Join Date: Dec 1999
Location: Big D little a-l-l-a-s
The bolt patterns are the same. You didn't say which manifold you will be using but for example, if you were to use a Edelbrock manifold, you would want to use the Edekbrock RPM manifold and NOT the EDELBROCK RPM PERFORMER manifold because the port size is SMALLER on the RPM model and it would at least match up somewhat better with the smaller ports on the heads. In either case make sure you use the manifold gasket that goes with the manifold you will be using and NOT a manifold gasket based on the heads you are using.
By the way, dual plane manifolds like these are much more forgiving than their single plane counterparts when it comes to mismatched port sizes.
Mike didn't ask which ones would be better!!! I'm sure he is aware that it would be better to match the port size of the manifold to the heads, but he COULD use a small rectangular port manifold like the Performer on oval port heads if that is all he has to work with. Performance would not suffer that much with this combination compared to the ideal setup.
NO it is not OK,
I am fortunate because I can afford the to buy whatever components are necessary to build the "PERFECT" setup. I then DYNO test the combination and I change the combination to one that works better according my DYNO testing. So basically I KNOW what works and what doesn't work and I can prove it. The surprizing thing about this is that you can effectively use mismatched components and get surprizing results. Not as good as using matched components mind you but still acceptable in most cases.
The whole point of this is that you HAVE to use less than ideal parts combinations because of cost considerations or parts availability, you can still get accepatble results. The reason I try to contribute to this site is that I have fun sharing my experiences with others and hope that they can learn from my mistakes and experiences.
Whether they choose to or not however is totally their choice as it is also yours.
END OF SERMON
[This message has been edited by sr71bb (edited 03-12-2000).]