Custom cam grind question

-
C

cudaracer

Well-Known Member
Joined
Oct 6, 2013
Messages
357
Reaction score
21
Location
Detroit/Michigan
What can you change exactly to make it custom? I assume anything, but don't know. I will be calling Hughes tomorrow, but was thinking about it at the moment.

I have decided on one of their cams, probably the whiplash, but I hope to customize it for the following reasons:

1. 110-112 lobe centers (seeking a bit more vacuum and a tad bit less lope)
2. Maintain or even improve the 30deg ABDC intake valve closing hard point (seeking to improve dynamic CR)

So just wondering what the limitations are for a custom grind. Below are the specs for the (2) cams I am considering as a starting point to best alter to get to where I want, which is immediate torque with best dynamic CR.

Cam #1 Whiplash:
.485/ .518 lift on 109 lobe centers (104 deg intake CL)
213 / 236 duration
Idle - 4200 rpm sweet spot
IVC is 30.5 deg ABDC (lower the better for raising DCR)

Cam #2 HEH1019AL:
.461 / .489 on 112 lobe centers (109 deg intake CL)
210 / 219 duration
Idle - 4600 rpm sweet spot
IVC is 34 deg ABDC


Thanks
 
Contact Scott Brown at http://www.buyracingparts.com. He's up near Lansing. He's a Mopar guy and builds some seriously good equipment. He builds everything, not just Mopars. I have some friends that run big block Buicks that swear by him. They run those stock appearing cars that lift the wheels and run in the 10's.

I'm not sure if he actually grinds cams, but he spec'd out a really good cam for my 340 that was not an off the shelf item. It's a dual pattern cam like you are looking at, too. I think he gives his specs to a place that makes them for him. He really knows cams and if nothing else would be a very good guy to bounce your thoughts off of. He can tell you if you are going in the right direction and why. I'm never going anywhere else.
 
I'm not going to answer your question direct but rather suggest that you learn about cams a good bit more first.

My advice is when you call up a cam grinder, and screwz have a good recommendation that I can stand by, tell him what you want out of your engine.

He is going to need a fair bit of information in order to grind you the right cam. So have as much info for hi as possible. Car weight, what exact transmission you have, engine size, gear ratio and tire size, (not rim size) current comp. ratio, heads, intake, carb size, exhaust type and pipe size. The more he knows what you have the better the cam will be. Hold nothing back from him. No secrets!
 
When you order a custom cam it means they simply select the most appropriate lobe size/shape from their catalog and phase the intake and exhaust to suit your application.

Any camshaft's lift is limited by it's duration. higher duration can allow for higher lift.

try to think of a cam's lobe like a pile of sand.. it can only be so steep. it quickly gets to a point where if you want to make it taller, it's going to have to be wider too.

If it's too steep it will wear out prematurely. Some high end camshafts have this in mind so they can make phenomenal power for a very short amount of time.

Off the shelf street lobes are usually made for a good compromise between performance and longevity.

Mopar engines have a larger lifter bore at .904" which increases contact patch on the cam. we have potential for approximately 7% more lift per degree of duration than a SBC camshaft but this can be strenuous on rocker gear. especially with a factory block's 59degree lifter angle.

You mentioned dynamic compression ratio. This is largely effected by the lobe separation angle. here is a basic comparison of wide and narrow lobe separation angles.

Wide - Lowers dynamic compression, decreases piston to valve clearance. spreads torque more towards lower and higher ends of the rev range at the sacrifice of some mid range torque. reduces valve overlap and therefore provides more idle vacuum and a smoother idle. A typical wide LSA is 110-116.

Narrow. Raises dynamic compression, increases piston to valve clearance. provides more peak torque at the expense of lower output at both ends of the RPM range. more valve overlap means less idle vacuum and a rougher idle. A typical narrow LSA is from 106-110.

Duration is simple. More duration moves the torque curve higher in the rpm range and create more overlap which will reduce idle quality.

true dynamic compression ratio cannot be calculated without knowing specifics about your cylinder heads and intake setup due to something called "intertia tuning", basically this is the very real phenomenon that occurs in which an an engine's ability to breathe and the port's cross-sectional area largely determines "how much" cam is needed to make it perform optimally.

But as said above, the more information you have about your entire combination and your desired result the more likely that a cam manufacturer can help you pick the cam that is going to have power where you want it and as much of it as possible!

The most important thing being to measure your static compression ratio accurately. if you tell them something to the effect of "it's got 10:1 pistons in it" they're going to know that it's probably nowhere near a true 10:1 and give you a conservative cam. Just an example but you get the idea.
 
X2 on Bullet.
They ground a custom cam for my 408 and I'm very happy with it.

Ted
 
What I cannot understand is, why you would buy from someone that's gonna rape you.
 
You must log in or register to reply here.
-

Back
Top