How far can the lash adjusters adjust?

Crazy_pilot · #1 07-05-2010, 07:36 AM

Looking at buying some Supertech valves on Ebay (link). The length stated is 92.10 mm for the intake and 92.70 for the exhaust. The stock valves I have on hand measure 90.12 (intake) 90.96 mm (exhaust). Can the HLA's take up ~2mm of length difference?

I'm going to contact Supertech directly about these valves, they don't appear on the catalogue.

Crazy_pilot · #2 07-06-2010, 04:25 PM

Bump for any idea? Supertech confirmed that they are valves for the EG33 with a +2mm length. Workable?

Cam · #3 07-06-2010, 04:35 PM

Just curious, what makes you want to increase the length of your valves? Do you have stock camshafts?

Since your camshafts are fixed (do not move relative to engine besides rotating) then the lobes will be in the same place when fully open (pointing towards the piston). From the tip of your cam lobe you only have so far to the top of the piston. Adding length to your valves could possibly take away your zero-interference condition. Just something to think about. Not sure if 2mm is too much, but if your heads have ever been resurfaced then that would make them even closer.

ZMan · #4 07-06-2010, 05:05 PM

Quote:

Originally Posted by Cam

Just curious, what makes you want to increase the length of your valves? Do you have stock camshafts?

Since your camshafts are fixed (do not move relative to engine besides rotating) then the lobes will be in the same place when fully open (pointing towards the piston). From the tip of your cam lobe you only have so far to the top of the piston. Adding length to your valves could possibly take away your zero-interference condition. Just something to think about. Not sure if 2mm is too much, but if your heads have ever been resurfaced then that would make them even closer.

I don't think he wants longer valves, rather the valves he wants to use happen to be a little longer.

Cam · #5 07-06-2010, 05:08 PM

Now that I read that again, you are definitely right

. My mistake.

I still don't think it's worth the risk. I doubt the lash adjusters would take up 2mm difference.

Crazy_pilot · #6 07-06-2010, 06:12 PM

Quote:

Originally Posted by ZMan

I don't think he wants longer valves, rather the valves he wants to use happen to be a little longer.

This is the case. I'm going to be replacing the head gaskets and refurbishing the heads and these valves look like an attractive option.

bazza · #7 08-20-2012, 08:26 PM

Did anyone ever test this for real and publish results? I know LAN's camshafts had lift figures of 8.1 mm and 9.3 mm intake and exhaust (from his site and discussions etc). Bare in mind stock is 7.1mm and 7.9mm lift intake and exhaust.

Which would mean the hydraulic lash can absorb:
* 2.0 mm intake side (base circle reduced from 32mm to 30mm)
* 2.8 mm exhaust side (base circle reduced from 32mm to 29.2mm)

I think the intake was only able to handle 2.0mm reduction in the base circle (1mm lift increase) due to "riding the journal" issues preventing the valve from closing - not sure how that works though, anyone care to explain? I'd assume that if this wasn't the issue, the hydraulic lash adjuster could handle 2.8mm increase on the base circle for the intake also.

Now based on the below figures concerning the journal sizes, I would've thought we could reduce the base circle to 28.4 mm (giving it 0.5 mm of room) and still be bigger than the journal (27.9 mm) giving intake lift of 8.9 mm and exhaust of 9.7 mm. Also Matt D's base circles were 28.95mm inlet and 28.60 m exhaust which based on my calcs gives him 8.6mm and 9.6mm... intersting.... trying to get my head around it.

For interest sake:

Camshaft journal OD from Tech manual:
#1 31.946 - 31.963
#2 27.946 - 27.963
#3 27.946 - 27.963
#4 27.946 - 27.963

Picture of stock cam next to Matt's regrinds:

Crazy_pilot · #8 08-21-2012, 05:48 AM

I never did end up buying the valves, on the advice of others that the EG33 top end is quite robust and shouldn't need more than a good cleaning to be factory fresh (which turned out entirely correct).

bazza · #9 08-21-2012, 08:44 AM

Quote:

Originally Posted by Crazy_pilot

I never did end up buying the valves, on the advice of others that the EG33 top end is quite robust and shouldn't need more than a good cleaning to be factory fresh (which turned out entirely correct).

Yeah I'm really only interested in an exact figure for what the stock lash adjusters can handle if the cams are ground and the base circle reduced, which is actually what the over length valves are for. Might see if I can measure one up on the weekend.