Im new here and bought a car thats already built. Its got Pro 1 cams and has a rough idle. The guy i bought the car from said that the cams being degreed is whats making it idle rough. It idles 1000 rpm and the wideband shows 14.5-15.0 AFR. The exhaust cam is +3* and the intake cam is -1* It idles right around 1000 but its not smooth. Sounds like my buddies DSM with 280's. Thank you for your help.

 

yes, thats called overlap

 

Add some fuel to the idle and it may smooth it out. It may also need timing adjusted. Pro 1's don't idle that bad. Once you hit Pro 2's you will start to notice some.

 

Here is a basic article about cams and what you need to know...

http://www.circletrack.com/techartic...e/viewall.html

 

Good link N3va...

I'd be careful before making changes to "smooth idle" unless you're just doing it to pass some sort of registration test.. The lobe separation characteristics on a lot of these newer camshafts are made for a reason. I've seen several Pro1 and even GSC T1 camshafts lose a lot of lower end torque and midrange power when people changed the idle characteristics to "idle smoother", by changing fuel/ignition timing just to sound smoother. This is both in the NA and turbo applications.

The cams were made to do what they do for a reason. If you want smooth idle, go back to ITRs. Let the "grown men" keep those camshafts j/k.

 

I am curious, in your opinion, how would changing only a couple rows affect mid range power? Changing a total of 6-10 idle cells in the 1,200 and less and less than ~16" of vacuum won't change much. Now, changing the cam gear settings, I would have to agree full heartedly.

 

I'm not a tuner, so I don't have an opinion as to that particular area. I can only tell you this from the tuner's testimonies we've been using for a lot of these cars for the time attack that this phenomena is highly correlated. It may not be 50hp or 100hp difference, but I have witness some changes in the lower end of about 15-30whp or so.

I'm experienced in many things, but as a Tuner, I'm not.. that's why I work with the Pros for that one.

 

Degreeing cams, when done properly should have 0 to do with idle. Pro1s and T1s have lobe profiles that can cause a lopey idle... that's simply the cam... and normally cams like what you have require a higher idle to pull enough vacuum to keep the car running, idle too low and there isn't enough vacuum being produced which causes the motor to stall.

If the head has oversized valves, don't touch the cam gears, as where they are set was likely to avoid valve to valve contact.

Also you can fiddle with the idle cells to make the idle more "smooth" but you can't totally get around the cam profile

Perfect example, the cam we put in our ls7 is so aggressive that on first startup with no tuning, it soundedlike a peperipheral port 20B. We messed around with timing and fuel and now it idles almost like a stock can car.... but you can definitely tell it has a cam due to the exhaust note and lope... you can't get around the can... period.

Take the car to a reputable shop and have them determine what needs to be done, you can't start screwing around with cam timing and tuning all at the same time.... that's a recipe for disaster.

 

what is the vacuum at idle?
are we sure the engine is not hurt?
does it comp out good? what are the comp numbers?

If something does not seem right, chances are there are not right. Check the basics before you modify anything.

Ive seen people start tweaking on the throttle stops to adjust the idle, saying their "big" cams are making it act weird. when it was a vacuum leak... don't chase ghosts
nail down if you have an issue, then do tests to determine what is the cause.

 

Its on Neptune for tuning. It idles at about 17in/hg. It doesnt have any vacuum leaks. Everything on the car is good. Just has a lumpy idle lol. Not even a huge deal, was just curious if the degreeing of the cams is the primary cause of it.

Compression test at 175psi across the board. Its and 9 to 1 motor.

I got the laptop with the car and know a little about tuning. But i did try modifying the idling cels and adding fuel. It didnt clean up, just dropped the idle from 1000 to up and down between 750 to 1200. Put it back how it was and back to idling right around 1000 with a lumpy idle.

Thanks for all the replies.

 

Definitely just the cam profile then.

 

Exactly. Just keep it as it is.

 

ive tuned several degree'd pro 1s and they idle just fine. they are correct, make it idle a little richer than you have and you'll be fine. it will not affect fuel consumption if its just idle and it idles low 14s compared to what you have now. at least nothing noticeable.

even pro 2s still idle good. just stay away from the vtec killer cams.

 

now ive never used these cams, but i think i remember reading that they like more timing at idle, somewhere around 20 degrees total. perhaps its to help increase cyl pressure to compensate for lost pressure due to cam profile as well as having a 9:1 static to begin with.... also bringing the afr down to mid 13s through low 14s usually helps a bit

 

Normally aggressive cams need more timing at idle, due to lobe separation, can profile, reduced engine vacuum, etc. It's pretty standard practice regardless of engine platform, I know our ls7 needed a lot more timing at idle when we put the torquer cam in.

 

I have a b16 in my emi w/ sk2 p1 cams, ferrea +1 valves,ferrea valve springs, guides and stock cam gears. i was thinking of getting sk2 cam gears. would i be able to use them gears w/o any issues?
I'm planning on just install the gears and don't adjust them. the timing is retarded on dizzy...i believed -2.
car idles at 1000 rpm and 14.5-15 afr.

thanks

 

No. you shouldn't have any issues using them, but its best to get your distributor back to 16* static timing and use the computer to make the better fuel and timing adjustments... But that can be done at dyno time. Right now, you seem pretty good to go.

 

Agree, I pro1's can idle really well. I have pro2's and it idles like stock. Make sure your cams are degree'd in first. Shouldn't idle rough. You need to go into your tables and fix it. When does it idle rough? when engine is cold?, hot? it is most likely in your idle tables.

 

I just want to know what the definition of "rough" idle is. I believe that's how they were designed. "Rough idle" isn't always a bad thing unless there are other issues involved in the system. No need to fix what isn't broken.

 

No love for the lopey idle in here huh ? I love the way my car cams on the GSC t1 cams. Im running 16 degrees and a normal a/f at idle and the car ran just fine at idle pulling 11-13 vacuum. The larger primaries and secondaries increases overlap on the the lower profile of the camshaft which is were the bom bom bom bom idle comes from. I love mine personally. IDK what the obsession with making these huge cams idle like stock is all about.

 

Are we talking this type of lope?


OR this type of "lope"...

 

Now THAT's good lope.. Not that "Boxer" Engine ****, either. MAN, ****..

 

I'm saying those cams pull enough vac. to idle like stock. If it idles rough he might need to look at some things. Or just ignore it I guess......

 

no.. Its just that its not idling "rough". It's a normal idle from the lobe separation. "Lopey"ness is by design in this case for these camshafts. "Rough" idle is described as erratic, inconsistent, and shows signs of ignition misfire, and timing issues. The fact that he has Pro1 camshafts more than likely means (assuming correct installation, Piston-to-valve, and valve-to-valve clearances and timing are within specifications), he just has lopey idle, not as though there's a problem.

Posting a current video of what he's describing is the best way to assist him in any needs he may have. Simply "rough idle" is too vague considering what he has.

 

I dont have a video of my car...but found this one. Mine idles pretty much exactly the same way.