Just heard about shimming

[Sam's GSX]

Ok, I have my block and head together, running bc272 and manley single springs, I had never heard about shimming till this morning, everything is installed and together, on stock seats and retainers,
So do I need to split the block and shin the springs?

 

[rabenne]

Def dont have to split the block. I assume you are talking about shimming the valve springs for proper installed height?

There are valve spring compressors that bolt into the cam caps. You can then remove the springs 1 at a time with that tool, and you wont have to split the block/head.

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[Sam's GSX]

Oh, I forgot I actually have that, I used a large c clamp to do the springs before. Ok, so I couldn't find any video footage of it, but are the shims something you can order? And is there a height for new springs? I definitely dont want to take the spring to some kind of shop to check them, I was ready to start the swap before I read about this.

 

[lasthope05]

On bc272 is not really necessary or critical.

 

[rabenne]

Kiggly sells shims:
https://www.kigglyracing.com/product-page/race-only-valve-spring-shim

You can probably find shims from other engine models that work on Summit or JEGS

The Seat Pressure @ installed height is where shims come into play. If your valve seats have been cut, then your valve would go up higher into the head when on the cam's base circle (aka valve closed position). This means when the spring is installed, it is compressed less than it "normally" would be. Compressing it less means it is producing less force because of that Hooke guy... F=-kx. By shimming the seat, you can increase the amount of spring pressure on the valve (x in the equation increases as you shim the seats). The key is getting proper seat pressure so your valves operate the way they are supposed to. Can you say f-it and send it anyway? Yes, and many people have. If you know for a fact your head has never had a valve job, you are probably safe. If you put it together and end up with symptoms of valve float, you will know where to start looking... Worst case scenario your combustion chamber hosts a piston & valve party*

Manley provides the specs below:

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[Sam's GSX]

I'm guessing the top one is single and the bottom is dual springs,
Ok I'm out of town and don't have the machine shop paperwork with me, but he definitely did something with the valves that left a green residue on them.
I then lapped the valves.
Hmmmm, this is definitely a cloud over me now, I had looked into valve springs a lot, and truly never heard about this, with my financial situation right now, I cant afford to buy specialty equipment to measure them, nor could I afford to take it to a machine shop.
I could possibly buy mild shims without measuring, I hate talking in term like that, because that's not how I do things, I'm just in a situation where I truly can't afford anything extra.

I was looking at kiggly and it looked like they were $9.50 for each shim, but stm has some for $9.50 for a set, so at least it wont be $150 for them

 

[rabenne]

Don't let me discourage you too much, lots of people have dropped-in springs with no problems. Your setup may work just fine, even if its not setup perfectly... There is clearly some leeway or people wouldn't be getting away with doing it all the time...

Hopefully someone else can chime in and give you some solid advice... sorry, I am not a reliable source of anything*

 

[Sam's GSX]

Oh no, you're fine, I'd rather people tell me the truth than suger coat it and my valves crash into the pistons,
I have multiple different calipers and other measuring equipment, so if its something I can do without splitting the block (or removing the valves obviously) then i dont mind doing the work.

 

[DSMPT]

You don't even need aftermarket valve springs for the BC 272s. The BC 272s are designed to work with the stock valve springs. Any aftermarket valve springs would work just fine.

I was looking at kiggly and it looked like they were $9.50 for each shim, but stm has some for $9.50 for a set, so at least it wont be $150 for them

You are confused. It's not for each. It's 9.50 for a set of 16 shims. I have ordered them.

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[Sam's GSX]

Ok so you are saying they are not necessary (the shims)?
And yeah sorry I worded that weird, what I meant was, because I found them for 9.50 at stm, that means the ones from kiggly must be 9.50 aswell (for the whole set)
I personally dont think I need to rev past 8k, that actually what I was looking into when I found out about them, I was wondering what others with this combo were running, rpm wise.

 

[1990TSIAWDTALON]

You will be fine. Don't worry about the installed height with that set of cams like Hiroshi says, unless for some reason someone has cut the valve spring seats like @rabenne mentioned. Your good.

 

[Sam's GSX]

Ok cool, thank you