Solid lifters and shims

[NitroDann]

Yes, its a B6 with custom cams.

Dann

[wozzah1975]

Those clearances seem excessive when the engine is hot. On my bikes the clearances are set cold and are about 6 thou on the intakes and 10 thou on the exhausts

The clearance that the cam manufacturer specify are pretty standard hot clearances.

Woz

[GP]

The clearance that the cam manufacturer specify are pretty standard hot clearances.

Mazda says cold as far as I can find, I think someone needs to ask cam manufacturer to clarify

[noobee]

Awaiting your latest PM.

Ok how much do I need to spend to get a micrometer good enough to measure these in order to order new ones?


You have been great thanks,
Dann

$ 59 next weekend I think (ad on back of silicon chip magazine)

http://www.machineryhouse.com.au/M012

I dont think you need anything more expensive to reliably measure.I'd be wary of cheap digital calipers tho,some are definitely not consistent.or they may give consistent readings,but a little different size than the micrometers at the shim grinders.
been using any old feeler guages(read cheap !) to set up desmo heads for 30 years,always checked em against good micrometers (free from work) and never had a problem.

a manufacturer can tell you what cold and hot clearances are because they know the expansion rate of the materials they are using,they have engineers to calculate it and will measure finished assemblies hot to check.a cam grinder or aftermarket valve manufacturer usually doesnt have that luxury,thats why they mostly give hot clearances,its safe and accurate.

Mick

[GP]

a manufacturer can tell you what cold and hot clearances are because they know the expansion rate of the materials they are using,they have engineers to calculate it and will measure finished assemblies hot to check.a cam grinder or aftermarket valve manufacturer usually doesnt have that luxury,thats why they mostly give hot clearances,its safe and accurate.

So why can't you use Mazdas clearances?
I have read that large clearances can cause problems on these engines

[sailaholic]

non standard cams often equals non standard clearances.

Sent from my GT-I9100 using Tapatalk

[noobee]

a manufacturer can tell you what cold and hot clearances are because they know the expansion rate of the materials they are using,they have engineers to calculate it and will measure finished assemblies hot to check.a cam grinder or aftermarket valve manufacturer usually doesnt have that luxury,thats why they mostly give hot clearances,its safe and accurate.

So why can't you use Mazdas clearances?
I have read that large clearances can cause problems on these engines

all else being equal,shouldnt be a problem.but we're not talking about all else being equal.me,i'd set em cold(only 'cause i'm too lazy for the rushing and the burning) but Dann's a fast worker and being young,any burns will heal fast!
Dann yes check cam caps(you prob already done that)the 14's are a worry,hopefully they are just settling.
Mick

[wozzah1975]

a manufacturer can tell you what cold and hot clearances are because they know the expansion rate of the materials they are using,they have engineers to calculate it and will measure finished assemblies hot to check.a cam grinder or aftermarket valve manufacturer usually doesnt have that luxury,thats why they mostly give hot clearances,its safe and accurate.

So why can't you use Mazdas clearances?
I have read that large clearances can cause problems on these engines

In theory if the cam does what it's suppose to do (eg: make more power) then the valve etc temps will change from standard, therefore all your factory specs go out the window.

A cam manufacturer grinds their cam lobes for a specified running clearance
In other words the specs on the cam are rated at that specific running clearance. Excessive clearance on any engine is a problem, but I'd hardly call .004-.005" excessive. It use to be a pretty common practice on a race engine to make the exhaust valve clearance wider than specified to close up the exhaust timing for a lower torque curve (old trick!).

When I put together my race engine I actually heated a spare exhaust valve to see how much it expanded to calculate the clearance, it was very surprising how much it actually grew in length at running temperature.

Woz

[NitroDann]

Yeah big custom cams. Im contacting a bloke regarding the cam caps in the next few days after Ive found a good measuring device, or borrowed one. Ive got most of tomorrow off.

Dann

[tbro]

Compensating for a Cold Engine When Adjusting Mechanical Lifter Valve Lash

When installing a new cam, the engine will be cold but the lash specifications are for a hot engine. What should you do on an engine with mechanical lifters? There is a correction factor that can be used to get close.


Engine respond to the actual movement of the valves. Since the valve cannot move until all the running clearance (valve lash) has been taken up, the amount of valve lash you use affects the engine’s performance.

The alloys of certain engine parts can be affected by thermal expansion in different ways, therefore the amount of correction factor to the lash setting depends on whether the cylinder heads and block is made out of cast iron or aluminum.

You can take the “hot” setting given to you in your cam manufacturer's catalog or cam specification card and alter it by the following amount to get a “cold” lash setting:

• Iron Block Iron Heads – Add .002˝

• Iron Block Aluminum Heads – Subtract .006˝

• Aluminum Block Aluminum Heads – Subtract .012˝

Remember this correction adjustment is approximate and is only meant to get you close for the initial start up of the engine. After the engine is warmed up to its proper operating temperature range, you must go back and reset all the valves to the proper “hot” valve lash settings.

This is from Crane Cams.

Terry

[wozzah1975]

Compensating for a Cold Engine When Adjusting Mechanical Lifter Valve Lash

When installing a new cam, the engine will be cold but the lash specifications are for a hot engine. What should you do on an engine with mechanical lifters? There is a correction factor that can be used to get close.


Engine respond to the actual movement of the valves. Since the valve cannot move until all the running clearance (valve lash) has been taken up, the amount of valve lash you use affects the engine’s performance.

The alloys of certain engine parts can be affected by thermal expansion in different ways, therefore the amount of correction factor to the lash setting depends on whether the cylinder heads and block is made out of cast iron or aluminum.

You can take the “hot” setting given to you in your cam manufacturer's catalog or cam specification card and alter it by the following amount to get a “cold” lash setting:

• Iron Block Iron Heads – Add .002˝

• Iron Block Aluminum Heads – Subtract .006˝

• Aluminum Block Aluminum Heads – Subtract .012˝

Remember this correction adjustment is approximate and is only meant to get you close for the initial start up of the engine. After the engine is warmed up to its proper operating temperature range, you must go back and reset all the valves to the proper “hot” valve lash settings.

This is from Crane Cams.

Terry

That is specific for v8 push rod engines, compensating for growth in the head and block where alot more comes into factor, eg: head and block grow different to push rods for a start.
Completely different scenario for shim/bucket OHC designs.

Bottom line though is correct, guide only and set HOT!!

Woz

[noobee]

I believe in this instance they are talking about pushrod engines,thats why they mention block composition.not applicable to OHC engines.
Mick

[NitroDann]

Yeah Im just going to borrow a good micrometer. Probably tomorrow. And order some shims.

Thinking about going bigger cams also. Quite a bit bigger.

But for now just a lash adjustment, and a new air filter. The current one is costing me heaps of power.

Dann