Just wondering I picked up a 1967 400 with 670 heads and my question is will it run on 93 octane or do I have to do modifications?

Too hard to know without knowing if stock or rebuilt and if the latter, which pistons were used.

The cam can also play a part. Generally, a cam with more adv duration is said to bleed off some of the compression, making detonation a bit less likely. An example might be something like a Pontiac "744" cam, which has 301/313 adv duration.

But, a small fast ramp cam, such as a Comp Cams XE262, which has only 262/268 adv duration, will increase cylinder pressure & chances of detonation.

Will retarding the cam help?

X2, what pistons are in there? 1st thing you need to know.

Have you tried it or is it not ina running vehicle?

It will run till you beat the rod bearings out of it when you get on it

I have a 389 with 670 heads. It pings at WOT but runs fine otherwise

I know I've mentioned this before, but on the 670 head question, I'm presently running a pair of them on a .030 over 400 with flat tops. Octane booster (cosistant mix) and keeping it under 180F has worked for me. It runs extremely well.

Thanks everyone I finally opened it up and it's all original stock. It has the 066 cam and flat tops. Now what's a good cam, intake and carb upgrade but not too radical, I want it to be a daily driver just with some potential. It will have headers and Flowmaster exhaust and it's a 4speed 3:55.

With 670s and flat tops, thinking around 460 lift and an adv duration of about 290 or 295 will give you what your looking for. 670s work well with a moderate cam in that range. As for manifold, the factory 4bbl one works about as well as the after market ones for what you're talking about. You will need some octane, (see how it runs to know how much, 93? Probably need higher) and some lead additive if you don't have hardened valve seats. I'm no expert, but that's my experience.
With those gears it should really scoot on the street.

Sounds like a good scenario for the Summit 2801 cam.

Thanks guys really appreciate your input! Cheers!