The car is running horribly: no power, severe vibration of the whole car in gear, and loud popping noises from engine compartment (not the carb it sounds different than that) in upper rpm range under WOT (in gear). The vibration is very bad at low rpm in gear (part throttle), but noticeable at all rpms and mphs. I can see (hood scoop) the motor vibrating in neutral but when I put it in gear it gets transferred to the whole car and becomes worse (can even see the headliner blur). Also a tapping noise under hood at idle and every other rpm too, but I think that may be rockers still. Would and exhaust leak cause similar symptoms for loss of power and tapping? Tranny mount for vibration? Rear end going? I think I have multiple problems here now. what do you think? Timing is set to 6* BTDC initial, tires have flat spots on them, but the vibration occurs even when not moving. Thanks!
John

P.S. I have a 2.73 open rear and stock TC so thats where some of my "sluggish feeling" is, but this seems like something else much worse.

 

Sounds like one of your plug wires is either burnt or cracked thru. As far as the ticking could be lifters, is it around your feet though, that would indicate a exhaust leak.

 

I'd suspect one single defect causing the whole set of symptoms.

Ignition miss, like the other post said, would be the first guess. Also check for carbon tracking in the distributor cap.

After that, it gets ugly: broken or loose valve train parts on an exhaust valve (not too bad); burned intake valve; blown head gasket (especially between #5 & #7).

 

I would say it's either two or three bad pugs/wires or your distributor is off by a tooth or two. It could also be that you need to adjust your valve lash... this would explain the "tapping"

The loud pops are probably unburnt fuel igniting in the exhaust pipes.

If the carb is old and you have noticed the problem getting worse over time then I would suggest replacing it with a new one.

 

Of course it could always be bad gas

 

Thanks to everyone who responded. I think I am getting too worked up over something that is probably stupid.
As for replacing the carb... I just did with a remanufactured one. Works great and solve a hundred other problems but this was occuring before I did that so that is not the reason. Plug wires are new but there is a possibility the headers ate them. I'll check the ignition system tomorrow. However, I also did a valve lash adjustment recently and took my time in order to make it perfect. I also have roller rockers and I think that is the tapping noise. It is driving me nuts because I thought rollers were supposed to be quiet. I thought of the bad gas too but I just filled up again and still does it.

 

New wires don't mean anything if you don't have wire looms. I have burned 3 wires until I finally got some looms. Plus I got some heat protective sleeving, it's a lot cheaper than new plugs, and the security of your car not running like crap is priceless.

 

alright I checked it tonight no burnt wires (i do have looms) but under the distributer cap on all the terminals there was a little carbon build up and it was on the rotor too. I scraped it off gently with a swiss army knife and put it back together. It runs MUCH better!! Its not perfect though and tomorrow I'm going to check the plugs cause the old carb may have fouled them.
I always fear the worst when things go wrong dont know why though. Thanks for smacking some damn sense and logic into me lol
John

 

# 4 cylinder was dead so I pulled the plug. it was damp with black flakes on it, but I dont think its oil. I think unburnt fuel. another thing I noticed is a dent in the valve cover OVER #4 and the dent is poking OUTWARD. This CAN NOT be good. I'm gonna open up the valve cover and get a look at the carnage when it cools down. I'll keep you posted.
John

 

sounds like a rocker let go or valve bent, forsure pull that valve cover.

 

well heres the damage:
1.) broken afr rocker stud with polylock still on it
2.) bent to allhell summit pushrod down in the lifter valley at the back of the block. (I have about 31 spare stock length ones and zero spares of the ones I need)
3.) both lifters on #4 came out of their bores
4.) broken part of stud w/ polylock still on it was jammed inbetween 2 coils of the exhaust valvespring
5.)one roller rocker was scuffed on top (I dont think it is bent or otherwise damaged, but not sure yet. I am glad I didn't get aluminum.

I guess I was pretty lucky considering I drove it so far and nothing broke off and went down into the rest of the motor.

Does anyone know where I can get just one or two pushrod that is .100" longer than stock? What about one or two polylocks? The ones I have came with the roller rockers.

Thanks,
John

 

Before you go just sticking new parts on there, you need to figure out what happened. Otherwise it will simpky happen again.

 

yeah, I don't get it. I have used the adjustable pushrod method to check the proper length and thats how I got the longer ones; the stock ones loosened up all the time and finally slapped around enough to bend one, because of incorrect geometry. Maybe the rocker stud was defective or it was damaged when the stock one broke, but I dont think that was the one that broke before. I am leaning towards defective because I have another one that wasn't machined right or something and it was real hard to thread the polylock on it. But that one hasn't broken. and I think all the other ones are still tight. Also, I made sure do the valve lash adjustment right the last time and I took my time. I don't know what else couldve caused it this time. But you hit it right on the head with your first post RB, thanks!

