Polishing and Porting?

[Basil]

Is this something that can be dome athome with teh right kit, or does it need to be done by a machine shop? Any good references if it can me done at home?

Second question - how much does it help?

 

[RonMacPherson]

take a new manifold gasket and mark where it fits on the cylinder head, use dykem(valve bluing or other such marker) to draw around the orifices of the gasket to the head, take a grinding tool and carefully remove the metal to where the marks are on the head, using a tapered pathway, and finish with a good polishing wheel don't forget to use the gasket to do the same thing on the manifold so you're matching the manifold to the head.

There used to be several good do it yourself sites on search engines for "porting and polishing" cylinder heads.

HTH

 

[eejay56]

Basil,
Check this out DIY Head Porting

 

[DrEntropy]

And Clive Trickey (no, really!) had a book on modifying LBC heads. Slanted to BMC units but the info is applicable.

https://www.jerrysscarcebooks.com/ap_clive_trickey.html

 

[foxtrapper]

Lets start with your second question first, as that's the most important one. How much does it help? Overall, not much. The more mild the engine and mild the driving, the less the gain. To the point frequently of being undetectable. A header will gain you much more than a porting and polishing job typically.

Not that some head work can't be effective. Starting with the valve job. A good multi-angle valve job improves things across the board. If there is a bad mismatch between runners, this can gain you a good bit. As well some shrouded areas in the head.

Porting is easily measured and done by a homeowner with even a dremel tool. Look for places that have a step in the way of the flow, and fix it. Don't bother with steps going the other way, as they hardly affect things at all.

Shaping shrouded ares can also be done by a homeowner with a dremel tool. But make sure you're doing things that actually work. Don't try to figure it out on your own, find a good reference. Otherwise you'll typically make things worse, or can accidently destroy the head by grinding through to the water jacket. Some areas are trickier than others. Removing a shrouding lip in the combustion chamber is easy. Pocketting work down in the valve bowl is much harder to do.

As for polishing, don't bother. It's a fractional gain on high end engines. It's a negligible gain to even performance reducing on a street driven engine.

 

[trrdster2000]

Basil, all good advise above. I can give you my experience on the TR 4 cylinder heads and you can take something away with that. Open the intake and exhaust to match the gasket, polished the exhaust on the value side along with the gasket side, leave the intake alone, as roughness helps in the tumble effect of gases into the combustion chamber. The area in the combustion chamber received very little work, but one important factor was around the spark plug area, round out the squared off area to enable the spark to spread out better. I took .100 off the head, being a bit safe, I think the book says .125. When finished I had a smooth and very quick engine, that was with all standard carbs and cam. That was the wife's car, on mine I did the same thing, EXCEPT, 2 inch SU's, Isky .428 lift cam, and value springs. Ran rough at idle, but after 2800 RPM's, hang on. I would not recommend this for street or cruising.
Wayne

 

[Monkeywrench]

Not that some head work can't be effective. Starting with the valve job. A good multi-angle valve job improves things across the board. If there is a bad mismatch between runners, this can gain you a good bit. As well some shrouded areas in the head.

As for polishing, don't bother. It's a fractional gain on high end engines. It's a negligible gain to even performance reducing on a street driven engine.

Basil,

There is some good advice in this thread. For a street only motor stick with a simple gasket match, clean up any casting flash, and get a very good valve job. Anything more is a waste on a street engine.

As was already said,polishing will hurt you on the intake side. You can expect very small gains by polishing the chamber and exhaust port, but it's not worth the time unless you plan on racing.

Now if you're building a race motor, then a good cylinder head makes all the difference in the world.

 

[DougF]

Another reference is Kas Kasner's competition manual. Good information material regardless of the degree of build you are planning.

 

[vagt6]

As you may know, Dave Vizard's manual goes into great detail on head work, Basil. I've got a .pdf copy if you wish, just yell.

--Mark