problem/question hks 272

[1fast97gsx]

What kind of vaccum are you guys seeing at idle with 272 cams? I got mine today and I only see 9-10 and the car dies if I tap the gas. Maybe the base timing is just off? I checked cam timing several times now and its right on.

Here is my post from another board:

"I installed a set of hks 272 cams today. I took my time and made sure I did everything correctly and then let it sit for a few hours before I tried to start it. As soon as I cranked it over it started right away and had a really rough idle ( which I was expecting ), however my vacuum was only reading between 9 and 10. I let it run for a few minutes and it stayed at 850 rpms and sounded kind of rough. I went to take it around the block and as soon as I stepped on the gas and let the revs drop back down it died out. I started the car back up and the vaccum was still at 10 and the idle was rough. The car will drive ok without any sputtering or anything, but it dies everytime I'm rolling and push the clutch to let the revs drop or if I just free rev it also. I checked the cam timing again and the marks line up 100% so I didn't just screw up putting the timing belt on.


The only thing I was still considering is maybe it's as simple as my base ignition timing being out of whack? I left the CAS exactly where it was set before the cam swap with the stock cams, but I can't get the car to idle long enough to actually move the CAS around and get a timing light in there to check it. To me it seems the ignition timing must be out of whack, but would that yield vacuum numbers as low as I'm seeing and having no driveability issues as long as my foot is on the gas? On decell my needle is reading around 15 for vacuum, however before the cams I used to get in the mid to high 20s on decel. Before the cam swap the car ran and idled perfect and at idle had a vacuum reading of 17. Could I be lucky and it be something as simple as the CAS being misadjusted or should I expect a major problem? I checked multiple times after I started the car and had the stalling problems and the cam timing is dead on and the belt tension is also correctly set. It's 2 am and I'm too tired to mess with it and have a busy day tomorrow so any help would be greatly appreciated."

Someone please help me figure this out!!!

 

[KLikLo]

Try bumping your idle to 950 with dsmlink. If you dont have dsmlink play around with your throttle cable setting to read 1% throttle. By the way, have you checked for a boost leak? Are you venting your bov to the atmosphere? It could be something that simple.

 

[just_passed_you]

I noticed the GM MAF in your galleries...
however the issue sounds identical to venting to atmosphere.

 

[1fast97gsx]

Yes I checked for a boost leak. My bov is vented however I'm using a translator and gm maf setup so that won't matter. My idle is set at 850 with my ecu chip, but shouldn't that be high enough to at least keep it running at idle even if it is a little rough? What vacuum numbers should I be seeing at idle?

 

[1fast97gsx]

I just let it warm up and I was able to set the base timing to 5 degrees. The idle is still horrible and only around 9-10 for vacuum. It shoots out little clouds of whitish smoke at idle now ( it's a cold rainy day ) and I did a compression test and got 150 across the board. 2 days before the cam install I got a 180 compression across the board. What's going on here???

 

[boostedinaz]

Your fist job is to set the timming. It may have seemed like you kept it in one place but that is very hard when you are swaping out parts like that. Once that is checked then you may have to bump your idle back up to comensate for the larger cams. I would go to about 950 or so this should keep it from stalling.

Anytime someone puts large cam(s) it will chamge the vacuum reading. Larger cams will pull less vacuum than cams with less lift or duration, so you would need to compare you vacuum reading with someone else who has 272's and the same idle as you. Before you do that though make sure you have all the other problems sorted out.

 

[1fast97gsx]

How would I properly go about raising the idle? If I adjust the biss it will go up for a while but then slowly make its way back down to 850 right? I wouldn't mind raising it to 1000 or so if it'll fix my stalling.

 

[boostedinaz]

On a 1G you have to gound the ECU and the ISC. That way they have enough adjusment in either direction. Then you set the idle with the biss. I am not sure how to do it on a 2G hopefully someone will chime in and let you know.

 

[1fast97gsx]

Yea I'm a little confused on how to do it on a 2g since the cas is originally not adjustable. I have a 6 bolt in a 2g so I have a 1g cas, however my wiring harness doesn't have the grounding clip.