Comp cams stage 2 big mother thumper cams?

[CarTramrod]

I am currently building a rpg level 3 gen 3 coyote. I have a gen 6 3.0 liter whipple and have an opportunity to get a set of comp cam stage 2 big mother thumper cams for half price. I am doing the pac 1281x springs already with titanium retainers, ferea inconel exhaust valves, ford performance lash adjuster, and gt500 cam followers. Would these cams be worth getting? If so what else to I need to use them? Do I have to lock out my cams or limit them? Any advice would be appreciated.

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[engineermike]

I'm not sure how much power they are worth or what other mechanical parts are needed to make them work, but I can speak to the tuning side.

Simple part first: First understand that when you run the stock Coyote cams at the smallest LSA they physically allow, piston to valve clearance is very small. This isn't an accident. Basically, Ford gave themselves the ability to run as much overlap as they physically safely can within the stock range of motion, without contacting the piston. What that means is that many, if not all aftermarket cams add duration only to the Exhaust Valve Open (EVO) and Intake Valve Close (IVC) sides of each lobe. What this means is you generally shouldn't need lockouts to make these work. Once you understand this, and if you've read any of Vizard's camshaft books, you'd know that the IVC timing is really the most power-influential cam spec. With the stock intake cam and 50-60 deg range of motion, it means you can run the IVC number at exactly optimum all through the rpm range. Since aftermarket cams add duration to the IVC side, that means at full advance (generally used to maximize low-mid rpm torque) the IVC timing is 20 or 30 deg later in the compression stroke, which allows a lot of reverse flow out the intake port (reversion) resulting in a loss of low rpm torque. Then, at high rpm, you only have to retard the intake cam 10 or 15 deg to get IVC to its optimum timing. As a result, WOT (Optimum Power or OP in Ford terms) cam timing looks very different with aftermarket cams. Stock cams might start at -20 intake and 15 exhaust at low rpm, then move to +15 or even +24 intake and 15 exhaust up top, swinging the intake cam up to 44 deg through the rpm range to optimize IVC. With aftermarket cams, this might be more like -20 intake +35 exhaust (you'd run the exhaust more retarded to get EVO where you need it) and only move to -10 intake up top, only giving you 10 deg movement. It really limits your ability to keep IVC optimally timed for max torque through the rpm range.

The more complicated part is the tuning. These coyotes in the mustangs are obviously and unfortunately MAF controlled, but there is a speed-density model that is pretty complicated. The model is used to infer or determine manifold pressure (MAP) for several reasons. Ones that come to mind are throttle angle control (it needs to know the throttle body pressure ratio to know how far to open it), determination of barometric pressure (it uses throttle dP to determine when choke flow occurs to infer baro), and some plenum filling and emptying calculations to have a more accurate cylinder airflow number in dynamic situations when the MAF response time is too slow. So, this speed-density model with aftermarket cams is grossly different than stock. Think about the late IVC at low rpm and how much air is pushed back into the plenum vs stock, which means less air in the cylinder for any given manifold pressure. And conversely, at high rpm you might get more air in the cylinder for a given MAP, which is the whole point. Basically, what I'm saying is the stock speed-density model will be very wrong for aftermarket cams, and if you want a real calibrator to actually tune this part, it takes literally dozens, maybe hundreds, of logs and iterations to get it right so they're going to charge through the nose for it. That said, I highly doubt you're going to find a tuner that really understands the SD model and how to fix it properly. I know for a fact that some of the biggest names don't even bother trying to get the model right and basically just hack and band-aid around it to try to cover up the problems an erroneous SD model causes.

Over the last couple of months, @tdstuart and I did this tuning activity on his car, which uses Comp cams, boss intake, and twin turbos. In the end, the inferred MAP matches actual MAP very closely and I'm very happy with the result. However, it was extremely tedious and very time-consuming.

 

[Optimum Performance]

I am currently building a rpg level 3 gen 3 coyote. I have a gen 6 3.0 liter whipple and have an opportunity to get a set of comp cam stage 2 big mother thumper cams for half price. I am doing the pac 1281x springs already with titanium retainers, ferea inconel exhaust valves, ford performance lash adjuster, and gt500 cam followers. Would these cams be worth getting? If so what else to I need to use them? Do I have to lock out my cams or limit them? Any advice would be appreciated.

Do you have the Long block with ported heads or the short block with stock ports?

 

[CarTramrod]

Do you have the Long block with ported heads or the short block with stock ports?

Shortblock with stock ports.

 

[Optimum Performance]

Shortblock with stock ports.

For the deal on them it wouldn't matter but the ported heads have different flow characteristics so companies like GSC offer different valve events to suit the flow curves. OZ tuning has done a lot of tuning development for several cam companies, if you end up putting the comps in.

 

[tdstuart]

My answer is if you are aiming for something like 1200+hp then get a dedicated blower cam if you want cams.

Even then lots of people have ran stock cams to 1500hp no issue. Once you are past that 1200hp point you can see gains of 50-80hp when swapping to a proper boost designed cam. And I’m talking swapping to a proper designed cam for high hp that will likely require atleast lockouts and possibly intake VCT delete.

If the car will be a street car even if on max boost you will be seeing 1100hp, I would stick stock cams.

I wouldn’t just chuck that comp cam in and hope for the best. At best you will get small gains, at worst your tuner will have a nightmare trying to get the car to be happy and may result in loss of power. Like Mike said tuning cams is very hard and to do it properly requires you to add a map sensor and do tons of datalogs to fix the speed density model.

TLDR do cams for max effort N/A or for 1200+hp race cars, everything else stock cams work great

 

[19BULLITTwhipple]

NO! GET AN FFRE SHORTBLOCK

IT WILL BE AT YOUR HOUSE NEXT WEEK.

Trust me you’re not going to want to wait 9 months for your motor. Stock cams are good to 1400, ask your tuner what cams to get.

 

[CarTramrod]

NO! GET AN FFRE SHORTBLOCK

IT WILL BE AT YOUR HOUSE NEXT WEEK.

Trust me you’re not going to want to wait 9 months for your motor. Stock cams are good to 1400, ask your tuner what cams to get.

Yeah, I tried and they said the blocks were on back order and the earliest I would get one would be mid August. I went rpg because they had the block in stock and it should be shipping out this week or next.

 

[19BULLITTwhipple]

Yeah, I tried and they said the blocks were on back order and the earliest I would get one would be mid August. I went rpg because they had the block in stock and it should be shipping out this week or next.

I have an RPG motor and have many friends with them. I really hope you get it on time.

Because I think you’ll be here for 9 months without a motor. I would love to be wrong. Great product but man I think you’re going to get every excuse in the book till like 2027.

I’ll genuinely be happy if you say “you were wrong” and post an update photo of a delivered shortblock.

 

[CarTramrod]

I have an RPG motor and have many friends with them. I really hope you get it on time.

Because I think you’ll be here for 9 months without a motor. I would love to be wrong. Great product but man I think you’re going to get every excuse in the book till like 2027.

I’ll genuinely be happy if you say “you were wrong” and post an update photo of a delivered shortblock.

I hope so too lol

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