cam advance vs. rpm range

So I have this 264/274 cam installed and it comes on hard at 3000 and pulls beyond 5500. It is still pulling hard at that point but I won't rev it past that because i have the 302 springs and I think that is plenty for them. I have the adjustable cam gear and I want to bring the rev range down at least 500 rpm and maybe a bit more. The adjustable cam gear is in 2* increments. Question: How many degrees cam advance per X rpm???

Because it is such a hassle (radiator, belts, front cover, etc) I'd love to nail this on the first shot. I want the cam to come on at 2500 (or less) and pull up to 5000 or so. I consider 5000 or so my redline, so anything beyond that is wasted. Yes, I know I'd get more power higher up. Next car, next engine. This one is a 5K engine.

Thanks,
James

You didn't mention if you even degreed the cam initially when you installed it. Also never assume that because the dots on the timing gears are aligned you are putting the cam "straight up" so to speak. You need to actually compare the intake and exhaust valves opening and closing #'s to the cam card, to make sure you aren't already way past or way under the recommendations of the cam grinder. Typically, 4°advance should lower your RPM range the amount you are looking for. Also, advancing the camshaft reduces your intake valve clearance with the piston, so check it out before you get into one of those situations. Advancing a cam isn't like advancing the timing, in that when you advance a cam, you are moving and changing the physical relationship between all (12) valves and the pistons by doing so which affects their clearance to one another, so if you don't know where they are in that relationship to start with, be cautious, and don't assume you will be fine without checking them.

8) i agree that 4 degrees advance will get you where you want to go. cnc-dude, our sixes are not interference engines, and the cam he has doesnt have enough lift or duration to cause any problems with piston to valve clearance.

Ok, he should be good to go then, just add the advance into it. Let us know how you make out with it.

Roger to all of the above. And I did degree the cam but it is clear to me now that I degreed it incorrectly. The result I got using the centerline method was to set it at -2* on the adjustable wheel. Clearly wrong but since the premise when degreeing is that the markings are going to be off anyway I figured "the numbers don't lie." Garbage in garbage out, I suppose.

Since that's the case and I now have real-world feedback from actually driving it that the cam is way retarded (can't even get it to idle below 900 rpm), I'm just going to dial it in by seat of the pants. So yes, I know it is supposed to be advanced by four degrees from straight up. Since I did a poor job with the degree wheel, I don't actually now where "straight up" really lies. So I return to the original question: does anybody know how many rpm change in the powerband to expect per x degrees of cam advance : :

Barring any "formula" to solve this, I'll just set it at +4*, which is six advanced from where it is, and call it a day. At least it will have lots of grunt! :rolflmao:

8) while there is now set number to indicate how far up or down the rpm range your peak power numbers move, a general rule of thumb is 2 degrees = about 250-300 rpm. understand though that this is just a rule of thumb, and that even changes the further each way you go. now if you have the cam installed 2 degree retarded, and advance it 4 degrees, you are at 2 degrees advanced. perhaps advancing the cam 6 degrees would be better as that would put you at 4 degrees advanced. your choice though.

falcon fanatic":322j84l5 said:

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Barring any "formula" to solve this, I'll just set it at +4*, which is six advanced from where it is, and call it a day. At least it will have lots of grunt! :rolflmao:

Click to expand...

That's what I would do

Since I have the same cam and am just about to put the new head on, I'd appreciate it if you'd go 6 degrees advanced, and let us know how she goes.

Are you going to degree it again?

I'm curious as to what speed you're seeing at that 5500rpm. Mine, in stock form, has never been able to run higher than about 4k rpm in third with the 1bbl. Have a couple of 2bbl to choose from.

Havent taken it on the highway Jackfish, so I don't know, but it would be over 100 for sure. Just been hitting first and second manual shifting, but mostly watching the tach and the road, not the speedo.

Thx rbohm for the approximation of an rpm range. Yeah, I guess I'll go to +4. if that lowers my rev range by 750 or so that will have teh cam come on around 2250 and pulling to around 5000, which should be great with this head I have and the stock TC I'm using.

