It's no secret that you can...
It's no secret that you can unlock power by porting your Mopar's cylinder heads. This month we'll show you three tricks to porting that you can perform yourself.
Porting cylinder heads is a blend of art and science, allowing more fuel and air into an engine's combustion chambers, and more exhaust gasses to exit, for a net increase of power and efficiency. And while maximizing the potential of a certain cylinder head requires experience, a flow bench, and likely a sonic tester, mild port work can be accomplished by the average mechanic if certain precautions are taken. We're not talking about performing an all-out race port job, but by removing a bit of material in certain key areas, the head's efficiency can be greatly enhanced.
This month we'll show you how spending a little time with a die-grinder and carbide burr can improve head flow and save you from paying someone else to port the heads for you. By matching the size and shape of the port to the appropriate intake or exhaust gasket, you can correct casting imperfections and smooth the transition of air from the manifold to the head. The bowl area of the cylinder head under the valve is also generally cast with extra material and imperfections, so cleaning the bowls is also time well spent. And finally, taking material out of the pushrod pinch area will improve intake flow without risking water jacket intrusion.
We're working on a pair of...
We're working on a pair of 906 heads that will be bolted on a 383 street engine, which is perfect for this type of port work. Though we'll be porting big-block heads, our techniques can be applied to any wedge-style, V-8 cylinder head. Gasket-matching ensures a smooth transition between the intake and head, and head and headers or manifold. It's generally safe to remove enough material from the intake and exhaust ports to match the shape of the factory gasket.
The next area that needs to...
The next area that needs to be addressed in most heads is where the intake port is narrowed to make room for the pushrod. Commonly called the pushrod pinch area, removing material from the port here will definitely increase flow and power.
The bowl area of the head,...
The bowl area of the head, beneath the valve seat when looking from the combustion chamber, is generally cast with extra material. We've also seen casting imperfections in this area, and protrusions that can be removed with a grinder. Be careful not to nick the valve seats!
Don't overdo it here, as it...
Don't overdo it here, as it can be easy to grind into a water jacket. You should just shape the bowl to match the circumference of the valve seat, removing enough material for smooth flow. An alternative to performing this by hand is to have a machine shop make a bowl cut on their valve and guide machine.
The pushrod pinch area is...
The pushrod pinch area is easy to measure with a gauge. Most cast-iron cylinder heads have plenty of material here, but make sure you measure each port individually as core shift can cause variances. Small block heads will be a little tougher to measure, so just take your time.
After porting with the die...
After porting with the die grinder and carbide burr, we used sanding cartridges to smooth the areas and remove nicks caused by the tool. This type of porting will definitely improve flow,....
....but isn't invasive enough...
....but isn't invasive enough to risk damaging the head. If you're not comfortable performing this work yourself, we suggest sending the work to a competent engine shop in your area.
Porting Combustion Chambers?...
Porting Combustion Chambers?
That's right. Part of porting cylinder heads is porting the combustion chamber as well. As the edge of the valve is shrouded by the combustion chamber, flow is impeded in that area of the valve. A simple fix for this is to simply trace the pattern of the head gasket onto the head, then take material away to give more clearance between the valve and the combustion chamber....
....This process will increase...
....This process will increase the size of the combustion chamber slightly, so that must be taken into consideration when calculating compression, but is easily accomplished with the same tools used for head porting. We keep a second-hand set of valves around and use them to protect the seats while grinding. Care must be taken to remove an equal amount from each chamber; otherwise volume will be inconsistent, possibly affecting performance. We suggest cc'ing the head after any chamber porting to ensure chamber volume consistency.