MIKE H

I am presently refreshing my 540, new rings and bearings.

I was playing around with the timing of my cam on a version of Dyno2000. I found that retarding the timing 4 degrees increased the horse power and also extending the horsepower over a wider rpm range, it also increased the torque and brought it into a higher rmp range. Are there any disadvantages to retarding cam timing that I might be missing. Would this also increase the chance of reversion by doing so ?

The following are my cam specks

54899 Lunati Camshaft RRB1-240-245 114 Chevrolet 454 96

Intake Exhaust
Valve Lift .612 .612
Lobe Lift .360 .360
Adv Duration .299 .304
.050 Duration 240 245
Lash 000 000
Lobe Centre 110 118

.050 Timing
BTC ABC BBC ATC
10 50 61 5

MIKE H

Any takers on this question, any input would be appreciated.

TomR

Install it at 110 degrees intake centerline. That thing will keep pulling right on up to 5500rpm! The only possible drawback could be a slight loss of low end power, but I really don't think you will notice it. Bottom line is if you have the right intake, carb and ignition set up you won't have a problem.

MIKE H

Thanks for the reply.

110 intake center is where I originally had it installed. It worked very well I was just wondering if retarding it further would be of any advantage or disadvantage.

35/25

Your cam is ground with 114 degree lobe separation, so by installing it at 110 degree intake centerline it is actually advanced by 4 degrees from what would normally be the straight up position. Most of the manufacturers grind their catalog cams with built in advance these days (that is, if you install it by aligning the timing marks in the normal way, the cam is actually advanced. In your case by 4 degrees). Depending upon the compression ratio of your motor and/or the rpm you wish to run it, I would think that the 110 degree intake centerline position would work well. If you retard it to say 112 or 114, you may give up bottom end torque and mid-range throttle response and may not see the horsepower benefit until you reach the upper rpm range. And even then, the gain may be marginal at best.

Rich

WildWarrior

I know this may get confusing , but I usually degree my cams with a bit of advance to get my Hp and T all in lower in the rpm range and also to compensate for the few degrees of cam chain stretch unless you use belts.

Unless you need all the power way up in the top of the rpm range when you retard the cam you sacrifice low end and mid range.


I would try 105 or 106 on the dyno program and see where she likes it for overall Torque and Hp closer together.

Also If you some day go more radical on a new cam, putting her in at 105 or 6 vrs 110 may be a valve to piston clearance issue.

However you install the cam if it were me, I would degree it, you can't always rely on the marks even if you do go straight up. Good luck!

RickR

With assymmetrical (sp?) cam lobes the intake valve max lift will be at a different point than the intake lobe centerline.
On a HP500 carb Crane cam the Intake lobe centerline is @ 105, max lift @ 108.
I would time for max lift with a degree wheel.

articfriends

iTrader: (1)

When i degree a unsymetrical ground cam i go .020 or .050 down from max lift each way and divide in half to find true centerline,Ultradyne recomends this method on their unsymetrical ground cams also,Smitty

cstraub69@comcast

You can't degree an asymetrical cam with centerline method, as smitty said you have to use duration method and degree by the valve events. Crane gives a good step by step instruction on this in the back of their catalog.

Chris

RickR

cstraub
Seems to me, when timing a cam, one of the most important valve events is max intake valve lift.