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Big valve head issues with clearances

Sweep

New member
Joined
Dec 29, 2014
Location
Peterborough - UK
Bare with me here as headwork is new to me.
I've recently had my 530 cut to fit 38/46mm valves, I also have a KG004 cam and double valve springs from KGtrimning, although the springs were probably overkill.
I got it all assembled last night and just went back out to check the valve clearance.
With the first two lobes at TDC so-to-speak, I cannot get even my thinnest feeler between the cam? Am I missing something or even done something incorrect?

Ben.
 
With the valve seats recut to fit the larger valves. The valves are higher into the head requiring a reshim. In extreme cases the stems of the valves may need to be cut shorter.
 
With the valve seats recut to fit the larger valves. The valves are higher into the head requiring a reshim. In extreme cases the stems of the valves may need to be cut shorter.


Sitting higher in the head depends if they put in new seats or cut the stock seats. A good shop will set the installed height the same.


Having said that, yeah, new cam, reshim, no question about it.
 
With the valve seats recut to fit the larger valves. The valves are higher into the head requiring a reshim. In extreme cases the stems of the valves may need to be cut shorter.

Exactly this.

Is the camshaft a stock base circle cam, or is it smaller?
 
Cheers chaps. How do I go about working out what size shims I'd need if there's currently no clearance? Should I take the shim out and measure between the lobe and top of the follower?

I'm not sure I understand regarding the cam being a stock base circle?

Ben.
 
You have to depress the bucket and remove the shims and then measure them. Subtract the clearance needed from the thickness of the shim measurement. Then install shims that are the new thickness needed. That should get you started.
 
Side note; If you bothered with those little rubber "valve hushers", make sure you're compressing them when measuring, or better still remove them.
 
Side note; If you bothered with those little rubber "valve hushers", make sure you're compressing them when measuring, or better still remove them.

Interesting, I'll give that a whirl!

For what it's worth, I measured from the top face where the cam cover bolts to down to the top of the valve stem on both this head, and a spare I have, the new valves are sitting 2 higher than the spare stock head.
 
2mm?!?!?!?!
With a stock base-circle camshaft, the top of the valve stem should be 1.023"/26mm from the valve cover surface. You can only go ~0.5mm either way of that.
 
I'm not sure I understand regarding the cam being a stock base circle?

Ben.

Some performance cams make the base circle smaller to get more lift for a given camshaft blank. or when a cam is ground on a OEM core. This has some advantages, and some disadvantages.

AnnotatedCamLobeSmall.gif


I do not personally know the specs of the KG004 camshaft, so I can't really say how the head should be set up.
 
2mm?!?!?!?!
With a stock base-circle camshaft, the top of the valve stem should be 1.023"/26mm from the valve cover surface. You can only go ~0.5mm either way of that.

Yes, 2mm! Shortening of the stem will overcome this issue I assume?
I'll measure the cam base circle and see what it comes out at.
 
Yes, 2mm! Shortening of the stem will overcome this issue I assume?
I'll measure the cam base circle and see what it comes out at.

Ok, that's not good news.

Okay so I have about 24.5mm from the top of the stem on the inlets and 24mm on the exhaust.
Cam base circle measures 36mm.

That's really not good news!

Quick follow up question: What valves are you using? KL racing, KG, etc?

If using stock length valves (KL Racing, KG, REV from Gary), see below.

Short answer: The machine shop who did the head work screwed up and machined the valve seats too deep into the head. This is very common when the shop isn't paying attention. The valve stem heights should always be kept to the stock height unless a smaller base-circle cam is being used.

Unfortunately, removing 2mm from the tips of the valves most likely isn't possible. I think this would result in the lifter/bucket/tappet hitting the top of the spring retainer, which will drop a valve into the engine!

Ways to fix this:

-Take it back to the machine shop, this is priority. They made the mistake. They will have to replace all of the valve seats and re-machine the seats. Let them know that the valve stem tips should be 26mm from the valve cover surface on the head!

- Find another 530 head and start over again.

-Find a camshaft that has a base circle that is 32-34mm. You will still need the valve tips ground down for this to work if the base circle is 34-33mm. Removing ~1 to 1.5mm from the valve stem tips is about the limit, in my experience.
 
Ok, that's not good news.



That's really not good news!

Quick follow up question: What valves are you using? KL racing, KG, etc?

If using stock length valves (KL Racing, KG, REV from Gary), see below.

Short answer: The machine shop who did the head work screwed up and machined the valve seats too deep into the head. This is very common when the shop isn't paying attention. The valve stem heights should always be kept to the stock height unless a smaller base-circle cam is being used.

Unfortunately, removing 2mm from the tips of the valves most likely isn't possible. I think this would result in the lifter/bucket/tappet hitting the top of the spring retainer, which will drop a valve into the engine!

Ways to fix this:

-Take it back to the machine shop, this is priority. They made the mistake. They will have to replace all of the valve seats and re-machine the seats. Let them know that the valve stem tips should be 26mm from the valve cover surface on the head!

- Find another 530 head and start over again.

-Find a camshaft that has a base circle that is 32-34mm. You will still need the valve tips ground down for this to work if the base circle is 34-33mm. Removing ~1 to 1.5mm from the valve stem tips is about the limit, in my experience.


Okay that makes sense, annoying as it may be.

So the exhaust valves are KG, and the inlets are from classicswede over here, both are stock length.

Do you know of any cams that use the smaller base circle?
For what it's worth, spec is HY35 on a custom stainless manifold, big front mount, 60lb DEKA and 012 AMM and 3" downpipe.
 
Okay that makes sense, annoying as it may be.

So the exhaust valves are KG, and the inlets are from classicswede over here, both are stock length.

Do you know of any cams that use the smaller base circle?
For what it's worth, spec is HY35 on a custom stainless manifold, big front mount, 60lb DEKA and 012 AMM and 3" downpipe.

KL Racing (Which Classic Swede carries) T2 should work. They suggest 2.5mm lash caps, and since your valves are ~2mm taller than stock.. it should work just fine without them.
https://shop.klracing.se/sv/artiklar/volvo-8v-turbo-kamaxel-klr-t2-2.html

https://www.classicswede.co.uk/B23230_stage_2_Turbo_camshaft/p1733344_16462873.aspx

T3 would also work, and might require 1mm lash caps in your setup. 1-1.5mm lash caps are very commonly used on air-cooled VWs, and they have the same size valve stem and tip:
https://www.classicswede.co.uk/B23230_stage_3_Turbo_camshaft/p1733344_17661768.aspx
 
I stock cams with a smaller base circle however that does not solve your issue fully. You would need to add a 2mm washer also under your springs to bring the spring pressure back up.

Replacing the seats and doing it correctly is the right way of solving this
 
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