Spent 3 hours driving there. Was supposed to watch the dyno, and it turned out I didn't even get to hear it run.

When I arrived, two of the guys working there were working on what appeared to be adjusting valves. I noticed the engine was warm, so I figured they did the breakin already. They were having problems finding a socket to fit over the rocker adjusting nuts, because the wall of the socket was too thick, and kept jamming in the rocker arms. So they ended up going to poly-locks. It seemed they were taking a long time tinkering with the adjustments. Well, that should have tipped me off...

At least two hours went by, and one of the guys calls me out of the dyno room to tell me he thinks there's a wiped cam lobe, and it won't be ready. Needless to say, I was a bit disapointed.

Now it will be at least another 2-3 weeks until it's ready for round two. What could have caused it??? I've heard of it before, but I've never had any cam problems with engines I've built myself!!

He says he'll find out when he gets it apart, and how this only happens every 1 out of 100 he builds, he'll pull off the oil pan and clean up any thing he finds, etc...

Not happy.....

 

A flat tappet cam that wipes a lobe right away is
a sign that the lifter for that lobe was not spinning in its bore. Have them check each lifter bore. A light honing may be required.

 

Its possible that they didn't remove the inner valve spring to break in the cam properly before running the engine. Then install the springs for the power runs. I'd find myself another dyno to run the engine on IMHO. If they don't have the proper tools to wrench on the engine to make any changes or adjustments, what good are thse guys?

 

That's what I think happened. I know they'd better clean up any shavings that may be in there, and check the lifter bores and valve train....

So far as the proper tools go...I don't think they've dealt with the Comp roller tip rockers much. Once we switched to poly-locks, it wasn't an issue. It appears it does require a special thin-walled socket that will fit in there right.

I'm the one that entrusted them to build this engine, so there's no doubt that they'll be the ones to dyno it. I told them I don't want it unless it's right, and they promised me it wouldn't leave until it is. I'll see....

 

I thought the springs were required to set valve lash, as well as actuate the valves?? Never heard of that, not saying you're wrong.

I guess maybe your referring to a dual spring setup of some kind??

 

With dual springs, either with or without a damper, standard practice is to remove the inner spring for break-in or to simply use lighter springs, if there's any possibility that the springs will produce too much pressure to allow the lifters to rotate at intial startup. Anything that results in more than about 350 lbs over the nose of the lobe is too much and should be adjusted down for inital startup. That's the most critical instant of a flat-tappet cam's life, is about the first 2 minutes of operation. If a lifter doesn't start spinning in the bores right then and there, it will eventually wipe the nose off of the cam lobe, and it's all over for that cam and lifters. That usually takes a couple thousand miles at most.

However, for one to completely wipe in only a few minutes of running, indicates something in the valve train is binding; most likely not enough installed height of the springs.

What springs are you using? What valves? What keepers? A quick and dirty way to get more installed heignt is offset keepers; you can get them in a .050" offset.

Most often if you're going to be running really high lifts, like above .600" or so, the right thing to do is to go to longer valves.

 

I serious doubt that they did that if they didnt have the proper tools to remove a rocker arm. A stock one at that after they built the motor?

 

You put stock rockers on this??? Well right there is the answer to why it screwed up!!!!

Don't tell them that; but what happened is that the rocker slot is too short, and the end of the slot hit the stud near max lift. I'll bet if you go look at the rocker slots and the studs you'll see that the rocker slot is all muchroomed out at the end toward the push rod and the stud has a gouge in it (or more likely, since it's a crap stock rubber rocker vs a hardened stud, a slight imperfection on the finish) where that place in the rocker slot hit it.

Stock rockers will usually go about .460" before the stud interferes with them and they cause valve train destruction.

You'll probably want new studs and push rods too, in addition to some real rockers, if the motor was actually built with stock ones.

 

He put the Comp Cams roller tip rockers on there. And for the record, I have them on my vert, and have absolutley no problem adjusting them with my Craftsman sockets.

 

No, I'm not using stock rockers - (Dart heads) -they're Comp roller tip rockers with 1.5 ratio intake and 1.6 ratio exhaust (I think...) could be the other way.

Manley screw-in 3/8 studs,Comp cam guide plates,Manley stainless valves 2.02 intake/1.6 exhaust, not sure on pushrods and standard hyd lifters. So far as springs go, I believe they are single -I don't know what brand but the sheet says "PEP" #059-117106, 1.250 O.D. with a seat pressure of 110 lbs.

And a Compcams XE274H cam (.490 lift@.050).

That's really all the info I have unless I call them.

EDIT: More info - Spring installed height is 1.730, Ex. guide to retainer 560, retainer brand name "PeP" VSR 105-1

Don't know if any of this info will help...

 

Well, I was there and I can tell you the socket would get piched in the stamping while adjusting on the nuts that came with it. That was using a spark plug socket which is no thicker than a standard one.....it needs a thin wall type socket. That's why they changed to poly locks. But the damage was already done by then...

 

{Huge sigh of relief} I'm glad they weren't stock rockers then, that would have been a major malfunction. I take ir these were the 1412s and/or 1416s then. I've had lots of those rockers over the years; it take a fairly thin socket like a Craftsman or the like to go down into them, a typical professional one won't. But, I doubt the type of nut had anything to do with it.

But, you said "stamping".... are these actually stamped, as opposed to the investment-cast steel? If so you may still be into slot interference.

IIRC Dart uses Comp 981 as their 1.25" spring; at least that's what their web page says.

The last thing that remains to check is the installed height then. That cam is right on the hairy edge of being too much for those springs, even with 1.5 rockers all the way around. 1.6s anywhere would be too much lift. Even a slightly lower installed height than their spec could easily send them into coil bind.

You might want to consider upgrading to 1.45" springs and retainers such as Comp 986 or 987 or the equivalent from one of the other major cam mfrs, just as relatively cheap insurance.

 

I have yet to adjust my rockers with it running because it was too tight to chance it running. Same rockers, Comp roller tips 1:6 's. I have a Craftsman 5/8 12 point socket and it just pinches it. I just made a socket on the lathe to cure this problem but I haven't tested it yet. The Craftsman socket was .857" in diameter and the one I made is .750". Only problem is this one is pretty thin in the corners, but should be fine for the rockers.

 

Thanx for the info. I'm starting to wish I just coughed up the extra $$$$ and just went retro roller....

But I know this cam SHOULD work. I'll call them and ask them if they installed everything that Comp recomended, or if I need to upgrade anywhere....I'm bummed over this. Everything in it is aftermarket except the block, and this happens.

Oh, and rjmcgee - that's the socket we needed!!!


Any other thoughts???