i know we have covered a lot about cams, but which system do you guys use? and does it work well? im going to either get the 264/264 set up or the 264/272 set up or 272/272... but i have a couple of quetions... a while ago i asked if we need to break in the cams and a lot of you said no. but every shop that i have talked to has said its a must. either by idling it for a while and then taking it up slowly threw the rpm range while u drive or by making sure i never hit too much boost and i was wondering if thats true... i dont really wana drive like a little old lady for a month. second the 264/272 set up is suppose to give me more torque... but i was wondering if i get that will it be back for my car since im sucking in less air then im giving out? and to those with cam gears is it the same low end torque if i just tune them? and how did you tune your cams and to what degree? vishnu has it at -3 and -3 i think.

thank you

 

I've never heard of anything about breaking in the cams, you should let it idle for a bit and adapt but most people just let a rip. I think it'd be hard to resist :-p

 

It is hard to resist, but it is something WORKS does recommend doing when installing our cams.

 

So do you recommend keeping the RPM to a certain level, what guidelines do you guys go by. What do you tell your customers?

Thanks...

 

I'm gonna put in a plug too for the answer between the 264/272 versus 272/272. Its my impression that if you already have adjustable cam gears (which everybody usually gets on a cam install anyways) you can adjust the 272/272 combo to have the same low-end / idle quality as the 264/272.

I personally think I want to go with the straight 272/272 combo and be done with cams.

Can somebody chime in on that specific question?

Thanks,

jcnel.

 

Hey guys,

I've been searching lately, since I'm torn between 264s or 264i/272e.

I did not find any back to back dyno runs to compare the staggered set vs a straight 264 set. 264s do seem to spool quicker, with a slight loss uptop compared to 272. The 264/272 seems like it would be a good compromise, but most empirical dynos seem to show they are all very close to eachother.

If anyone has more info that would be great.

Course, I have to make my car stop misfiring/boost cutting/stumbling first.

FB

 

So what are you actually "breaking in?" The bearings? certainly not he lobes as they are acted on by rollers. Since cam bearing diameters are small and cam turn at 1/2 the crank rpm surface speed on the journals is very low so whats up?

 

I think AMS has a dyno chart on cam combo's on their website.

edit: opps sorry guys forgot to put up the site addy www.automotosports.com

Click on the EVO, when the page comes up look on the bottom left under tech articles.

 

My 264/272 at 0/0 feels like it has more bottom end off-boost torque than stock. Spool is quicker than stock too. Mine only have about 120 miles so I'm still keeping RPMs below 5000 or so until about 200 miles. I'm not avoiding boost though. I think the RPM puts a lot more stress on the top end than the boost. Staying out of boost is something I'd do with a new bottom end.

By the way, just because the 272/272 with -4/-1 (or similar) cam gear settings might idle well, that doesn't mean that you aren't losing mid range power compared to a smaller duration combo like 264/264 or 264/272 run closer to straight up. Widening the lobe separation (when you retard the intake more than the exhaust, or retard the exhaust more than the intake) will help idle and top end but it will decrease mid range torque.

 

Hi,

Yeah, I have seen that article. It's on a DSM, but should be somewhat similar.

Per that article, the staggered set (264/272) actually spool earlier, but doesn't really seem to have better top-end like I thought it would. I would have thought straight 264s would spool sooner and give up more on top...

EVO8LTW, you have no cam gears, right? Idle is ok? Do you have afc or flash or anything?

Thanks,

FB

 

I am also torn between the 272's and 264's. I am worried about idle quality and passing emission tests. That is why I am leaning more to the 264's although the 272's are better power wise.

 

I have a mail-in Dynoflash and an SAFC. The idle sometimes goes lean when you roll up to a stop, particularly when you are on the brakes. Vacuum drops a few inches, idle gets lopey and AFR rises to about 18-19:1 and then adjusts back to 14.7:1 and smooths out. I added fuel at 800-1000 rpm with the SAFC and the issue is almost completely solved. A custom flash probably wouldn't have this issue at all. Idle is good. Not like stock, but not just a tiny bit choppy. An uneducated ear wouldn't notice it. An educated ear might think you need new plugs.

 

Great info, thanks.

I like the idea of early spool and same or slightly better top-end. I would probably go mail-in flash (TT or Dynoflash). There is a place in MA that is going to be doing reflahes (KTR), but it's going to be spendy (650) with dyno tuning more on top. Maybe in the future.

FB

 

Get to 264's , 272s are lumpy and not date night frendly . Both make within 5hp/5tq of each other . Iam learning the hard way..

 

I'm running 272/272 at -3/-3; I get the occasional lean-out/stall at idle but Shiv is going to tune my baby this Saturday and I'm hoping that goes away. W.R.T break in .. you've changed key engine components, its best to be kind to them for some period to make sure that everything is settled in correctly. I threw a couple of odd OBD2 codes in the first 500 miles after I put the cams in. I'd recommend turning the boost down to 1 bar (about 15psi) and take it easy for 500 miles. Keep the pressure off the engine until everything is happy with its new home.

Its all about discipline, IMHO.

Then again, I'd highly recommend getting hit by a car and spending 6 months in the hospital if you are having problems quitting smoking ... it worked for me ...


-- dave