11:1 or 12.5 compression?

[hondarider#10]

i was thinking about putting a 440 kit on my 400 but i wasn't sure wat is better to have 11:1 compression or 12.5:1 and wats the difference between the two?

[CHEVYZ]

Higher compression usually gives better performance...assuming it is the same type of piston. At the same time, the higher the compression, the greater the chance that you will have to run race fuel...and that can get expensive. With the 12.5:1, you will probably need to run at least a mix of race fuel, whereas with the 11:1 you may not.

This can be broken down into sooo much technical talk, and if you pay attention it is well worth the read. If you search you can probably find the info that you need....or someone may chime in. (Unfortunately, I am not one of the guys that can help you with that).

Good luck, hope you get what you are looking for.

[Metzroth]

With 11:1 comp. you can run 93 octane pump gas. With 12.5:1 you will need to run race gas. Race gas is extremely expensive and its not very convenient to have to run it. If you build a 440, you will need HD head studs and a big bore sleeve. I would reccomend upgrading your oil cooling system as well. If you just want more power and want to stay reliable i would stick with a 406 or a 416. Get a cam, 11:1 compl., a K&N airfilter, a full exhaust, and some headwork and you will be happy. There will be alot of people with 440's that will disagree with me and say they are just as reliable as any 416, but I've heard lots of horror stories about overheating and blown headgaskets.

[Ruby Soho]

youll need a HD crank for the 12.5:1. stick with 11:1, you can run pump gas. 12.5:1 is gonna require you to run race fuel.

as stated above, with the 440 your going to need the HD studs, sure some people get away with not doing them but you better be safe than sorry if you wanna ride. also you should install the HD cam chain (crf450 is the same thing for half price). i havent done that, and mine is fine but once again you should do it. you don't have to upgrade your oil cooling system but its a good bonus. ive heard the CBR1100 oil cooler is a great upgrade

[mod440ex]

i had both in my 440, i had a je 11 in it to start with and when i rebuilt it i put a 12.5 wiseco in. i didnt have a heavy duty connecting rod, not saying it wouldnt be a bad idea, and i ran mine for 3 yrs with no probs. if you can find a local airport near you they sell 100 low lead and thats what i ran in mine. its about .75 more a gallon than 91 octane. but unless you are going to be racing i would go with the 11:1. The extra wear and tear and heat that you will produce really isnt worth it.

[davetheslave]

read the mods in my sig......no crank or rod upgrade. And that being said, the 12.5:1 hasn't given me any problems at all, and probably put 50 hours on it so far

[CHEVYZ]

Originally posted by davetheslave
read the mods in my sig......no crank or rod upgrade. And that being said, the 12.5:1 hasn't given me any problems at all, and probably put 50 hours on it so far Same...I see the HD crank as a good idea, but not a must. I would say that if you are going with the 440, definately get the HD studs and cam chain also.

On the 440 note specifically, I wouldn't go 440 unless you have already had all other work done. If any, a slight overbore with a good cam, port work, filter, rev box, exhaust, and carb would be a nice setup.