Cam Tech Thread

Jeremy, as many others have said, this is an awesome thread. What about degreeing cams? Your thoughts? Yes I have looked at all the different threads on degreeing cams; but still walk away semi-puzzled. I see different approaches when installing cams through other threads...

This is my understanding - In order to get the most out of your cams, especially if they are "radical", you would want to go ahead and degree them. If the ICL is perfect in terms of what is stated in the cam card, there is not as much of an impact? Typically, the grinds can be up to as many as 4* off in terms of what is stated in the card detail... Do I have that right? The motor is out of the car so this would be the time to do it if I must.. I was wondering how much do you lose in power if the if you are off more than 1* ??

If not using vct, adjustable cam gears allow you to degree the cam (advance or retard) after being cut.

Cams are cut with a centerline as stated for the cam for optimal all around performance this is valve event timing in relation to tdc. You can refer to the advancing or retarding the cam to see how that affects things on the first page. But in short advance builds more low end torque and retard builds high end power. If you have adjustable cam gears you can degree the cam (install it with advance or retard) to optimize the cam on your setup. Or a trick is to time it off a tooth in either direction to do the same thing and locking the cam or still use vct. When using vct it can be ideal to spec a cam with advance cut in then use vct to retard the cam in the upper rpm range to maximize performance. if you already have a cam and want more advance or retard you would use one of the methods stated. 9 times out of 10 just install the cam and time it with the crank.

The purpose of vct was to remove the need to "degree" a cam as you can adjust the timing to optimize performance through the rpm range.

o2sys said:

For a centrifugal type blower, is a blower cam or N/A cam better suited?

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The blower grinds are arguably better suited to a centri than to a PD blower. Since a centri needs RPM to build boost, the extra scavenging from the exhaust valve being open longer will help build cylinder pressure before the blower is spinning fast enough to make significant boost, you don't need this as much for a PD blower.

It still wouldn't hurt to have a blower grind mated to a PD blower, no?
The only issue with building cylinder pressure early is the lack of traction I assume.

Since the PD blower makes boost instantly, you don't need the overlap, plus the blower also helps to push the exhaust out of the cylinder as well so it doesn't benefit it as much. One benefit may be that with the PD blower, some of your boosted intake charge will get blown out the exhaust valve at lower engine speeds making the power more manageable.

PD blower cars are probably the least sensitive to cam timing changes compared to a N/A, centri, and especially a turbo car.

Boost bypasses the restrictions of the intake path. A better air intake path (heads, cams, etc.) is always going to be better but boost pushes through the restrictions, to a point.

The ICL to degree or set the cams to for a locked out 3v is going to be right around 108 degrees for a cam with similar durations to a 127550.

YMMV. I've done a bit of airflow testing with various cams and imo you can't go wrong with a locked out 3v cam set to 108 icl provided it has close to the same durations as a 127500 or 550.

However, your setup will be unique. I've only done the testing and logging with my setups. I have seen a D1 prochaged motor gain over 50rwhp by going from a 127350 at 108 icl to a 127550 cam. The motor had ported heads and was pushing 23psi, at that level the 550 cams really came through. IMO it's pretty hard to beat a 127550 for a blown 3v.

For those looking at lsa keep in mind that a stock cam has 114.25 lsa. Most turbo cams also have 114, most blower cams are 113 and most serious n/a cams are at 112. Not that much difference. The big exceptions are comp 127300 and 350. IIRC they are 115 and 116 lsa. Supposedly better for a turbo to build boost faster. Never had a turbo to test airflow on so I'm just repeating what some smart people have reported.

Knowing the ICL is going to go a long way for a 3v with active vct. Something like the Hot Rod cams have an icl of 92 iirc and require a bit of retard at higher rpms to ensure optimal airflow. They also need a very different injector timing, something that is plotted by looking at the cam profile and adjusted in the drive by wire parameters. Failure to account for this change will result in raw fuel being blown right out the exhaust and pretty bad mpg.

The reason for adjusting the injector timing is to have the injectors start to spray prior to the intake valve opening. This provides a fuel puddle that will be available when the intake valve starts to open. Proper injector timing makes a difference and imo it's the reason why some people have increased power with Hot Rods and some people only have a raw gas smelling exhaust with poor driveability and no power increase.

Do you recall what size pulley you were using to make 23psi on a D1 Procharger?

46addict said:

Do you recall what size pulley you were using to make 23psi on a D1 Procharger?

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That wasn't my setup. It was a friends and I don't remember what he was using for a pulley. IIRC he was making right around 670rwhp on a Mustang dyno. I do know that he put a set of real slicks on his car and pulled off a 9.99 @ 140. This was with a 281 and about 9:1 compression with a manual transmission. IIRC he had a faceplated TKO at that time.

He was also kicked off the track when he came to the ticket booth. He didn't have a cage or chassis cert but did have an NRHA license for much faster times so the track officials were pissed that he did this.