Planning to install a 1200 conversion kit; 10:5:1 with WISECO reverse dome pistons on my 1996 883xkh Hugger. Can I still use the stock 883 heads and cam?

 

Yes!!!!!!

 

i was considering installing hammer performence 1250 kit with the original 883 heads , they advised me not to because once i start with the heads i would have to replace other pistons etc so 2x work and pistons ... would this also be the case with an S&S kit 1200?

 

S&S 1200 upgrade works fine with 883 heads. Just finished mine on 2001.

 

NO!

10.5:1 is too much compression for the stock cams. As far as the stock heads, as long as the pistons are designed for the stock heads, the OP should be fine. The problem is, running a much bigger than stock cam will run you into valve to valve and/or valve to piston clearance problems pretty fast.

 

Why don't you contact these guys, they make the pistons, they should have the answers. Don't take our advice if you can go right to the source.
http://www.wiseco.com/

Or, Hammer Performance may be nice enough to give you some trustworthy information, maybe you can purchase the pistons from them.

You can already see our advice is all over the map.

John

 

I got my info (NOT advice) directly from Hammer. But I agree, the OP should contact the sources directly as well.

 

I did a Hammer 1275 kit on my wife's 2005 883C using the stock heads with no problems. 1250 kit works too. Runs great. Not sure about the Wiseco set up but the Hammer kits run 10.1:1 compression with the stock 883 heads, 10.5:1 if you do a 30-degree conversion (headwork).

Hammer kits

 

Stacks of experience in here with Hammer kits, even some threads giving details of member's installations, so spend a little time looking back at older posts.

 

This is the right answer. 10.5:1 with the stock cams really pushes the cylinder pressure, and you could cause a detonation related failure. 10:1 is the most you should go on the stock cams.

Youtube video vgclz3FOq_Q (Google it) describes why and how cam timing and compression ratio get matched to each other.

The second comment above is also correct. But to be more specific, what you have to watch out for is a cam spec called "TDC lift". Stock 883 heads can't handle much TDC lift in the cams without causing piston-to-valve and/or valve-to-valve contact. That's because the chambers on 883 heads are shallower, and to make the valves reach these shallower chambers and to make the valves close enough together to fit within the 883's 3 inch bore, the valves are longer than 1200 valves. Well, that means they start out closer to the pistons and closer to each other to begin with. You're basically taking a chance of p-v and/or v-v contact running any cams with a TDC lift of over about .200" on either valve.

The fix for this is to "sink" the valves in their seats, thus moving them farther from the pistons and farther from each other. But that makes the chambers bigger, and making the chambers bigger will lower the compression unless the piston is changed to compensate for it. So you see, pistons, cams, and the head work really need to be a matched set. You can't think of them as independent pieces, you have to think about how they interact and make sure they're all going to fit together and work properly for optimum performance. Youtube video flgdYTCfXuU explains the issue in more detail.

Because of this requirement that pistons, cams, and head work be matched to each other, building a motor incrementally over time is an expensive way to go about it, because you end up buying some parts twice. Nobody makes a kit that allows you to get around this fundamental issue, because it's just physically impossible to do so. Be very skeptical of anyone who claims otherwise. It's up to you to be informed and make informed decisions. Watch Youtube video flgdYTCfXuU, it's all explained.