Shaved head and manifold/block interference

[2long]

As I am installing a low port head that was previously shaved, I am having trouble with the rocker gear geometry (so I am using one shim under the rocker pedestal) and also with the exhaust manifold now interfering with the block head so that it can't be tightened up.  Is it ok if I shave the manifold flange so it fits?  Does this mean my compression ratio is going to be really high?

 

Dan

Edited December 15, 2018 by 2long

[ed_h]

Dan--

Maybe you already know this, but shimming the rocker pedestals will alter the geometry on the valve side of the rocker.  Enough to matter?  It's a matter of opinion, but to maintain factory design geometry with a shaved head, you can use shorter push rods.

Ed

[Ian Vincent]

Dan,

when I first rebuilt my engine the head was shot and the only replacement I could find at short notice had been seriously shaved. I put 3mms shims under the rocker pedestals and didn't have any problems. 

I had to open out the combustion chambers to get the CR down to a reasonable figure for road use.

shaving the exhaust manifold face won't affect the CR.

rgds Ian

Edited December 15, 2018 by Ian Vincent

[Dick]

Also with an excessively shaved head, make sure that there is clearance between the underside of the head extention where the thermostat fits and the waterpump.

[iain]

It’s perhaps easier to relieve  the interference by using a small grinder on the block. It’s normally the external webs on the manifold side that cause the interference with the manifold.

Iain 

[2long]

Gulp - DIck's comment is spot on and the top of the water pump/housing is actually touching the underside of the head extension where the thermostat fits.  So off with the water pump to grind the top of it a bit to create a bit of clearance, and double check the torque of the head?  Or do I have to redo the head gasket?

Edited December 17, 2018 by 2long

[Motorsport Mickey]

Hi Dan,

No big deal with the juggling of the clearances.

As Dick points out above the early cylinder heads when skimmed often touch on the top of the waterpump housing. TerriAnn does a good job of listing the different heads and the different ways to gain those clearances...see here. 

http://www.tr3a.info/FAQ_heads.htm

On the later 3/4/4a  heads there was a chamfer cast into the head that gave the necessary clearance, you can emulate that with hand tools gaining the clearance needed, go easy at it and all will be well. Yes the block will respond well to a little dressing on the "flange" areas (where there's a thickening web on the block) to give clearance against the manifold that intrude in there.

I take it the head is on and torqued up, if you can get the water pump off without undoing the head I would think you may have got away with it, but if it's immovable I would undo the torque on the head in reverse order and just "ease" the head upwards giving easier access to remove the water pump. If needed the head can be removed entirely to allow you to attack the thermostat casting area underneath. The gasket only knows it's been compressed, but it's not been heated and so no setting or changes should have happened to it's make up. When the water pump is back on and you have clearance there just retorque the head as normal using the correct sequence back up to the 105.

regards Mick 

 

Edited December 17, 2018 by Motorsport Mickey