I have the same deal on my car. I'd have to go back and look at the dyno sheets (Mike has them posted here) but we set an arbitrary cutoff of 4,800 and it was still pulling strong. But it has no gust at lower rpm. I set mine up "straight up" as indicated but did not degree the cam.
Now, no one will know for sure without degreeing the cam but on the first pull the dyno guys were like "you got the cam set up slow?" These are guys that do dyno runs all day so their intuition ought to coun t for something.
Mike and i talked about it and agreed that if i was not going to degree the cam then I should advance it a minimum of 4 degrees.
I may do nothing as I have a dependable daily driver with no bad habits and the power is there when I want it, when it kicks down either passing or accelerating on the on-ramp.
How is your idle?

I'm trying to degree my cam at the moment and the numbers are whacked.
Probably my methodology, but I'm trying to follow the instructions for taking measurements at .050 on either side of maximum lift.

I'm getting 64° before max lift, and 152° after.
Add together and divide by two is 108°. So where does that leave me?

Am I on track here? :help:

Kind of annoyed that they don't give the specs without rocker ratios added in.

The other way you can do it off their card, is with the event timings - watch the dial gauge for when it just starts to rise on the intake lobe, and note the degrees. Once over the lobe tip, note the degrees when the cam no longer lifts the valve.

Do the same for exhaust valve and note readings. There's usually slight "jiggliness" due to the surface finish of a new taper ground cam.

You need to set up the dial gauge with a solid lifter and the gauge nub positioned directly inline with the pushrod - use a damper spring only on the valve, and a used gasket for correct clearance.

Compare all numbers with the cam card and see where it lies on the average.

At .050 lift the dial reads 1°, and on the other side of the lobe @ .050 before closing it reads 213°. Does that not equal 212° of duration, rather than the advertised 214°?

Where I'm having trouble is the 20° and 64° specs.

How do I interpret these numbers?

Forget the .o50 . The event check height on a R ACER BROWN CAM IS .018 try that. The intake opens 20* btdc The intake closes 64* abdc The exaust opens 69-- * bbdc T he exaust closes 25--*atdc. Work with it till it makes sense. Ajust check height a few thou and move cam until all four event jibe. Also do not read the degree wheel.count the degrees to top dead center or to bottom dead center.

Well I'm glad I'm not the only moron who can't figure out how to degree a cam correctly, in spite of having all the equipment, instructions and data. Off to the garage to pull my radiator, belts, and timing cover. Oh sh*t, I forgot to borrow a harmonic balancer puller Still, miles to before we get there...

hi ho, hi ho...

I wonder if they used .010 for their measurements, because it would seem that at that lift I can hit that 69° bbdc mark on the exhaust.
Or my cam is advanced. I mentioned a 4° advance to the shop when I had it built, but they said they installed it straight up. But who knows for sure?
I don't want to pull the cover as those gaskets are hard to come by and aren't cheap up here.

Thanks for the tip I think it was the bbdc and abdc measurements they use that confused me.
It would appear they take their measurements @ .010 because I was able to hit the 69° and 25° mark pretty close at that lift.
My hillbilly method of measuring may leave something to be desired, but with the head off I had to stabilize the pushrod somehow.
Homemade degree wheel!

Actually, the washer is a great idea. i won't tell you what I used

Well, only took an hour to get everything off and the timing cover loosened. Shoulda gone to get that balancer puller first, becasuse now AutoZone is closed and I'm stuck. Coulda been done tonight.. Instead I'll have to drink beer and watch the Grand Prix of Monza.

Follow the cam degreeing instructions on isky's & comp cams website for the proper degreeing of your camshaft.
All you need to get the intake centerline is .100" on either side of the nose of the camshaft & go from there.
2 degrees is all you need for the best top end, if you want more low end go with 4 degrees advance.
I am new to this forum, but all i read is the use of stock ford 302 valve springs.
These springs are junk & under the necessary #'s to prevent valve float at higher rpms.
That certain someone who recommends them is an idiot.
You need springs with at least 80-100# seat pressure & a damper inside the valve springs.
Outlaw

DAYYYMMM! Nice introduction.....