Depends on the cam. I just did a GT40 head swap on a roller 351W with 1.7's and the stock F4TE roller cam. No worries with the stock cam and bottomend. Reused the stock pushrods too. I looked back and see you've got a .484 lift cam, that'll change to right at .514, might want to check for coil bind. I've run 1.7's with a B cam, the B cam's lift was .510 with 1.7's. I did however change the springs to a set of Comp's spec'd for a similar cam.
I'm dropping off the heads at the machine shop to check spring pressure and coil bind and either use the springs on it or buy the correct springs and retainers. But yeah cam is a .484 lift. I am looking forward to having the extra lift
The stock GT40 springs are too strong for a flat tappet cam. It will eat the cam and lifters after a while. You NEED to get springs that match that cam.
Heads do not have stock springs on them they are unknown beehive springs....... thsts why the machine shop is checking for spring pressure so we know what's there and if it needs to be replaced with a flat tappet friendly set of springs.
Well my life just got much simpler. Had a friend offer me a set of 289 heads. Ported 3 angle valve job with new oversized valves and seats. New .510 lift springs ready to bolt on in trade for the gt40 heads. He lost his bottom end and built a roller so he doesnt need them anymore. Any idea what a ported set of 289 heads flow vs stock gt40 heads? I won't complain about the extra compression either
Don't know how ported the 289 heads are, so no way to tell. I have a list of the ford small block heads and their flow numbers at home, and stage 1 2 3 porting for most of them for comparison. Any idea how big the valves are on the 289 heads. Keep in mind, your buddy is willing to trade you even over for the gt40 heads, so apparently he wants them for some reason...
Found it online...except this one does not have ported 289s in it. http://www.carbdford.com/tech/flowdata.htm
Even stock GT40 heads will slightly outflow a mildly ported 289 head and will have a better combustion chamber design too(although about 6cc bigger.. but that's what flat milling is for anyways. Also consider that to install larger valves on the 289's requires slight unshrouding of the valves in the chamber which makes the hit on SCR not quite as bad when comparing them there apples). With those larger diameter beehives we discussed previously.. which are easily around 150lb seat pressures) and having the roller rocker conversion done already.. he's getting a major bargain in a trade like that. JMO PS.. you want the smaller diameter beehives(26981 or 26918) for a flat tappet. They're so light with their little itty bitty retainers that they'll easily outrev that cams power range anyways.
Turns out the springs were not beehives. They are just some sort of dual spring. Machinest told me he tested them and the exhaust were only good for about 470 lift max and that was pushing it. I'm guessing someone had these on a stock cam roller motor. What is flat milling?
New springs to work with my cam cost me $15. I got them at cost. You should be able to get them for $20 or so. Get them! Enjoy the ride!
Cool. They said about the same thing. Total cost with retsiners and them checking the heads is about 70.
If you have an 80-85 block, you may not have wanted the extra compression anyway. Those blocks have thin decks and with too much compression they're hard to get head gaskets to seal.
