Head porting and polishing, can I leave the valves in?

Hi! I got my new aluminum head in today and I would like to port it and polish the impurities in the combustion chamber a bit. Do I have to remove the valves to do it?

You could, but you could also do more damage! How are you going to account for matching the CC's? Since the only two I know of are Edelbrock and Hesco, I can't imagine them having any "impurities or imperfections"!

Ok. I guess I wrote it in a bit of a hurry. I didn't mean impurities, more like roughness from casting, I've heard that polishing the combustion chamber can help keep the chamber clean. I haven't decided on what to do yet. Is there a lot to gain from matching the ports and the gasket? The improvements over the old renix are already pretty obvious.

The chambers get matched to each other (not to the gasket while that can be done)!

I think I'll just leave it alone. Don't feel like fing up the head....

Some roughness in a cylinder head (ports/chambers) is acceptable and even beneficial because it creates turbulence which promotes better mixing of the air/fuel mixture. Unless you see major casting flaws (think every 4.0 intake manifold you've ever seen. *roll eyes*) I'd say leave it alone. Worst case scenario, I'd say get get some buffing wheels and compound and polish the chambers to a mirror like shine. I've heard of some engine builders doing this, the theory being that this directs heat away from the chamber roof, reducing carbon fouling and heat that is transmitted to the coolant. I'd still say remove the valves and clean everything really well if you plan on doing this.

Gasket matching ports is a bit more involved. To do it properly, you need to make a template out of a piece of steel or aluminum and bolt it into place, torqued to spec, with the gasket installed and mark out the areas where material needs to be removed. This is because compressing the gasket will cause it deform a bit, which can cause you to remove too little or too much material.

Since you have an aluminum head, have you considered upping the compression ratio? The easiest way to do this that I know of would be custom-made pistons, but there's plenty of companies that make them. I know that's typically a engine rebuild procedure and 4.0's run forever beforw they need a rebuild, but with an aluminum head you should be able to run around 9.5:1 on regular, ol' low-octane pump gas, safely, and with no real drawbacks other than extra power...

Far easier decking the head to up compression than aftermarket pistions. Especially for just a 1 point increase. With the proper gasket you can almost get 1 point.
Because the 4.0 is a low rpm motor i wouldnt worry to much about gasket matching unless there is a serious difference and even then i would just blend the edges abit.

Thanks for your input JeepNoob. I'll leave it as is, I got the old head of today (1990) and boy it looks like a hackjob compared to the edelbrock. This is for a stroker, I'm looking at a 9.7cr, l'll be running 95 octane with 98 available if I run into problems.

Borgli said:

Thanks for your input JeepNoob. I'll leave it as is, I got the old head of today (1990) and boy it looks like a hackjob compared to the edelbrock. This is for a stroker, I'm looking at a 9.7cr, l'll be running 95 octane with 98 available if I run into problems.

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I'm curious as to why you don't want to run reg(87)?

95 is the lowest available where I live at the moment. I've heard that 95 EU is 91 us? They use a 10% ethanol mix here.

When porting cylinder head combustion chambers, especially if you want to protect the valve job, you should have some scrap/old valves to put in.

That way, you don't risk messing up the new valves you want to use.

When porting runners, yes, you have to remove the valves, and you want to do this before any valve job work is done.