Originally Posted by F-BIRD'88
The 416 heads work much much better with full home porting and larger 1.94x 1.60" valves.
Use cooler Champion RV8c plugs (.035" gap) and set timing to 34-36deg BTDC
The distributor could use a recurve.
Make sure the carb is jetted right. If its too lean @WOT it will be more sensitive to knock.
Generally with the lowly performer manifold you want to block off the heat riser passages at the gasket as this manifold tends to run too hot with open heat risers. The plenum gets too hot.
The real cr may not be as high as you think. Many rebuilder flat top pisotns have a reduced compression height at TDC.
The 94 octane gas is pretty good stuff. It may run very well as is.
Why don't you post on how it runs.
If it does prove to knock on 94 once these details have been looked after
its not that hard to fix.
A good opportunity to yank the stock 416 heads and port them yourself. (If I can do it you can too)
Deshrouding -clearance relieving the 416 chamber walls for the larger 1.94x 1.60 valves results in larger 62 64cc chambers.
When you are generous with the porting you gain a good bit of power with these
heads on 350's. That will keep you out of the bars for a few nights.
The stock vacuum advance from a stock GM HEI will be a problem with the agressive high compression ratio.
You would want to get a fully adjustable Crane vac adv unit. Needs custom setup for rate, limit and start point.
I wouldn't have a clue where to start with home porting lol, I have a dremel...! I would love to spend some time porting these, just have no idea where to buy bits, where and how and how much to port...its all voodoo to me....I was going to leave the vacuum advance disconnected on it btw. My driving is typically at 3000rpm all the way to work on the highway, then lots of short light to light bursts....and last question, can you explain blocking off the heat passages in the perfomer? Thanks guys.....really appreciate the help