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Discussion Starter · #1 ·
I'm thinking about pulling out the XE284 cam out of my 402 in my Chevelle and replacing it with a flat tappet solid cam.

Looking at Comp's selections I'm debating on a few:

XS268S 1600-6000 rpm band, .553/.568 lift, 230/236 dur @ .050
XS274S 2000-6400 rpm band, .568/.578 lift, 236/242 dur @ .050

But then again I'm also interested in Lunati....and being that the Voo Doo cam is the hot ticket right now, I'm curious as to if the Voo Doo line offers a flat tappet solid for big blocks?

What other brand of cams offer a solid flat tappet cam for big blocks?

What I'm working with is a 402 with a .030 bore, 290 oval ports with 2.06/1.72 valves, stock deck height with (I think) a .039 gasket, .180 dome Speed Pro pistons, 1.7 rockers, RPM intake with 750 Holley, TH350 with 3000 stall, 4.10's out the back pushing a 3620 lb car (with a 185 lb driver
) I do have power brakes as well as 1.75 primary headers thru a 2.5 inch exaust. And I may degear the car down to a 3.73 later on....still deciding on that one.

I'm going to guess the XS268S would be the best cam but what about the XS274S? Would either have enough vacuum for the brakes?

I'd also like to know what type of Lunati solid cams would work?

My car is street and strip use.

Also what kind of power gains are to be had going from a hydraulic to a solid lifter cam?
 

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I think you will be happy with either cam as there is very little difference in vacuum (about 12-14 pounds) with this cam. The hydraulic to solid will buy you a lighter tappet with higher RPM potential provided you replace the springs with ones recommended by the cam grinder and install them correctly. The down side is lashing valves and valve noise (which I consider a plus personally) and the fact that you know there is the amount of the lash that isn't going into lift.

As an aside I also addressed the Xtreme Energy grind in another post.


Big Dave
 

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In my personal opinion,picking a camshaft is not like deciding if u will go with onions,or pickles on a hamburger. u sound like u have all the information needed to accuratly pick out a cam,the question i have is,what do the heads flow? this is an important factor as well as at what rpm do u want to make max horsepower? i've put together many effecient high horse motors, and in my opinion crane is one of the best camshafts out,they offer a True billet camshaft with a reliable distributor gear,call the cam company,tell them the intake runner size,flow numbers,and all the other info u listed,as well as what u are doing with the motor, and what u want out of it,and they will tell u the best cam for your application,other wise its just a guessing game and why wast your money and not be satisfied? just my opinion,thanks--Dan--70novadisease
 

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Discussion Starter · #4 ·
I've not had the heads flow checked but I did read somewhere they were still flowing with a .600 lift. Alot of folks have told me to keep the lift around .550 and the duration at or less than 230 on intake @ .050.

I've always heard Crane was a good cam but they're behind the power curve in terms of the latest technology....I have heard Lunaiti hold the current technology record with the Voo Doo line of cams.

As of this morning I've considered maybe going to a solid roller but don't know if it's worth the effort...it seems like it some ways....no break in, less friction, it's new school technology and I've heard todays oils are more comatible with rollers more than they are flat tappets....although I'd think any flat tappet made today would be up to snuff with the current oils....the downside is the price and ofcourse I don't know if I need any machine work done on the heads/block to accept any kind of a roller cam.
 

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The solid roller has been around as a hot rod option since 1963 with Racer Brown and Isky. There isn't any machine work to consider for the block. Heads may have to be machined to accept BBC size (OD) valve springs needed to control the heavier than a flat tappet lifter at high RPM. Oil is an issue with all flat tappets, new or old as the chemical content has changed from the era of flat tappets to roller equipped cars used today.

Only down side to a roller is the cost of the kit. After that it's all down hill :hurray: and fun ride that can be.


Big Dave
 

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Discussion Starter · #6 · (Edited)
Thanx Dave, sounds like the roller is the way to go.....now all I gotta do is figure out which one to go with....I don't know what kind of piston to valve clearance I have.

I do know as of right now the XE284 that I have seems to have no issues. I've wanted to try one of the Lunati Voo Doo rollers (listed in my other thread) but I'm afraid they "might" be too big....
 

