I'm still in the process of my 78' FLH 80 upper end rebuild, and the deeper I go, the more I find needs replacing.
I'm going with 7:1 low compression pistons, and wondering if I have to change my cam or modify the heads at all?
The cam that's in there now is pretty badly pitted and needs to be replaced.
I'm looking at an Andrews "A" grind cam at JP Cycles part # 432-775. Good? Bad? Will it work?
I plan on running solid lifters also.
Is there anything else I shoud be concerned with?
Any info would help. Thanks!

 

go to J&Ps web site and click on tech, in there you'll find (selecting a harley davidson cam)

 

why such LOW compression?? you can go 8.5:1 and still have a VERY reliable engine.

 

Thanks for the replys.
I like the idea of low compresson to run regular gas and to make it as easy as possible on the starter.
I'm not looking for performance, just a crusier.
I'll check out the JP Tech forum. Thanks again.

 

yeah, but 7:1 is WAY under stock. you can run pump gas on anything 10.5:1 or lower.

 

Don't go to the 7:1 comp pistons. Been there, done that. I already went down that road years ago on two shovels based on bum advice from those supposedly in the know. You will loose more power than you think with no real benefit as 8.5:1 will do just fine on today's gas. Had a '77 FLH full dress with windshield and in a head wind, you could really feel the power loss. Went back to the 8.5:1 and the difference was immediate and quite noticeable. ALSO, if you combine a hotter cam with more overlap (BH) with the lower compression pistons, it'll be the worst of both worlds and it will really run like a dog. Ask me how I know about that one.

 

One more thing, if you do decide to stay with the 7:1 pistons (I wouldn't advise it), stay with a stock FLH grind cam. You need a short duration with the low compression or else you will have hardly ANY torque. Also, if you're not into higher revving performance, and it doesn't sound like you are, don't do the solid lifters. All you'll get is extra noise. For a cruiser, stay with the hydrolics and enjoy the quiet without having to worry about valve adjustments.

[IMG]local://upfiles/30261/CDA48D1C0B3D4B9EAE80C74D30872542.jpg[/IMG]

 

Thanks for the info guys. I already got the 7:1 pistons, and I just ordered the Andrews cam, #1 grind, made for low compression.
I'll try it. And if it's horseshit I'll repower next winter.
Live and learn I guess,Thanks

 

I have a early 78FXS[points] and put in an Andrews AB[and solids]from Jirehycycle and can really feel the difference.

 

You will do just fine with the '1'-grind Andrews. A good friend has a '74 Police Special, and is running low (7.5:1) compression pistons on a stock 'H' cam. Very good performer for what he wants. Road cruiser. I advised him to go with the '1'-grind if he ever wanted to get a bit more pep out of it. The '1'-grind raises the effective compression back up to somewhere around 8:1 - 8.5:1.

My advice to those who want to these bolt on/in mods to their Shovels, is to actually go with higher-domed pistons, for a bit higher static compression. But then, install a cam that reduces the effective down to something very near to stock. My reasoning behind this is that the Shovelhead ports are way to big for low-end performance, combined with basically the same domed pistons of the previous generation of Big Twins. They just don't make the vacuum for a smooth idle, unless you reduce the intake size (manifold, carburetor). If you look at the Panhead setup, they have small intake ports, a short intake manifold, and a long carburetor (Linkert) with a small venturi. Makes for higher intake velocity, smoother vacuum at low RPMs, and a strong torque engine on bottom end. Of course they run out of steam at around 100 mph. So what. They're cruisers. But, back to my reason for the hi-domed pistons. These will make for higher vacuum at low RPMs, but with the right cam, near stock compression, able to run on pump gas with no problem. Plus, you will have the crisp throttle response of the old Pans with Linkerts.

Jack

P.S. - I'm not advocating tearing down a perfectly good running engine to do such mods. Wait until it really needs that build. Then, you have something else to consider. You have options with low or high domed pistons. More with high, I'm thinking.