Did I screw Up? With my cam.

[concobra]

Hello Big Boss

Thank you for the kind words. Given your choice to stay with the large cam and low compression may I take the opporutnity to offer some suggestions to help compensate for this combination. Some things I will suggest may seem to oppose my initial suggestions but we are now dealing with conditions that are not optimized. Thats OK your eingine will still make good power.

What needs to happen now is to to focus on creating high initial runner velocity to help pack as much air/fuel charge into the cylinder. There will be a top end power sacrifice to do this do but there are no free lunches in engine building.

1. Advance the cam to 6 degrees if you can. Watch your intake valve to piston clearance. You need at least .080". If you cannot get 6 keep as much advance as possible. This will create more vacuum and Cold Crank PSI. You will loose about 200 RPM at the top of the power curve.

2. Stay with a two plane manifold. This is not the best choice with the cam but the need to keep vacuum high is more important to help fill the cylinders. Don't cut down the center divider as suggested before. Again velocity is king. May I suggest the Edelbrock Performer RPM. This manifold has good plenum size balance and smaller gentle curved runners that promote good velocity. It will help attain a good flat torque curve. Port match with the exception of the bottoms of the intake runners to the bottom of the head ports. The low riser floor is too low for good short radius turn to the valve and keeping the air/fuel mix high in the port will help.

3. Carb would be a Holley 850 HP. May I suggest contacting Patrick James of Pro-systems. He builds my carbs and I have nothing but respect for his knowledge and expertise. His website is www.pro-system.com. Even if you already have your carb. send it to Patrick to have him calibrate it. It will save you time and money in the long run.

4. Timing will help. With this low a cylinder pressure you will be able to get away with high initial and full timing. Try 20 degrees of initial and curve to be fully in by 2000-2200 RPM. Don't be surprised if the engine likes 40-42 degrees of total. Remember that you have a lot of area to create a combustion cycle in. This will create vacuum and the more vacuum the higher cylinder filling. You may need to use a high torque starter but it is worth it to keep the timing way up.

5. Please consider the use of a multi-spark CDI ignition enhancer such as MSD. I have experienced these adding as much a 3" of vacuum on a back to back / with and without test.

Good luck and be safe

Concobra