Here is the build: 2006 Heritage EFI I am hoping someone could give me some input on the cam and head gasket before I put it together. I also want to stay with chain drive.

Bore = 3.905 95.81 ci
Heads = 78 cc's Milled .050, Ported, Polished, Stock stainless swirl polished exhaust valve, Oversize 1.90 stainless swirl polished intake valve
Head Gasket = .045 stock
Pistons = 10.25 SE high compression cast enlarged valve relief
High lift .64 S&S valve springs
650 feet above sea level
Compression releases
Arlen Ness Big Sucker
D&D Long Riders
T Max AutoTune

Big Boyz shows I am at 10.59 : 1 compression ratio and 228 cold cranking compression with a stock cam.

I have an SE-204, SE=211 and SE-251 on the shelf in the garage. The question is I want the power band 2200 to 5000 RPMS. Mostly in town riding only 15% 2 up riding. Should I use one of them or sell all of them and get something else
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My advice. Ditch the HC pistons and go with a set of flat tops. Way too much compression with 78cc heads and domed pistons. Well over 11:1 static compression. Also ditch the stock head gasket and go with a .030" MLS gasket. This should put you in the 10.2 :1 range. Perfect for say a Wood 6 cam. power right where your looking for it.

 

Bigjoe makes a very valid point.
But, IF, you are at 10.59 cr, then a Wood 8 may be your man.
Scott

 

What #'s are you using for piston dome volume and deck height? I'm coming up with well over 11:1 compression with the dome pistons.


K.

 

I get similar numbers in my calculator. The head/piston combination does not work; the CCR is unmanageable. Heads or pistons need to be replaced and pistons are the chepest way out. No need to 86 the pistons, just have the domed shaved off and make them flat tops.

Of the cams you listed, the SE204, with a .045 head gasket and a set of flat top pistons is the only one that comes close; static 9.9; corrected 9.29 and CCR 189psi. Corrected and CCR are great for the power band you are looking for but at 9.9 static, the SE204 can be a bitch to tune with the ground in advance.

I am curious about the 3.905' bore. IIRC, SE pistons are only available in one OS, .010". So, it would appear that your bore and pistons don't match up. If your bore is truly 3.905", the SE pistons will not work as the largest OS available is 3.885". You could use a set of 3.938" pistons and increase the displacement from 95" to 98", just need to hone your cylinders to fit.

In summary, regardless of bore, you need a set of flat top pistons, .030" head gasket and any cam of your choice with an intake close of 40*-44*. I like the Woods 5-6 or the TMan 590 or 625 since your heads can handle the lift.

You did not mention throttle body. With ported heads and long cams, you might benefit from a larger than stock or larger injectors.

 

Thank you for the obviously well thought out reply's. The flat top piston makes sense, got to check how much to shave vs purchase. The pistons are new old stock SE .030 over, part number 22184-99. NCT you are correct the static compression is 11.1 :1. I am also getting that the cam of choice is probably a Woods? Got to get on Flea Bay, LOL

 

.030" OS pistons explains the bore.

Shaving piston domes to achieve a target CR can be tricky. While one might assume that shaving the dome from a HC piston to convert it to a flat top one might assume that the resulting dome volume (for calculation purposes) would be -1.5. However, that may not be the case, particularly if the valve reliefs have been modified.

Whoever shaves the dome should take actual measurements to determine dome volume, before and after a cut. There is a procedure for that which requires that the piston be place in the cylinder with a "gapless" top ring to prevent fluid from passing; some grease is often used to help seal the ring. Piston placed exactly 1" (to the top ring) down in the bore,; that volume can be calculated. Then fill that volume with a fluid, everyone has a fluid of choice; the difference in the calculated volume and the actual volume is the dome volume. Remove the piston and take a .010" cut and repeat measurement. This will provide the data you will need to determine how much to cut from the dome to hit the target CR. You can use any variety of compression calculators and, working backwards, calculate the required dome volume. Apologies if you are already familiar with this procedure. Any qualified automotive machine shop or engine builder should know what to do.

There are so many cam choices that selecting one can be confusing. Again, using the compression calculator you can back into the appropriate intake close timing for your application. Then look at the available cams with the appropriate intake close events and pick one; there really isn't that much difference once you narrow the field down. The only thing to remember about Woods cams is that Mr. Woods tends to grind aggressive ramps and some of his grinds are noisy.

 

Thank you, this has been a huge help and saved me a lot of grief down the road. I found a very good machine shop in Fort Worth that will bore match the cylinders and pistons. The bore will be $69 per cylinder, shave the pistons for the appropriate CR at $24 each, and gap the rings. With all of this done the worksheet looks like this:

.030 head gasket
Heads the same
Bore the same
piston dome volume -1.0 to -1.5
I am going to use the SE 204, I already have it
Static compression 10.18:1
Corrected compression 9.58:1
Cold cranking compression 197 to 199

I think this is close to where I want to run at. Does this look correct? You guys are very good in the way you explain things to us laymen and provide choices with opinions rather than trying to force a personal preference down someones throat.

Thank you
Tim

 

I don't really see a problem with running 10.5 -10.6 comp unless your going to keep your stock cam,which you already said your not.Make sure your numbers are correct though.I'm running 11.2 with a Woods 68G cam.210-212CCP.If you choose a later intake close cam,At least 40 or later it's going to bleed off the compression anyway!!! I would pick something between a 40 & 50 intake close to give you some tq & hp.Woods cams like Compression anyway.Call Bobby Woods, & ask him what he thinks will work with your set up!!!

 

With the SE 251 cam and a .040 head gasket, leaving the SE 10.25:1 SE pistons in the calculator shows Static compression at 11.39:1 but the corrected compression with the cam at 10.16:1 and cold cranking compression at 212. The intake close is at 46. With compression releases will that work or am I asking for trouble.