[RobMcQuarie]

Ron,
I'm a little confused as to what you are exploring here. Are you thinking that the Edelbrock heads would be an improvement over the Blue Thunder's? The Edelbrock's are actually a budget oriented street head, positioned between the stock iron heads and a high performance race type head like the Blue Thunder. When we are building a 460, we use the Edelbrock's for mild non-stroked motors or, especially, truck 460's. We use the Blue Thunder's for any high performance or stroked application. The E-bock's flow better than stock, but not as well as the BT's. And the aluminum BT heads don't weight any where near what the iron heads do. The BT's and E-bocks are close in weight. If you have the Chev exhaust port version of the BT's, they will weight a few pounds more, but they have excellent flow.

Nick, your mechanic is correct in having you replace the Edelbrock valve springs-they are ok for a very mild build, but are not the best choice for higher performance as they are an inexpensive part used to keep the assembled heads price down. At the same time, he will need to check (and probably re-do) the valve job.