Adjustable rockers question

[mopar Joe 65]

I want to purchase a set of rockers , PRW 3344011 amazon can't tell me what size hold down bolts come with it . Iam using my stock heads and they use 5/16 bolts, i was going to buy a set of comp cam rockers but they are for aluminum heads with 3/8 bolts. I dont want to drill and tap my heads but i dont want to order them if they dont fit. If any body knows please help.

 

[Davea Lux]

You will need to find someone at comp cams that actually knows what they are doing. You will need to contact technical support. I am pretty sure that the rockers for aluminum alloy heads use a different offset and are not the same as the ones used on stock heads, but like everything else in after market performance, it will depend on which aluminum head the rockers are spec'd for. As an example If you specify you are ordering adjustable rockers for stock 906 heads they should have a listing for them. You will also need to know if the adjustable rockers require a specific, usually shorter push rod. It is usually better to buy the camshaft kit that comes with the camshaft, rockers, push rods and rocker shafts so everything is compatible. Depending on the lift and operating range of the camshaft, higher performance valve springs might also be required.

Dave

 

[mopar Joe 65]

Thanks Dave, i was going to use my stock steel rockers but i installed this rv cam and lifters then found out they require adjustable rockers so i dont want to spend a lot of cash on rockers, i actualy bought a set of speedmaster rockers and i sent them back they wouldnt even come close to fitting i could have made them work maybe if i took out some of the shims but i think you get what you pay for? Anyway these PRW rockers look like a good set for a reasonable price ? You would think they could tell me if they fit my stock heads ?

 

[Davea Lux]

Thanks Dave, i was going to use my stock steel rockers but i installed this rv cam and lifters then found out they require adjustable rockers so i dont want to spend a lot of cash on rockers, i actualy bought a set of speedmaster rockers and i sent them back they wouldnt even come close to fitting i could have made them work maybe if i took out some of the shims but i think you get what you pay for? Anyway these PRW rockers look like a good set for a reasonable price ? You would think they could tell me if they fit my stock heads ?

Thanks Dave, i was going to use my stock steel rockers but i installed this rv cam and lifters then found out they require adjustable rockers so i dont want to spend a lot of cash on rockers, i actualy bought a set of speedmaster rockers and i sent them back they wouldnt even come close to fitting i could have made them work maybe if i took out some of the shims but i think you get what you pay for? Anyway these PRW rockers look like a good set for a reasonable price ? You would think they could tell me if they fit my stock heads ?

The only way to know that with any certainty would be to check the application specs. That will require a catalogue or some one who knows that info specific to the rocker set number (I don't). I am curious as to why you are installing the RV cam. That cam is a low end torque, low RPM camshaft and is not really suitable for any type of performance application (Think truck cam).

Dave

 

[CBODY67]

(Wondering WHY the alleged need for adjustable rocker arms, too?)
What motivated the cam upgrade, just curious. What timing specs (on the timing card)?

Anything you might need from ClompCams should be in their online catalogs. There ARE several!

CBODY67

 

[mopar Joe 65]

The cam i bought is a .477 / .480 " comp cam they said it was one step above stock and i could use my stock heads. If i had it to do over again i would go with the eddy top end kit with the aluminum heads but i already had my heads rebuilt.

 

[Davea Lux]

The cam i bought is a .477 / .480 " comp cam they said it was one step above stock and i could use my stock heads. If i had it to do over again i would go with the eddy top end kit with the aluminum heads but i already had my heads rebuilt.

Those lift numbers are a good deal more aggressive than what would be found on an RV cam, so I don't think this is an RV cam. I assume that this is a solid lifter cam which is why you need adjustable rockers. A typical automotive stock cam in the mid to late sixties for a B/RB engine would have been .425/.430 lift. You will need to check the valve clearance as you could run into issues with both the valve springs and the valve to piston clearance. What is the operating range for this cam? It should be listed in the paperwork that came with the cam. There should also be timing spec's for the cam, usually with that much lift, some advance of the camshaft timing might be necessary. It will depend on the duration of the cam.

Dave

 

[Xenon]

i could have made them work maybe if i took out some of the shims

The cam you have listed is a mild cam. Close to a stock hi-po cam...
However, what should concern you more is WHY there are any shims on the rockers...
I can not famtom any engine needing rocker shaft shims especially on a cam of less than .500
when using hydraulic lifters .......


Brand:COMP Cams
Manufacturer's Part Number:CL21-223-4
Part Type:Camshaft Kits
Product Line:COMP Cams Xtreme Energy Cam and Lifter Kits
UPC:036584046653
Cam Style:Hydraulic flat tappet
Basic Operating RPM Range:1,600-5,800
Intake Duration at 050 inch Lift:224
Exhaust Duration at 050 inch Lift:230
Duration at 050 inch Lift:224 int./230 exh.
Advertised Intake Duration:268
Advertised Exhaust Duration:280
Advertised Duration:268 int./280 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:0.477 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:0.480 in.
Valve Lift with Factory Rocker Arm Ratio:0.477 int./0.480 exh.
Lobe Separation (degrees):110
Camshaft Gear Attachment:1-bolt
Grind Number:CRB XE268H-10

 

[moper]

Yeah - why the shims? The XE268 can be used with stock arms, and stock type lifters. You should be running the 911-16 springs, which don't require any special machining on the heads to run. And with the 822-16 lifters you don't need any adjustable rockers.

