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Discussion Starter · #1 ·
Hello guys, I am in the process of getting my Dart 350 shp put together and was getting my cylinder heads taken apart to clean up my valves and the heads only have around 2 thousand miles on them over the last three years being in use and while blowing the heads off with air it was discovered that before I had the valves taken off out of all 16 valve springs there was a broken damper on the heads. I bought these Dart pro 1 platinum 200cc aluminum heads from competition products and they put there own valve spring kits on them and they said they came with howards valve springs and they list a part number and looking up the part number it says a dual spring with damper with a 1.430 O.D. but the springs that they put on my heads were 1.515 and to me that means they are not the correct part number they list being on them.

Anyways back to the vale spring damper being broken. My Father was the one who caught it and he checked all the other springs and there was no sign of any binding while the heads were in use on my old 377 shp build. I have never raced or taken this thing over 5500 rpm and have never been hard on it. My cam is a Mike Jones hydraulic roller 268/272 220/[email protected] 510/510 lift with 1.5 roller rocker arms. I don't know what the specs were on the springs since I have a conflicting number with competition products on what they said are on there assembled heads. My question what could have caused the failure? Never had this happen before. I am using Howards aka Morel hydraulic roller lifers with the link bar with the bigger .750 roller wheel and standard travel plunger length.

Anyways I went ahead and had to buy a new set of springs and matching retainers from comps cams and comp cams recommends 986 or 987 dual valve springs for there hydraulic roller cams and the two different part numbers are the same exact springs just with different installed heights of 1.75 vs 1.8 which changes the lift limit and open and seat spring pressure. These are the same dual springs that Dart puts on there assembled heads as well.

My question is the springs being at the 1.75 installed height has a 132 pound seat pressure and 290 plus ope pressure and .540 max lift with .060 safety margin. The springs installed at 1.8 as around 139 seat pressure and about 320 pounds of open pressure and a max lift of around .590 with a .060 safety margin. Should those springs even in the 1.75 height be more then enough for my roller cam? I know they recommend around those specs and I had an older 350 with a set of Dart shp 180cc aluminum heads with a similar sized camshaft from lunati which was a voodoo hydraulic roller cam with oem roller lifters and it never seemed to have any problems and was in excellent shape when I sold that build about three years ago.

I don't race this thing and won't take it past 5700 rpm at the very most and don't do anything more then just cruise with it. Hope to hear back from you guys who are are more experienced with these things as I am still new for trouble shooting things like this as I have never had this happen before. The one spring that the damper broke on looks fine and no signs of any damage to the springs. All my guides are still in excellent shape as are my valves.

Thanks guys
 

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The thing I would be concerned about is that the retainers are actually not bottoming out on whatever valve seal you are using, and that there is no coil bind when at max lift. Its good to quote specs but you should actually verify these things. .060 is not a lot of space and mechanical things don't always work as expected. Put your springs in a vise and tighten each one till it reaches coil bind. Don't over tighten. You can put a strip of paper between the coils to tell when they touch. Then measure the distance between the vice jaws with a dial caliper or inside micrometer. Write each one down.

Take a valve checking spring and install it on each valve. Then put a dial indicator on the face of the valve and push on the stem until the retainer bottoms out. Then you know for sure how far each valve can open before hitting the guide or the seal. You can get a 2" travel indicator at Harbor Freight for about $20. You need a stand also to hole the indicator.

You may be able to put the dampener springs in place and check them, but it might take a little creativity to hold the head and push the stem. Maybe a couple brackets temporarily welded to the table surface with one bracket having a threaded hole to allow tightening something against the stem. I made a machine out of an old wood lathe that lets me mount heads and rotate them to perform these tasks as well as some other head tasks, Can also polish crankshafts with it and check camshafts.
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Too involved for most people, but some simple brackets welded to a table (temporarily) will suffice.
 

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Discussion Starter · #5 ·
Wow that is some creativity there ekimneirbo and a genius idea you had with your old lathe. Thanks guys a bunch for your input and is much appreciated. I never thought of using the comp checking springs for those purposes. I don't have a mic to check the valve spring height but I have dial calipers and also I already have a dial indicator gauge along with the stand for checking such things. I will go about checking some things over tomorrow. I don't know how the springs could have been lacking any oil as all my parts such as the the top of the valves looked like brand new and my rockers looked fine of what was on the engine before.

The other springs looked just fine and the dampner just broke straight across and the springs were just fine looking and nothing weird or out of the ordinary. I need to get me a checking mic to help make things work easier. The newer springs will be better and allow me more clearance from the rocker arm and retainers as with what I spoke about in another post. Lucky for me I was able to get my short block sold so it gave me some much needed green backs to take of some things that came up unexpected. Will see how it comes out and my fingers crossed that all checks out good.
 

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Discussion Starter · #8 ·
Yeah I am guessing it was just a bad damper because everything else looked like brand new and there was no signs of anything going wrong or binding in anyway. I had less then two thousand miles on them and 90 percent was in town driving averaging 1600 rpm while cruising and 2500 rpm for a few miles on the highway. I had maybe 20 or so 4000 plus rpm launches while tuning my vacuum secondary opening on my carb but nothing radical. This is something that I have never had before like I said and from now on I am going to start a regular checking of those a few times a year even though I don't drive much just to be safe on things. Never thought of that happening but with engines and mechanical stuff anything can happen.
 

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Yeah I am guessing it was just a bad damper because everything else looked like brand new and there was no signs of anything going wrong or binding in anyway. I had less then two thousand miles on them and 90 percent was in town driving averaging 1600 rpm while cruising and 2500 rpm for a few miles on the highway. I had maybe 20 or so 4000 plus rpm launches while tuning my vacuum secondary opening on my carb but nothing radical. This is something that I have never had before like I said and from now on I am going to start a regular checking of those a few times a year even though I don't drive much just to be safe on things. Never thought of that happening but with engines and mechanical stuff anything can happen.
Do you have steel shims/ spring cups under the springs on your aluminum heads ? If not the dampers will dig into the spring pocket & that can cause damper failure AWA damage to the head .
 

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Discussion Starter · #10 ·
Yes I do have shims and I do believe what are called spring locators as with the dual spring setup that was originally on the heads are a thick hardened steel piece that goes around the valve guide area under the valve seal and sits just below the valve seals and fits the inside diameter of the inner valve spring to locate it and keep it from moving around.

The outer valve spring and damper are fitted over the inner spring and all are located that way and it goes out just past the dual springs and sits tight in the valve spring pocket. Any shims are underneath it. Sorry if my wording sounds kind of weird as I have less then a handful of times I have had to mess with cylinder heads and springs and stuff as like I said this is the first time I have had this happen and I have read more then I have messed with cylinder heads.
 
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