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keep in mind that with any solid cam,u will endure alot more maintance,as far as adjusting the valves,i run solid cams in my race car,and i dang near have polylocks with wing nuts on them,just so your aware that u don't just dump it in and go like a hydrolic cam.--Dan
 

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Discussion Starter · #8 ·
Thanx....I understand solid lifter cams aren't necessary "maintenance free"....then again this car is not a daily driver and I'm after all the power I can get from a 396/402 so I think it fits the bill nicely.

Now my biggest problem is selecting the cam that will work best...I'm hearing stuff about this "piston to valve clearance"....as stated my current cam works fine w/o issues, I'd guess either the XS268S or the XS274S I mentioned would work without problems....I'd definitley swap the springs over....

Now I'm also wondering when i order the cam if I should get the lifters that Comp recommends to use with their cams (Comp line of lifters)? Or should I order the Comp cam and get the Isky red zone(?) lifters? There's another brand that I can't remember the name of but supposidly they're like the top lifters on the market.......???????????

I've also heard as far as piston to valve clearance....is dicated by the duration rather than the actual lift itself.....is this so?

I'd still like to go roller lifter, alot of the roller lifters have higher durations than my current cam and much higher lifts too. That's what's got me wondering about if i can run it or not.

I'm in the middle east fighting a war right now, and I have the $$ to order my cam now and have it ready when I come home next year....just wanna get it right the first time. :)

Another thing I heard was I need to get a cam on a billet core and not a cast core....does this sound right?

Also what kind of power increases/decreases would I see with going solid anything over the current XE284 cam I have now?
 

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I don't think any one offers a mechanical roller cam on a cast core. Many offer the billet forged steel core with a pressed on cast distributor gear to avoid having to go the brass distributor gear route (a definite plus) since the other option is a Melonized gear (I personally do not like them) or a plastic gear for only $120 bucks from CompCams that is supposed to out last five or six brass ones.

Yes you must check the piston to valve clearance and the point of maximum interference isn't as you would expect at TDC but about 40° before TDC. The safest approach to this problem is to pull a head and place modeling clay on top of the piston. Oil up the valves (so they don't stick) bolt the engine head back on (just snugged up with the old compressed head gaskets and about eight head bolts across the head) and then turn the engine over carefully by hand for at least three full revolutions (or six times past TDC since the cam operates at half of the crank speed). Pull the head off again and slice the clay in half. Peal off half of it and measure the difference from the squished part to the piston top. Add 0.040" for safety (heat expansion, weak springs, over rev) and that will be the max lift you can run with the duration for that cam.

Isky "Red Zone" lifters is the first "street use" roller lifter ever invented. They are tried and proven to prevent premature lifter failure due to lack of lubrication. Bear in mind that roller lifters used to rely upon splash lubrication for oiling. Well racers have long ago used dry sumps, windage trays, and crank scrapers to get every drop of stray oil under control and off of the rotating assembly. In doing so they removed the only way the roller lifter was lubricated. Ed Iskyderian (and most of the cam grinders now copy him) was the first to realize this and cut two small oil grooves that internally oil the roller tappet bearings, even at idle to prolong the life of the part. Like I said Comp and Crane and the others now offer a similar design, but Ed's (Isky) still works fine and deserves the business for creative thought.

For any given grind, a roller will offer better performance than the flat tappet can provide because the lifter isn't digging into the flanks of the cam lobe with an aggressive lobe design. The roller allows the lifter to roll up the flanks like an Abrahms going over a mud brick wall instead of crashing into it like a Humvee would. :thumbsup:


Big Dave
 

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Discussion Starter · #10 ·
Thanx Dave. I'm being told a lesser duration cam than the one I have now should work. I wished I was home from this war so i could check the pv clearance with the clay as you mentioned.

I'm kind of eying this cam as I made this in another thread:

Engine specs:

402 bbc, bored .030, block not decked, actual L34 396 block
Speed pro .180 dome forged pistons, 4.154 bore
3964290 oval port heads, 2.06/1.72 valves, heads not milled, L34 heads
1.7 rockers
Performer rpm intake, 750 Holley v.s., Mallory large body HEI ingition,

TH350 trans, 4.10 gears, Hughes 3000 stall, pushing a 3800 lb (with driver) Chevelle equipped with power brakes.

