selecting a roller cam for a 496 BBC

[grumpyvette]

Sometimes life blows... Removed my intake due to a small coolant leak and found 3-4 of my flat tappet lifters do not look very good even though I did the whole break-in procedure when installed the cam as per Lunati's chart. Cam looks good to the naked eye... (Voodoo # 60204). At this point I don't think I want to chance it by installing a new cam and doing the whole thing again... I'm afraid will get the same results or risk damaging my expensive low end in the long run... Too bad because the cam was great. Now thinking of going hyd. roller with this Voodoo grind:

Advertised Duration (Int/Exh): 282/290
Duration @ .050 (Int/Exh): 231/239
Gross Valve Lift (Int/Exh): .600/.600
LSA/ICL: 110/106
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 2200-5800
Includes: Cam Only

Part Number: 20110712
Previous Part Number: 60212

Engine is a 496 BBC, all forged 4340
10.3 compression
Brodix Oval port heads w/rpm intake mild port work
850 holley VS
Comp Cams steel roller rockers
Billet double roller timing chain

Already have a set of roller springs, double with damper (new in box) 135# seat and 370# open @ .600 lift.

My concerns are:
Is this cam a good choice for replacement? Don't want to over cam... Even though my car is light and has a manual trans, 95% street use and cuising.

Will these springs work? I know BBC valvetrain is HEAVY... Cam specs show .600/.600 lift.

Pushrods... Checked geometry with the cam I have now and stock lenght were best, is there a way I can determine which lenght to use? Don't want to wait 2 months to get my cam and then 2 months more for the pushrods... Probably the ones I've got won't work (too bad because they are .080" one piece steel)...

Cam does not state if dist. drive is iron, which I presume it is.

Will reliability really improve with a roller set? That's my biggest reason for the switch. Power was incredible before but again if I'm maxing my credit card wouldn't mind a few more, hopefully I can do the whole deal without breaking my bank account...

Sorry for the long post, hope to get good input from people who know a ton more than me!

If your going to run the car on the current pump octane fuel that roller cam,that you link too with that timing in a 10.2:1 compression 496 is too mild to allow it to run on pump gas youll need a bit longer duration, now obviously youlll want to consider the gearing in the drive train, the car weight, intake design and a dozen other factors, but a dynamic compression closer to 8.1:1 and a LSA thats in the 105-108 range generally runs very well in a 496. every choice you make WILL EFFECT the performance of related components and be a compromise in some area , why not talk to 5 or more cam manufacturers and get their input/
Id also point out that the VAST majority of the times Ive looked into WHY a cam starts losing its lifter or lobe contact areas its almost always related to either a clearance and geometry issue or lack of adequate lubricant flow volume SO I'd strongly suggest a good deal of clearance,checking spring load rates,valve train geometry and checking into cooling lubricants is done well before the new cams broken in even if its a hydraulic roller cam
something closer to THESE TWO matches the engines needs, but again, check out what several manufacturers say then make a choice[/b]
http://www.claysmithcams.com/bbc-477-to ... -6000-rpm/

http://www.summitracing.com/parts/hrs-cl120405-08

why not call
crane,1-866-388-5120
crower,1-619.661.6477
erson,1-800-641-7920
lunati 1-662-892-1500
isky 323.770.0930
clay smith 714-523-0530

THERES A TON OF GOOD RELATED INFO IN THESE LINKS
viewtopic.php?f=69&t=5123

viewtopic.php?f=52&t=4299

viewtopic.php?f=52&t=1477

viewtopic.php?f=52&t=1070

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=727

http://www.projectpontiac.com/ppsite15/ ... calculator

 

[grumpyvette]

So far only David from Lunati has responded a request. He recommends this Bootlegger cam (guess they want to sell the new stuff):

11232HR
232/244 duration @ .050"
.585/.585 lift
108 LSA and 104 intake centerline

keep in mind the cam manufacturers need to find a compromise,when dealing with every request, simply because theres no way they can predict your tolerance for loss of street ability, like lower vacuum for brakes, non-smooth idle,etc. or your real knowledge of how to tune a car or what you really expect so they tend to be a bit conservative, your engine really wants a high 230-mild 240 @.050 lift duration, to allow it to breath efficiently, above about 3500rpm, but the gearing and some other factors in the parts selection somewhat restricts the rpm level that will work well, simply because your going to spend about 90% of your time well below the rpm range where the engine potentially makes its peak power,(5000rpm-6000rpm) so its a bit crazy to cam the cars engine for a narrow rpm range you'll rarely use, most of the time and they concentrate on the part of the rpm band where you will spend 90% of operational time.
the combination of reduced rotational friction and increased actual valve lift off the valve seat time will generally result in a 5%-10% increase swapping from a flat tappet vs a roller lifter cam.

