I am building a TFS headed 406 with a XE274 hydraulic flat tappet cam and planned on using crane full roller 1.6 rocker arms. I wanted to use these to get a little more duration and lift. I have watched mechanic friends break in flat tappet cams and feel comfortable doing it myself. I was just talking to a guy about my setup and he said that I shouldn't use the 1.6 rocker at all with the xtreme energy cam, he said they have such agressive ramps that the tappet will dig in. Especially on break in. I called comp cams and the tech said I shouldn't have any problems with what I currently have. For the record he said it wouldn't be a bad idea to use a 1.5 rocker to break the cam in.

Should I just use a regular old used set of 1.5 stockers to break the cam in and then swap over to the cranes. Or use the cranes from the get go. Thanks for any help

 

You will be fine. I would worry about proper break-in procedure far more than rocker ratios.

I don't see how rockers will affect anything for the break in. The only thing rockers really do is bring the pushrod closer towards the head. And if you look at it, there's nothing that can cause as far as lifters digging into the lobes. Either way, the lifter is confined to its bore. The pushrod seat is cupped so the pushrod itself can sit on an angle and not interfere with lifter motion. The only way you could cause digging into the lobes is by switching to a larger spring that would offer more "resistance" as the cam opens a valve. Consider: rockers do nothing more than convey the lobe profiles into valve openings. Think about how many people out there have broken in a flat tappet cam with aftermarket lifters...me being one of them.

 

I agree, just hoping I wasn't missing something with this XE cam that was different than other flat tappet cams.

 

You are cool to use them. SOmetimes, though, depending on cam and springs, you should use break in springs. You should be ok though.

 

Actually rocker ratio CAN affect cam breakin. The pressure on the cam lobe is increased by the same ratio that the valve lift is increased. So using a set of stock ratio rockers to break-in a flat tappet cam makes sense, particularily if it is a really big flat tappet cam.

In fact you will find that Comp Cams ( and others ) offer special " Break-in " rockers with ultra low ratios such as 1.2 to 1 to lessen the loads on the cam during break-in.

It is easier to swap in a set of low ratio rockers than to swap back and forth with " Break in " springs, when you're building a lot of engines. Another trick ( as mentioned ) is to break the cam in using only the outer springs on a dual spring setup. The more aggressive the cam and the stiffer the springs the more critical it is to either use low ratio rockers or remove the inner springs during cam break-in.

With an XE 274 I wouldn't be too worried.....although breaking in with the 1.5 ratio rockers woul be a good idea IMHO. Removing the inner springs during break-in certainly won't hurt anything that's for sure

BTW. Summit has an awesome spring compressor tool ( heads on car ) for only $49.95. Really slick and makes changing even " Triples" a breeze. Part #906784

 

Springs are stock TFS 195cc head 1.47 single spring. Good to .540 lift, with 1.6 I'd be right at .519.

 

Well, don't plan on running more than 6,000 RPM....I doubt that a single spring is up to the task. Particularily with 1.6 ratio rockers and a Comp cam ( Agreesive ramps ). I'd think about getting some decent dual springs. I prefer Isky or Crane. Comps off the shelf units sometimes tend to be a bit on the soft side for the cams they use. Particularily if you are using a Cam that is at the upper range of a recommended spring package.

TFS has done the smae thing that Edelbrock did. Cheaped out on some of the components. Edelbrocks valve springs ( Performer RPM heads ) are supposed to be good to .550 lift....and they are. Trouble is that even with a fairly mild cam (218\228 @.050" ) I stated getting valve float at around 5,900 RPM. Mind you, I was running a hydraulic Roller lifter and those are rather porky. You might get away with it using a flat tappet cam....but keep the revs down.