Whats the difference in Head CC's

[firehog383]

If I have 10.5-1 compression with 83 cc heads, or 10.5-1 compression with 76 cc heads, whats the difference going to be. Will I get more power or torque with the smaller combustion chamber or the larger one?

[DEW2112]

The one that gets better volumetric efficiency! Google that one and figure it out.

[Kivaari]

More information please

[Mo-Dog]

Wouldn't you have more overall ci displacement (with everything else being equal ) if you get the same compression with more volume in your heads? Sounds like the 83cc head motor would be bigger...

Originally Posted by firehog383

If I have 10.5-1 compression with 83 cc heads, or 10.5-1 compression with 76 cc heads, whats the difference going to be. Will I get more power or torque with the smaller combustion chamber or the larger one?

[Totenkopf]

Originally Posted by Mo-Dog

Wouldn't you have more overall ci displacement (with everything else being equal ) if you get the same compression with more volume in your heads? Sounds like the 83cc head motor would be bigger...

DING! DING! DING! DING!

we have a winner!!

[claydbal]

firehog, the cc relates to a particular build, you dont just bolt on a certain cc head.

[firehog383]

Lets say I'm going to build a 103ci engine for a bagger. I'm looking for torque from 2000 rpm up SE HTCC heads are 83cc combustion chambers with HTCC pistons 10.5-1 compression, SE pro heads are 76cc combustion chambers at 10.5-1 compression. Using the same cam, TW-6. I know what heads flow more, are the larger heads with the bigger chambers better in the high rpm range. I hope I explained this right.

[jerry34208]

The heads with the bigger combustion chamber will need domed pistons to get the compression to be the same as smaller heads.
While one of those combinations is gonna win out over the other, which one is best at a given RPM is not directly related to the size of the combustion chamber.

[Totenkopf]

Originally Posted by firehog383

Lets say I'm going to build a 103ci engine for a bagger. I'm looking for torque from 2000 rpm up SE HTCC heads are 83cc combustion chambers with HTCC pistons 10.5-1 compression, SE pro heads are 76cc combustion chambers at 10.5-1 compression. Using the same cam, TW-6. I know what heads flow more, are the larger heads with the bigger chambers better in the high rpm range. I hope I explained this right.

If you want torque everywhere.... increase your displacement and step on the compression. Then, let a Pro figure out the heads, along with the cam, pipes and intake for your mission.

[firehog383]

Cubic inches are what they are and is independant of the combustion chamber. Displacement is determined by the swept volume of the bore and stroke. I don't see how the combustion chamber size would alter that. Maybe someone could explain this better. I'm getting ready to build my engine and was curious as to the combustion chamber size and torque.

[wfolarry]

If you can get the desired compression with a flat top piston this is the preferred way IMO. In your example given a choice I would rather have the smaller chamber.

[Totenkopf]

The cam choice dictates the compression. The chamber volume is dictated by the compression, relative to the displacement. There are variations of trading dome or dish volume for chamber volume but in the end, it has to be set to a net cc's to achieve the desired compression.

I agree with Larry, for a reasonable street motor, a flat top piston is hard to beat with a small-ish chamber. The problem is, with the 76cc chamber and the Wood TW6, your compression would be over 11:1 and the ccp is 217 psi. Why not use your stock heads and have them modified to work? Roughly 85-86cc is what you need for that cam.

[firehog383]

Would the TW-5 have more compression or less .575 lift 234 duration. Thanks for your help.

[firehog383]

I already have a set of S/E heads that have been cleaned up a little, and a set of woods TW-5 chain driven cams that are bolt in for theese heads roller rockers and S/E support plates, stroker flat top pistons that are 10.5 static for the heads. I got a deal on the heads and had a local head porter clean them up. Will this work or am I better off starting over.

[joelp34252]

I run a 103 with woods 6h cams in a bagger that is very strong. Flat top pistons and 210 lbs compression. You need to make sure to have a good exhaust and good ignition with a good tune though with high compression.
Joel 2001 FLHT