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BBC Chevy Comp Cams 566/566 Xtreme Retro Hydraulic Roller Cam 11-456-8



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BBC Chevy Comp Retro Style (flat nose) Hydraulic Roller Cam.
566/566 Lift 242/248 Duration 112 Lobe Sep. 
Xtreme Marine or Street Rod Camshaft 11-456-8
This cam has a flat nose for use in early or late model roller blocks and non-roller blocks. We have this cam available in an oe step nose also in our other listings. The part number for it is 01-456-8
See dyno reports below.


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Part number: 11-456-8
566/566 lift.

242/248 duration

112 lobe sep.

This cam is our most popular choice for our street rod bbc engine builds.

Comp Cams 'Xtreme Marine & Auto' Step Nose Hydraulic Roller Camshafts.

Cam info:

This cam is one of our official cam choices in our line of bbc engines. It is the perfect size to offer the best balance of power while putting a relatively low amount of stress on the valve train. This profile is somewhat easy on the valve train, and makes a great amount of overall power on bbc street rods. This cam is somewhat aggressive for 454 engine builds, and just right for most 496 bbc street rod engines running on pump gas. Compression ratio in 454/468 engine builds should be around 10.8:1 or higher for best results, and around 10.4:1 or higher in 496 engine builds running pump gas. For engine builds in the 540 up to 572 this cam is an excellent choice for those wanting a high level of street manners, and excellent bottom and mid range power. 

This cam has a very unique profile. One of our former cam choices that was similar in our engines was nearly identical in lift and duration and had a 110 lobe sep, and it made approx. 35 hp less on every combo we ran it on. Our new Comp Cam is set up with a 112 lobe sep, yet still makes so much more power, and with the 112 lobe sep, creates a safer setup overall for the engine than a 110 lobe sep.

This is an amazing cam in every respect. As you may know, there are many aspects to a cam’s profile besides lift, duration and lobe sep. and Comp Cams has produced an excellent cam that works very well in all bbc street rods. We’re going to list below our actual dyno results on every size of bbc engine we have dynoed with this cam. We have used it in at least 600 bbc engines, from a 454 up to our 632 in the past couple of years. Of the three Comp Cams we use, this is our second most popular. 

We offer two more amazing Comp Cam profiles that we’re very proud of. For those running the smaller bbc engines, we recommend our Comp 547/547 lift cam for improved low end response. If you’re building a 454/468 engine, this cam would be considered aggressive, and would require compression ratio numbers in the range mentioned above. For those building a 496 or larger and want the decent bottom to mid power available in a hydraulic roller without having to spend huge amounts of money to stabilize the valve train, then this cam choice is the perfect choice for you.

This cam will allow safe operation of the valve train. It's not going to give any problems in the long run if you’re running decent hardware and lifters. You should run a higher than normal grade lifter. Regular drop in roller lifters may not work properly with this cam. This increased lift and duration will bring the spring pressures up on the nose somewhat high, and that's desirable to maintain valve train stability, but regular lifters may have an issue with this increased pressure.


Below are our dyno results on some of our engines with this cam. Your results may vary depending on intake choice. The horse power numbers will always improve anywhere from 5-10 more than what the dyno results show after the rings have fully seated. 
Dyno reports below. More coming soon.
This particular engine had our Bravo heads and a single plane intake, and made 723.5 horsepower with this cam.
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Official Dyno report with this cam choice, AFR heads, a dual plane intake, a Holley Super Sniper fuel injection system, and an MSD distributor. The torque in the low rpm range with the EFI system is very impressive.
572 w/566-566 cam super sniper dyno photo 1a210250-7b77-4a4f-b9a8-208bc7d2969e.jpg 
  572 w/566-566 cam super sniper graph photo fb24254b-3b10-4349-9e99-7bbeea984bba.jpg
Official Dyno report on our 555 engine with this cam choice, Bravo heads, a single plane intake, and an MSD distributor.
555 566/566 dyno photo 89c548d2-8923-4722-90a6-ece01053991a.jpg
555 566/566 graph photo e05df7b1-ab3f-44b6-bddd-c7ebc96494e8.jpg
Our regular Howards Tie Bar hyd. roller lifters were on the verge of valve float at peak power rpm on the smaller bbc engines. As you may know, the smaller cubic inch bbc engines will require a bit more rpm to make max power, and right at 6000 rpm, the regular street tie bar lifters were allowing light valve float to enter the picture. This is evident on the dyno, as the engine takes a sharp nose dive right about 5900-6000 rpm.

Truth is, prior to this rpm, the hp numbers were not climbing the way they should, and minor valve float was taking place earlier than 5900. Valve float to a minor degree can allow a valve to come loose from its locks. This could spell instant doom for your engine. It would be fair to say that most dropped valves in bbc engines happen when the rpm is taken past the valve train limits.  Each time minor valve float comes in, it is weakening, or may we say, creating excessive wear on components that eventually lead to a dropped or bent valve.

