Advancing a cam

[fivelugshortaxle]

I know there's topics on here about it but they don't really seem to answer the question. Deciding on a cam for another build. Going with a custom Steve Long grind. Exr 304 specs are 264@ .050 and .399 lift at cam.

Having it made on a 110 lobe and having 4 degrees of advance build into the grind. In layman's terms, what will the overall result be?
_________________
Good things come to those who wait.
2332 with lots of goodies....
Rotating assembly balanced by Brothers VW
4340 84mm crank
AA 94mm p&c' s
Total seal 2nd ring, rest are Grants
5.5 h beams
Magnum straight cuts
Steve Long XR310 on a 106
CB 1.4 rockers
CB Magnaspark 2 distributor
NGK D7ea plugs
A1 lowdown 1 3/4 with single muffler
Dellorto 48's with 40 venturies
Kennedy Stage 2 with Daiken disc

[UK Luke 72]

Odd you're having a cam ground with such adventurous specs without understanding how lobe separation and timing affect things..
In theory widening the LSA and advancing have opposing effects, one raises peak torque rpm but lowers peak torque whilst the other lowers peak torque rpm whilst increasing peak torque
Perhaps straight up on a 108lsa would've yielded the same results? I doubt it...

If it doesn't get derailed in usual 5lug fashion it could make for an interesting thread.
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[OLD VW NUT]

If you're considering doing this you should ask the cam builder what the effects will be on the engine - that's their job. You must have been thinking about this for a time - why do you think it's worth it? You obviously believe its a good idea - why?

As for the net results? It may move the torque up the RPM range. Probably not by much. You can buy adjustable cam sprockets. Why not use one of those? If you don't like the advance you'll be able to retard it to stock spec or even retarded some. You'll need to remove the oil pump to change the advance mechanism but with this reground cam you won't have that option - you'd need to pull the motor and split the case should you find you don't like the characteristics of the regrind. Better fully understand what you're doing before you jump into this.

What I like about that grind you're going with is the somewhat gentle ramps on the lift. That should help keep lifter bores within spec. Your cam is similar to the 2242 Eagle cam I used in my 2110 build. I use 1.25:1 high ratio rockers. Works pretty good for all around driving.

The 2242 Eagle profile:

Adv. Duration 298°
Dur. @ .050" 248°
Lift @ cam .389"
Lift w/1.1:1 Rocker Arms .428" (my total lift is .486")

I'm also using Manton chromoly pushrods. They add some to the noise present but aren't overwhelming.
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[fivelugshortaxle]

[fivelugshortaxle]

[Alstrup]

He is correct, and then again not. You cannot say so unless you know the exact combo. X heads and y cam may work awesome while X heads and Z cam will be a dawg.
List the specs youre considering, then we can tell. T

[mark tucker]

just hope it dosent eff up your DSR......DCR...rsvp....rip?thats it letter rip!!!

[fivelugshortaxle]

[Alstrup]

OK. In MY opinion.
Even though the Super Pro´s have very good flownumbers and general port velocity, they - are - on the large side for a cam in the 260ish degrees @ 0,050" range and it would definitely be a lesser desireable choice to chose a cam with higher lobe center. What you want is a cam that has the behaviure of making good DCR relatively early in the rpm. That means that the XR 300 cams in general are excluded. Your best choice will be a cam ground on 106 -108 LC and then adjust the rpm band with the duration and lift, roughly spoken.

I would simply get a cam that is ground on 107-108 LC. Then advance it to where you want the intake to open and let the exhaust do what it does. Slightly "big" heads like that typically likes the intake LC to be at 105-106 LC. Then you chose the behaviure you want. You say that you want the power to keep up to about 6200 rpm. That´s no biggie.

In my book that gives you these options, plus one or two.

CB 2288.
Pauter T1E8
Web 86b installed on 106ILC.
Engle FK45 installed on 105 ILC*
Even the FK44 on 106 ILC*

* I would have these ground on a fatter lobe so they are not so harsh on the lifter bores. But that´s me.

And yes I would also stay with a good 1 5/8" header when lower rpm torque is more important than peak hp.

[fivelugshortaxle]

[mark tucker]

just put a super charger on it and it will pull.

[clonebug]

[fivelugshortaxle]

[Alstrup]

Yes the. XR300's have gentle ramps. Too gentle imho. Because on such engine it will cost you 15 hp maybe more plus 10 to 15% torque. Then whats the idea in spending a lot of money for a powerfull engine.
If you want lower rpm torque you have chosen the wrong cylinderheads. As such. But many things are possible if you do it right

[fivelugshortaxle]

Still playing around with cam ideas. All parts are ordered and I'm awaiting delivery. Case should be done soon also. Went with another set of SLR treated scat lifters..they arrived today. Magnaspark 2 distributor from cb arrives tomorrow. Went ahead and ordered a fresh set of AA 94mm p and c's..all ordered Grant rings and total seal 2nd rings. Taking zero chances with AA to b's.

The newest idea I've had is another xr310...tbis one on a 110 lobe. And advanced 2 to 4 degrees. My understanding g is that the wider lobe will spread out the torque and peak later in the rpm's...and advancing it will bring it down to where the torque builds earlier....and with the 110 lobe it should drop off later.
_________________
Good things come to those who wait.
2332 with lots of goodies....
Rotating assembly balanced by Brothers VW
4340 84mm crank
AA 94mm p&c' s
Total seal 2nd ring, rest are Grants
5.5 h beams
Magnum straight cuts
Steve Long XR310 on a 106
CB 1.4 rockers
CB Magnaspark 2 distributor
NGK D7ea plugs
A1 lowdown 1 3/4 with single muffler
Dellorto 48's with 40 venturies
Kennedy Stage 2 with Daiken disc

[modok]

If you widen the lobe center, then advance it the same amount, then the intake events are the same, and what you have moved is the exhaust. Exhaust opens sooner and less overlap. I don't think that will do what you expect.

[fivelugshortaxle]

[modok]

Basically, yes. You have less overlap, and closing the intake later, so, probably, however....if you don't have enough overlap the mid AND top end could take a hit.

Are these the old super-pro or the new super-pro?? they grew you know

[fivelugshortaxle]