I have a receipt for a Type IV camshaft 391 lift 270 dur. I would assume that is 391 degrees lift and 270 degrees duration but when I went to webcamshafts.com (make sure you don't abbreviate web address ) the specs for all their cams, even stock, were much higher lift, higher duration. What I really want to know is, can this cam be used with a modern digital fuel injection system? How does lift and duration dictate carbs or FI? Assume D-Jet stock/factory FI, I'm not a fan or carbs.

Camshaft specs can be confusing. The .391 figure you quote is lift. This could be lift that is physically ground into the camshaft, meaning how big the 'bump' on the lobe is, or it could be the amount of lift measured at the valve. These can be different because rocker arms typically have a ratio and don't actuate the valves 1 to 1, so a .391" lift at the cam equates to a higher/larger figure when the ratio is applied and the lift is measured at the valve.
270 duration is a measurement of the number of degrees the valve is lifted off its seat. Important to note this is crankshaft degrees and not degrees or camshaft rotation. Lift duration also is measured in different ways, used to be the degrees of rotation were measured from the time the valve was opened/lifted .005" off it seat to the time it was within .005" of being closed/back on its seat. Typically meaningful flow will not begin until the valve is .050" off its seat, and the measurement of duration at .005" and at .050" is much different. Duration at .050 will be somewhat less than that measured at .005" but I believe most new cams are measured at .050" of valve lift.
In my experience more radical/wild cams mess up stock carbs that depend on strong manifold vacuum signals to open/start circuits flowing. One for instance is the power valve in a Holley carburetor, it is designed to open when manifold vacuum drops and enrich fuel flow to the engine like when the throttle is opened and additional fuel flow is needed. It depends on a certain amount of vacuum to keep it closed at idle, but hot cams decrease idle vacuum, to the point where it can actually drop and allow the power valve to open at idle = lots of black smoke out the exhaust. I am old school, I like carburetors but they are nearly obsolete I will admit. Good fuel injection systems outperform carbs by easily measured margins. Injection is the way to go for performance and economy.

Spec would be a stock lift with more duration, only about .030 less lift but same duration than a WEB 86 carb cam.
I'd say Carb cam. NFG for stock FI

Any cam can be used with aftermarket electronic fuel injection. radical cams will be harder to tune than a stock cam.

Do you think this cam is too radical for Megasquirt (or similar type) EFI?

I think you need to know this important difference between carbs and fuel injection, and what effect a cam has on this.

Fuel injection squirts all of the fuel needed onto the closed intake valve. When the intake opens, and the piston is moving down, this fuel squirt is the first thing sucked into the cylinder and is followed by extra air that is swirled or mixed with the fuel squirt in the cylinder. It's like making a cake, you throw the eggs and oil into the container, then add the flour to the container, and then mix. It's the in-cylinder MIXING that makes the right fuel/ air consistency. This precise squirt/add a volume of air and mix process controls the emissions.

Carbs work by suction and spray gas into the air stream rushing into the cylinder. The carb jets are tweaked so the correct amount of fuel is metered into each unit of air passing through the carb. When the intake valve opens, the fuel and air that is sucked into the cylinder is already mixed.

Remember that 270 duration you mentioned? That number indicates how much rotation (in degrees) that the cam holds the valves open. The larger the number, the longer the time for the fuel/ air charge to flow into the cylinder. More fuel/air mix in the cylinder usually means more power. Carb cams use more duration than the factory fuel injection and here is why.

There is this other little thing where the exhaust valve and the intake valve are both open when the piston is going down. This is called overlap, and is used to take advantage of the exhaust suction. Careful cam design can allow the overlap to suck more charge into the cylinder, and enable you to get more power.

Here is the kicker, with a hot cam and large overlap, some of that fuel air charge goes out the exhaust port. With a carb, it doesn't matter as the fuel/air is already correctly mixed going into the cylinder. With fuel injection, the fuel squirt is sucked into the cylinder first, then the air, and then the in-cylinder mix. With a cam with a lot of overlap and fuel injection, you can lose a lot of the fuel squirt down the exhaust, and end up with a lean mix in the cylinder, higher running temperatures (bad), and low power.

