For the people who think I'm dumb enough to use LT4 springs, scroll up to the beginning of the thread, believe I stated that I was using the Comp cams springs, like a 986 part #. The reason I believe the valve is hitting the piston is because only the exhaust valve pushrods are bent, If it was mixed up between the two, I'd lean towards a spring bind or something simple. We arent talking slightly bent either, these pusrods are borderline snapped in half, one looks like a snake. The heads are still on the car, so I have no idea if the valves are bent.

 

Ok I was wrong I didnt state that. But to clear it up, I am using the bigger springs. The springs say they need maching, what type of machining do they need? I put the springs in the head without machining anything. The heads had been to the machine shop b4 so I thought it was possible he made extra clearance for the lt4 spring I had ORIGINALLY used. But the springs and cam all went in at the same time. As far as timing gears go, I'm using the cloyles double roller set, same set I used b4 with the hot cam, All the dots are lined up so I dont see any reason for this problem to be occuring.

 

So you used springs that say they need machining, but you did not have the heads machined? The seats usually need to be widened. If the spring is not sitting down in the seat, you could get coil bind.

If your Cloyes set had the different crank position slots, did you use the right one to install it "straight up"?

At any rate, something is very wrong for you to get bent pushrods just from cranking.

 

According to Comp Cams coil bind occurs at 1.150" for the 986 springs. The exhaust lift on that cam looks like .576" with 1.6:1 rockers. What is the installed height on your springs?

If the spring seats are not machined you will lessen the installed height, of which you are already very close to bind.

There's a very good chance you're stacking the springs solid before full lift. This'll bend pushrods in a hurry!

 

Also when you installed the springs did you shim it to get the correct seat pressures? When I installed my EX612 springs I didn't shim it to get the correct seat pressure and floated my exhaust valves...which caused them to smack the pistons and bent all of my exhaust valves. I eventually went with Lloyd Elliot heads to solve my problems.

The LE heads have the CC 986 springs on them but the springs were set up for a smaller cam...so I had a reputable head shop shim it so that I could run a 236/242 on a 110lsa with those springs. So you might consider getting those springs checked out and set properly.

-B

 

The problem is you rocker arms. if you are still using the GM rockers they are only good to like 550 lift. then they hit in the trunions. GM specd their rockers diffrently than the regular crane gold for durabuility reasons.

You are exceeding the lift that that rocker can handle. thats why you are bending pushrods.and only on the exhaust side where the lift is on that cam.

 

Well, I dumb as a rock when it comes to these things, but...wouldn't shaved heads along with big valves (especially if the seats weren't ground for the large valves come into play?

 

I think the problem is the rocker arms hitting, thanks for the help. The machine shop machined the seats the last time I had them in there, called them and asked about the new springs and he said he machined extra so I should be good to go with the bigger springs