I need to pick a cam for the 496 i am building for my 68 ss.I decided to go with a hydraulic cam.The car is mostly driven on the street,only about one trip to the strip a year.The car is a 4-speed with 3.73 gears power brakes and steering and I am planning to install vintage air.The engine will have about 10 to 1 compression and 074 heads and a 163 intake(GM dual plane aluminum).For now I was planning on using a 750 vac secondary holley carb.This car will see alot of miles in the summer so I don't want to get too crazy because it needs to be dependable.I was thinking of somthing like a comp #xe 274 h-10 274/286-552/555,230/236@.050 with a lobe sep of 110.I don't care what brand it is I was just using the comp for an example.Also what is the thought about using aluminum roller rockers on the street will they hold up?Do I need to run a stud girdle because of the 074 heads(they seem to have alot of rocker stud boss problems)and if I run a stud girdle will they clear stock chrome valve covers if I run spacers or thick gaskets?I would like to keep from going to a roller cam if I can because of the expense.Thanks Bill.

I think your in the ballpark with your choice of cams. Very realistic for the street and without over doing it as you say! I don't think for this cam and your appication that you need a stud girdle. I think BBC hi-perf rocker would also be best for your app. Unless doing some serious racing save your money and put it in upgrades somewhere else! Amazed how so many people try to run such huge cams on the street! I think your playing it smart! I had to go to valve cover spacer on my race car with stud girdle as double gaskets kept leaking. Then you may have clearance with power brake booster etc. Again for app. not necessary! Goodluck with that streetable 496! ;)

I personally would go with an Isky 280 Mega hy-cam on 110 centers and recomemded valve springs. It's 280/232, 110/110(?), .565" lift.

(A powerful cam)... I figure a 496 can pull one fine..

I went with a good old CC 282S solid cam only b/c I wanted a "street" solid cam for my 496.

And yes, stock rockers are fine, imho..

pdq67

I'm running the 074s on my 505. I had mine flow benched and compaired them to a set of 781s that I installed 2.19/1.88 valves and pocket ported and blended. Then we flowed the 781s on the same bench same day as the 074s. I was surprized at how close the numbers were, especially at low lift. I have the numbers if you want them, it might help you with your cam choice.

What I'm getting at is, your heads with the long stroke 496 and dual plane intake will be able to make good power with a small cam like you are looking at, but you will be leaving a LOT of power on the table. I had a .230 / .544 Lunati in one of my boats with a 468 and it idled almost like a stocker and made 450HP. In a 496 it will act even smaller. Cubic inches tend to tame a cam that sounds ratical in a small engine.

Small cams are more streetable and in the long run I think alot of people get tired of the lumpy idles of the bigger cams. But I think with you heads, engine size and manual trans you could run something in the .236 to .240 @.050 dur. range and still have a fairly good idle and use much more of your engines potential. Jusy my opinion.

kamero68,

Please post those flow numbers between the 781's and the 074's. It would be interesting to see the comparison.

Thanks. smile.gif

I'll try to get the #s posted tomorrow, I,m doing my end of the month books tonight. I hate it when work gets in the way of cool stuff.

I'd like to see them too.

STRONGLY advise you consider using the extra long rocker studs on the exhaust side of those heads. I lost a boss. Of course, the motor was seeing 7200-7300. It **might** not be an issue for a sub 6500 motor.

You might want a cam that gentler on setting the valves down on the seats as in the new VooDoo line from Holley/Lunati. Those are soft heads, and although you have steel seats in them, I would not be partial to a "hammering" action with my camshaft.

According to Harold, you defitnely want to phase the cam advanced in your application, it will bolster the velocity through the bigger ports,

e.g., the VooDoo 60204 installed at +6 advanced would be a screamer!

http://www.holley.com/HiOctn/ProdLine/Products/IEC/IECC/Voodoo.html

Thats not long duration for a 496. Harold would likely prefer you go one size bigger with the 4.25" stroke, i.e. the 60205.


I've had NO problem with the Crane Energizers so far for 20K street miles seeing stiff rpm ( for a mild street engine anywaY. Some time ago, competition products had the Crane Gold rockers for $240, w/o the gold anodizing. Thats a decent deal, although long slot stamped would be more than adequate.

Thanks for your help.I will look into the VooDoo cam and the crane rockers.I had heard that the comp XE cams set the valve down hard it probably would not be good for those old heads.What about those new lifters that have been advertised that have the .020 hole in the bottom for more oil flow to the cam lobe?

they won't do a thing for your valve seats. on the oil hole, if QA is bad and the cam is soft, the oil won't hekp much there either.

Tom

I'll 2nd the long thread studs, and we are talking about the threads that go into the head, not the top side that your rockers go on. they help spred the load, but I dont think you have much to worry about with the smaller cams you are looking at. Alot of the 074s broke the rocker bosses(mine included) when people ran them with the springs needed for big solid rollers. But...you never know.

Oh yea, I posted the flow numbers on a thread called "074 and 781 flow numbers"

Well, I broke mine spinning the tar out of it ( may have floated the valve, but I dont think so), with 115/340 pressures. It was a simple solid flat tappet, a gentle one to boot, the old Crane F304-2.

William, I run the oil bleeds, for a bit of insurance on break-in and for the continuous idling a street car might see running a fairly aggressively-ramped cam.

its only for solid flat tappets, not hydraulic cams though. Don't fret about it. Just TRIPLE check everyhting before you fire the engine and using a lighter single spring for can break-in is always a plus. Most, but not all, cam failures are due to a small detail being missed somewhere.

I guess we will see how my 074s hold up. I'm running a hyd roller with .632 lift and 148/400# springs. I got my heads used, they were on one of my jet boats when I bought it. There are three stud bosses that have been repaired before I got them. I ran them for about 30 hours on that boat and saved them when I changed motors in it. Now I have about 250 miles on them on in the Camaro.