MidnightBlade
Shiftin' Smooth
What all is possible to do to the stock heads to get a few more ponies out of a 94 factory turbo? Set all costs aside, just looking for some insight on a future build ill be working on.
Cleaning up the castings to a smooth surface is never a bad idea. Gary will be along to fill you in on his experience with working on the ports.
Heath
Gary is there a area of the exhaust port that a person should really stay away from when porting???
As far as water jacket areas??
The easy answer is yes and no... This is what I mean... Looking at the exhaust port as the head sits on the engine. That top mount there is no cooling surrounding that area. Only under the floor of the exhaust port and the sides is there coolant working on them. At the thinnest area of the roof the cast iron is just over 3/8 thick solid metal. 3/8 equals 0.3750. To measure this you need a very special dial caliper to reach in for this. Nice tool to have too. So any material removel on the top should be little more than cleanup to the surface finish you want. But as for the radius just after the seat you need to smooth that out to increase flow. I use a burr on the back side. I can supply the type later on but its best done opposite of the normal way we use a burr on the tip. Remember these are not gasser engines where porting can ruin the heads. Also we never turn much higher rpm than 3500 rpm. So push this higher and get away with it but for how long is still up for thoughts. These bottom ends are heavy and designed for about 3800 rpm max. I think Mel can tell you what the pumps are going at that rpm. Our engines rpm is decided by the amount of fuel being pumped into it. No throttle body or carb butterflys cutting off the air. We want fuel for power and rpm. The design of the injection pump is to get fuel to the engine and limit the rpm be gorener taking fuel away from the engine at the pumps designed rpm red line. Recall some idi engines like found in a bus or big rig dump truck have a red line of around 2500rpm. Install an injection pump off a pickup truck with a differant gonener spring and see that same engine rev to 3800 rpm. Then go a litle more and install a gm gonener spring and see the rpm jump to 4400 rpm... Smar engine doing much more rpm just by a spring change...![]()
I have access to a flowbench and all the tools required for the port and valve work, one of my good friends is alao a pro at port and machine work so this will be a very low cost build. Im also pondering the design of some custom intake and exhaust manifolds for better flow to and from the head. If everything goes well, ill be getting the heads pulled and start the porting tonight after work