I rebuilt my 327 and within 500 miles it started ticking in the valve train .I pulled the heads and found that all of the guides were worn (egg shaped) ..Took the heads back to the machine shop but they had no answers. they replaced the guides and things were fine for another 5-700 miles but now I'm hearing the same ticking again..the bottom end is all new ,pretty much stock ,balanced and is tight ....the heads are stock 194's ,some port matching with 302 valve springs with comp magnum steel roller rockers...The cam is a comp 280H hyd...The motor rocks !! ,Pulls real hard up to 6k no complaints there !! Any thoughts would be greatly appreciated

Better start looking at the valve train geometry!

If the pushrods aren't the right length, you'll wipe guides pretty quickly.

Any chance you've got positive type (sits right on the top of the guide) valve seals and they're so tight the guides get no lube?

Schurkey, Thanks for the reply...At this time I cannot say what type of seals they are ...First thing tomorrow I will contact the shop that did the work and ask...About the push rods , I believe they are stock but with the stated cam and rockers should I be using a different length or type ?? I assume you are refering that I might have some what of a side load on the stems ??? Thanks again for your input ..This Problem has been driving me nuts ....

Schurkey,

I contacted the shop and he said the seals are O ring type on all stems with umbrellas on the intake stems ??

Are those the "positive types" you refer to in your note ? He said the springs ,rockers and p-rods should all work with that cam ...
He mentioned that maybe I am "leaning out" in the upper RPM range and getting to hot . But my spark plugs say I am running rich ...Dark ,slight wet looking to me .

The seals you have are not positive seals - you should have no problem with them oiling (or even over oiling) the valve stems.

All i can do is give you some questions to check out -

do you have guide plates, and are they wearing at all?? did you check the pushs rods by rolling them on a glass sheet to see if they were bent?

Are you running a tight compression or super high lift? did you check to see if the valve to retainer clearance was alright?

No, I do not have plates ....Yes , I did check the push rods..they are straight as a pin . In fact, prior to knowing that the guides were worn I thought it was the lifters so I replaced them and the push rods (2nd new set)

Compression is about 9.5 and the cam (280H comp)lift I believe is 480 ??...

Not sure about the clearance...Would the machinist have checked that during the head work ???...Thanks for your help by the way

These are the only ideas that I can come up with.

First, the builder said that the components should work with that cam. Well, "should" needs to be changed to "do". I would have them (and you should watch) assemble the valvetrain on one cylinder and cycle the motor through one revolution. Check the pushrod length, the retainer to guide, valve spring coil bind, rocker arm to retainer clearance. With a .480" lift cam, all of these should be fine with stock components, BUT when you have a problem you need to go back and check everything.

Second, are you getting any oil to the upper end of the motor. If you are running stock rockers, are the pivot balls starting to gall? Take the distributor out and try priming the motor with a priming tool. Be sure that it is a oil pump primer that completes the oil passage like the distributor.

Keep us posted.


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R.J.
1972 Chevelle
TC Member #1525
RJ's website (http://www.buffnet.net/~airrj/)

[This message has been edited by airrj (edited 06-07-2002).]

Thanks for your input guys..I plan to pull the distributor and check for oil in the top end ...I will post back with what I find .......
P.S. I am starting to think about changing to aluminum heads (RPM'S)and different rockers after I make sure I am getting oil up to the top end

In my opinion you really need guide plates on that thing - screw in studs and guide plate will not set you back that much.

However - im not sure that is even part of the problem

When the new valve guides were installed, were they "knurled"? If not, that could very well be your problem.

Red,
Sounds like a valve train geometry problem to me. Do some searching on the internet and you will find several sites that explain it very well. I am pretty sure all the cam manufacturers have it on thier web sites, or in thier catalogs.
The other remote possibility is that something is wrng with your machine shops valve seat grinding or cutting equipment. If the valve seat runout is much more than .002" it can kill the guides very quickly. I doubt that this is the problem since they have done the heads twice, but you never know.
Reno....knurling guides is 1950's "technology" if you can even call it that. Look at any oem or aftermarket head...all of them come with smooth valve guides. There are replacement guides available that have a spiral oil groove cut in them, sort of like they are threaded, but this is NOT the same as knurling. A smooth guide works just fine.
Let us know what fixes it http://www.chevelles.com/forum/smile.gif

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

1971 Heavy Chevy - original owner
Team Chevelle #100

Well guy's , Took the heads off and back to the shop Sat morning...Called me today and sure as sh!t , the guides are wiped again Some more than other's but still ALL of them are Sh!t again...Not front to back but towards the intake man and exhaust man ...He said he was going to go thru them top to bottom....I found that the oil supply to the top end was minimal ...Not much squirting out the tappets (top of p-rods) ...Makes me wonder if a passage might be plugged...I have great oil pressure 40#-60# ...I have to tell you ,even with the valve stems loose in the guides ...That little mouse just plan "ROCKS" But I am thinking about pulling the short block out and tear it down just to make sure everythings cool in "bottom end land"....I'll keep You all posted...

Just remember to say to your self "I love my hobby". Days like today can be tough to remember this, but it is fun to wrench on the Chevelle.

Keep us posted.


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R.J.
1972 Chevelle
TC Member #1525
RJ's website (http://www.buffnet.net/~airrj/)

red68camino, I'm going to make a couple of guesses and you tell me if these things might be possible.

When you first took the cylinder heads to the machine shop, they told you that all of your valves could be re-used and that they would be just like new after they did all of their machining. When you got the heads back, everything looked like new cast iron, the springs you gave them (or asked for) were installed and all you had to do was paint them and install them.
The entire 'valve job' probably cost less than $150.
The guides wore out quickly. (you said that).
The machine shop didn't know what could cause that kind of accelerated wear but they would be nice and 'replace all the guides' again anyway. (you said that too).
Now 'the 2nd set' of valve guides have exhibited the same accelerated wear.

Your rocker arms are fine.
Your pushrods are the correct length.
Your lifters and pushrods are delivering plenty of oil.
YOU did everything right.

You need to find another machine shop. Any machine shop that's been in business for any length of time would be able to tell you that the machine shop that did your heads:

Glass beaded your old valves and only knurled your valve guides. Valve stems are all made of various types of stainless steel; some better than others. Glass beading a valve stem turns it into a nifty little stainless steel file that quickly 'machines' it own little path through a stock cast-iron valve guide that was only 'knurled' (a real, bronze-aluminum valve guide is a different story). Knurling isn't the same as actually 'replacing' the valve guides. It's a real quick and cheap method of tightening up old, loose cast-iron valve guides and it lasts as long now as it did back in the 30's when a valve job was probably about 5 bucks. If they wouldn't have glass beaded your valves, they would've lasted a little longer but, only a little and you wouldn't have been too impressed at the sight of your old, worn, polished valve stems shining through your new valve springs.

No, I think you did everything right like you should have. You better go get those heads and take them to another machine shop. A good machine shop will charge you more to just replace the guides with new, REAL, valve guides than the entire cost of the first machine shop's entire valve job.
Yes, it is expensive but, how much would you charge (or pay) to take your heads off again and again.
Oh, ask for the 'old guides' when you pick up your heads. See what they come up with for that one.

You're OK. I don't think the machine shop is.

Just a guess,

Louie Hammel