exp comp cams pushrod to short ?

[fordguy]

ordered this cam http://www.summitracing.com/parts/cca-35-308-8 machine called and said the pushrods were about .100 shy. Any thoughts on what is going on? I am going by to take a look today. Pushrods and rocker arms were damaged so, we did not notice that until he went to assemble, he did check length, not sure if he used a good stock pushrod or length checker pushrod. he mentioned the base circle was smaller. confused on this one, will also give comp cams a call.

 

[BroncoKelley]

If the base circle is smaller (and by the looks of the cam lift it probably is) then you will need longer push rods or valve lash caps to make it work. I ran into the exact same thing when I put a cam in my 5.0 mustang with .529"/.544 lift. Of course it would have been nice to know that at the time I ordered all my parts!?!?!?

 

[fordguy]

yeah I am a little dissappointed in comp, never got any of that info. they seem to indicate it was a drop in replacement. thanks broncokelly. stock pushrods are damaged anyhow so i have to replace.

 

[Timmy390]

Had the same issue with a Crane cam for my 390FE back several years ago. Ordered the pushrods cam and lifters as a kit and the rods were too short. I called Crane and they were like....Yeah we know......

I was pissed......Set my build back for a bit.

Tim

 

[savage]

I think its always hit or miss with push rods when rebuilding, what head gasket was used, if the heads were resurfaced, what rocker arms were used, etc.. when I had my 302 rebuilt, the shop waited till the cam and heads were on to see if I needed to change the push rods.

 

[74strokerbronco]

things that effect pushrod length, CAM BASE CIRCLE, block deck, heads milled, which heads, head gasket thinkness, rockers, valve stem height, lifters. all effect pushrod length. every build is different and every build requires builder to check pushrod length for correct geometry. most mild aftermarket flat tappet hydr. cams are nothing more than a regrind of a factory cam and in order to gain lift and duration the cam base circle must be made smaller. . example factory cam has .300 lobe lift and a BC of 1.5 and with 1.6 rockers net lift is .480. To change said cam to .520 lift the base circle must be ground smaller by .025 giving a lobe lift of .325 and net lift of .520 and a base circle of 1.475 that only accounts for lift , if one is adding duration the base circle has to be further ground to have material on the lobe to further grind the lobe profile. I have seen base circles shrunk as much as .200

this should be over in tech I would think. .

 

[blubuckaroo]

I can't understand why pushrods would be supplied in the first place.?:? There are just too many variables. Providing generic sized pushrods would just encourage people not to check. Sure you may be able to adjust it out. It will run, but it won't be right. Sort of makes you wonder how many motors have valve train geometry issues because of this stuff.

 

[fordguy]

I can't understand why pushrods would be supplied in the first place.?:? There are just too many variables. Providing generic sized pushrods would just encourage people not to check. Sure you may be able to adjust it out. It will run, but it won't be right. Sort of makes you wonder how many motors have valve train geometry issues because of this stuff.

i did not want them to provide pushrods, i wanted a cam that would drop in using stock geometry. i was hoping to avoid changing stock geometry, but that ship has sailed. they said spring change was all that was needed. this is a completely stock build with no deck height change, standard gasket, etc. we were going to check pushrods regardless. once i found out it was the base circle i understood. builder told me that but i missed that part in our initial conversation. i am good now, rant over. thanks for the help.