One Bugpack 4063-10 question.

[rbeeson]

Can I run this with 1.4:1 rockers?

[Ohio Tom (DdK)]

Nope. Too much lift for the duration. It will have super fast accel/decel rates. Likely to eat out a lifter bore or make for bad valve float.
Just my opinion...

[rbeeson]

Thanks Tom. If you will let me go past my one question. I am building a 2276 with CB Performance Wedge Heads (44x37.5)(Flycut to 46cc) 1.4:1, CNC ported w/Big Beef manifolds and 48 IDA. Going in a street legal rail buggy and I want to lean heavy on the radical side of performance rather than economy but still run on 93 octane gas. What cam do you suggest?
Thank you,
Reese

[Meandean]

With a 2276cc engine and 46cc combustion chambers you will have approximately 12:1 compression ratio.  Even with 48 IDA carbs. and the wildest cam you can buy I don't believe that you can operate an air cooled engine on 93 octane gas for very long with 12:1 C.R.

[stealth67vw]

With a 2276cc engine and 46cc combustion chambers you will have approximately 12:1 compression ratio.  Even with 48 IDA carbs. and the wildest cam you can buy I don't believe that you can operate an air cooled engine on 93 octane gas for very long with 12:1 C.R.

How do you know he's at approx. 12:1 without a deck height given?

[rbeeson]

With a 2276cc engine and 46cc combustion chambers you will have approximately 12:1 compression ratio.  Even with 48 IDA carbs. and the wildest cam you can buy I don't believe that you can operate an air cooled engine on 93 octane gas for very long with 12:1 C.R.

My original plans were w/zero deck, an intake closing of 62, 5.39 rod length, 0.060 copper gasket of 11:1 SC and right at 9:1 DC. 93 octane should support this. Granted this might be on the ragged edge but this was my calculations. However my cam has been taken out of the equation so I have to get another cam. If I go with an intake closing faster than 62 I might have trouble with pump gas hence the 4063-10 that I have but it will not work with 1.4:1 rockers. I already have the 1.4:1 rockers and would like to use them. Just asking for some advise/opinions.
Thanks in advance
Reese

[Ohio Tom (DdK)]

My recomendations:
FK-8 / FK-45 for street primary driving.... Or, FK-10 / FK-46 for a few hundred more RPM powerband (streetable, but soggy low range.).

11/1 S.C is a little high for pump gas.
You can get away with 10/1 or 10.2/1.
Race gas blending will wake it up alot...

I built a 2110cc street motor for Jacob (Gascap) with FK-45, K-Roc prepped Oval port CB heads. 10/1 compression ratio. Ran nice and cool on pump gas, ran high 12's on race gas.
Awosme powerband.

[2DubTech]

I second the FK-45.  Loved that motor 9.5:1 compression with wedgeports on 91 pump gas 28 degress total advance on a 100 degree day. Ran 13.0 @100. Felt like had power everywhere.  That being said my best friend has same setup but with the new CB 650 springs and FK-46 and that feels the same as the 45 but with more top end.

[Meandean]

How do you know he's at approx. 12:1 without a deck height given?

I'm sorry, I pushed the wrong button on my calculator.  The actual compression ratio will be 11.1:1 with .060 d.h.  I still challenge the choice of 93 octane fuel in an 11.1 c.r. air-cooled engine even with big carbs and a long-overlap cam.   In my opinion it will pre-ignite enough to drastically shorten the life of the engine.

[stealth67vw]

I'm sorry, I pushed the wrong button on my calculator.  The actual compression ratio will be 11.1:1 with .060 d.h.  I still challenge the choice of 93 octane fuel in an 11.1 c.r. air-cooled engine even with big carbs and a long-overlap cam.   In my opinion it will pre-ignite enough to drastically shorten the life of the engine.

I agree with you there, but who's to say he's not running .100+ deck height?

[maui]

I say you can cuz I ran 10.5 with 91 super for long time with 32 deg adv. It's all in the cam and the chamber shape and a good ignition and jetting and rod ratio. I ran FK87 with 1.4s and 0 deck with 60 copper. I also tried 100 deck and it pinged like no end but with 60 it neva. I also say that with big engines, the big cam is no problem cuz it going clear fast and you will be in the sweet spot quick. You jus got to get use to driving it and then it going be no problem. But like the other guy said, the engine not going last long before rebuild  but it going be fun while it last. Mine ran 210 and 220 when I go long hard runs but with good oil it's no big deal. I did choke burnouts and drive to the track and do mid 12s and I said as long as I stay having fun it's worth it.