We have many allies against such problems, and without spending a great amount of money, including the lightweight PBM Competition valves, and Comp Cams light weight springs and retainers we use in all our bbc heads. We also use high quality lightweight roller rockers. Read below for more info on things you can do to prevent problems in the valve train when running cams in the upper lift range. If you think you can get by with a slightly smaller cam, we offer a cam that is identical in its overall design but has a lower lift, 547/547, and a reduction in duration. It would be better suited for the 454/468 pump gas street rods in our opinion, and is less demanding on what type lifters you use. 

Listed below are a few important solutions to preventing valve train issues while having maximum performance and longevity in your engine when running large lift cams.

The solution to running a hyd. roller cam of decent size in a bbc engine is an easy, low cost fix, thanks to the Howards Max Effort lifters and Comp lightweight springs. The cost is only slightly more than the regular Howards street tie bar lifters, and they are undoubtedly the most stable hyd. roller lifters on the market without going to all out racing hyd. lifters. The Max Efforts are also very quiet. Not sure what rpm range they can remain stable at, but we have pushed some of our bbc engines up to the 6500 rpm range in order to establish the fall off point of a particular build. Fall off on hp levels are gradual up to 400 rpm past the max hp rpm range when using these special lifters, and that's the way it should be. We now use these lifters with all three of our bbc cam choices. 

The next big cause for valve train instability when running a cam in the upper lift and duration range on a bbc engine would be having spring pressure that is too low. Regardless of what some may say would be the correct spring pressure, we know what it should be for safe operation and good performance. The numbers are slightly high, according to some uninformed authorities, but running too low of a spring pressure will assure valve float when running a cam of this size.

If you have weak springs or wrong pressure ranges in your setup, then you must correct this. We offer a proper set of Comp valve springs that work perfectly with this cam. They do not require unusually long valves. We’re very satisfied with the seat to nose ratio. These springs are also much lighter in weight than previous springs we have used, and that's a real plus when trying to stabilize the valve train on a bbc engine running at near or above 6000 rpm. 

As you may know, there are larger lift bbc hyd. roller cams on the market, and we have used them for those running Pro-Street setups. Those also require a different type of lifter and special springs than what is used when running our regular Comp Cams. Our experience is vast on how to properly setup your valve train, due to the fact we have dynoed so many bbc street rod engines.

Big block Chevy engines pose a problem when running healthy sized hyd. roller cams if the valve train is not setup properly. It is essential that you address this before you start your build. 

We also offer this cam in a step nose oe roller style for use with later model blocks or blocks with a provision for a cam locking plate.

Please read the complete ad before purchasing this cam. If you're not sure if this cam is correct for your application, feel free to contact us for technical support.


If you would like expert cam recommendations for your engine, contact us (through the "seller information" tab with the information listed below. We will tell you what cam is best suited for you. Running a cam that is too big in a given combination is not only pointless for making increased power, but creates a increased loss of drivability and unnecessary wear on the valve train. You must have sufficient cubic inch and/or compression ratio, coupled with correct size cylinder heads that will allow enough flow, to justify a particular size cam. Bottom-end and mid-range performance are always affected when you increase cam size, but it would be affected even more if a cam selection is over-sized to the point that no top-end power is gained. So choosing too large of a cam becomes a two-fold problem. Tuning also becomes more difficult with larger than needed cams. 

For a recommendation on the best cam for you, please contact us with us the following information: 


  • Vehicle model or weight.
  • Engine size, (cubic inch)
  • Approx. compression ratio.
  • Cylinder head runner size.
  • Single or dual plane intake, (if dual plane, what model)
  • Final gear ratio, and overall tire diameter if known.
  • Transmission model.
  • Converter stall range.
  • Your hp expectations, and how you will be using the vehicle (cruising, street, strip, show car, etc.)
  • If a lopey idle is highly desirable. The size engine you have determines this with a given cam choice. We can tell you exactly what a particular cam will sound like in an engine.
  • The brand and type/series of lifters you are running. Very important!


Should a problem occur, please contact us. If a return is necessary, please contact us for an RGA number and return authorization. The RGA number must be included on the return label. If an item is returned without an RGA number, it will not be processed.






If you checkout and start over, the auto calculator will not recognize the multiple purchases, and there will be no shipping discount. 


FedEx is our primary shipper. We are unable to ship to APO/FPO addresses. Help us ship your order promptly by including your physical address at checkout. If your order MUST be shipped to a PO BOX, please contact us by phone. Additional charges may apply. Below is a map representing the estimated delivery time to get to you from our location.


FedEx Home Delivery delivers Tuesday - Saturday. If a package leaves here on a Thursday, and you are in a 2 day delivery zone, your package will deliver to you on Saturday. If you are in a 3 day zone, and your package leaves on a Thursday, you will not receive it until Tuesday. Expedited shipping is available upon request for an additional fee. Please contact us for rates.  

Hawaii and Alaska have a 6+ day estimated delivery time.

The shipping quoted in this ad is only for the 48 continental United States. If shipping to anywhere else, please give us a call or email us for quotes. The half price shipping on all additional items also only applies to items that are being shipped in the 48 continental United States

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