Vintage Mustang Forums banner

1 - 5 of 5 Posts

·
Registered
Joined
·
814 Posts
Discussion Starter #1
I have the pre-rail, slotted push-rod hole, '65 289 heads. At how high of a camshaft lift, do I need to start worrying about the length of the slot in my rocker arms? I have a new cam with a .471 lift, intake and exhaust. I did not want the extra expense of roller rockers at this time. If the stock rocker arms do not have enough slot, to make the most use of the cams lift, can they be modified (ie: lengthen the slots)? Any suggestions of a less expensive alternative to roller rockers?
Thanks!
 

·
Registered
Joined
·
514 Posts
I installed a .460 lift cam into my 289 and I had the rocker bind problem. I used a die grinder with a cylinder shaped grinding bit to lengthen the slot on the rocker arms a bit. It worked well, I did one mocked it up on the engine to make sure it wouldn't bind and then did the rest to match the first. One of my old Ford performance books shows this as being a common mod with higher lift cams. HTH

65 Fastback 289 4spd in storage :-(
91 CRX Si... A.K.A. my go-kart with AC!
 

·
Registered
Joined
·
1,888 Posts
You should have no problems with the slot of the rocker arms, with a cam of that lift. The only suggestion I would make is that you might want to upgrade to a little better valve springs than stockers.

I do know that if you go up to a cam with around .520 lift, that you will run into some coil bind with stock spring and then the problems can begin, i.e. broken rockers and bending pushrods.

Rob
Member: Slightly Modified
66 coupe 302
66 fastback 351W
 

·
Registered
Joined
·
1,669 Posts
I used a Comp Cams original factory Hi-Po replacement solid lifter cam during the engine rebuild on the '65. Gross valve lift is .478 intake, .475 exhaust. No interferance at all, but I also stayed with the 1.5:1 rockers. I would not think your combo is going to be aproblem

65 Hi-Po F/B
67 GTA F/B (small block)
MCA 27479
 

·
Registered
Joined
·
10,587 Posts
I ran a similar cam from Isky in my old street racer years ago and did occasionally snap a stud, likely from slot bind....I was young and ignorant of these issues back then....

If you lengthen the slot as indicated in other posts, be sure to use a hard roll to chamfer the edges, especially on the side facing the ball, of the slot extension. Just a light chamfer will do....it'll make life easier on the ball...

IMO, anytime you depart from the stock factory parts, it's a good time to learn and implement the blueprinting process...IOW, checking clearences and measurements...
In this case a little strategically placed putty or dykem blueing will tell you how close your slot and stud are...

Overall, I wouldn't be worried, just aware of the changes and the possible symptoms that may result...

Good luck!

Pat
http://www.jps.net/binay/webdocs/strtmstng002_sml.JPG
 
1 - 5 of 5 Posts
Top