I looked at the heads earlier and I noticed a number on each of them under the intake ports. The 74 heads have the number D50E and the 68 heads say C80E. I also noticed the 68 heads have red valvesprings and was wondering if they came from the factory that way? Thanks, Ford Guy
Those D5 heads are not 74s. D5 means 75. The way the casting numbers work, they could have been original on any engine 75 or later (later to a point). However they would not be original on anything before 75. The C8 is a 68 (or later) engine part, and yes they often come with colored springs.
Ok, I think I am going to go with the D5OE heads, but now I have another question. Are the stock rockers, studs, and valvesprings able to handle the performer rpm cam? It's lift is .496/.520.
Nope. .470" lift is okay... .480" is iffy... .500" or more is a no-no. I have seen studs pull with .470" lift. I am running .488" lift, and nervous. Those press in studs pull out easy. Edit: I just noticed you want to use stock springs. Am I reading right? You don't want to do that. You will probably wipe your cam. ALWAYS match your springs to your cam. Stock springs are only good for stock cams. BTW: If you really want that cam grind, hopefully you haven't bought it yet. I can save you some dough. TRW makes those cams for Edelbrock to slap their name on. TRW sells the same exact cam for less. They also supply Summit's house grinds, which are same specs also, for cheap.
Well, unfortunately I have already purchased the cam and I guess I will have to have screw-in studs installed and I will have to get the right springs. Thanks to everyone for all of your help, Ford Guy
If you have "rail" rockers you won't need guide plates - using them can cause more problems. So when you take the heads to the machine shop for the screw-in studs let them know which rockers you are using.
You can't use rail rockers with screw in studs. They are not adjustable. They do not have long enough slots to handle a great deal of lift. AND With some aftermarket springs/retainers they can ride the retainer and drop the valve. You can use aftermarket 1.6 long slot Chevy rockers with screw in studs and guideplates if you want a cheap alternative to roller rockers.
The rail rockers use a valve with a longer stem that sticks up from the retainers so the "rails" go down either side of the stem. You can use those rockers with screw-in studs, I have done it. They don't have slots long enough to handle .5 or more but if the cam you use only has .478" of lift at the valve they work just fine. The springs and reainers still use the groove in the valve to locate them - the longer valves have the groove cut at the same height as the shorter valves, the tip just sticks up farther and the rail rockers are good to go. The non-adjustable part of the late rockers is the shoulder on the stud. If you are not using positive stop studs the rail rockers are adjustable. Rail rockers were used on the SBF's from 1966. They are not "the performance alternative" but they do work for cams up to about .5 lift.
He is using more than .500" lift though. Even though rails were used since the 60s, Ford never used them as adjustables. K-codes with adjustable rockers used heads with cast in guide slots and non rail rockers. By 69, Fords were actually using guide plates when adjustable rocker equipped.
Rail rockers started in 67 on the std 289 until mid 69 302s and were FULLY ADJUSTABLE. Fords "change L4" brought us non adjustable valvetrains which also brought us longer valve tips and longer pushrods. So a 1974 valve with 1968 pushrod will NOT work as 68 valve tips are shorter. Though not as short as a 66 or earlier 289s with non rail rockers. From what I recall 1979 was when block deck height was changed.
If you are going to use the D5 heads, I would use the exhaust valve spring retainers and springs(or probably new ones) from the C8 heads(if the D5 heads have the thick rotator- retainers on the exhaust valves). You might be able to get by with stock springs if they were still as new, but you would still need to check for coil bind at max lift. If the springs need to be shimmed to get the pressure back to stock specs, I am sure they would coil bind at the lifts of the cam you have. We have ran the exact same lifts of your cam on a set of stock C9 heads with #940 competition cams springs(approx. 240 lbs. open pressure) using press in studs and stock rail rocker arms for several years on the street(driven hard a lot) and had no problems. Another problem you might have with the D5 heads is the lack of adjustability with the positive stop rocker arm studs. It might work out, but if the valves were too tight or too loose, you could use poly locks(Mr. Gasket #922 I think) or a kit made by comp cams that includes a crimped style lock nut. Although I have never had it happen on any of my engines, I have seen a few press in studs start to pull out, but I am not sure it wasn't because of too much spring pressure or coil bind of the spring. I have never ran into rocker arm slot to stud interference with stock rockers up to .527 lift, but if the geometry wasn't right(wrong length pushrods) it might bind with less lift than that.
It was the D4 blocks that had the extra .023" deck height to lower compression. Did wonders for quench distance. I used a 1974 D4 block for my 347 stroker, had to have .025 milled off.
I have rail rockers (with roller tips) on my 302, and they are adjustable. Of course I am running only .456 lift...
Do a search an talk to manufactures on rockers. Cleveland looks like the same rocker as bbc but the distance is longer between tip and push rod. Harlem Sharp if not mistaken had this info. Not sure on 302 but worth checking! Guys have run cheby rockers an has worked, my thinking is it's not worth it
