[madbronco]

I'm currently building a 351w, it has a set of ported 351 hi flow heads on it, bored out .040 with new pistons and stronger rods. The problem is that i have burned up 2 new cam shafts. they were both broke in. Any help would be great..thanks
JAY:banghead :banghead

 

[Gacknar]

The problem is that i have burned up 2 new cam shafts. they were both broke in. Any help would be great..thanks
JAY:banghead :banghead

Could you elaberate a little pleas. Tell us what you mean by burned up.

 

[Tunedup]

by burned up im assumeing you mean your wore a lobe off it. Are you running the correct valve springs for that cam installed at the correct installed height? How about the geomerty of the pushrods? are they correct? Did you break the cam in correctly? 2000-3000 rpm for 30 mins. Did you change the oil and filter right after break in?



The list goes on.... lets know exactly what you did.

chances are you have the wrong springs for the cam or the springs are installed at the wrong height.

 

[Midnight Rider]

what kind of cam are you running? what are the cam specs? are the rocker arms hitting the spring retainers and binding? are the rods hitting the cam (sometimes a problem with high lift cams or stroker motors) ?

 

[madbronco]

the cam and lifters, springs, and rods are all matched. i did break in the cam at 2500 for 25 minutes, and changed the oil after break in.i'm running 110lbs of spring pres. with a high volume oil pump. i,m also running roller rockers:shrug :banghead

 

[Fireguy50]

:twak Still didn't tell us what happened

 

[Tunedup]

Are the springs set up at the correct installed height?



example1: If the spring installed height is less then what is recomended then the spring will have more force then advertised and will accept less lift and will also go into coil bind sooner.



example2: If the spring is greater then the installed height the spring force will be less then what is recomended and could cause the lifter to bounce and eat up the cam.


I assume you checked your retainer to guide clearance??

By rods do you mean pushrods? You cant buy them in a set matched to an engine... Cause 3 engines put togeather with the same parts will likely requier 3 diffrent lenth pushrods to get the correct geometry.



How long did it take for the engine to eat the cam? Did you use assembly lube?

 

[ValkariaKid]

I'm still waiting to hear what he means by "burning up two cams"?

....never heard of that before.:shrug

 

[madbronco]

by burned up i mean on the first cam i burned off .010ths off the #5intake lobe, on the second cam i burned off #3 exhaust lobe. i checked all my clearences. checked for coil bind, and lifter slop. the cam i'm running is a 280/290 dur. 214/224adv dur. 480/490 total lift. i have a total of .545 to .555 before i start to coil bind. my lifter plungers are depressed .045 to.05. my local engine builder worked with me on the second cam and can't figure out what happened to the first cam and is even more confussed on the second one.:banghead :banghead :twak

 

[The Yak]

Hydraulic cam I presume.

Are the lifters changed each time the cam is replaced?

Check the valve spring pressures again, they might have lost some tension, beating the cam to death.

 

[ValkariaKid]

hmmmm......

Were there any bent pushrods?

The reason I ask is because they would be the first to go if there was an interference problem (coil bind, valve/piston contact).

They'd go long before you wipe out a lobe on the cam.

Were those bad lobes actually abraded (worn down with visual "scorching" present) ?

 

[ValkariaKid]

oh yeah....

i'm running 110lbs of spring pres.

Which do you mean?:
-Spring rate (as advertised)?
-Spring rate installed (closed) ?
-Spring rate open?

A few more Q's

-Which roller rockers are you using?
-Stock pressed in studs or aftermarket screw in studs?
-If pressed in studs did you ever check to see if any started pulling out? (might cause those roller rockers to bind on the stud)


Assumptions:
-You're using moly lube on the cam lobes
-You're using new lifters with each new cam
-You're checking the pushrods for straightness (roll them on glass)
-You're using the correct pushrod lengths (only known if individually measured on a 351W)

 

[madbronco]

Assumptions:
-You're using moly lube on the cam lobes
-You're using new lifters with each new cam
-You're checking the pushrods for straightness (roll them on glass)
-You're using the correct pushrod lengths (only known if individually measured on a 351W) [/B]

all of your assumptions are correct. i checked all my pushrods for straightness, i measured all of them for the correct lenght which i got straight from ford, i'm using crane energizer roller rockers, and by saying 110lbs of spring pres. i mean over the nose of the rocker. i appreciate all the help...:thumbup

 

[Tunedup]

It sounds like you have done everything correctly.


What I would do now is get yet another cam and lifters.

Install it 100% by the book.

Start the engine with the valve covers off and make sure the push rods are spining and oils comeing out of each one.

If they arent spining you have a problem with the lifters binding up. and thats whats causeing your problem.


Im not sure about the quality of small block ford cams as of late but, The small block chevy cores have gone to crap big time. Can anyone say chinese steal......

 

[ValkariaKid]

After thinking about this for a while something dawned on me...

There's something you're not telling us.

I mean.. what actually happened to prompt you to remove the cam in the first place?

.010" off one lobe will not make your engine run so badly that would make you think that there's a big problem that would require removing the cam. In fact you wouldn't even notice it at all.

Something must've happened.
What was it?

 

[Fireguy50]

yeah, it takes big problems to get noticed.
I noticed this:

 

[madbronco]

Originally posted by ValkariaKid [/i
.010" off one lobe will not make your engine run so badly that would make you think that there's a big problem that would require removing the cam. In fact you wouldn't even notice it at all.
Something must've happened.
[/B]

the only thing that happened other than the cam lobe being worn off was the lifter on the same lobe that got burned was worn the same amount(.010). that is it, the engine was not over granked, it started on the 3rd try. before we even started it, the engine was primed for 15 min. with the engine running we notice a slight knock after 20 min. we pulled the valve covers and checked the pushrods and noticed that one of them was sloppy.that is what promted us to pull the intake and check the lifters . thats when we found the problem..:banghead

 

[ValkariaKid]

That still doesn't sound right because...

my lifter plungers are depressed .045 to.05.

The lifter would've taken up the .020".

And I don't are what anyone says... wearing out a lobe on a cam inside of 25 minutes just doesn't happen unless there's some seriously mis-matched parts, or some really bad initial adjusting going on.

Which brings me to ask:
How are you setting/confirming the valve lash?

(Adjustment is done by using different length pushrods if necessary)

FoMoCo gave you the Stock Length for the pushrods of a STOCK motor.
They don't know if you had your heads milled, your block decked, how much the valve seat was machined durring your rebuild, what springs you're using or what height they're installed at, or if any of the rocker studs are still at the stock height.

If any of these were done then the length that FMC gave you is worthless.

 

[ValkariaKid]

BTW...

Ryan that's NASTY!




...yet morbidly cool at the same time! :toothless

 

[madbronco]

everything is untouched. the block was still good so we did not touch it. the heads were new, so they were good. we used a pushrod checker to make sure all the numbers were correct. we even checked the lifter bores to see if they were sticky and they were fine... oh ya we checked the new heads for flatness to.
thanks for the help...:twak :twak