Hello,

I have a 2002 Dyna, stock 88" engine except for S&S 509 cams. I have stumbled upon a set of S&S 79 cc heads at a good price, I thought they would add some extra compression and also better flow than the stock heads.

But then I read somewhere at the S&S homepage that the 509 cams are not compatible with 79 cc heads, and I'm wondering why that might be.

Static compression will be 9.4:1 using 0.030" head gaskets, and ccp will be 190 psi.

The 509 cams have early intake closing, 18 degrees, but so does other S&S cams like 551 and 583.

Can anyone think of a reason to not use these heads and cams together.

I have emailed S&S tech support but their answers were confusing, they said compression would be to high using these heads, but they also said max compression for 509 cams is 9.5:1 so it's a bit confusing.

Any input is appreciated

 

Looks like you have done the math; I would proceed with the heads. Of course, rejet the carb and a progammable ignition wouldl help dial in timing.

What is that ribbed cover over the cam chest?

 

Thanks, I will proceed then. I will get either a Dynatek or Daytona Twintech ignition module.

The cam cover is made by Roland Sands, I think it is called "nostalgia".

 

Daytona Twin Twintech 88 is the ignition you want. You will have to play with the settings but several members use that ignition and if you post something like "DTT Ignition Settngs" I am sure some will reply. I installed that ignition on my all bore 107" but ran a custom map, so I can't help with settings.

Good luck.

 

I would expect that SnS is assuming that the heads are being used in a 95 with flat tops?

In an 88, CR is lower..

 

I think the S&S tech support is more focused on the newer bikes with M8 engine, odd questions about older bikes will get very rudimentary answers.

I got some more reply though, they said compression will be fine but valve to piston clearance might be an issue so I will look in to that.

Running the 509 cams is just an intermediate solution until I can afford going to 97" and 570 or 585 cams.

 

The tech makes a good point. Intake valve is larger and the piston may need the relief cut larger/ more to the outside edge. TDC lift on that cam is about 0.2" It's something, I always check..

Hope you have an ignition module in the budget..

 

To illustrate Max's comment about valve relief.

 

I checked my S&S catalogue, it says you can run these heads with stock 88 pistons and 570 cams. 570 have .187 lift at TDC and the 509 have .174, so going by that it should be fine.

An ignition module is in the budget. it seem the DTT is preferred over Dynatek so I will go for that, even though here in Europe the Dynatek is significantly less expensive for some reason.

 

Yeah, It all depends on where the valve sits in the head reverenced to the surface of the head. IIRC the SnS 76cc heads use a 1.94 valve. If that valve is say 0.030 below the gasket surface at 0.178 lift then with an 0.030 headgasket and 0 deck you should be good.. Valve relief is not needed.. Early TC SE heads with 1.90 intakes did have an issue.