Bent Valves, AGAIN?

[Ls7camaro]

I need some help. 400 SBC .030 over, 5.7 rod. Hyperutectic pistons, comp cam, solid lifters, scorpion roller rockers with stud girdle, Dart Iron Eagle 215 head. The problem is this, valves seem to be open, not closing right, Last year the motor was up and running and then bent pushrods and bent valves, this year, went to the dyno figuring that was all corrected, had the heads fixed with new valves (5 valves) and back to valves sticking open. I need to pull the heads off and start looking, but any help would be very much appreciated. Any suggestions when I pull the heads off I am figuring that I need to check the pushrods to make sure they are correct length. After that, could the piston to valve clearance be too tight? Whats the best way to check that with the engine in the car? is there any other issues to look into that you can think of???

[chpcamaro]

do you have to lite of a valve spring and the valves are floating or check the guides i would bet they are grabbing the valves when they get warm.

whats the valve spring closed pressure and what kind of cam flat tappet or roller and solid or hyd.

[chpcamaro]

ok here are easy things to check and easy ways
1. first check valve spring pressure. if you don't have a tester get something like this http://www.summitracing.com/parts/MOR-62390/ if the pressure is good go to step 2
2. next set #1 cyclinder to compression stroke use a pair of calipars and measure spring height the adjust valve down 50th's then roll the motor over back to compression stroke again if no valve cleance problems then go to step 3
3. check your push rod length if you don't have a check get one of these for 3/8 rocker stup http://www.summitracing.com/parts/PRO-66789/ and if you have 7/16 rocker studs http://www.summitracing.com/parts/PRO-66790/ if all checks out good go to step 4
4. pull heads and have the guides checked by the time you get here you should have your problem figured out.

if i missed something anyone please add to it i hope this helps you find your problem quick and easy
thanks
rob

p.s. let us know what your cam is and one of us can give you what you should have for pressure when testing

[DOTracer]

I'd also verify the valve to guide clearance. Buddy of mine had problems with his Cleavland Ford. When the motor got warm the clearance would tighten up and pinch a couple valves. He bent pushrods, wore down flat tappet cam lobes, etc.

[Ls7camaro]

Here is the cam that was put in.

Duration @ .050 Intake 250 Exhaust 262
It is a comp cam Part# 12-609-5 Grind # cs-285B-6

[chpcamaro]

well i would say you want around 125 to 130lbs on the seat no less

[Ls7camaro]

Ok, guys, here is the issue, so far that I see, I took the passenger side head off, and there is a clear mark where the valve hit the piston. What is the best way to measure the correct Piston to Valve clearance. I think the plan is to have the the valve taken out, fixed and check all the other valves, then I need to check the piston to valve clearance, I am thinking of using a thick head gasket, the pushrods are 7.800, two of the rockers look beat up, so I think I need two of those, but looks like just the one valve. Not sure, but I think that the block doesn't sound like its square.

[DOTracer]

Ok, guys, here is the issue, so far that I see, I took the passenger side head off, and there is a clear mark where the valve hit the piston. What is the best way to measure the correct Piston to Valve clearance. I think the plan is to have the the valve taken out, fixed and check all the other valves, then I need to check the piston to valve clearance, I am thinking of using a thick head gasket, the pushrods are 7.800, two of the rockers look beat up, so I think I need two of those, but looks like just the one valve. Not sure, but I think that the block doesn't sound like its square.

Take the heads to a machine shop for clearance checks. They use a micrometer to measure the valve stem and a special dial bore style gauge (inside mic) to measure the inside of the valve guide an subtract those numbers to give the clearance.

I'd recommend having both heads inspected completely so you don't go through this all over again.

[Ls7camaro]

what is the best way to check the piston to valve clearance? use playdo or clay?

[DOTracer]

what is the best way to check the piston to valve clearance? use playdo or clay?

best, No, easiest/cheapest, Yes. You can pick up some modeling clay from Walmart or Michaels. Playdo would not work well.

Coat the valve face with oil so it doesn't stick to the clay.

[Ls7camaro]

So if the Piston to valve clearance checks, should be at least .100 on Exhaust and .080 on Intake, then it has to be the valve to guide clearance making the valve hang open? Heads are going to a shop today, once they get checked out and all the valves checked, I'll put them on and check the Piston to Valve, any other reason the valve would hang open?

[Bruce69Camaro]

The method I was instructed to do was pretty simple and for me, the hardest parts was making the tool to do it.

The tool had to be made out of a heavy gauge metal and it resembled the tool used to check spring compression.

I slide this tool onto the rocker arm, brought the piston up to TDC, placed a dial indicator on the valve spring retainer ( I think) and pulled back on the handle of the tool to open the valve. While I was pulling back on it, I was feeling for it to make any contact with the piston. If it did, you then check the dimension on the dial indicator and this would be you P to V clearance.

Like I said the hardest part was making a tool, because they don't sell something like this, or at least I don't know of any.

[DOTracer]

The method I was instructed to do was pretty simple and for me, the hardest parts was making the tool to do it.

The tool had to be made out of a heavy gauge metal and it resembled the tool used to check spring compression.

I slide this tool onto the rocker arm, brought the piston up to TDC, placed a dial indicator on the valve spring retainer ( I think) and pulled back on the handle of the tool to open the valve. While I was pulling back on it, I was feeling for it to make any contact with the piston. If it did, you then check the dimension on the dial indicator and this would be you P to V clearance.

Like I said the hardest part was making a tool, because they don't sell something like this, or at least I don't know of any.

TDC is NOT where the P to V clearance is tightest.

[Bruce69Camaro]

That comment was my mistake, it's been sometime since I did this and I can remember bring it up to TDC and using the dial, rotating it until it was at the highest point before it dropped back down.

Thanks for pointing that out.

[chpcamaro]

hey Ls7camaro what have you checked so far so we can try to help you go in the right direction?
and where are the rockers beat up do you have pictures of them this could be a good indication of what is going on