 

wow, that's tough bro. Hope you get it all straightened out.

 

Thanks man. Does anyone think I should buy a set of ARP pro series rocker studs and some high-end pushrods? Maybe a stud girdle?

 

What rockers are you using? Are you running guide plates? What cam? What valve springs?

Push rods and studs don't just up and break for no reason. Something broke them. You're just looking at the symptoms, which will repeat themselves if you don't identify and cure the underlying cause.

 

I am running comp cams pro magnum rollers 1.6 ratio, comp cams high energy 268 cam:
.484"/.484" lift w/ 1.6 ratio rockers
218/218 dur @ 0.050"
My afr heads came with afr guideplates, afr valvesprings:
hydraulic lifter springs Part # 8020 which are 1.450" springs
and summit 4130 steel pushrods part #SUM-G6400100 which are stock length +.100 and hardened for use with guideplates.
I can't think of anything wrong with this setup other than cheap rocker studs from afr (like $18 for all 16 so maybe they use cheap materials). I've heard that there is something about using certain rockers (self-aligning vs. non) with guideplates, but I thought I was ok with mine. Maybe not?

I dont know, I'm trying to brainstorm here. What about a broken/slipping timing chain? I guess that would cause more catastrophic failure that what I have though. I honestly don't know enough about this stuff to make an educated guess about the cause. This is my first car, first build up and first failure.

 

If you have self-aligning rockers and guide plates, then you're in trouble. What you have is 2 systems fighting each other to guide the rocker to where each of them wants it to go, so everything is in a bind 100% of the time.

Look at the guide ridges on the affected rockers; I'll bet you'll see evidence of stress.

Other than that, you choice of parts doesn't seem out of line. It should work.

 

Does anyone know if comp cams pro magnum rollers part #1302-16 are self-aligning or not? I don't think they are because I can't find the "guide ridges" you are talking about. I've been thinking and I think what happened is the lash on that one cylinder wasn't perfect and it came loose. the pushrod slapped around and got jammed under the part of the rocker close to the stud and since the pushrods are 4130 chromoly steel and the studs seem to be a cheap material, it beat against it several times per second until both failed. That is the only cause I can think of. Anyone else have a scenario that could have happened? I am going to check the cam for damage by looking down into the 2 lifter bores while I rotate the engine. I saw the base circle part yesterday and it looked ok, but I want to make sure the rest of it is. I even checked for bind at low speed last time I installed all this stuff, but I'll check it again.

 

1302 is not self-aligning.

What was going on right before this happened? What RPMs has the engine seen lately?

Loose rockers shouldn't cause anything like that to happen. Old cars run hundreds of thousands of miles with the rockers banging loudly.

 

yeah its been only a couple hundred miles since the last valve lash adjustment I did, and it didn't get any louder than it had the previous couple time I did them. So, I thought I was in the clear.
The only symptoms where what I described in the first post, which at least some of was due to ignition miss like you said. I did push it hard about 3 or 4 times during those miles but only let it see 5500 rpm MAX. However, in order to make keep it warmed up and since the tranny isnt shifting right, I have been manual shifting and keeping it in second gear a lot. but I have 2.73 rear gears so that's not really abusing it. the temp never got above 200, i guess cause its relatively cool out.

 

Nobody has mentioned it yet, but with such valvetrain carnage...

Have you checked for coil bind? Have you checked the valvespring tension? Are you restricting oil to the top of the motor and the valvesprings aren't getting oil to cool them? Have you gotten the motor into valve-float at all?

I would replace ALL the springs, any pushrod which is not absolutely perfectly straight, any rocker with any sign of damage (check the bearings too), get some ARP studs for the rockers... my 71 RS used to have mr. gasket rocker studs, one of those broke on me in a non-coil bind situation, went to ARP no problems since...

put it back together, check geometry very carefully, make sure springs aren't into coil bind at max lift (you may have to get one solid lifter to test this so that the hyd. lifters don't eat up your true max lift)...and as someone else mentioned you shoudln't be using two methods of alignment...either self-aligning rockers, or guideplates, not both...

nick

 

The whole valvetrain is brand new. valvesprings came installed by afr on the heads as did the rocker studs. I have honestly put about 3-400 mi on all of it since mid october when it was finnished. I didn't do anything on purpose to restrict the oil, and there is at least some oil getting up there, don't know how to tell if it's enough though. No valve float, I've taken it up to 5500 rpm only a few times which should be no where near valve float. I doubt the springs are stacking up because I only have .484" lift with the 1.6 rockers and all AFR told me was not to go over .550" with these springs. I'm using only one method of alignment (guideplates). I took what I though was great care to select good parts and install them properly. This is really aggrivating. But please keep the ideas coming. Thank you!