 

[CBODY67]

"The shims" are there to partially do the same thing as the adjustable rocker arms. To place the plunger in the hydraulic lifter more toward the top of their potential travel in their individual bores (inside of the lifter) so that more rpm can be attained by the engine. "Lifter pump up" used to be a big deal for hydraulics in the '60s, at higher rpms. Engines with stock adjustable lifters, as small block Chevy engines, could be adjusted to either the stock setting or the "hot rod, higher rpm" setting, as desired. Putting the plunger more toward the top of the plunger's travel allows any "pump up" from higher oil pressure be minimal. Shims were more common on Oldsmobile engines, for example, it seems. This is why a somewhat common adjustment for small block Chevy rockers is the 1/4 turn preload rather than the 1.5 turn preload on the rocker arm adjuster nuts. Enough preload to keep things quiet but not enough preload to prevent top rpm capabilities, which then become limited by the valve springs and such.

I'd ALSO check the height of the valve guides and any "closeness" of the valve spring retainers to the guide bosses at max lift, probably .500" valve lift, for good measure.

The OTHER thing about the intensity of that lift/duration interaction is that you could well need better valve springs so the quick and greater up-and-down don't cause the springs to weaken with use! Something that most cam manufacturers don't really admit to, but engine builders can see more of it in their customer's drag race engines.

In one particular case, the "bigger" cam had more lift and less duration. Valve springs weakened much earlier. They went back to a little less lift and a bit more duration (same basic area under the lift curve) and then the springs lasted much better. Drag race ets were marginally-affected.

One caveat of tech support is that although they are supposed to "know something" about what you're trying to accomplish and how to get there (with their products), they might be reading from the same catalog information YOU are looking at yourself, as you talk to them. Looking at the coordinated products you might need. IF they can tell you "Why", that's important! More than just "Our engineers recommend __________". If they know "Why", they might not legally be able to tell you, possibly, which has some product liability issues involved. In other words, they are telling you what they've been told to tell you. Be that as it may.

Comp's website is neat as they have the "build an engine with our cam" program you can use to project what your engine might produce in horserpower, torque, and dyno curves of such. Possibly THREE of their individual products might produce similar power curves (not more than 10 horsepower apart!), as you look at when it all happens to best determine which one might be better for your purposes. Best to download the program rather than use it on their website, from my experiences.

What's the ultimate use of this engine? Just curious.

CBODY67

 

[mopar Joe 65]

Thanks guys for all the input, i guess i misled you on the shims i ment the washer type shims that are on both sides of the hold down blocks, they said i don't need them but i thought they would line up a lot better with the valve stems than they did ? I will enclose a photo of the cam i got, it says i can use my stock heads and so on but i did not see where i needed adjustable rockers until i installed it and it says in the instructions they are required ?

 

[CBODY67]

I suspect it would be more "docile" in a 440 than a 383. FWIW.

 

[moper]

Those are to spread the support across the shaft and space the rockers properly, You have to run those, yes.
Adjustable rockers are only required if you are running the anti-pump-up 867-16 lifters. The standard 822-16s do not require any adjustables.
In both cases, you must make sure the lifters have proper preload. With the 822-16s that would be .050-.100". That's a large window and is usually in spec with typical rebuild work and parts. With the 867-16s the preload is .005-.015". That's a lot harder to hit without using adjustables which is why they say they are a must with those lifters.

 

[mopar Joe 65]

The lifters iam using are comp cam # 145-1001 its what they recomended for there cams. I will enclose a picture and discription of them.

 

[mopar Joe 65]

Somehow i posted it twice.

 

[70bigblockdodge]

Your reading too much into this. Your valve to piston clearance is huge in a stock engine and the chance of your valves hitting the piston without a complete mechanical failure is slim to none. Use your stock rocker arms and push rods. Anything with less than 300° duration and .500" lift is not pushing any limits.
Yes good rocker arms will net you power due to better geometry and a more true ratio, like maybe 5 hp at the levels you are at, and not from the rockers you are looking at.

 

[mopar Joe 65]

If i run the 822-16's with the cam i have do i need adjustable rockers ?

 

[70bigblockdodge]

If i run the 822-16's with the cam i have do i need adjustable rockers ?

Moper listed those in his post as not needing adjustable rockers. The other anti pump up lifters are for stock racing classes where you have to run hydraulic lifters bit need the engine to rev really high. Your cam and pistons are not designed to do this.

 

[mopar Joe 65]

Thanks for the info, do you think I can run my stock rockers with the cam and lifters I have now ? I don’t really want to bother with rollers if I don’t have to.

 

[moper]

No offense but Source is not about supplying really good tech.
The Comp catalog lists the 145-1000(822-16) with an optional 145-1001(867-16). That's the same for all the XE line including the XE Hi-Lift. If it were me, the Hi-Lift versions would get the 867-16s. The other XEs really don't need it. I've run the XE294H to 6500 with standard lifters with no problems... Source wants to sell you more parts.
The plain lifters are fine for the cam you have. Source # 145-1000