Hi, I've been trouble shooting my car for a couple of weeks now, and have had some very knowledgeable people look at my engine, and the general consensus seems to be that my timing is off a tooth (retarded). So, since i'm in that area and i've got about $500 saved up, i'd like to put a bigger cam in. The cam i've found that seems like what i'd like to put in is an Edelbrock Performer RPM cam (224/234, with about .5" lift on both). Sound good? My question is, in the edelbrock catalog they have a notation "adjustable valvetrain required". Now, the local guys said that it's not REQUIRED, but it would give me some extra revs at the top end. However, as i don't have a TON of money at the moment, i'd like to stick with what i have (positive stop, stock rocker arms). Now, i do realize that i will HAVE to put new springs, retainers, and locks in, but do i HAVE to have an adjustable valvetrain to keep from ruining something? The studs are press-in, by the way--this is a set of 1970 351W heads. I already have the recommended valve springs, though not installed. Listed pressure is 110-120lbs. I also plan on upgrading my current 4bbl intake to something designed for a 1500-6500rpm range. Does anyone have any suggestions? I like the looks of the "air gap" performer RPM, but i was also wondering about the Stealth and such as i don't really like edelbrock for some reason--although i don't doubt the quality of their parts. Any suggestions for a good cam and intake combination are welcome. As for the rest of the engine: 302, .040 over 351W heads, 60cc chambers with flat-tops good exhaust, MSD, demon vac. sec., etc.... Thanks!
you dont HAVE to have true adjustable valvetrain for that particular cam, but you will have to check a few things. Check to see if the rocker arm doesnt bottom out in its slot with that much lift (I dont think it will). Also check if there's enough clearance between the rocker arm and the spring retainer. Most importantly, make sure the lifters are preloaded correctly. Usually, .030" of preload is plenty. I dont know exactly what size thread the '70 windsor heads use for the rocker studs, but if they're 3/8, you could get by just using some aftermarked posi-locks, like normally used with screw-in studs/roller rocker arms. If they're the traditional 5/16, you could get by using a washer to "shim" the adjusting nut up some to reduce preload if needed. Normally, the washer is put between the nut and the ball pivot, and it has to be right at the 5/16" size so it will bottom out on the "bottleneck" of the stud. There are some 5/16" posi-locks out there, but they're hard to come by. I actually put a set on some old '68 302 2v heads on our street rod mav. They've seen a couple missed shifts (7000), many, many 6000 rpm passes, and around 10,000 street miles---and no problems yet. They all said it cant be done, well, welcome to the wonderful world of hot-rodding: Sometimes you have to figure out things that others say is impossible. As far as intake manifolds, I've always run RPM intakes, with the exception of a vic jr on the 351. I love them, they pull hard from idle all the way up to about 6800-7200 ,then start to sign off. Dad's running an air gap on my old engine, and I ran it up to about 7700, and that's when the RPM heads started wheezing. I'm sure it'd pull harder, but it wasnt making any power. I like the plain ol' RPM for street duty, the Air gap for mild racing. I have tried a stealth on the 460 in the truck, but I'm not sold on it, it seems a bit lazy below 4000 rpm. They say it works from idle to 7000, but I think it works better at higher rpm. That's on a 460 though, so I really cant compare it to a 302. Hope this helps
How much compression does the motor have? I would be hesitant to put a 234 @ .050 cam in a motor that did not have at least 9.5:1 compression.
The heads have 60cc chambers and they have been milled (how much i am not sure), and the engine has flat top pistons. I figure that should put me somewhere close to 9.5:1, right? Aside from the heads not being wonderful (better than stock, but nothing fancy), i'm pretty sure the motor can handle a cam that size. I also live at a higher elevation (5700ft) and live about a mile from elevations ranging from 5,000 to 12,000ft, and i have been led to believe that a larger cam is very helpful at these elevations.
At higher elevations you mention, the air pressure is less. Compression would be more important and a cam of the RV type good for pulling hard, using at least 87 octane gas. Carb jetting also tends to be a little smaller. Same amout of fuel with less air = richer condition. At the higher elevations, an engine acts like it has a restrictor plate under the carb as compaired to operation at near sea level.
