I have a 10:1 big block with iron heads. It’s 95% drag race 5% street driven. For performance what would be better, 93 octane street fuel or the 110/112 I’ve been using? Heads do not have hardened seats. Or another option I haven’t tried. Thanks.

RR

I'd run 93 , with a sip of 110 for lead..........80 / 20 or so should work.

93 hands down....I was at 10.7:1 with mine on 93 and went 9.70 on it with no issues...That same engine is now in my engine builders car with iron heads running on 91 and we went 10.72 with it last week....See my what will it run thread for more detail...

Too much octane is a waste of money and in some combos will slow you down! After a WOT pull do a plug check.That will tell you if you need more octane!

If you're running race gas now then try 50/50 mix with pump gas and see how the engine likes it. If it works okay or better then try 80/20 pump gas to race gas. I wouldn't run 100% race gas in an engine like that, it usually doesn't work great. 50/50 pump gas will probably run better and make more power but you'll have to play with it to find out for sure.

I'm at 12.2 compression with aluminum heads, but I use the VP 112 which translates to 108 octane to keep the carb clean and lean away from all that corn chowder Ethanol.
I just can't get anything decent below that octane rating that has some of the " velvety smooth" stuff in it.
Aluminum heads are a little more forgiving with the compression depending on quench compared to an iron head.

OP: Yes, more or less, a mixture of about 70/30 would keep me asleep at night.

JUNK at the PUMP nowadays though.

It should run faster w/ 93 octane. Unless you have open chamber heads and no quench, then you may need the extra octane to keep it from detonating.

FWIW...my 11:1 hemi slows down a tenth and a little over 1 mph on VP 110 versus 93 pump gas.

My 470 dyno mule ran the best with 50/50 mixture of non-ethanol premium and Hot Rod 102 unleaded race fuel. The engine sounded fat and lazy on 100% race fuel and was crisper on the 50/50 mixture. I do not know the chemistry that was going on inside the engine but the engine made more power and ran better at 50/50. It didn't like 100% pump gas that well. The 100% pump gas was sooty. We played with fuel several times while I was dyno testing that engine and finally decided the 50/50 mixture was the best option.

I didn't see the octane as the problem , but without hardened exhaust seats , a little lead is a very good thing.
Especially since it will see street time.
Additives aren't cheap.
A sip of race gas ought to do the trick I figure.
And besides.........who doesn't love the smell of race gas being combusted ?

My effective CR is 12:7 on pump junk and runs great with 4 lbs of boost through the exhaust out the rear bumper.
Aluminum hemi head