Bottom line- factory fuel injection cams have been carefully designed to offer minimal overlap (and minimal duration) to eliminate the loss of the factory fuel squirt down the exhaust.

It's a Fat FC441 camshaft. Their Catalog recommends it for 'small displacement carburated engines' but of course it could be used with aftermarket FI, or even highly tweeked D-Jet (a lot of work). I wouldn't recommend using stock D-Jet, though. I'm running a FC440MP camshaft which is slightly milder with stockish D-Jet, and on the low end and part load it's pretty contankerous.
Mark D.
:EDIT: You can always call Fat Performance and see what they recommend.

This needs some clarification....

It is 100% true, for a batch type injection system. The D-Jet and the L-jet systems are batch injection systems. They spray their fuel on the back of the valve, and it sits there until the valve opens.


It is not true for a sequential system. A sequential injection system has a cam sensor that measures the degrees of camshaft rotation and uses that to time the injector pulse so that it injects fuel only when the intake valve is open. This actually produces more power than the batch injection, as it increases the velocity of the fuel/air mixture.

Plus, the sequential injection can handle more cam overlap than a batch type injection.

Most new injection systems are sequential, as they get better mileage, more power, and lower emissions out of the same engine. Most of them are programmed to default to a batch injection on the loss of the cam sensor (limp mode).

I color between the lines. The first post says "Assume D-Jet/factory FI....."

A lot of testing was done to compare sequential and batch injector firing and there was very little if any power difference between the two for an emissions regulated engine. I think it was the complexity/cost of the early sequential control systems that drove that decision.

Hey Clay, are you sure about these statements?
"A sequential injection system has a cam sensor that measures the degrees of camshaft rotation and uses that to time the injector pulse so that it injects fuel only when the intake valve is open. This actually produces more power than the batch injection, as it increases the velocity of the fuel/air mixture"....

I'm REALLY interested in knowing how the additon of a cam sensor can "increase the velocity of the fuel/air mixture"...

I think you forgot to mention the changes to a bunch of parts (other than the sensor) to get those more power/ high velocity effects.

...well back to discussing the cam specifications.....IT is important to know how the camgrinder -RATES his cams.....is the 271 duration rated at ...020THS...or ....050ths.....unless you have the timing tag/paperwork/ from the camgrinder, and the spec sheet /with the cam marked.....all of the conversation about your cam is meaningless and a wild ass quess....with out the confermations, the only way to know what you have is to mock up in a partially assembled engine and do actual measurements to conferm what you have...duration and lift....also...remember german camgrinders use .040 ths-thats ONE millimeter as the RATING specification.....even if you have to shitcan that cam, due to a lack of confermable information....your better off, so don't look back with any regret....a well made cam, from a reputable camgrinder...is one of the most important parts in the engine.(purchase new lifters when you purchase a new cam.).............murray.

Yep. I copied the lift and duration from the receipt.

.....HOW F.A.T. cams are rated...at .020/ or.050 is NOT specified in their catalog.(with their cams list.)....so you will have to call to find out ..............m.m.

The difference is small, but it is there. When you inject fuel in a batch mode, it is getting injected into a port with no air movement. So some of the fuel injected drops out of atomization. When you use sequential injection, the air is moving when the fuel is injected, so it never drops out.

Yea, it is miniscule. But the auto manufactures would not go to the expense of the extra parts or engineering needed to do sequential injection if it didn't have a benefit in HP or MPG. And almost all of the new cars are sequential injection.

I figgured.

The swept volume of the cylinder doesn't change. So to increase the velocity of the air fuel mix requires one or more of: a manifold size reduction, a higher rpm, a supercharger, a turbo, or a hotter cam with more overlap.

Using a hotter cam is dicey with the narrow operating window of the factory EFI. If a hotter cam is used, then a programmable EFI system and lot of tuning/exhaust gas sniffing is required.

It's not for everyone. Sometimes you can use somebody's injection table, but change one variable (stock muffler or Bursch) and yer on your own.

................and wouldn't increasing the fuel injection (injectors) PRESSURE,(atomization) as well as a specific spray pattern(to accomodate/ optomise the injectors location be of benefit?..............mm.