Comp 910 valve spring questions and installation

[cpdenton]

i have rebuilt heads Already. At the time, I decided to just have the springs put back in as they were in good shape.

Now that I am about to install a typ4 cam, I need to change those out to the comp 910s before I install them(not sure if I will build a short block or just go with my runner)

It has been said a .030 shim is just right and I want to make sure I get these right. Do the stock retainers work?

Comp sells shim kit. Pn#4754. Spring Shim Kit: 1.437" O.D., .645" I.D.
Is this what I need to order?



Is there a way to make sure I am doing this right, as in what do I need to measure to make sure they are installed to spec? Any advice would be predicated and might be worth a full write up as I install these so other can match it when they install the camshaft.

 

[cpdenton]

Also, my heads have been surfaced a few thousandths, and the valves recessed the proper amount to fall within spec, does this change the amount of shims I might need to get the proper seat pressures on the valves?

 

[icanfixall]

What the shim does is creates spring pressure needed. So leats say you sunk the valves an additional 15 thousands in the heads. Well using the original valves you are going to need a 15 thousands shim under it to get back the closed and open spring pressure. I have really made my comments simple but someone with vast valve gemotery knowledge like Russ will know exactly what you need to do.

 

[cpdenton]

Thanks Gary. I thought that is what the shim is for, to make sure the springs are at the right seat pressure. Now, I just want to know how to measure that pressure and make sure I am right.

 

[79jasper]

There's tools for that. Lol

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[cpdenton]

There's tools for that. Lol

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There are, but I am not smart enough to know what style is best, so I asked.

 

[79jasper]

Me either. Lol
There's a spring height tool. Comp 4929.
Then there's spring pressure tools, but they're all expensive.
Maybe can get @typ4 in here. @IDIoit may have some suggestions also.

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[IDIoit]

with the comp 910's and the shims, the work has been done for you.
if you buy the new springs theres no reason to check them.
this is more for checking pressure when you don't know the springs rating.

spring rating is set to cam specs.
they usually give you cam card with said specs.

here is a tool used to check spring pressure on installed valve springs, kinda pricy.
http://www.ebay.com/itm/LSM-Racing-...:g:9OIAAOSwHnFVv35A&item=131480950181&vxp=mtr

I would build another short block with this cam,
the pistons should be cut to eliminate valve to piston contact.
my heads were machined to max out the recess in the heads, and I still had very slight contact without cut pistons.
this cam is awesome if you can get it right.

 

[cpdenton]

So, I just need to install the springs with the .030 shim and I am good to go?

I am good with that.

Looking at the power stroke guys that run these springs, seems as though they like an installed height of 1.75 inches to give them approximately 130 pounds of spring pressure. Maybe I should shoot for that 1.75 height.

 

[79jasper]

Everything I saw for the idi said 1.80

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[Hydro-idi]

I would build another short block with this cam,
the pistons should be cut to eliminate valve to piston contact.
my heads were machined to max out the recess in the heads, and I still had very slight contact without cut pistons.
this cam is awesome if you can get it right.

X2.

 

[cpdenton]

I have gone out and done some math in the 7 degree weather we had this morning.

The typ4 cam I have has lobe bases anywhere between 1.467 and 1.485. The lobes at maximum lift are all between 1.750 and 1.763.

So maximum lift of the cam lobe could be calculated at most being .298 inch.

Multiplied by rocker ratio of 1.5, max lift of any valve could be .447in.



Comp 910 springs bind at 1.28 and are rated at 323 pounds at 1.35in.

So take the open load rating @1.35in and add our maximum lift I figured of .447in and I come up with 1.797in.

At 1.85in the comp springs are rated at 94pounds of seat pressure. Quick math tells us that each .05in smaller adds 22.9 pounds of pressure.


So, setting the springs at 1.8inches will yield 117 pounds of seat pressure, which is 44pounds stronger than the stock springs are rated, and 125 Pounds stronger at 1.35 in max lift (compared to the stock cams max lift at 1.4)




I will be getting a valve spring micrometer and setting all my valve springs at 1.8in. I am curious how much valve recession contributes to needing to shim up the springs higher than we normally would.

Thanks for letting me talk this all out.

 

[typ4]

The easy way to state this is installed height factory is 1.80 iirc. So, get to that then add the .030 shim to the 910 spring, I was doing this with new stock springs with good results.
My next heads will have smaller stem valves if I can find them in the right length so the valvetrain is lighter.
And Im still working on a better close to "drop in" cam, but the next version will be a kit with springs and shims, also lifters by request.

 

[typ4]

CP, if that cam makes the valves hit let me know. I have a new one with less lift, 278 lobe lift.

On this subject, I have talked with a gent last month with an all stock engine, cam and all ,that is interfering on 3 cylinders after a valve job. Soooo these things are really close stock.

 

[cpdenton]

So Russ,

This cam has been around for a while from what I understand. Have people always needed to shave pistons and all this to make sure the valves don't get hit by them? Seems like folks have just recently started to have some of these problems.

Did something change with the cam grinder or grind?

I am also going to make sure recessing the valves did not change the amount of shims I need to make the correct shim pressure.


Also, what is the best way to check if I have interference before I start the engine? Install everything and turn it all over with some clay in tHere or something?


Thanks.