early SC heads on later SC motors

[dd74]

If anyone out there has put early SC heads (with the larger ports) on a later SC engine, what were the results? I'd like to read about such a mod.

Thanks in advance.

[Wayne 962]

I doubt it would do anything at all...

-Wayne

[jluetjen]

... unless you change the cams and/or the cylinder capacity, as well as the injection system. Basically, if your engine's requirements for air are not going to change, the porting will have little affect. If you change your engines requirement for air by changing the items above, then the porting may have a great affect in making the updates successful.

[dd74]

So if I was changing to 964 cams, or 20/21s, are you saying the older SC heads would be beneficial to a later model SC engine?

Thanks

[Superman]

Without changing anything else, larger ports and intake runners would only result in the same volume of air movign through a wider path. On toher words, the air would go slower. I wouldn't be surprized if this hurt performance. And now for the rest of the story:

John Walker once (months ago) mentioned a later SC engine onto which he attacheed the early SC heads and entire intake. The fuel distributors are different, etc. He said that car had a fistful of torque. He was very impressed, and it is not easy to impress someone who has seen as may 911s as John.

[dd74]

What sort of change was involved with the fuel distributors? We're getting into territory unfamiliar to me...

Thanks

[john walker's workshop]

it also got B+B headers and the complete early intake system, including early fuel dist (no frequency valve), and larger sensor plate. it did run stronger than the average SC. the 80 heads were just opened up to match the early port size. i suspect the headers had something to do with it. if you want to open the ports for more flow, you gotta improve the exhaust too, or there won't be much improvement.