A nice little 3.8 build....my own
08-12-2008, 12:06 PM
#1
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Thread Starter
A nice little 3.8 build....my own
I was going through some pictures and thought I would post some of my rebuild as we talk about what it takes to build a strong TT motor. Aside from the obvious things like head studs, oil pump, rods etc.
One of the problems with punching the motor to a 3.8 is the spigot opening and the amount of sealing surface for the original oring. What you will find is there is not a proper amount of surface to seal the cylinder. So we have to machine the inside of the spigot and custom fit special orings to seal against the surface of the barrel. Notice the Carrillo rod hanging out.
The next picture is the Piston itself. Here we have machined a 2 step copper flame ring into the head. Notice how the piston protrudes past the barrel. This was done only on the 993TT so that the combustion mark was above the sealing surface of the head to cylinder mark. Additionally we have fitted a two ring system. The first ring seals the cylinder to the head, the second one is based on its end to keep the head from shifting. So imagine the head starts to lift, the ring stays in the path of the combustion as not to destroy the surface and or leak. If you didn't have the ring on end like this as the head came down it would also shift and move causing a leak. Both the cylinder and the head have to be machined together.
Notice the reliefs in the piston to accommodate the new larger valves?
This next pictures shows the enlarged valves, twin plugging and the grove for the flame ring.
The next picture is the process we do to the heads that strengthens it up as not to concave the hole around the stud in allowing the TQ setting to be skewed to the head. Once the head is heated and boost is applied the head will grow and expand even though the head is secured with the studs. In time this pressure will pull the metal in allowing this area to weaken and not be flat. By welding in the edges and machining them this weld goes down the side. It keeps the integrity around the head stud holes.
next pic....porting and flowing the heads. People often leave HP on the table. With some work and a flow bench and a whole lot of hours the heads can pick up significant lost HP. Notice the clean up work and blend around the guide.
Last but not least, the springs and retainers. I can not tell you how many factory heads we pull apart and see the spring walking on the seat. Very few springs are set correctly even from the factory. Additionally few actually pay attention to coil bind of the spring and simply throw cams in hoping for the best or not even thinking about it. Originally i did a very aggressive set of cams that were looking for very high RPM so bind and float was a very important issue to resolve. We use custom springs and Ti retainers.
I will continue to post pics as I find them or as we get caught up and progress continues.
One of the problems with punching the motor to a 3.8 is the spigot opening and the amount of sealing surface for the original oring. What you will find is there is not a proper amount of surface to seal the cylinder. So we have to machine the inside of the spigot and custom fit special orings to seal against the surface of the barrel. Notice the Carrillo rod hanging out.
The next picture is the Piston itself. Here we have machined a 2 step copper flame ring into the head. Notice how the piston protrudes past the barrel. This was done only on the 993TT so that the combustion mark was above the sealing surface of the head to cylinder mark. Additionally we have fitted a two ring system. The first ring seals the cylinder to the head, the second one is based on its end to keep the head from shifting. So imagine the head starts to lift, the ring stays in the path of the combustion as not to destroy the surface and or leak. If you didn't have the ring on end like this as the head came down it would also shift and move causing a leak. Both the cylinder and the head have to be machined together.
Notice the reliefs in the piston to accommodate the new larger valves?
This next pictures shows the enlarged valves, twin plugging and the grove for the flame ring.
The next picture is the process we do to the heads that strengthens it up as not to concave the hole around the stud in allowing the TQ setting to be skewed to the head. Once the head is heated and boost is applied the head will grow and expand even though the head is secured with the studs. In time this pressure will pull the metal in allowing this area to weaken and not be flat. By welding in the edges and machining them this weld goes down the side. It keeps the integrity around the head stud holes.
next pic....porting and flowing the heads. People often leave HP on the table. With some work and a flow bench and a whole lot of hours the heads can pick up significant lost HP. Notice the clean up work and blend around the guide.
Last but not least, the springs and retainers. I can not tell you how many factory heads we pull apart and see the spring walking on the seat. Very few springs are set correctly even from the factory. Additionally few actually pay attention to coil bind of the spring and simply throw cams in hoping for the best or not even thinking about it. Originally i did a very aggressive set of cams that were looking for very high RPM so bind and float was a very important issue to resolve. We use custom springs and Ti retainers.
I will continue to post pics as I find them or as we get caught up and progress continues.
08-12-2008, 01:16 PM
#4
Rennlist Lifetime Member
Thread Starter
LOL, yes it sure is!! I love this little car. I can't wait to drive it.
Street and track. It has 9K on the clock now, all track miles. So the car is set up for it. I originally built the motor with the track in mind and have since toned it down so it can be on the street as well. The cams were the biggest issue for street, so I am using a little less profiled cam. It still has huge vlaves, ports and so on. I plan on using a pretty good size turbo, leaning towards something the size of a Gt3078. Haven't made my mind up totally on that.
Funny thing is, it will make more than Monster did and hopefully on race fuel lots more than my 997TT
It is my wifes car though
Street and track. It has 9K on the clock now, all track miles. So the car is set up for it. I originally built the motor with the track in mind and have since toned it down so it can be on the street as well. The cams were the biggest issue for street, so I am using a little less profiled cam. It still has huge vlaves, ports and so on. I plan on using a pretty good size turbo, leaning towards something the size of a Gt3078. Haven't made my mind up totally on that.
Funny thing is, it will make more than Monster did and hopefully on race fuel lots more than my 997TT
It is my wifes car though
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08-13-2008, 11:44 AM
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Stephen,
Cool stuff! I ran into some of your guys at Road America and Brainerd at the Club Race.
What car is this going into and what did the motor start out as? (what did it come out of)
Marty
Cool stuff! I ran into some of your guys at Road America and Brainerd at the Club Race.
What car is this going into and what did the motor start out as? (what did it come out of)
Marty
