12.5:1 vs 11:1

[d90rick]

Quick question. Everything else being equal in an engine build, how big of a power/torque difference would there be between a 12.5:1 & 11:1? 416 bore, obviously race gas w/the 12.5:1 & lets say race in the 11.1 as well for comparison purposes

Of course because i am considering between the two. Running race gas is no biggie to me. I will be doing xc racing/riding btw


Thanks!

[Wheelie]

Theoretically the 12.5:1 will make about 10% more power than 11:1.

[05DodgeDakota]

I say go for it! I have a 12:1 416 and it makes good power. Compression is where the power is at. Next time I'm going 13.5

[400man]

I know alot of people on here will say NO on the 12.5:1 for a trail/XC bike because of the extra heat. The HD head studs will be a must though if you want it to last very long. but if you are a fast rider and keep a good fast pace through the woods to keep the air flowing on the motor, you probably wouldnt have any major issues with it overheating.

[tri5ron]

X2 on the HD studs, and you should also consider installing a spal fan, and possibly a larger oil cooler.

[slightlybent47]

I have 4 years riding and racing on my 416 12.1/2:1 build full race port #2 cam and 450 carb, and I’m still using the stock head studs. Since I run race gas anyway I’ve been thinking on bumping it up to 13:1 on my next build.
As long as you get a bigger oil tank and a spal fan you should be fine with a 12:1 provided you have it jetted correctly.

[CJM]

Personally speaking, 10% more power isnt a whole heck of alot when you think about it.

Now if you did a 13:1 or 13.5:1 then I would say its worth it-but at that point its reaching the limits of the engine and you might as well buy a 450.

Had they the foresight to have added liquid cooling to the EX engine it would undoubtly be the single best 400cc engine ever made. But that didnt happen and we got 450s.

[chronicsmoke]

Originally posted by CJM
Had they the foresight to have added liquid cooling to the EX engine it would undoubtly be the single best 400cc engine ever made. But that didnt happen and we got 450s.

x2

Next time I throw a piston in the EX it will be a 12.5:1.. but who knows when that will be.. damn reliability.

[cheater13]

I got a 12.5:1 without HD studs but mine isn't bored and it runs really good. I got a good many compliments about it when people rode it about how snappy and quick it is.

[ish416]

I've been running my 12.5:1 for several years with stock cooling and no issues. If you run good fuel and have the jetting spot on, you should have no issues.

As far as power, I would say your peak HP wouldn't change more than a few tenths of a HP. However, you will have a noticeable gain in torque. My friends 11:1 426 W/Stg 2 hotcam and my 12.5:1 W/XR cam and FCR has a ton more torque than his quad. I think his quad runs better in the last 3/4 of rpm but mine feels like a diesel. It is absolutely amazing how much torque this quad has.

People on Raptor 660 and 700's have commented on how much torque my quad has.

But in all honesty, if I were to do it again, I would go 11:1. I learned a lot about fuels and such so it was a good learning experience but it has been a pain in the rear finding a source of good fuel on the cheap. As I cannot justify race gas when I hardly run it in any of my other vehicles.