car is at my mechanic, I did most the work, just had him do the valve adjustment. He's trying to tell me my cam is too big(224/236) I think its gotta be a vacuum leak but the mechanic is stumped. ideas? probable culprit? tia

 

224/236 too big


According to my Scanmaster at idle, my MAP reading is 18 with BAR being about 30. Stock MAP was around 12 IIRC.

Gotta a leak somewhere. Should hear it sucking i would think. Obviously, check the hoses and intake gasket seal.

 

I agree or the valves are really out of adjustment..more than likely too tight.

 

I tried doing the valves 1st myself first trying to adjust them w/ the engine running. it would idle fine but I coulnd't get them quiet enough w/o stalling it out. so I tried adjusting them w/ the EOIC method but the engine wouldn't idle afterwards or rev up, so I re-adjusted them a few times all w/ the same result.
..if it had a vacuum leak would it run w/ loose valves but stall like it normally does when the valves are adjusted properly?

 

I would be absolutely sure the valves are adjusted properly and then check for vacum leaks. Take a propane torch like a plumber uses and turn it on so there is a little bit of gas flowing from it. With the engine running...put it near the intake to head seals and around any vacum hoses. If there is a leak..the rpm's will go up to a noticeable extent.

 

Is "4#" actually 4psi? That would be about 8"Hg vacuum. You should be getting an MAP code for low vacuum. That's less vacuum than most people see with the CC 306.

 

he told me 4lbs and didn't mention if any codes were being thrown. I thought it was kinda ridiculous to suspect the cam personally.
raw propane? no thanks, I don't want that going into my engine.

 

Ok..as you wish. I have used propane for that test for many many years to include lt1s with no issues. I still think you have valve adjustment problems. Did you put the cam in yourself? If so..are you positive that the dots lined up properly also?

 

What the hell does 4 pounds mean?

 

An unlit propane torch is a common method used to find a vacuum leak. Don't let it scare you.

Could be a combination of a vacuum leak and mis-adjusted lifter preload.

A 224/230 cam isn't too "big" and shouldn't be a big problem to tune unless it was ground on a really tight Lobe Separation Angle. It'll call for a PCM re-programming though which should include raising the idle RPM.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!

 

http://static.flickr.com/1/123940602_913ede42a7.jpg


Link to PSI Vacuum to HG" of Vacuum

 

FWIW, my 224/230 cam is on a 107 LSA. Beutiful idle with 128/128 BLM most of the time but never more than +/- 10 points with any given cell. No big splits either.

 

Think about it this way: You had the engine idling but was too noisey for you to put up with. Then you tightened the adjusting nuts (trying to quiet down the valve train) and now the engine won't idle and the vacuum is low.

If I got that right, what does that tell you?

The tightening you did is now holding one or more valves open when it/they should be closed. Because of that, the vacuum will automatically be lower.

Reset the lifter preload PROPERLY. Idle will return (as will noise) and vacuum will return.

As far as the noise, you may be just one of the many guys suffering from the same thing. That complaint is found on all of the six of so Forums I visit on a daily basis. Most of the guys complaining are running CompCams Pro Mag RRs, but a few are running Crane Golds. Seems noise just comes with them.

The quietest I've read about are Scorpions which, by the way, are the ones I'm running on my 388 and on my son's 96 LT1. I'M RUNNING 1.7s and he's running 1.7/1.65s. They're extremely quiet and not even more noticable than the stock ball and sled rockers.

If after you correctly re-adjust the preload and the noise still remains, check for an interference issue. Many times the underside of the rocker arm will contact the valve spring RETAINER that'll result in noise. If that's the case, a longer pushrod will create the clearance you need.

If all of that checks good but you still have the noise and you decide you can't live with it, all I can suggest is different rocker arms.

Hope this helps.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!

 

107 is on the tight side (my son's is on 108) but my buddy's cam is on 105 and he's having a nightmare of a time getting it tuned. He's running longer duration than we are though.

Without a tune, even the 108 my son has idled and ran like crap; I mean I had to two-foot it just to keep it running at a stop light. PCMFORLESS cured that with a re-programming. Now it hits like he wanted and makes the Corsas really talk.

I stayed with 113 because I like smooth and even pulses. Attribute that to my old age, but back in the day things were different . . . LOL.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!

 

My engine builder was really worried about the LSA, but it has never appeared to be a big problem other than possibly hurting the MPG's and emisions a bit more.