I dont wanna appear stupid, i know what a cam is and what it does.... thats basicly it.
when I got this old truck the woman said they put new heads on it (428 heads, said as if it was something fantastic... I dont see from research here the big deal) and she said something about the CAMS they put in.

Since I am always puzzeled about the idle quality It has me thinking they may be connected because...

ok short story time. Recently I was out with my bro he was hetting his blazer fixed at a shop and some gal came i with an older jeep that idled rough and rocked the whole damn car. I ask her jeeze whats wrong with the thing she said (a blue streak of mechanical jargon) that it had "high lift cams" and they gave it more power but made it idle kinda rough.

Since of late i realize most of what folks tell me about everything is pretty much BS, I ignored it and stored it in my head as an interesting factoid i may need to know.

It dawned on me this morning, the chick that sold me this truck was rambling on about the 428 heads and the cams they put in like it was as cool as the water into wine trick.

not knowing what she really meant, my head stored the unknown jargon away and registered "good, the heads and cams are relitivly new, i like that"

I think but I aint real sure... she also said "high lift cams".
it is entirely possible, she was snowing me to sell the truck.
If she wasnt.... what, exactly are high lift cams for, could she really have put them in this 73 390, with the better than sliced bread 428 heads she was going on about and would these aforementioned cams make the truck idle kinda on the rough side/and is that ok?

or were both of these gals full of it?

the jeep chicks jeep did have some get up and go visable torque, or maybe I was just impressed by her shorts and the noisy sidepipes...

its hell being a man sometimes, we have such limited attention spans.

 

first thing its not cams, its just a single cam, and yes they very well could have put a bigger higher lift cam in it, if it was big enough it would make the motor idle rough like it was lopping, a bigger cam means theres morelift on the valvesso it gets more fuel and also lets air out quicker, most people when they rebuild a motor will put a bigger cam in it.

 

I figure there are 2 parameters that make a cam "bigger".

1. Lift- how far does the valve open from the head
2. duration- how long is it open.


I think the duration, more than the lift will effect the idle quality. My Crane 349521 has substantial lift at about .600". But the duration is manageable and therefore my idle is decent with decent vacuum.

Get the cam specs. Don't let anybody tell you it idles rough because of a "big cam", when it could be poorly tuned or have other problems.


I can't think of any reason to put really "big" cam in a jeep???

 

see, I learn stuff everyday... thanks!
anyway of telling for sure other than taking the engine apart and measuring it?

yea that jeep ran pretty freaky but seems like the owner was pretty pleased with it...

my engine lopes a bit no matter what i did to it but that coulda bben from the old distributor& points, I'll know as soon as I pop the new ones in if it makes any difference.

one cam... gotcha. I was thinking overheads there is one on each head.... right?
this engine has one right above the crankshaft... I forgot.

 

Yeah, only one cam in an old 390. The only w;ay it would have two cams is if it were a 427 SOHC - 1 cam in each head and a 6+ foot timing chain. Cool motor, lots of power, but too much to go wrong.
As far as your idle is concerned, if your carb is fresh and tuned, your timing is accurate, and your vacuum is all set and the motor "lopes," then you probably have a longer duration cam. ...The advantages of that would be better performance at higher RPMs when the motor is moving more air.

Let us know what you find out, this sounds interesting.

-Patrick

 

Actually , it's a single camshaft, with 16 cams on the shaft