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Im putting some Vortec heads on a 70's 350 block. I was woundering if anybody knew if the pushrods are the same length for these heads or if I will need different length ones. Also, I had the valve guides machined for more lift, BUT, does anybody know if the pushrod holes in these heads will have enough clearance for the extra lift (.504) Or will I need to cut those alittle bit?
Anything else?
i have a 283 with vortec heads with a 468/489 lift cam and i didnt even grind down my retainers. i havent had any problems with that. pushrods should be the same leingth.
i will be building a 383 or 406 with the same heads and i will be machining screw in studs, guide plates and thats about it. with that much lift and guide plates, you might have to drill out ur pushrod holes a bit. aka 1/2 in. drill. just make sure u have the right angle.
also, just sayin so you know, once you have machined the heads for guideplates.. (and screw in studs) you no longer need self aligning rocker arms.
They do take a different intake manifold and the bolt holes are different?non existing in th e middle
yep, 4 each side. none in the middle... you might also want to check, but with mine, my manifold only required me to tighten them at like 10 or 18 lbs. dont quote me on how much it was, but i know it wasnt much. spark plug placement is a little different as well but any of the small block plugs will work.
On the ones I have used there were little bosses in the heads where the bolt holes would of been so I drilled and tapped them
I do think you will need to in Large them Pushrod Holes even with 1.5 Rockers . What Rocker arm Ratio are you Going to Run ? And did you also have Screw in Studs installed ? You use the pre-Roller Cam Pushrods 7.800" std Length with a Flat Tappet Camshaft set up .
The main thing to check ontop of binding/rubbing issues ,is the proper contact on top of the valves,this usually dictates pushrod size.
Here is a good summary of Vortec head info from the old Sallee Chevrolet web page:
http://www.sallee-chevrolet.com/Cyli...ads/Vortec.cfm
If you use stock rocker arms (guided type), you shouldnt have any pushrod problems.
This web page also discusses the misconception that there the two casting numbers are different in performance...like the web pags says, there is no difference.
The Vortec head has no water passage into the manifold, hence it does not need the center bolts. The eight manifold bolts are special in that the bottom into the head to keep nimrods from overtightening...a common Chevy manifold and valve cover problem. My name is Mike and I'm a nimrod too...I'm guilty of past overtightening and slathering the gaskets with goo to try to seal them.
mike in tucson