Topic: cam and rocker/follower interchangability

[timtune]

I'm on a budget and hoping to buy as few new parts as possible.

I've got 6 motors I'm picking parts from to build one good one. Four 73Ks and 2 78Fs.

The cam from the F looks great and the lobe height and base circle specs are good based on my Clymer(Haines??) manual.
Can I use it in a K motor? The manual only has one set of specs for both F & K cam. With a second spec for automatics. Was the 78F cam different than a K cam?

Also can I mix and match cam follower (rocker arms) from K and F models?

[Jerry Rxman Griffin aka MuthaF'er]

Yes and yes.

The F2/F3 cam was probably the hottest stock cam followed by the F0/F1 and K0/K1. Good choice. Use the valve springs from the F2 also. Stronger.

[timtune]

So the head components (less the larger F valves) are compatible between the K and F? That would be great news.

Will the F3 ('78 F) cam make much of a noticable difference in performance when mated to a stock K motor?

[Jerry Rxman Griffin aka MuthaF'er]

Yes.

The increased performance will depend on which year K but should be an improvement especially between 73? and 76 K's which were detuned.

[timtune]

I've come this far why stop now?

I have plastigaged one of the F motors and found the crank to be good. Is there any advantage to using that bottom end verus one of the Ks? (I know the final drive sticks out more- not a problem)

And a big Thanks for the quick response JRG!

[754]

I think you can use the F springs in the earlier heads, but not the top collar and keepers.

[MRieck]

I think you can use the F springs in the earlier heads, but not the top collar and keepers.

Correct Frank....F2 springs work with early retainers

[timtune]

And the bottom end is interchangable too?

I want to use the F final drive with the K transmission gear clusters.

[754]

I dont know if its the F final drive.., but since i put an F motor in my mileage , has been always bad.
 Are you ready for all the changes, should you put sn F motor in an earlier frame ?

[timtune]

I've got a 76 F frame is that a problem?

[timtune]

I was over this before as I now remember. 76F frame but with Comstars and triple discs. I seem to recall I made spacer to make the comstars to work. Been a long time.

[Don R]

 My F was happier with an 18 tooth front sprocket, the top two gears are lower if I remember correctly.  The F cam is a good choice, mine seemed torquey but I had too much fun revving it and tagged a valve using stock k springs.  The 78F front sprocket is 10mm further out, it can be used by matching the rear cush drive.
 
 

[timtune]

Is that 10mm accounted for if you use the Comstars? I set mine up about 10yrs ago and can't remember

[754]

Ok , so frame does not affect it.
 If you have lomg shaft motor, rear sprcket must also move out , its all in the sprockrt carrier. What came with the Comstars or 77 and 78 K carriers and inner spacer is fine.
Lets assume you havr all that...
 Now the issue is which swingarm ? and your shock angle on chain side would be affected.

 Read the swingarm to axle size thread in this section.....

[timtune]

Thanks Again! Will have a read.