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TwinTurbo boosting 12psi


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That is the least boost I can run because of the wastegate spring. HOLY MOLY! Can't keep traction under 45mph so it is hard to tell how fast the car is. The 16G's hit very hard and quick and the car pegs 7K rpm too quickly. I think I am blowing through the stall as it hits close to 7K even in 3rd gear. Definitely the car is making much more power at 12psi than it did at 18psi on the old setup. I can tell this by the way it lites the tires up at speed. It used to spin the tires and then stop and now it spins them and keeps spinning them at 45mph. The biggest problem I had with the old setup was that the cam was not properly installed and the car fell on its face at 5800rpm. After Sunbelt installed my new cam and reworked the valve train it is pulling to 7K and not stopping. I guess I am overly impressed after driving my wife's Geo Prizm for 10months! DOH! If anyone is in the Tallahassee area, feel free to come by and I will give you a ride and you can be the judge. I have to admit, I am impressed!

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Guest Tim78zt

Congrats, James!

Have you ever said which cam you are using? I'm running the stock turbo cam and , as you probably know, it runs out of breath at 4800 rpm. What was it about the cam install that was incorrect? And what was reworked in the valve-train?

Will you be bringing it to the Nat'l Convention?

 

Tim78zt

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Well, I hate to air dirty laundry, but....

When Sunbelt setup the head they did not set up the valve train correctly. My valves are the Nonturbo valves and are .080" longer than valves for the P90 head. To get around this you must shim the cam towers and redo the lash and rocker arm geometery. Well, I have paid a guy in Houston to do this, ProAm, and they did a good job. When I had Sunbelt port the head they did not reinstall all the shims nor did they setup the rocker arm geometry correctly. Because of this, 9 of 12 rocker arms where pivoting on the edge of the spring retainer. I wondered why my valvetrain was so damn noisy. Someone there knew there was a clearance issue because 2-3 rocker arms where ground on the underside to clear the spring retainers. Needless to say I was pissed when I discovered this and sent the head back to Sunbelt. Jim agreed someone at his shop had screwed up and offered to fix the problem. At that time I decided to spec the TEP cam and after getting back the results I told WebCams to literally throw it into the dumpster. I had WebCams modify their 155 grind.

155 grind

I had them take the lobe centers from 109deg to 110.5 deg. You can see the difference between gross duration and duration at .050" is very small, this give you an idea of the quick ramp rate and it seem to work well so far. I will have to get this thing dialed in to really know if it is doing well. Anyway, 3months later Sunbelt returned the head and did a good job.

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Guest Tim78zt

Well, Pete, now you got my curiosity up!! What springs did you end up trying, James? Web Cams doesn't really offer these cams for turbo applications. Is that why you spec'd the grind you did? I understand a turbo cam uses a lot more exhaust duration. Is that correct?

 

Tim78zt

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