Now bear with me... trying to use up some parts and have a decent running engine. Have a 1971 steel crank 9 to 1 440, stock bore, great shape, reringed and bearings. Stock 346 heads need work, I have a set of 915s with all of the work done. Could I use these on this engine without changing pistons and still run on 93 octane, or am I barking up the wrong tree! Going in a 69 satellite cruiser, not race car.

Will work fine on 93.Would be curious to see what cam but for a cruiser detonation should'nt be an issue except maybe in the hot summer months if at all.

I have an old 484 purple shaft or a new comp xe 274 that I could use. Wouldnt be against getting something else. Also have a performer manifold, will run headers, not sure on carb. Car is an automatic with a 2600 stall and 323 gear, but have 391s in the garage if needed/wanted. Thanks!

How far down are the pistons in the hole? You go too far and modern gas, no matter the octane, will not be ping friendly.

Good question, no answer, the engine is actually a couple hours away or Id measure. It is a 71 engine with stock pistons and bore, but I was just putting things together in my head

Do you guys think I am getting a whole lot more compression with this head swap, or not enough to worry about? I heard somewhere that an old racer trick was to put 915s on a hp440 and you get about 13 to 1 comp., different starting comp ratio I know, but definately not what I want! I am not really an engine builder, I usually just freshen what is there and go with it. Thanks!

I's ude what ever heads are the best..meaning need the least amount of work. If they are both thet same then yes the 915's are better. They woun't give you anything close to 13:1 maybe a half point higher than the open champer heads.

Awesome, Thanks!

That would be right about what I was looking for, I thought the heads might wake up the engine a little bit. I had been reading about quench and was thinking that my pistons might not be optimal for the head, but I'm not sure it would matter all that much in this power level.

Another thing to consider is that your 71, 440 was originally assembled with a steel shim head gasket that was approximately 0.017" thinner than most replacement head gaskets.

Randy

The 440 6 pack had a "true" compression of right around 9.7.1 & thats with open chambered heads that came on it, The 71 440 "might" i say might but you should measure have the pistons down around .080"-.090" in the whole, if so, with an open chamber the compressions around 8.6.1, You should be able to run the 915s & be fine on pump 93, the compression will most likely be around 9.2-9.3 with a steel shim gasket, You can't really say it'll have better/good quench, but it should have a better burn do to less chamber volume in the head, an old trick is grind off any casting flash & smoothin out the chambers, this will prevent any "hot spots" that can cause detination, run a plug 1 step colder then stock, like a J11Y, The XE274 would be my pick, plenty of torque & good power & vacuum, It will still be a strong runner with 3.23s, will kick ass with a set of 3.91s. Drop a 750dp & an RPM.