Hemi cam advance

I need to advance the cam in my KB to gain extra valve/piston clearance, what parts are available for this task, gears or cam drive plate?

Arias reccomend 0.175" valve/piston clearance, currently at 0.115".

Cheers Ray

 

go to this site and you will find the pitfalls of to much piston to valve clearance.http://www.findarticles.com/p/search?qt=david++Reher&qf=free&qta=1&tb=art&x=0&y=0

 

valve clearance

eli,
be sure that when checking the clearence you do it 10 degrees before tdc.
Of course you know that when you change the cam timing either advance or retard one valve will loose clearance and the other will gain clearance. The required clearance depends on what rpm and wheather you are running a blower or not. You should have enough clearance to either advance or retard the cam timing without valves hitting the pistons.

 

By advancing the cam 2-4deg will give me the clearance I am after, I also have plenty of intake clearance to allow for the reduction, it also appears quite fortunately on my many simulation programs to be a better cam timing event as well, so back to my original question.... are cam gears or cam drive plates available in differing degrees of position for a KB Blown alcohol, alloy rodded engine?

 

your gear drive (asuming that you are using one ) should have provisions to retard or advance the cam built right into it.some even have numbers stamped right into them. by the way .175 is way to much,unless you got real crapy springs, .125 ex/.090in is plenty, and you will have better quench area

 

Eli, I am setting the clearance according to piston manufacturer (Arias), now I am aware that they will probably specify more to be on the safe side of things.

As far as I can tell on my gear drive I can not see any way to adjust cam timing, the crank gear has a single key-way, the idler is an idler gear, the cam gear can be rotated to match other bolt holes but surely if these bolt holes match up again then the teeth of the gears must be back in the original position, i have already tried this in 3 different positions but no timing was affected, I was thinking that the cam drive plate may have different pin positions?

Ray

 

Gear Drive????

Ray,
I don't know what kind of gear drive you are using but I have never seen one that you could not change the timing by rotating the cam gear to another hole alignment. Some have 9 bolts and some have 12 bolts. The one's with only nine holes effect a greater change per hole than the 12 bolt gears.
If this is a blown engine and you only have one key in the crank you might consider having a second key way cut, not for timing but the single key might give you a problem.

 

As luck would have it, I have a 7 bolt hole gear and it turns out to be a Donavan gear drive on the KB, if that makes any difference. So I have tried all bolt holes and not a shread of timing difference measured at the lifter both at .050" and the moment the lifter starts to rise.

So a new thread witha new question....

 

Cam Gear

Hi Raymond Shoot Me A Email To Info@rbssuperchargers And I'll Send You A 7 Hole Cam Vernieer Chart. This Tells You The Timing Advance Degrees By The Hole That You Use.

 

Wouldnt it be a whole lot easier to just get a degree wheel?

 

I think what he is saying is that his bolt holes versus the teeth are coming out symmetrical, thus no change. He has to be using some kind of degree wheel or degreed balancer to know this.

If the cam spud has a dowel pin you may have to do it Chevy style with an offset bushing.

Have a safe race
Dave Koehler
www.koehlerinjection.com

 

Hi JR, I printed of the degree gear from the RCD web site as advised by another ITA member and discovered that for my gear to advance the cam I must install all 7 bolts, on previous measurements i was moving the gear and checking visually for bolt hole alignment and then installing only 2 bolts opposite each other, thinking that this was fine but obviously with the small increments of change the other bolt holes must pull the cam around a little.

A trap for young players i guess, thanks for all replies

Ray

 

Ray, I'm new here, don't want to step on any toes, but I get the feeling you could use a bit more information.
In order to install your cam correctly using a multi hole cam gear, use your degree hub to set your crank to cam specs, minus the 4 degrees you want to gain your needed clearance. then with dial guages on lifter, turn crank to the usual .050. using your pump drive or allen wrench.
BE VERY CAREFUL !!!! DO NOT MOVE THE CAM!!!!!!!!
Now line up the cam gear so ALL the holes line up and install ALL the bolts snugly. If you try, and get none to line up perfectly, you may want to invest in a 12 hole set up. Much more accurate. Anyway, now you can rotate and check all your clearances. Make sure you put a dab of thread locker on the cam bolts if all checks out and torque to spec.
Hope this helps.
Ed.

 

Back "in the day", all that a hole to k hole or b hole to d hole stuff was just toooo confusing. We measured the bare lifters, picked 2 the same length and put them in #1. Rotated the cam to overlap, put a tool bit across both lifters and jiggled the cam till we had even contact across both lifters. Set #1 @ TDC. Trial fit gear till you find where all the holes line up. install ALL bolts. You now have the cam at "split overlap". If you want to advance the cam, say, 4 degrees, remove all bolts, remove top gear, turn crank BACKWARDS 4 degrees, refit top gear as above. Cam is now advanced 4 degrees. Simple...and fast.

 

Thanks guys, this site rocks for credable information, I installed the cam with .132" lifter rise at TDC which is the reccomended install point. My cam grinder gave me all of the info you could possibly imagine to do with the cam and I then went about setting at .145" @ TDC which is 1.1deg advanced and it all finally came together with .125' exh valve/piston clearance, the problem I had was the fact that I wasn't allowing the 7 bolts to be in position to truly advance the cam but I have double and tripple checked the install and all is good now both at .050 and seat to seat timing.

Cheers Ray

 

Chuck, i still do it that way, P/S a hemi runs the best at 7 degrees advanced

 

The Dreaded " K hole "

WOW.... does that bring back memories!!
We ran an Arrow funnycar with a Donovan with that gear drive " back in the day " and the K hole was a running joke! LOL........that and " watch your head " !!!!
CMD

 

Yup, "Leggit and Duck"

 

You forgot 1 important thing. If your using a plunger and dial indicator type degree tool, you have to make sure the wheel on your degree tool is the same
diameter as the wheel on your lifter. This will affect cam timing. A smaller wheel on the indicator will make you retard the cam and a larger wheel will do just the opposite.

 

And there you go, the old way, your using what you run in the motor so there are no hidden mastakes, like my spelling/ ha ha, it just cant get any simpler. KISS, (keep it simple stupid)