 

and BTW:

If the 0.484" lift is specced lift, then it's at the 1.5 ratio..

at 1.6, you have 0.516" lift.

your valvesprings are rated max 0.550"

 

yeah the specified lift is .454" , I already added the amount for the 1.6 to make it .484". BUT i was just comparing the stud that broke and one that didn't and I noticed this:

The rockers' cylinder parts were/are sitting on the part of the stud that is threaded.

Should they not be doing this? Should they only be on the solid part????

On the NOT-BROKEN one, the threads are starting to get flattened from the rocker arm at exactly where the other one broke.

How is the rocker arm supposed to keep from moving up and down??? the only thing keeping it from moving up and down on the stud in my motor was the balance between pushrod and valvespring. Is this not good?

The overall length of these studs, including the part that goes into the head is about 2.5" and most of it is threaded, except for about .600" at the bottom of the part that sticks out.

 

nevermind, i need to read what you are writing! I found your cam on compcams, the lift is as you say at 1.6.....it's 0.454 at 1.5...

I don't know...that's not many miles for such a catastrophic failure... your springs should easily handle the lift...

maybe the rocker stud broke initially and that's what took everything out. the only other thing i can think of, is make suer the rocker isn't hitting the valve spring or anything....

When the rocker stud (mr. gasket stud) on my 71 RS broke, it damaged the rocker bearing at the same time...but i didn't have any other damage, the pushrods were fine, lifters stayed in their bores...but i pulled over immediately to the side of the road (2 blocks from home). when a valve quits opening and a v8 starts pumping a dead cylinder, it feels so bad!

 

It's been a few years since i've had to look at rocker studs, but i think mine were threaded pretty low too (that is, the rocker was on a threaded portion of the stud), even the arp's...but that's based on memory only. the polylock is what holds the rocker down....it acts as a pivot point. If the fit on the stud was really sloppy, I'd think that would be a bad thing (the rocker could rock back and forth and beat up on the stud)...

Since everything else seems to be in line, I'd get the ARP studs and give it a try.

 

yeah thats what I'm thinking. Now, should I pay for their "pro series" which have a 190,000 psi tensile strength and are $55 or the "high performance" which have 170,000 psi tensile strength and are $29. The AFR ones I have are about $18 and I don't know what their made out of or what tensile strength they have. I know price isn't always dependent on quality, but I think this might be one of those cases where it is. Oh and the pushrods I'm using just say hardened steel for use with guideplates, but they don't say 4130 chrome moly like I thought. These cost $30.50 and the 4130 ones (cold forged, one peice) are like $90. Should I upgrade those too?? AFR's install instructions for the heads say to use "thick wall, chrome moly, heat treated pushrods". Either way I have to buy a another whole set of each pushrods and studs.

 

Straight from ARP's web site:

PRO SERIES
Designed for competition applications, ARP’s Pro Series rocker arm studs are made of premium grade 8740 chrome moly steel and heat-treated to a tensile strength of 190,000 psi.

HIGH PERFORMANCE SERIES
Made of 8740 chrome moly forgings and heat-treated to 170,000 psi. Excellent for E.T. Bracket Racing, limited rule oval track competition and street use. Tip ground flush for optimum adjuster seating.

As for the pushrods, dont know what to tell you. you definately need a set compatible with guideplates, but your cam isn't that high lift or fast moving to need special pushrods....

check comp's recommendations for the pushrods..see how much theirs cost?

anyone else have pushrod thoughts?

nick

 

thanks for the info. I just ordered another set of the same pushrods, and a set of the "high performance" arp studs. it was only like $67 total and now i'll have 15 spare pushrods in case this doesn't solve the problem. I'll keep you all posted on what happens, thanks for everybody's help
p.s. when I said this I guess I was trying to ask if it was correct for the rocker arm to be up in the middle of the rocker stud with nothing underneath of it. the only thing holding it up is the pushrod on one side and the valvespring on the other, correct? I knew that the polylock was what kept it from flying of the stud, but I seem to remember the stock stamped steel rockers resting their pivot on the bottom of the exposed stud... maybe I'm just remembering wrong. Could someone straighten me out?

 

there is nothing that holds the rockers up...the spring pressure holds it solidly against the polylock (roller rockers) or against the spherical pivit ball piece (stock rockers).... even stock weak springs have at least 60lbs of seat pressure, plenty enough to hold the rocker against the pivit/polylock!

 

:hail:

nice z28, by the way 91!