ok i just bought a set of 906 casting vortec heads... i belive these are the better flowing heads from the L31 motor.... i belive not sure... but what i need to know is what all will have 2 be done to get them to accept a lift of .534? i plan on running a comp 292 cam with 1.6 rockers, i know i need to have the head set for screw in studs, but what bout the spring seats and the guides and so forth and also the hole where the push rod comes up throught the head would that have 2 be elongated (sp)? these heads are going on a 383 so all help would be great thanks agian......

 

Hey, i've got the vortec's on my engine as well, and with the 1.6 RR's on my XE cam, I'm at a .530" lift all around. In order to handle that, I called jegs and found out which Comp springs matched the cam I got, had them installed on the heads and also had screw in studs installed. They didn't do anything to the bores of the pushrod holes, and i've had no problem, so i'm sure you won't either. As far as accepting the over .500 lift, that was all I had done (I also had them milled, and a 45 degree valve job at the same time). So just get the screw in studs and springs that are matched to your cam and can handle the .534 lift.

 

see below

 

I was just informed Chevy Hi-performance retracted that statement about the 906 vortecs, I stand corrected!

 

retracted what statement sweet?

 

No, it wasn't.

They may not have told you; but they also shortened the top of the valve guide. If they hadn't done that, the bottom of the retainer would slam into the top of the valve guide at about .480" lift.

The tool that they used to machine out the spring pockets for the higher lift springs may very well have been one of the ones that cuts the guide at the same time. That's the easy way to do it, all in one step. But not all shops do it that way.

Don't think you're going to get that much lift on a set of 906 castings without shortening the guides; broken valve train parts will be the result.

 

yea i thought they needed to be milled thats why i am asking... didnt want to turn the motor over and have a big problem after it was put together....

 

If I remember correctly .520 was the maximum lift I could safely run on my vortecs before the clearances were too tight. It was even less with the stock valve seals. Keep in mind vortecs peak out at .500 lift so why go too far past it?

 

safe as in what before u hit the piston with the valve or just bottoming out the keeper to the head? please explain in detail... the cam i am getting had a lift of .501 but i wanted to add 1.6 rockers.... and it would go to .534 so....

 

I'm talking about valve guide to retainer clearance. Use 1.5 rockers, you're wasting your time and money any other way.

 

the vortec heads loose flow after .500 lift. if you're at .534" with 1.6 rockers, then you should switch to 1.5s and drop down to .500 lift. It will actually make more power this way. Also you can buy a valve seat cutter and a guide cutter from summitracing, but for both tools and the arbor you're looking at an added 100 dollars. What I did was simply order a valve train upgrade kit from competition products. they valves are taller, about .1" so you will have the clearence you need. the kit also comes with howards cam valves springs and 10 degree retainers and locks and valve seals. The kit is good for up to .510" lift and only costs 99.95, or you can get the better springs and have clearence for .570" lift. that set is $130. I know that sounds really cheap for valves, springs and the lot, but they make their own valves and the springs are only $30 to buy anywhere. it is a really nice set for the money, I know a guy who's running a 650 hp camaro using a set, so they wont break or anything like that. the part numbers are 851295 or 851395. for stock valve sizes. they also sell larger valves at the same prices. competitionproducts.com

 

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