I have a 79 block, with 69 heads I beleive, I will check casting numbers and upsate tomorrow. I have comp cams springs, comp cams 1.72 magnum roller tip rockers, 3/8" motor sport guide plates, arp bbc rocker arm studs, lock nuts and 8.690" 3/8 pushrods. My problem is I cannot set the rockers properly to get the motor to run. When I set the rockers with stock length pushrods 8.550" they were too tight and the motor would not turn over. I switched to 8.690" and loosened the rockers off until it would run, this was 2 full turns, you can wiggle the rockers!! The rockers would back the nuts off. I thought I needed longer pushrods to make up the slack but when I took my pushrod length checker to a hot rod shop they told me that my
problem was the rocker arms. they showed me that the rocker arm when it was held at the position it should sit at the roller sat almost a 1/4" infront of the valve and they showed me that pushrods would correct the geometry. I asked comp cams if there are different rockers for 72 and below heads and they said no. I checked what I ordered and they match up, the rockers also have 1.72 stamped in them. I don't know if there are special rockers made for early model heads. Or if I can go back to a stock rocker arm set up due to the lift of my cam .554" or because the heads were machined for studs. I have no idea what is wrong because I ordered everything new and out of jegs and summit, usuing only name brands so why won't these parts work. I have been fighting with this problem for months now and if anyone else had had problems like this please let me know what I nned to do to fix it. Any help you can give me would be a lifesaver. Thanx.

 

I think you need shorter pushrods.My motor needed shorter ones to get the geometry right they were to far out on the valve also.

Dennis

 

well ! are you adjusting each and every valve when that cylinder is at top dead center? was the person who shaved the heads for your guide plates experienced? maybe he cut to much off the tops of the stud mounts. did you use a push rod length checker ( a push rod that is made up so it can be adjusted to find the correct lengths )? when you talked to the rep you mentioned about the years 1972 and earlier, that could be a mistake '68 thru '71 is cast one way , and 1972 started the fulcrum type rockers, different from the positive stops of the earlier ones. these are the type of rockers that are like the stock ones right, they just torque down. just some of the things i can think of for right now. CJ...........

 

Harland Sharp claims to have a different style rocker for the EARLY 460 heads. Call their tech line and ask them about it. Im guessing this is your problem.

Nathan

 

You need to use your pushrod length checker on each valve to get the overall correct geometry on your valve train.

Valve grinds and new valves will change the depth of the seat. Ford originally recommended + or - .060 pushrods to correct this problem for stock rebuilds, but that's not a real solution for your application with heads machined to accept guide plates.

Cobrajet is correct about the '72 heads. All '68-71 had screw-in studs and in '72, with the exception of the PI head, Ford went to fulcrum style rockers.

When you get the correct geometry figured out, use Crane Kool Nuts on your rocker arms. They have an Allen lock screw in the nut that will allow you to set lifter preload and eliminate the nut backing off because it isn't torqued onto the stud.

 

Is the cam hyd or flat tappet. I don't understand why the engine would be too tight with shorter pushrods. On my pulling engines, I use stock bbc studs, rockers and exh pushrods out of a 366/427 truck block. (budget/wife,etc) With hyd cam I just go to zero lash+1/8 turn. this is on dove heads. I was told that if you put a piece of paper between the rocker and the valve and rotate the engine by hand, the paper should not be torn but if it is torn then the pushrods are the wrong length. don't know if this would work or roller tips. good luck



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