Hello All, I bought a rebuilt 302 for my comet a little over 2 years ago and it has a 3 year warranty on it, well now the 3 years is almost up and i would like to put a camshaft in it and was wondering what is the highest lift/duration i can go with on the stock heads/springs?
A good "RV" cam with a high lift and short duration is what you need for that. Too much duration with low compression (8:1 in a stock motor) will bleed off too much cylinder pressure and it will be a dog. I wouldn't go over a half-inch lift (.5oo) . You will need new, stiffer springs with a higher than stock lift.
https://www.summitracing.com/parts/sum-3600/overview/make/ford Same cam that Edelbrock sells as their Performer + but less than half the price.
If I were to change the valve springs how would you guys feel about this kit? Would it be to much for a stock engine https://m.summitracing.com/parts/cca-k31-250-4
That's way too much cam for a stock 302. And with a lift that high, I'd be concerned about piston-to-valve clearance. The previous two cam recommendations were more in line with your requirements.
Bigger isn't always better. As mentioned too big of a cam on a low compression engine will bleed off too much cylinder pressure and probably make you slower and get worse economy. Are you looking for more power or just to sound cool? If the latter just unplug 1 spark plug wire, it has the same effect and its free.
Get the smallest Thumper cam Comp makes,that should do the trick,Lunati Voodoo will do the same thing.
To make it reasonably drivable on street any cam with duration greater than approx 215-220*@.050 should also be complemented with higher stall converter and/or more rear gearing... I added a small increase in converter stall to my Comet that's using a Lunatti Voodoo of 207*/213*... That cam has probably a 20* increase in duration over stock... While a rumpty rump cam sounds really cool, 99.9% will quickly tire of it in a daily driver...
I am having my tranny rebuilt with the $9 clutches and also a shift kit (havnt decided which kit yet) and going with a higher stall torque (also havnt decided which one yet so if their are any recommendations please feel free to let me know) I will be replacing the third member with a rebuilt posi unit and 3.55 gears. My comet is by no means a daily driver sometimes I'll take it to work but other then that I just put around town and the occasional trip out of town for a car show/meet
If I were changing cam; I wud install the cam kit w/ all that comes w/ it. I wud wait till I got the funds to do it all at once. I believe best results come, going that route.
couple of random thoughts... PTV related issues with smaller lift/duration cams are less of an issue on factory parts combos. Your piston/block heights are also much more forgiving due to greater clearances as well. Higher lift cams(over about .500" lift) will generally require new rocker arms with longer slots to avoid binding/bending studs. Go with roller rockers and be done with it. Stock springs are absolute junk when it comes to performance of any type. Used ones can come in below 70 lbs at installed heights of 1.7" You want at least 100 lbs on the seat(@1.7") with smaller'ish cams and cheaper replacement springs. Budget springs WILL relax so start with a tad more than you need so they'll never fall below that number after they're seasoned a bit. Old chevy Z-28 springs are dirt cheap, lighter 1.25" diameters, and allow for about 105-110 on seat @1.7" installed height. 96' on up Vortec retainers are cheap and much lighter than the factory pieces(also 1.25").. still accept 11/32" locks too. Spend the extra few bucks on machined locks over the cast pieces. Very cheap insurance. My advice is to avoid wider lobe separation cams(Fords alphabet cams and most other cookie cutter types like posted above) like the plague on these factory headed(exhaust is poor.. needs split/more duration)/lower compression/smaller CID motors. 110° or even a custom ground 108° of similar timing spec's(Comp Cams and many others will grind customs for free) to some of those other ones will be worth another 5-15 ft/lbs and make noticeably more average power. You only feel the power peaks for a moment in time.. it's the higher average power that adds most of the fun on the street. Especially when gear limited. Tighter LSA cams will also add a bit more rumpity rump sound without killing torque like some other cams would. The one I would pick would be this one. Uses the newer 351/HO firing order too. The cam Tom mentioned above would be my next choice although I would probably advance it by another 2° for this particular motor. http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=875&sb=2
Also,if you have over 300 lbs of open valve spring pressure you are going to need screw in studs,guide plates & hardened push rods.As you will soon see that when you go down this road the $ can add up quickly,along with many complications,but hey,thats the fun of it.
Dan makes a good point above. The z-28 springs are under 300 open pressures.. but pinning the studs is prudent advice and cheap insurance in the long run. Every 720° of rotation may not be enough to start pulling studs on its own.. but after 10's of thousands of them things may start to move after a while. Or just bite the bullet and have them pulled and machined for screw in studs. But.. as he also eluded to.. once you start sinking that kind of time and cash into poor performing factory iron.. you may be better off starting out with a new/used set of entry level aluminum castings. Unless it's rare higher-performance iron or originality is a key factor.. machine work and parts tossing at this type of stuff is rarely ever worth the investment.
