will I have performance or interference issues if I run a larger (1.74) exhaust valve in my 65 413, or will I have to notch the cylinder?
I had a set of 440 stealth heads on 413 the exhaust valves are1.81 got the rpms a little to high and all the exhaust valves hit the edge of the cylinder .it is real tight fit
Do yourself a favor and replace the 413 head with a 906 or 452. The ports suck in the 413 head. It will be a waste of time and money putting in a bigger exhaust valve. You will be performance and money ahead.
The problem with 906 or 452 heads on a 413 is the chamber size, you will drop a full point in compression. All 413s came with closed chamber heads....... so you need to use a closed chamber head. The larger valves do offer a performance bump but a set of closed chamber 915 heads from a 1967 big block is what you need for the biggest performance gain.
That's not enough as they probably came from the factory with the steal gasket. The chamber size differences is 86 + cc to 75 cc between the heads. I would not put open chamber heads on a 413 unless you had no alternative or custom pistons.
the open chambers are less likely to detonate. it really all depends on your intentions with the engine as to what heads to run. that will determine what other parts to use. the 413 is kind of a odd ball. pistons are not readily available so custom made ones are usually needed. the small bore shrouds the valve. the stock heads suck. but if all you need it for is a cruiser its fine. if its a performance engine I would start with a 440. max wedge excluded in these comments.
You will be fine, but as stated you want a set of 915's if you're going to run OEM heads, the factory 413 heads are not great. We ran a set of 915's on our 413 and it was a fine motor, it just had some run on issues when it was hot out. I still have the motor sitting with about 20k on it, but if i was going to run it again, i'd look at a set of aluminum heads to tame that run on issue and for improved breathing.
The Jalopy Journal
