onmy2ndsc

1982 vs. 78/79 911SC, know facts. The 1982 SC has 34 mil head intake and intake manifold (runners, the 78/79 is 39 mil. The air box is different as well as the manifold boots. Now the question. I have done a rebuild on my 82 with larger barrels and matched 9.8 to 1 Max Moritz Mahle pistons, 964 cam profile, ported and polished heads with the intake port matched to 42 mil, opened the throttle body 3.5 mil and have SSI heat exchangers with a sport muffler from AJ's. It is rear wheel dyno at 166 hp and a flat torque curve at 175. It seems that I did not gain much. Is it the air flow?? Can I fix it by extrude honing the manifolds and getting them to 36 mil and very glossy? The engine runs good and feels strong but does not have the torquey feel of my last 78 after similar mods. It is my thought that the engine is opening it's mouth so-to-speak to breath and it's having an asthma attack. What do you all think?

THANKS!!!!!!!

willard

Ask Squire...

onmy2ndsc

Willard:

Thanks for the suggestion. There are a couple of other shops/owners that I have greater confidence in and have discussed with mixed opinions as you might guess. I am planing on sending the runners to "extrudhone" in Calif where they will run an abrasive media through the runners under hydraulic pressure gaining a very polished 1 mil all the way around (2 mil Diameter) and I understand the "media" takes the most out where needed which is in the bends. More air is almost always better than less air and I am virtually certain it will increase the "pop" of the car and add to a noticeable gain. I was just hoping that someone else had already experienced something a little more concrete.

I know a lot of you are a lot more knowledgeable than I.....hasn't someone questioned, diagnosed or wondered what the air flow difference might be with 5 mil difference in the runners and how that might affect performance. Much is discussed regarding exhaust but my experience with motors in general is that they have to breath better to need more exhaust capabilities.

Thanks again

Howard

I'm no expert, but generally speaking when you increase the intake port size you will lose low end torque. You may gain top end, at the expense of driveability, low , and mid range. The other problem with your setup may be the CIS system, it's not ideal for a performance upgrade. Maybe you can upgrade to a 3.2 injection with DME, much better than the CIS.
Good luck !