I had him figure out the depth of the step on the Proform gauge. Mine is 0.140 (pretty close to that 0.150 your were thinking of Raz)

Frankly , they're stumped as to what's causing the problem. And as to why the rockers on the #2 cylinder intake & exhaust sides were burnt. They said on occasion the pushrod oil holes and the rocker oil holes donít quite line up properly and cause some oil starvation, but to have 2 of them defective, side by side, was kind of long shotÖÖ so they suggested I install an oil deflector on top of the valve train. Said they have suggested installing one ,on occasion, on roller tip equipped rocker assemblies, but they don't remember ever doing so on a stock-type rocker assembly. (sounds like a crutch to me)

One possible clue I did notice last night. On the rockers that were burnt, the darkest area (representing the hottest area) on the rockers was concentrated around the slot, where the rockers attaches to the stud. Donít know if that might help diagnose the problem.

And last note (this time), we hooked a drill up to the oil pump to check oil flow. All lifters pumped up fine, so I donít think thatís the problem.

Any other ideas folks?

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rico 08
Member
posted August 14, 2003 04:08 PM
I wonder if the rocker stud mounting bosses are machined correctly,that would be two side by side and either be too loose or too tight.


dirtracer7
Member
posted August 14, 2003 08:30 PM
I had roller tip comp cams rockers that where getting blue in the fulcrum area and i installed moroso oil deflectors and have'nt seen any signs of heat since.All rockers appear as they did when they where new.They worked for me , solid cam .560 lift 7000 rpms.there is also something called cool nuts from crane? which i think help direct oil to the fulcrum and work as a heat sink to.They won't fit on comp roller tip rockers though.


RC Racing
Member
posted August 31, 2003 12:15 PM
Just a couple of closing notes just in case anyone was interested or in some way may find some of this helpful.

We believe what happened is this:
1) When cam went flat, pushrod was slightly bent. I failed to check the condition of rods when the cam went flat. I merely replaced cam & lifters (I say "merely"...) along with dropping pan, cleaned it, etc etc
2) Once rod bent, it was weakened. During next time out, weakened rod bent severly and rocker fell out of position.
3) With no rod & rocker in place to open ext valve, exploded charge in cylinder had no way to vent
4) Compressed charge drove intake pushrod through intake rocker.
5) And lastly, apparently burnt appearance on stock type rockers not all that unusual. Especially on cylinders #1 & #2 (which get oil last)

So recapping, I replaced rods and installed oil deflector. Since then, 3 races on heavy tracks (equate to hard on motor) and everything looks good to go. (crossing my fingers though)

PS Thanks for the assistance Steve H.

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BK19
Member
posted August 31, 2003 12:25 PM
just 1 question are you rocker arms 1.5 long slots ?


RC Racing
Member
posted September 02, 2003 10:14 AM
BK, yes they are.

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race2j2000
Member
posted September 07, 2003 11:39 PM
i have had problems that are very similar to these .... i have a full roller setup and i have found that the rockers were hitting the retainers ....so this problem was causing all the bent push rods and broken lifters so just alittle advise .valve train geometry is very important and must be close to perfect for optimal performace....and just goes to show you that no matter how much money spent you must have proper geometry for the valve train ...that is the bottom line...


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