I'm getting my heads done currently and want to know if my calculations are good on the CCC, CC, and SC and if the plan I want to employ will work before talking to the guy doing the heads and BB kit.

I currently am running the Woods TW5-6 in the 96 and want to setup the heads to run these cams in the 107 and have the option to switch up to the TW-777 or TW-888 if the upper revs are too disappointing.

Now the TW5-6 needs a bunch less compression than the 777 or 888. Based on my calculations I can have the heads setup to run the 5-6s with a .045 gasket and if I want to swap up to the 777 or 888 drop to the .030 gasket and have the compression right.

Here are my numbers, someone please check me. I will discuss with the guy porting and supplying bb kit but want a sanity check before I call him back.

Heads= 85ccs

Woods TW5-6 107(3.9x4.3) .045 gasket = Static(10.16:1), Corrected(9.47:1), CCC(197.8)

Woods TW-777 107(3.9x4.3) .030 gasket = Static(10.45:1), Corrected(9.54:1), CCC(199.6)

Woods TW-888 107(3.9x4.3) .030 gasket = Static(10.45:1), Corrected(9.50:1), CCC(198.4)

Finally if the numbers work I understand that I will have to ask the porter to check valve to valve clearance for all cams that might be used. Spring pressure should be close between them as they all are same lift although the 777 and 888 have more duration and steeper ramp so they prob would need a bit more but idk.

 

 

JMHO but a .030" head gasket would be my choice regardless of cam selection and the heads would be prepped to deliver the desired CCP with that gasket. Again, JMHO but backing off a bit to keep CCP closer to 190psi and/or corrected to about 9.4 would be my goal but it's not m bike.

I know you assumed 85cc but that could vary; have seen them at 89ccs but chamber volume can be manipulated as required. Also don't know if you have allowed for deck height which could be +.007, or thereabouts and should be included in your calculations. Also haven't mentioned pistons but the numbers posted would appear to be flat top pistons. However, a 3.938" piston will be an aftermarket purchase and you need to be sure about the dome volume which can vary from manufacturer to manufacturer. Comprende?

 

Yes sir I gotcha.

I'm having someone do the heads so they will be cc'd.

I did not reduce for valve pockets and as far as I know they are not domes.

A couple questions if you will:

1. Just curious why do you feel the .030 is the only way to go?

2. How much difference is there between the 9.47 and 9.50 setup compared to 9.4? Do you feel I would be in detonation territory?

 

The .030 gives a tighter squish band, better performing. And personally the compression you stated are real good, no issues there, I've done it a tick higher on mine and no issues. Being conservative at 190 ccp is fine but not as snappy on the throttle. And I see damn hot summers here in fla.

 

Agree with ntraindavefl; optimize squish to optimize fuel burn.

Compression is a personal choice; not saying the corrected CR you have targeted is bad, just saying that the difference between 9.4 and 9.6 (which is as high as I go on a street motor) doesn't show me much in TQ/HP off the dyno. I do live in south Texas and we are seeing 100*+ temps right now which can bring on some detonation. An example is a 95" motor I built in '06 that ran great until July and then, on really hot days, the motor would ping; corrected CR was 9.27/CCP 192. I could pull timing out but the motor became a turd. I change cams and dropped corrected CR to 9.1/CCP to 186 and could ride the bike year round with no issues and no loss of power. Peak numbers stayed the same and the curve was nearly identical. Having said that, I currently run an all bore, carbureted 107" in my '02 FLHT at 9.4 corrected CR and CCP about 190psi. That motor runs on 87 octane fuel year round and makes 124TQ/110HP, never a hint of detonation. Like I said, it's a personal choice and I tend to lean to the conservative side; each to his own.

 

Thanks for the replies guys.

I think I might go up 1cc on the heads to 86ccs which will give a little more breathing room on the corrected compression. This would also allow we to drop to a 0.040 cometic on the TW-5-6 to further optimize squish band.

I don't want to deal with detonation at all. It gets hot here too in Eastern NC and I ride all year.

going up one cc puts corrected compressions at 9.47(TW-5-6 w/ 0.040 gasket), 9.45(TW-777 w/ 0.030gasket), and 9.41(TW-888 w/ 0.030 gasket). All CCC numbers were in the mid to upper 190s.

@djl and @ntraindavefl how do those numbers sound?

 

Not a fan of Woods cams but the numbers are fine. Install compression release and use them.