Here's the deal: my current cam is a Comp hydraulic flat tappet, model XE284 with a 240/246 duration @ .050, .574/.578 lift. I want to replace it with a solid cam, prefferbly a roller.

I have been told as far as piston to valve clearance the duration of the cam dictates this more than the lift.

The cam I am looking at is a Lunati solid roller Voo Doo cam, p/n 60230. It has a 231/237 duration @ .050 and a .629/.639 lift with 1.7 ratio rockers. Lunaiti says it is a good cam for am 396/402.

I can't check my piston to valve clearance with this cam as I am in the middle east fighting a war and won't be home for months. My wife said I can spend the $$ now if I want to get this cam.

I'm wondering if the duration thing for the piston to valve clearance is true and what the chances are it would work fine in my engine without any mods other than new lifters and springs (already in check)?

My main reasoning for a cam swap: to gain more power while not being so tempermental and still having power brakes to boot.

Thanks!!!!
 

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The VooDoo cam sounds like a winner once you verify it clears. You are getting near the tight end of stock clearances as I was running an L-88 with about 245° duration and 0.712" lift about thirty years ago and it needed to have the pistons fly cut to clear, so I'll wager you'ld be better off safe than sorry with a bent valve by measuring first.
 

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Discussion Starter · #12 ·
Looking at Comp's selections I'm debating on a few:

XS268S 1600-6000 rpm band, .553/.568 lift, 230/236 dur @ .050
XS274S 2000-6400 rpm band, .568/.578 lift, 236/242 dur @ .050
I just got word today on my engine, the bottom cam would most likely only last until 6k then it would be done, what that is I don't know but I'd love to know.

I'm also interested in what other cam makers equate to in terms of performance and reliability.
 

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Having addressed most cam questions; it is time to look at the heads. At 6,000 RPM you are running out of the stock oval ports efficiency range by 5,400 RPM even with a 396. If the motor will spend most of it's time above 4,800 RPM (as in oval track racing or marine use) then I would begin to look at the rectangular port heads off of the old 396 375 horse motor as an option.

If this is a street cruiser were you only occasionally tach it to 6,000 in first or second to dust off a ricer then I wouldn't worry about changing heads. You must ask your self how serious are you about your pursuit of power.

I would pocket port any head I had off of any car as the factory castings are only minimally machined to get the motor running (not to win a race). A three angle valve job (four angle if you are thinking about serious power) with back cut valves and an un-shrouded combustion chamber is a minimal level of machine work. Pocket porting cleans up the long side and opens up restrictions on the short side to let the motor breathe along with reducing the area (increasing the volume) of the port by blending the valve guides and minimizing their restriction. David Vizard wrote an excellent article in Popular HotRodding magazine a month or so ago addressing this issue.

The port work you can do yourself with a 1/4 inch drill and a kit from standard abrasives for about $40. If you want to get more involved a Makita Model GE0600 die grinder and rotary files can be had at Home Depot or Lowes (Pick up some JB Weld while your are there in case you hit water). Most first time hobbyist and quite a few "pros" who do not own a flow bench have a problem removing too much material, or worse wasting time polishing ports. Do not fall into the that trap; just limit your efforts to beburring casting flash and removal of material around the guides. Then concentrate on the valve throat to smooth out the machined steps to a gradual radius.

6,000 RPM doesn't sound like much right now (especially after hearing stories of 331 and 302 small blocks winding to 8,000 and more), but wait until you get some seat time. A 396 at 6,000 will push you into the seat and bring a smile to your face (and scare the bageezes out of anyone running a two liter motor).

Hope you and your fellow troops make it back soon, safe and sound, and wish you a happy Thanks Giving. :waving:



Big Dave
 

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Discussion Starter · #14 ·
Big Dave I thank you for your words of advice.

However, the engine is already together and running, just that I've decided the XE284 cam is a little too much for my engine.

Now if I had the heads off I'd consider the pocket porting and the installation of bigger valves. Perhaps one day when I have the time I might take them off the engine and perform some magic. But for now I'm going to leave them on.

I am aware I'm probably leaving some power on the table by not doing this.....I just don't feel like tearing half the engine back down right now.
I'm willing to do what's necessary to do a cam swap. I figured I could get one of those tools that allows you to blow compressed air in the spark plug home and then change valve springs and retainers with the heads still on the engine.