If you had a 3.73:1 rear gear and a bit higher compression theres no doubt at all you would need a 240-245 @.050 lift intake duration to allow a 496 BBC to breath with a set of oval port heads.
remember many customers complain if the car doesn,t drive like its stock at lower rpms yet they expect it to sound like a AA fuel funny car at idle and go like a rocket, all from the same cam, thus the cam manufacturers are in a tough place they tend to know from experience that adding a bit extra exhaust duration to get that rumble at idle and keeping the intake duration low and the LCA fairly wide (FOR A GIVEN APPLICATION) is a bit of a compromise giving a little more sound at the expense of potential performance yet still maintaining a bit better drive-ability
that LUNATI cam timing in my opinion at least shows the fairly tight LSA that will allow the engine to breath during the overlap cycle and a decent lift that will maximize the CURRENT valve train limitations all important factors here! it will more than likely work rather well BUT require premium octane fuel to delay or prevent detonation, it should work well if installed strait up,on a split over lap vs 4 degrees advanced that change would also make the cars engine less likely to detonate on crap gas, kill a small amount of low rpm torque and gain you extra upper rpm peak power so Id certainly think about degreeing in the cam at split over-lap

RELATED INFO
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viewtopic.php?f=52&t=3802

viewtopic.php?f=52&t=181

 

[grumpyvette]

Got a response from howards cams:
Grind 120265 110
237/243 at .050, .635/.640 lift
110 LSA
Seems to be a better fit than the Bootlegger type. Even maybe better idle quality also with my 4.25 stroke, so might be fair down low and still pull better numbers.

Spring recommendation is 98529, 135 seat 340 open.
Looked over and is just a single spring with damper, very similar to the ones that came with mi Brodix heads (140 closed, 370 open), although brodix states .600 max lift.

To me they sound too soft but don't realy know. My heads do have 11/32 stem valves so these are a bit lighter.

What do you think of this combo?

obviously youll need to verify ALL your valve train and piston to valve clearances when you degree the cam in
but that howards cams looks close to ideal using my soft ware

THESE LINKS SHOULD BE HELPFUL
viewtopic.php?f=52&t=528

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=90

viewtopic.php?f=52&t=1489

viewtopic.php?f=52&t=399

viewtopic.php?f=50&t=724&p=1021&hilit=print+wheel+degree#p1021

viewtopic.php?f=52&t=198&p=46839&hilit=adjustable+guide+plates#p46839

 

[Chevytu]

I'm leaning towards the Howards grind as it seems to suit my combo better..
Does the higher lift affect durability for street use? lift is .635 / .640

The boolegger cam has the tighter LSA at 108, but the Howards grind the longer duration and higher lift. I guess the Lunati cam has more exhaust duration for that "race car idle" sound many are after, but my thinking is it must take some performance out in order to give it to you...

Brodix tech did say that because RR heads have stock exhaust ports, a little more ex. duration might help the engine breathe, more if it has a complete exhaust system, which in this case I do. Still I think the Howards cam packs the biggest punch plus idle quality they said will be just lopey with the 4.25 stroke, so that's good news when you get into stop and go traffic... No need to wash your cylinders out of oil or put out a lot of stuff into the air everyone breathes.

I measured the springs I got out of my RR heads, I can go to .700" lift and beyond and still the middle coils have about .080 clearance so I think they would work for either cam. All info on coil springs is a little confusing: Do you need a total of .060 clearance between the active coils or that is the clearance for the complete spring before you run into coil bind?

These are supposed to be rated al .600 lift (at that point they have 370# open pressure), but still have clearance for more, although al .700" the outer coils are starting to contact each other, which I guess happens on all springs though. Seat pressure is 135-140# at 1.95" install height

 

[grumpyvette]

if you can get .700 lift before coil bind you should be fine, obviously youll check rocker geometry, valve train clearances and push rod length, piston to valve clearances ETC. and yes check with the cam manufacturer on load rates but that looks to be well within the expected range also
Grind 120265 110
237/243 at .050, .635/.640 lift
110 LSA

 

[Chevytu]

Cross checked my springs and they should work, these are the specs:

Made by Bullet Cams
140 seat @ 1.950" installed height (mine actually measured around 135, although to be honest I only checked one)
365 open @ 1.350" (.600 lift) (mine went to 370)
Coil bind @ 1.170" (.780 lift)

Cam's lift is .635 /.640

Only concern from the links you provided me is that the cam is for sure a cast core, forgot to ask Howards... Hope it's still durable.

I went ahead and melted my credit card today... Almost chose a Voodoo cam with a bit more duration and less lift (same LSA), part nbr. 20110713 but maybe that was going a bit overboard

Went with the Howards grind, a set of their maximum effort hyd rollers (these have .750" wheels) and a new aluminum timing cover that I can remove without dropping the pan and also has an access hole for checking cam end play (hope it's worth it cause its a little over 200 US). I was thinking of ways to reinforce and modify my stock cover, but after 750+ on cam and rollers I didn't want to cheap out... I do like to make work with what I have though

Hope it works very good, now just have to wait 2 weeks to get the parts delivered from the vendor, 40+ days shipping, install, check geometry to get pushrod lenghts, and then another 40 or so days for the pushrods... :cry:

Thank you for all the help