Devdog108

Hey all, I am new to the site here, but have been browsing in the background. I am hoping someone can help me. This is my first engine build and i have taken my sweet time with it. So here goes.

I have an 86 F-150 that my dad bought new in 86. It had the 4.9 liter in it and we came across a 69 fairlane 302 in good shape. I sent the heads off to be cleaned and fluxed, and we went thru the block and cylinder walls and everything looks great. We decided to to put a new cam kit in it from Lunati(mild street cam with lifters, springs, retainers etc.....and 1.6 pushrods). I decided to go ahead and put Lunati roller rockers(1.6) on it instead of the stamped steel self aligning rockers. We put a edelbrock performer intake, and edelbrock 650 with an electric choke and she fired right off on the first start. Heres where the problem comes in.

I have done the roller rocker arm adjustment 5-10 times , it starts, and runs great. Once it cools, i noticed its a bit harder to start so i decided to look at my valve train(repeatedly this has been an issue hence the 5-10 adjustments) and EVERY SINGLE TIME the rockers have moved off the valve tips. Ive checked and double checked the adjustment, push rod length with a checker etc...but they will not stay straight on the valve tips. For the life of me i can't figure out why. I know I'm on the base circle of the cam, i tighten them down until its zero lash, then give myself 1 full turn and tighten the poly lock. I then add about another 1/8th just to ensure its snug....but they ALWAYS move.....and now I'm at a loss.

one friend suggested that i may need valve guide plates, but these are pressed on studs.....

Matthew Burr

those heads are designed for very specific rockers with specific ranges etc etc and are not considered adjustable.

the proper method for setting the rockers is really just setting the nut to the specified torque and then checking the clearance. if it's out of range you get a different sized rod to account for it. with the different cam and roller rockers etc that you have i would imagine that the pressed on stud isnt able to account for the range of motion that everything is requiring and you will probably need new heads or to pull the studs and install threaded bolts that are actually adjustable

at least thats my understanding after having done the research in order to rebuild mine

Matthew Burr

you might be able to get away with getting the next smaller push rod for that particular valve though...

Devdog108

I appreciate that Matthew, here is my conundrum. With the correct roller rockers, and pushrods, I'm dead on with my tolerances. I did every valve individually. So the adjustment on the stud, or clearance, is exactly what it should be. Putting a shorter pushrod in it will throw my tolerances off....on all 16. That's he confusing part. The adjustment for rollers vs. the oem is completely different. You are correct on the torque specs as a good mechanic friend said the same thing.....then I took a pic of the roller rockers with the poly, and he said oh, I have never done those.....

Matthew Burr

have you tried replacing the one lifter?

machviii

When I copied and pasted this from notepad, i left off the actual solution which was at the end. Sorry for any confusion if you read it before I fixed it.......

The previous response to your question was partially correct, but is completely missing the issue. First of all DO NOT RUN THIS ENGINE until this issue is fixed. You have a fairly high risk of damaging the engine. If the rocker falls off the valve, it can hit the retainer, causing a valve to drop, or you could damage a rocker, pushrod, etc.

There is a simple reason for your issue, and a simple solution.

Ford non-small blocks use self aligning or 'rail' rockers. The tabs on the tip of the rocker sit on either side of the valve keeping it in alignment. High performance models like the 289 HP use non-rail rockers, but add a guideplate to keep the pushrod aligned. This in turn keeps the pushrod end of the rocker in line and the front stays on the valve. You currently have neither alignment type.

When you change the cam, you need an adjustable valve train which the stock press in studs do not allow. This is why there is a mention of using different length pushrods in a previous response. This is only for small changes and does not pertain to your engine with the new cam.

There is an inexpensive solution that will allow you to use your new rockers, and fix this problem without removing the heads. It has been out for over 20 years and has been proven to adapt your heads/rockers to adjustable to ensure everything works as intended. It does have limitations, but unless you went for a high lift cam (not sure of exact limit - check with Crane or parts supplier) you'll be fine.

You need the 'Crane Rocker Arm Guideplate Conversion Kits 36655-16.' It costs around $140 from Summit.

Good luck with your project.

Devdog108

Thanks Mach....makes sense. I have an itch for AFR or TW heads now....LOL. Pricey, but fun nonetheless. I probably won't do much beyond what we have done already to the valve train and cam etc, but who knows. With the stock heads, I may just pull them. They are basically brand new after the machine shop was done. I still haven't decided but I can tell you I have found my latest addiction....lol. Someone had told me about the valve guide plate conversion once upon a time. Maybe it was Summit when I bought the chromoly comp cam rods....I don't remember.