[larry]

QUESTION ABOUT MILLING OF A HEAD .070. WHAT IS DONE ABOUT THE DEVELOPING TIMING SLACK. HOW WAS THAT MANAGED?

 

[Unknown User]

Check out The Datsun Z Garage.
Basically, shims are placed under the springs and cam towers.

> QUESTION ABOUT MILLING OF A HEAD .070. WHAT
> IS DONE ABOUT THE DEVELOPING TIMING SLACK.
> HOW WAS THAT MANAGED?

 

[norm]

> QUESTION ABOUT MILLING OF A HEAD .070. WHAT
> IS DONE ABOUT THE DEVELOPING TIMING SLACK.
> HOW WAS THAT MANAGED?
Larry look at my response to shaving head for compression on this forum it explains in detail what i did!

 

[Unknown User]

> QUESTION ABOUT MILLING OF A HEAD .070. WHAT
> IS DONE ABOUT THE DEVELOPING TIMING SLACK.
> HOW WAS THAT MANAGED?

People put shim's under the cam towers. This isn't the best way to get compression though, because you then have to change the rocker arm angle and have to find the proper size valve stem lash pads which can be kind of expensive buying a lot of different sizes and getting the right ones. This type of adding compression isn't recomended, it's better to get a new piston to do it right and you will prob. get more cam wear doing it the other way not to mention valve guide wear. The shims are really good for using when small amounts are taken off the head during normal resurface during the heads long life on the engine and it's a chancy shortcut to higher compression at best. I wouldn't do it.

 

[Unknown User]

Re: how high ?

> People put shim's under the cam towers. This
> isn't the best way to get compression
> though, because you then have to change the
> rocker arm angle and have to find the proper
> size valve stem lash pads which can be kind
> of expensive buying a lot of different sizes
> and getting the right ones. This type of
> adding compression isn't recomended, it's
> better to get a new piston to do it right
> and you will prob. get more cam wear doing
> it the other way not to mention valve guide
> wear. The shims are really good for using
> when small amounts are taken off the head
> during normal resurface during the heads
> long life on the engine and it's a chancy
> shortcut to higher compression at best. I
> wouldn't do it.

Mine has apparently been through a performance rebuild with high compression. From the info I've got, this was accomplished with both flat top pistons and shaving (maybe resurfacing?) the head. That leads me to think the compression must be skyhigh, yet it drives beautifully. No pinging.
I am told the intake and exhaust are larger than stock(?)

What do you guys make of this? How high is my compression?

 

[240Dave]

Need more info

> Mine has apparently been through a
> performance rebuild with high
> compression. From the info I've got, this
> was accomplished with both flat top pistons
> and shaving (maybe resurfacing?) the head.
> That leads me to think the compression must
> be skyhigh, yet it drives beautifully. No
> pinging.
> I am told the intake and exhaust are larger
> than stock(?)

> What do you guys make of this? How high is
> my compression?

Just saying you have flat top pistons and a shaved head isn't really that much info. Static Compression ratio, which is what we're talking about concerns piston diameter/dished or domed or flat top/stroke/head cc/head gasket cc
Please post your piston diameter/crank stroke/type of head i.e. E88, P79, etc.../How much was shaved/Type of head gasket (stock, HKS, other).
So, repost with that info, then we may be able to help you.

 

[Stan]

> People put shim's under the cam towers. This
> isn't the best way to get compression
> though, because you then have to change the
> rocker arm angle and have to find the proper
> size valve stem lash pads which can be kind
> of expensive buying a lot of different sizes
> and getting the right ones. This type of
> adding compression isn't recomended, it's
> better to get a new piston to do it right
> and you will prob. get more cam wear doing
> it the other way not to mention valve guide
> wear. The shims are really good for using
> when small amounts are taken off the head
> during normal resurface during the heads
> long life on the engine and it's a chancy
> shortcut to higher compression at best. I
> wouldn't do it.

 

[Unknown User]

Thats all I got Dave.

> Just saying you have flat top pistons and a
> shaved head isn't really that much info.
> Static Compression ratio, which is what
> we're talking about concerns piston
> diameter/dished or domed or flat
> top/stroke/head cc/head gasket cc
> Please post your piston diameter/crank
> stroke/type of head i.e. E88, P79,
> etc.../How much was shaved/Type of head
> gasket (stock, HKS, other).
> So, repost with that info, then we may be
> able to help you.

Thats all I got Dave. Sketchy details, no specifics.This was my cousin's baby, I don't doubt it when he says he spent a lot of money on the motor.

It's a 76 L28. Beyond all that was described earlier, I'm told it also has a mild cam and the ports have been cleaned up. It has a 6-into-2 header and 2.5in exhaust. Nothing exotic like a HKS head gasket or anything like that. The intake system and fuel injection are stock.

Any guesses what the compression might be? How many horses does a set-up like this typically produce?

Thanks in advance. simon76z