Newbi Gt40 Rocker Head Question

[ks65stang]

I bought some rebuilt gt40heads for my 289 (non p), cheaper than rebuilding my 289 heads. I know about the combustion chamber size will affect compression and am correcting this with new pistons. Castings are f3ze aa & f1ze aa I was told these are off an actual 5.0 cobra.

I bought these bare w new springs and valves only. My question is do I need guide plates to run roller rockers and if so do I need to mill the heads? What size thickness of push rods and studs? I will buy pushrod tool to check lenght. I want to run 1.6 full roller rockers unless machining is required and i will run stock stuff. From what i read these heads ran 1.7 full roller rockers from ford?

Thanks in advance!

 

[88LX5.Oh]

You need guide plates when you have a stud mount rocker arm. If you have a pedestal mount style head, then no, no guide plate required. Also, you'll need a hardened push rod for use with a stud mount rocker arm.

And I do believe the '93 Cobra's ran a 1.7 roller rocker from the factory.

 

[ks65stang]

Well i guess i dont know if i need pedestal mount or stud mount? Please educate me. Thanks

 

[RangerJoe]

The Cobras came with 1.7 Roller Rockers from Ford, they were made by Crane. They are a pedestal mount rocker, meaning they are held on with a bolt and not a stud. You can add studs to your 40's, along with guide plates, but it does require machining. That adds alot of cost to your budget heads. I run an original set of 93 Cobra rockers and have had no problems with them. You can also buy them aftermarket. They require no maching and bolt right on.

Joe

 

[ks65stang]

Thats the info I was looking for!!! I'm not going to machine the heads. Any good suggestions on where to buy a pedestal mount full roller for $200 or less. I have found used original Cranes on eBay but I rather buy new. Thanks for all the help so far and more questions to come.....

 

[RangerJoe]

You could probably buy some Proform brands for that much, but they are junk! Seriously!

Cjponyparts has FRPP one's on sale for $257 right now, free shipping.

http://www.cjponyparts.com/ford-rac...io-cobra-style-302-351w-1978-1995/p/M6564A50/

Joe

 

[ks65stang]

I think I will buy the Ford Racing from CJ's. I was originally going to buy a 1.6 vs. the 1.7.

Is the 1.7 ratio going to be an issue w/ my setup? My 289 was bored to 4.040 and I am using slightly milled Ford Cobra GT40s heads w/ 63CC chambers (we guessed 63CC due to the milling). My machinist suggested a flat top hyper piston which is supposed to give me 8.7 compression w/ a 65CC head. I plan to run an Edelbrock camshaft with specs. of 204/214 duration & .448/472 lift. I do not know the piston specs (height) till they get here later this week.

So do I sound like I am running any risk of a valve and piston collision w/ the 1.7 ratio rocker. Please forgive me I am very novice to engine building.......

 

[Gearbanger 101]

You should really discuss that with your engine builder. Piston to Valve clearance will depend on many factors. How much has been milled, the type of pistons, whether it has valve reliefs cut into it, cam choice, etc. The best way to know for sure is clay the head. Put a stock, stamped steel rocker on just for fun and see where you're at. FYI, 1.7 rockers don't add as much total lift to the cycle as you might think. The clearance differences are minor.

Also....Stangnet members get an additional 6% discount on top of the listed prices, so make sure you bring that up when buying these rockers.