Hughes Cam

Posted By: Hotlumpy

Hughes Cam - 08/17/10 07:10 PM

I've been running a 243-248@50, .550 lift hughes cam in my 413 Small block for a few years on the factory Edelbrock Valve springs. No valve float problems, but I can't get it to idle. Should I swap in the Hughes dual valve springs or not? would this even affect idle?

Posted By: ahy

Re: Hughes Cam - 08/18/10 03:43 AM

Springs would affect it at high RPM with instability and valve float. They should not be a factor at idle. Idle is mostly a factor of tuning. With a fairly big cam you may need to drill a small hole in the throttle plate to get enough air in the engine w/o opening the blades too much.

Posted By: 451Mopar

Re: Hughes Cam - 08/18/10 03:43 AM

The valve springs won't effect idle. Check the carb to see if your too far into the transition slots. You may need to drill the throttle plates?

Posted By: mark7171

Re: Hughes Cam - 08/18/10 04:45 AM

Try a carb(mighty demon,Quickfuel) with adjustable air bleeds, with that much cam it is more approriate. Drilling throttle plate holes is not the way to tune.

Also give it at least 18-20 degrees of inital mechanical advance.

Posted By: bobby66

Re: Hughes Cam - 08/18/10 05:43 AM

Initial timing plays a big part in idle quality, too. 20 degrees at idle would be a good place to start.

Posted By: 451Mopar

Re: Hughes Cam - 08/18/10 04:16 PM

Quote:

Try a carb(mighty demon,Quickfuel) with adjustable air bleeds, with that much cam it is more approriate. Drilling throttle plate holes is not the way to tune.

Also give it at least 18-20 degrees of inital mechanical advance.

I think you may be refering to something like the Demon idle-eze baseplate that has an adjustable air bleed through the base plate, and not the mixture air bleeds?

http://www.barrygrant.com/demon/default.aspx?page=10

Drilling the throttle plates has the same effect without having to buy a new carb.

Posted By: Crizila

Re: Hughes Cam - 08/18/10 06:42 PM

Quote:

Quote:

Try a carb(mighty demon,Quickfuel) with adjustable air bleeds, with that much cam it is more approriate. Drilling throttle plate holes is not the way to tune.

Also give it at least 18-20 degrees of inital mechanical advance.

I think you may be refering to something like the Demon idle-eze baseplate that has an adjustable air bleed through the base plate, and not the mixture air bleeds?

http://www.barrygrant.com/demon/default.aspx?page=10

Drilling the throttle plates has the same effect without having to buy a new carb.

Yes thats the carb I am running on my 408. The cam I am running ( Hughes HEH4650AL ) is one size larger than yours. I have to run my "idle-eze' screw wide open and even then getting enough air in at idle is marginal. My 4 corner idle mixture screws are open 1/2 turn. More than that and it runs rich at idle. Throttle blades are also open to the max without dipping in to the transition slots. Motor idles rough, but still pulls about 10" HG at idle. I didn't have much luck messing with the idle air bleeds on my Demon. Didn't seem to make much difference.

Posted By: fox

Re: Hughes Cam - 08/18/10 11:03 PM

Quote:

Springs would affect it at high RPM with instability and valve float. They should not be a factor at idle. Idle is mostly a factor of tuning. With a fairly big cam you may need to drill a small hole in the throttle plate to get enough air in the engine w/o opening the blades too much.

i've seen more than one case where the weak springs were letting the valves bounce at idle.
No other changes and new springs made it idle much better. This motor would not run to 4500 with the weak tired factory ones!!

Posted By: Hotlumpy

Re: Hughes Cam - 08/19/10 07:11 PM

I think I will swap in my Hughes springs just for the hell of it, but I have already drilled 1/16 holes in the primaries. Car was Idling fine, then I had to pull the intake & distributor (to get the water neck bolts out after they broke off) Upon re-assembly the car dies quick when I put it in gear unless my timing is way up. Used to Idle fine @ 13btdc initial, I have no vacuum leak that I can find and New power valve (3.5), and tweaking the carb idle mix doesn't help. New Plugs & Wires, I am at my wits end with this! What else could cause it to die when it runs through the rpm's fine?