I have a set of 416 heads that I am looking to put on a 350. I wanna know if this is a good move or not. The 350 has a Performer-Plus camshaft, Performer intake and 600cfm carb, Streefire distributor. The car is going to be a daily driver. What kind of performance gains are there from doing this and what kind of compression ratio will I be looking at.

Also, I plan on porting and polishing the heads and intake to match.

 

Your compression may be around 10.0:1, but that's something you have to measure for and calculate yourself.
The ports on the 305 and 350 heads are identical, but unless you open up the 416's for larger valves, you may not get a performance increase.


Here's some information you may consider here:
https://www.thirdgen.org/forums/tech...rings-l98.html

 

This can work very well for you if you tend to the details.
The cr you end up with will depend on the final chamber volume of the heads and the piston type and deck height and the gasket thickness.
If the pistons are dished type you won't even get close to having enough compression ratio to have tuning issues.
Use a thin .015" shim head gasket for this dished piston 350 w 305 heads combo.

For flat tops use a .040" felpro gasket.

While you are porting your 416 heads, deshroud the chamber a bit around the valves. Especially if you splurge for larger 1.94x 1.60" valves to gain flow. This will improve flow and open the chamber up just a bit over stock.
Degree the performer cam to ensure its timed correctly and while you are at it correct the balancer timing tab/TDC point. Setting the spark timing accurately is critical. Timing tabs are almost always off at least a bit from indicating true tdc.

A slightly larger cam with 211 to 216 intake duration and 218 to 224 exhaust will work better (.442in-.465"ex lift)
but the performer cam is ok.
The hot setup with ported 416 heads and a mild cam like this is to run a 1.6 intake rocker and a 1.5 ex rocker arm. This split ratio set kicks up the intake valve net valve lift to take advantage of the improved high lift head flow with ported heads.

Use premimum 92+ octane fuel. Regular 87 octane gas is not going to work. Use Champion RV8C or AC delco R42T spark plugs gapped at .035".... Stock plugs are too hot for this high cr motor.

These are the right plugs for this combo.
Set the spark advance accurately for 32-36deg at max mechanical WOT advance and limit vac advance to around 10deg at hi vac cruise on the hiway. Excessive spark advance is not your friend.
Most "stock" distributors have too much vacuum advance for a hi cr motor.

Especially if you don't use the OEM EGR system.
Limit it to around 10-12deg.

You'll find the performer manifold works best with blocked off or very restricted exhaust heat riser passages.
The carb just runs way too hot if the exhaust heat passages are left open. Block off completely or block one side off and restrict the other side so only a bit of exhaust riser flow gets up under the plenum.
A Divided plenum type edlebrock wooden carb spacer helps too.

 

All good info. I ported the bejesus out of my 416 heads, including opening the chambers to 64cc's and using 1.94" intake valves. I went aggressive on my cam and whatnot though. See sig.