Street Mav Well I think the RPM cam is to much. The 224 at .050" lift is a bit much. Find a good Crower or Crane cam with around 215 at .050". You'll find your timing can be a enemy at higher alt also. A cool air system will help a lot. As for the timing chain slipping a tooth? I doubt it. The timing chain is so loose it's slopping and your timing is all over the place. If it had slipped a tooth, it would have slipped a bunch until you put your valves into the pistons. Only way it could be a tooth off is if someone put it in that way. The plastic teeth a quiet and designed to last only about 75K miles. As for the heads studs? Find a store that has the highest grade of 5/16 fine "lock" nuts and use them. Double nut them for safety. Just as Ford did in the Boss 302s, Boss 351s and 429 SCJs. Get the Comp Cam roller tipped rocker arms. The factory ones are trash. Cast and not good for higher spring pressures and lift.
They cam mfgs request that you put adjustable valvetrain components in this application because the incresed spring pressure and more radical valve lift will pull the press in studs out of the heads over time. As they pull out, your valvetrain gets looser and clatters and wears improperly. It really isn't very expensive for a shop to install screw-in studs, and they will never pull out. Do it. It's worth it.
just an added note, it all boils down to this: Adjustable valvetrain isn't REQUIRED, but it is reccomended. It's kind of "cheap insurance" in the long run. I havent had any studs pull out, but have heard of others having that problem. Oh, and that RPM cam, personally if it was me, I'd go a little milder than that one...it's designed for engines 10:1 or better with ported heads, aftermarket free-flowing exhaust systems, higher-stall converter, etc. We ran a Erson HI-FLO 1H cam for eeons, matter of fact, we still have one in the street mav. It pulls well from 2500-5800, probably would pull harder with good heads as the ones I have on it now are bone stock. It's a 228 duration @.050", .504 lift. It has a definete idle chop @ 900 rpm, but with tuning it will smooth out quite a bit. I highly reccomend it. Part number E210421, sold new for $89 4 years ago. That cam will give you plenty of grin with a basically stock engine with intake and carb, but will also allow you to "grow" later when you add heads, bigger carb, converter, and gears.
too big The only thing worse for a daily driver than a too-big carb is an engine saddled with too big of a cam thats long on duration. Long duration hydraulic cams that are 225 degrees at.50-inch for example sacrfice idle manifold vacuum, which reduces the signal to the carb. This means that you must increase jetting to prevent the engine from bucking or surging at part throttle. The result is an over-carburated, overly rich , sluggish engine at speeds below 3000 to 3500 rpm. The reason most people choose a long durationcam is for that lumpy, drive-in idle, If you like that cool sound choose a shorter cam with a tight lobe seperation such as 106 to 108 degrees. This will create that choppy idle but will also improve low speed torque so the engine isnt so much of a stone. Another way around a long duration cam is to use a set of variable-duration hydrualic lifters.These use more clearance in the lifter,which has the effect of shortening the cam duration by a few degrees. This can improve idle quality by a couple of inches of manifold vacuum and restore some lost drivability without sacrificing much top-end power
If you want that nice lumpy sound just remove a vacuum line I ran really fast on a mild cam, and it got great MPG and had great drivability too. I recently went to a bigger cam, and while I think it made a minor improvement in power (haven't gotten to the track yet) it is definitely not worth it, the car feels like sh*t at part throttle now.
Re: adjustable valve train My machinist has a motor he put in his son's Ford Ranger that was originally a roundtrack race engine. It's a 302 with flat tops .030 over. The heads are early 289 small chamber milled to 46cc-that's a tight fit yielding 11.6 according to his calculations. The motor was built to class specs for the track with the stock valves and rocker arms. the only change to the heads was milling and the addition of screw-in studs. I purchased ARP studs myself fairly cheap from www.fastvalves.com D&E Performance in Fla. This motor has a solid lifter cam with about .540 something lift and runs fine. I don't recomend the solid cam, but this shows that with the installation of screw-in studs, you may be able to wait on adding roller rockers, guideplates etc. (also cheap at D & E). Just make sure your stock rocker arms will fit the screw-in studs. Just limit the duration on the cam you choose. Mine came from Holman Moody-240XX. It wasn't cheap though, but works great behind a C4 with no stall. Just my $.02
