Hey guys,
I'm new to this forum and I'm hoping somebody might have some ideas to help me. I am currently in the middle of restoring a 1984 Corvette. I have converted the motor over from crossfire injection to carburetor. My problem is im getting excessive valve train noise. I have a comp ***** Tumper cam, new lifters, and just recently installed comp magnum rockers and new pushrods. I have adjusted the valves according to the procedure comp laid out in their instructions. (ICEO) When the motor is cold there is not much valve train noise, there is a little but very minimum. After I drive it for a little while and the motor warms up, the valve train is quite noisy. I am currently running royal purple 10w-30 and im wondering if im running too thin of oil or if it is possibly a different problem. If you have any idea, please let me know.
Thanks!

 

What kind of fuel? Also, since you're carb'd now and with the different cam, are you sure on timing? Are you flat tappet or hydraulic liftees? You may need to add zinc additive as well.

 

This is wrong.
It will be close but youll get that warm noise like you describe

Exhaust valve starting to open adjust your intake
Intake valve starting to close hit your exhaust.

If you do them strictly ICEO youll get noise.

Aftermarket cams with faster ramps wil make a slight amount roller rockers too.

Oil is fine

 

What preload did you use with those rockers? I also installed comp ultra magnum rr and it was 1/2 turn past zero lash. Might want to double check that.

 

Here is the situation that I face.
I bought the car with the motor and most of the work done. Ever since I got it, it has always had some ticking and almost knocking in the valve train. At first I was gonna try to just adjust the valves thinking maybe the guy before me just set them wrong. When i pulled the valve cover i noticed that some of the rocker arms were not riding perfectly centered on the valve. I went ahead a pulled a push rod and found that most were slightly bent, maybe eight of inch out of true. I did some research and found that the max lift on my stock heads is .480. My exhaust and intake on my cam are .479 and .489 respectively. Therefor, the rockers were hitting on the slot before the valves fully opened causing bent push rods. I went ahead and ordered comp magnum rockers and pushrod kit and installed in and Im still getting some valve train noise. I run premium 93 gas, and I have the timing set at 45 degrees total timing. I belive that is all right. I called comp today and they told me to switch to a synthetic blend and not too use a full synthetic oil (Royal Purple) because it lubricates too well and the lifters will not create the correct wear patter on the cam. I stepped up to 20w-50 and definitely noticed a improvement but it still seems to be noisy. I have always heard setting the valves as following, exhaust opening adjust intake to zero lash then tighten a additional half turn. Then turn engine till intake starts to close adjust exhaust to zero lash then also tighten it a additional half turn. If there is another better procedure I'm willing to learn. I have been fighting this for almost a week now and i really appreciate your guys help.

 

You did it right.

Are the retainers hitting the guide perhaps? Did he put the correct springs in? What heads?

If you have a rocker arm that seems like it keeps getting loose.
If the stud isnt loose and the pushrod is straight you may have a lobe going bad on you. A broken spring or damper could make a similar sound.

If it were me Id put the brakes on pull the intake look at the bottom of the lifters.
Youll know just by looking at them if theres an issue
If those are fine then fuss around with the springs trying to find out whats going on there.

 

It is a hydraulic flat tappet cam. Here are the specs
http://www.compcams.com/Company/CC/c...?csid=108&sb=2

 

Its stock L83 heads with casting number 462624. He said he put comp valve springs in it but i don't know anything about them. I don't understand what you mean when about the retainers hitting the guide?
I have been kinda restraining on pulling the intake but if it comes too it its not that bad.

 

this sounds like your problem

Id look into the springs binding or the retainers hitting guide (raised piece the valve seal inside the spring sits up on)

he obviously didnt check into this before he put that cam in, just the audience those were intended to lol.

 

From what I understand to check spring binding, you rotate engine until valve is open all the way and check the clearance between the coils in the spring. Is this correct? Also, how do i check to see if the retainer is hitting the valve guide?

 

What other mods have been done to the car to support a pretty wild cam like that ***** thumper-how much vacuum are you pulling at 1000 rpm??? That cam has 80* of overlap which for a farily stock motor and stock gears would be a real dog on the street and idle like chit. I am wondering if the previous owner installed a set of Rhoads lifters to calm that cam down??? That would explain the noisy valve train as the rhoads are a little noisy for sure. Have you tried to adjust the rockers with the engine running to see if you can eliminate the noise? And I assume you are using the Comp polylocks on your rocker studs?

 

total timing may not be part of the noise, but seems like 45* is about 10* too much. no spark knocK?
I guess I have never checked total timing on the HEI with the ICM controlling all but base timing.

 

Right now I am running stock torque converter and stock gears. The performance off the line is pretty crappy, it wont even churp the tires. Idle varies, out of gear it idles about 1200 rpms but when in gear at a stop light it has a hard time idling, tries to idle around 600 rpms. You have to keep you foot on the gas. But as soon as you hit the power band on the cam it will throw you in your seat. Vacuum at 1000 rpm is about 12". I Have tried to adjust them while running but its hard to pin point which which arm is making noise plus it makes a horrible mess. I bought a kit from comp that included new rocker arms, pushrods, rocker ***** and lock nuts. Here is the kit I have
http://www.compperformancegroupstore...t_Code=1412-16

 

I don't believe he used rhoads lifters. I feel that he would have made a point to tell me that... but maybe not lol

 

I cant remember exactly where the timing set, i think its 25* base 10* mechanical and 10* Vacuum advance for total of 45*. I have aftermarket hei distributor with adjustable vacuum advance canister and I had to put a advance curve kit in it.

 

sounds right with that setup. recently set one up for a 454 Camaro, close to your numbers, maybe less base tiimng. didn't actually measure the vac advance, so total base/centrifugal was 36*.

just curious.

joe

 

Do you have a vacuum advance distributor or all mechanical?
If all mechanical thats way too much

Have you had the dist curved? that will make a difference.
You need a much larger converter and fine tuning (curve/carb) and it will idle in gear fine.

These are obviously separate from your noise issue.

Once you adjust the valves are you finding the same ones coming loose?

 

I hate to say it but I believe you might consider biting the bullet and getting a milder cam that will work better with your stock 624 heads. A lot of guys buy those thumper cams for the sound they make and then find out they are not very streetable in a fairly stock motor. Even if you get the noise problem solved you will still not like the cam. If you want a cam with a rump rump idle look at the old Crane 274H06 Sat. Night Special, a short 218-218 duration, .450 lift for stock springs, on a tight 106 LSA that gives you that idle sound you want and is very streetable. I have one in my 84 and worked very well with my 624 heads, 14-15" vac. at 1000, around 12 at 800. Lots of low and mid range power. I recently installed a set of Summit cast iron large valve heads, actually they are Dart SS heads with the Summit branding. $630 shipped to my door and really are great heads and now I have even more low and mid range plus it pulls like a freight train from around 3000 rpm up to 5100. There are many cams out there that would work a lot better than your thumper. Good luck.

 

It is a vacuum advance distributor with a advance curve kit set at 25* base + 10* mechanical + 10* vacuum advance.

I plan on putting a larger converter in the future

As far as the carburetor, I'm currently running summit 600 cfm carb and tune it using vacuum gauge for max vacuum.

I have been learning a ton through out the process of tuning this motor. It has been a great learning experience. The drive-ability has improved 10 fold since i have got the motor, constantly finding ways to make it better and better.

If worse comes to worse i did not buy the car for the motor. I have another stock crossfire motor sitting in my garage with only 39000 original miles. I just like the challenge, If i can get the motor running well its just a bonus. I like the challenge. Down the road i will probably build up my other motor. Hoping this motor will hold me off till then