As a lot of you know I sold my 95 LT1 to another forum member. Since he has had the car there have been a lot of issues with the valvetrain. I put ported and polished heads, Ported intake,1.6Roller Rockers,and a cc306 cam in the car. It drove perfect for me and made awesome power. A couple months after I sold it, the valve dropped and hit the piston, demolishing the piston. The engine went through a full rebuild after that and there have been even more issues pop up since then. They had to mill the heads to fix the damage done to them when it blew. The machine shop installed new valvesprings....

The first issue it had it bent a pushrod very bad, it almost twisted two pushrods together. We then installed hardened pushrods thinking that would help the issue. A hundred miles later it broke a valvespring. After reading the box of the springs, they only hold .500 lift. The CC306 is .544/.576 with the 1.6's. A friend of the owners came out and tried to diagnose what was going on, he says its coil binding. He thinks in order for it to work the heads must be worked over with longer valvesprings.

I just dont see why its this much trouble, many people run this cam with no issues... does anyone have a solution?

 

If it has the wrong springs on it you have no choice but to get proper ones. Coil bind will cause the symptoms you have described, ie broken valve spring, and bent pushrods. It could also damage the hyd lifters.

DO NOT drive it anymore until the valve spring situation is resolved.

If you can get me his current set up height, I can help you with part numbers for the proper valve springs.

Will

 

The engine builder said it was somewhere between 750-800. I would assume thats in .750... I dont know much about this area of the engine build. What should it be?

 

This is a no brainer. Get the correct valve springs for the camshaft. There is no way you can run springs that are only good to .500 lift with a .576 lift camshaft. I suggest looking into the Comp Cams 918 Bee Hive springs, they are good to ~.600 lift.

 

Most stock length valve SBC's set up at 1.700-1.750 with standard retainers and standard locks.

Aftermarket manafactures make + or -.050 locks. There are also retainers that will give you +.050 on you valve spring set up height. As you can see with the proper selection of retainers and locks I can get him an additional .100 or -.050 if he needs it. BUT you need to know excally where he stands now on set up height to make the proper parts selection and valve spring selection, because there is the question of how far the valves were sunk in the heads when the valve job was done. His set up height could in reality be anything. It's not as easy as just throwing a set of 918 Comps on it and thinking your good.

Different valve spring need different setup heights to work properly. The Comp 918 set up at 130lbs@1.800
The Crane 99893 set up at 120lbs@1.875
The Howards 98432 set up at 135@1.750
The Pioneer 98213 set up at 120lbs@1.800
All are good to .600 lift or better on a hyd roller if set up according to the mfgr specs. This is just a drop in the bucket of springs availiable that will get the job done, and with everything in this world some are better suited than others depending.

Also the last thing I would do is take the word of a machine shop that put .500 lift springs on a .570 lift camshaft. Ask the owner to either buy a good 6" dial caliper and a set of snap gages (or borrrow some) to measure it himself. Of course he can always take it to a good machinest or mech who is trustworthy, has the proper tools and can measure it for him.

Once I get that info I can make a better valve spring retainer and lock combination recommendation for you.
Will

 

I'm the other forum member, 95bluebomber is my cousin he is helping me out, because he knows more about this then I do. I will see what I can do about getting the info you need. Thanks for your help it is really appreciated.
JAY

 

don't buy the comp 918 beehives ,lots of broken engines from them lately.i was on z28.com and there was a big thread on all the carnage,apparently comp switched suppliers and had there springs made in mexico to save money and there is a bad bunch of springs out there.Check to make sure what you buy isn't the lot number that has the problems,or buy the patriot springs (comps old supplier).

 

I just sold a cam set up for .575 lift w/ 1.5's. I think you'll find the biggest problem is retainer to seal/guide clearance...hence the need for +.050 locks. The latest batch of 918 springs are fine, call Comp, but they've got things handled. I used their 10 degree steel retainers and some +.050 locks. You will have to shim up the springs again to get the seat pressure up...otherwise it's valve float city. I got up to about 115lbs before getting .060 away from coilbind. It's a great little recipe.

 

Hey everybody, it turns out that the valve springs were set at the wrong height. 95bluebomber and I measured the setup height at 1.697" and according to comp it should be 1.800" with the 26918 beehive springs and retainers. I guess I'll see what happens with this new $300 setup. Thanks for your help JAY

 

How in the world did they get that installed heigth????

 

No the installed heighth was 1.697.... the retainers are inverted down, causing the low install heighth. The new heighth will be very close to the recommended 1.80 Comp recomends.

 

Since the heads were milled did you shim the rockers or get shorter pushrods? This might also cause low install height. Was the motor backfiring at all?

 

How would milling the heads affect the valve spring's installed heigth?

 

The measurement is with the rocker arm off

 

I just got done building my 383 LT4. I had to run 7 degree locks to get my springs to 1.800 install height. I also had to run a - .100 pushrod to get my geometry correct. You need to pay close attention to all the little details when setting up valve train or you will end up with broken springs.

 

He is confused. It would not have any affect on the valve spring install height.

Depending on haw far they were decked, it could mess up his valve train/rocker arm geometry and piston to valve clearance but thats it.

On another note Blue Bomber:
Make sure you use the hardened spring seat locators under the springs, I assume you got 2.020 by measuring without them from the retainer strait down to the alum head. Regular valve spring shims are not hard enough to use directly under springs with as much pressure as the Comp 918. Without the hardened locator under the spring they will eat the rather soft shims up in no time.
Will

 

Whoa... you are in Bardstown! What about a helping hand? We sure could use it... the local machine shop did all this work and its been impossible to get straightened out. I am not all that familiar with valvetrain geometry. It would be nice to have someone shine some light on this situation.

 

I didnt get a measurement of 2.02 J wrote that wrong. The measurement was 1.697 and that was from the shim to the bottom of the retainer. The shims are .030

 

This is as good of an explanation as I have seen of how to properly map out your rocker arm geometry. Quite easy actually. All you need is an adjustable pushrod. You can also try the ones you currrently have to see how close you are and go from there.

http://www.holley.com/data/TechServi...20Geometry.pdf

Will

 

Understood.

I take it you are going to be using different retainers and or locks.
Will