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I'm putting a set of Vortec heads on my sbc 400 my cam has a lift of .443/.465. i've heard a lot of different things about the highest lift vortecs can take without machining ive heard .420-.550. which seems a little high. I have matching springs, Competition Cams 742-16 Steel Retainers, with locks, do not have new valve stem seals yet. I'm wondering if with what i have if i can use this cam with theses heads without cutting the valve guides down. any help would be greatly appreciated.
There is lots of bogus info concerning these heads. I think this tutorial sums it all up pretty nicely.Quote:
Originally Posted by micaiahbur14
http://www.crankshaftcoalition.com/w..._cylinder_head
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Welcome to CHR!
The article referenced by Tech is really spot on. The stock Vortec is limited to .420 lift. You will find people that claim to have the stock heads with more lift but one of three things exists with a claim of a stock head running with greater than .420 lift; a) damage is being done (or has already been done) to the head, b) the measurement was done incorrectly (actually .420 or less) or most likely, c) the individual doesn’t really know what the net lift is. The most a stock Vortec head with stock components will safely accommodate is .420. Anything more requires machining the valve guide boss and the valve guide as well as new seals.
With proper machine work as outlined in the article, it is possible to have up to .600 lift on a Vortec head which is more than sufficient for all but the most radical valve train combinations. The pushrod holes should also be enlarged to 1/2" if you'll be using other than stock 1.5:1 rockers. As to the valve seals, see the pictures below.
Best of luck and let us know what you're building.
Again, welcome to CHR
Glenn
yep did a set long before the big net were guys said it could not be done .set them up on the seat and guide machine drop down on the spring pocket then clean up the guide with a seal cutter tool for a 531steel clad rigid chimney viton seal thin wall steel wall if need the od diameter or std 531 seal. i stop using them white PC seals long ago hate them things pure junk use to spilt before you could get then on . i still have them two small trays in my seal cabinet is till they started making the steel wall only viton seal for trip springs with a od of 500 it was them white bastards or NO seals at all :) or a sbc o ring on the EX valve and some RTV in the valve keeper lock gap to slow some of the oil down :) the new chevy casting there is no guild holes to open as its a self guided rocker there is no pushrod holes
Yep---years ago cut spring pockets, guides for seals and shortened, also machined for screw in studs---if you think you need more lift than you can get with those mods, you use longer valves
i was cutting down studs and tapiing them on the mill with a tilt table on it for this small machine shop in town i told him i did not care if i did them or not i think they found a guy that was 10. bucks cheaper then me . boring out the push rod holes were fun i always was waiting for the drill to grab and take the pinch out of the intake portQuote:
Originally Posted by jerry clayton
So question? I'm building a sbc 400 my cam has a lift of. 443/465 and duration of do you think that this cam with vortec heads would work good? and if al what intake would you recommend for this build? Any other suggestions would be greatly appreciated. I'm trying to keep this build kk.d of on the cheap side.
measure the space between your valve retainer and the seal!!!!!!!!!!!!!!!!!!!!!!
How exactly do I measure the distance? this is my very first engine build so any help would be awesome.
Yeah, and leave 0.060" safety margin added to the lift to counter valve float.Quote:
Originally Posted by jerry clayton
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Here's a nice little tutorial for you. You use snap gauges to find the distance from the spring seat to the underside of the retainer....Quote:
Originally Posted by micaiahbur14
https://www.lunatipower.com/Tech/Val...pringTech.aspx
and here's another one from the crankshaft coalition, showing the use of a snap gauge to find the distance.....
http://www.crankshaftcoalition.com/w...ve_spring_tech
You can also do this the low-tech way by cutting a piece of clothes-hanger-wire to the length you are seeking and holding it in there with needle-nose pliers.
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