To be honest with you if I could make this engine pull hard up to 6000 rpm as is, I'd be a happy camper.

I built it to be a weekend street toy to dust off ricers, LS1's, 4.6's....and I also had in mind running it at the track and hopefully running high 11's though that probably won't happen w/o nos or a bigger engine.

I've never heard of the oval ports running out of breath around 5400 rpms....I have heard they run out of breath closer to 7000 but I don't intend to ever spin my engine that high.

FWIW I found an article where they did flow testing on big block heads, and the heads like I have flow past .600 lift.

The engine will probably spend most of it's time in the 2000-4000 rpm range as it does now under normal driving. At the track I plan to run it balls out to 6k.

Another thing too....I'm thinking about later on (a good while from now) building a 454 for the Chevelle and putting this engine in my dad's 68 Camaro as it was originally a 396. It has a Muncie M22 with a 3.55 rear gear with a 27 inch tall tire.

I'd leave the trans and rear gear in the Camaro as they are and put in my engine. The bottom cam looks nice but not sure if the top cam would work better with a 3.55 gear.

Now I know I'm all over the map on gears and such but I was also planning on running a 28 or 29 inch tire in the rear of the Chevelle, hence why I'd need the lower gears....

Someone else mentioned there'd be no change in vacuum on either of the two solid cams I mentioned as opposed to the one I have now, and that I'd need a 112 lsa.....but on the other hand I've also heard duration plays a role in vacuum.....?
 

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just get all your head spec.sflow lift etc.then your engine specs through it on dyno2000 with the cam that you choose and see how well it performs..i dont ever recomend a cam, every motor, car, trans, stall, gears is different..ive used this program 4 times and have been off 5hp..good luck
 

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Discussion Starter · #16 ·
Well unfortunatley I don't have DD2000 which i hear isn't all that accurate anyways.

I don't have flow numbers for the heads.....

I'm not even at home....

I'm in a foreign land fighting for our countries freedom....I'd give almost anything to be home with my wife right now and working on my car....as you can see I'm pretty limited in what I can do right now.....

Some other folks have recommended the 402A2LUN cam but Lunati says the power doesn't come on until 2400 and runs up to 6800....yet they recommend a minimum of a 2500 stall and a 3.55 gear....might work in a 454 but for a 396 I think it would be a real dog.....if not that I'd have to wind the **** out of it to get it in it's power band....
 

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Discussion Starter · #18 ·
Please tell me more about it.....where does the power really come on? What gear you running? What trans? Stall? 1/4 mile times? Trap speed times? Vacuum?


Thanx!
 

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its pretty accurate, as long as the person using it has all the correct info..ported, h20 flow numbers, valve overlap, lift duration, compression, intake specs etc....
2400 rpms isnt bad at all..whats your normal cruising speed?? most dyno pulls aren around 2,000 rpms which is typically where your power comes in at and dies off 6,000..if your heads flow better at the bottom end and dies off at 6,000 which if you have stock heads will be the case, you need small duration, small valve over lap, but big lift...im just saying, since you have time. do a little bit of homework..if you pick to big of a cam with a small stall and little compression its going to be a terd

and if its to big you can actually loose bottom end power. my old cam out of my car didnt come on 3,500 and ran til 7,800 ask phillip he heard it..lol

which is stupid for the street, but i had a friend recomend that cam, and i listened..when i switched to my good flwoing brodix heads over my stock cast irons i lost even more power on the bottom end. at 2000 i was making 245 hp, but at 7,200 i was making 440..but my heads stop flowing at 6,500 so it was pointless..so i built a cam to my head and engine specs and now im at 345 at 2000 rpms and reaches 414 at 6,200 i have all my low end grunt back. which is alot more practical..

just trying to help you pick out a cam ONCE..im sure your head flow numbers can be found, if you wanted to search for them i can help you..
 

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I would go for the Lunati 402A3Lun:

Advertised Duration IN/EX: 276/284
Duration @.050 IN/EX: 243/251
Gross Valve Lift IN/EX: .586"/.600"
Lobe Sep Angle / Intake Ctr Line: 110/104
Valve Lash IN/EX: .026"/.030"
RPM Range: 2500-6800


It would be really nice in your 402. Smaller seat to seat timing than your current cam, more duration at .050 meaning faster ramps. It would be a real hot 402.
 
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