no vacume becaus cam is to big? is this possible?

[nieo]

hey i have been having troubles with my duel zone climate control since i put my 235 235 110lsa cammed ls2 in to my gts coupe...
so i went down to local work shop and he had a look at it and was saying it was a vacume problem he checked all hoses and they where fine then he pulled one off and said there was no vacume and was saying the cam was maybe to big and has no vacume at idle ?
Is this possible he was saying maybe i need a vacume pump fitted or a bigger vacume ball. just wondering what u guys thought before i go buying a vacume pump

cheers
shaun

[Peter B - CV8]

Yep, you have discovered one of the side effects of running a good size cam = lower vacuum. I'm guessing the climate control problem rears its head more often when you are on the brakes (and using up vacuum in the brake booster).

[nieo]

but it seems to be all the time.... it sometimes flicks to the other settings when i get up in the revs a bit but thats it... and when it does flick up to the other settings such as floor and top vents it only comes out a little bit like the vents only open a tiny bit or something

its strange.

[GMMAD]

http://www.compperformancegroupstores.com/store/merchant.mvc?Screen=CTGY&Store_Code=CC&Category_Code=VAC

[joffa]

i wouldnt have thoght that cam would be big enough to cause vacuum problems. the 232 i used to have never had any dramas like that? what if you bump the idle speed up a little?

[ringram]

Check manifold pressure at idle. My 230/238 is around 50kpa. Which is quite a bit off the stock 38kpa or so.

[blackass]

is there a little "x" in the left hand corner of your trip display??

[stompa]

maybe air con gas is low

[bush_basha]

maybe air con gas is low

it wouldnt be the gas, because that would still pump out air just not cold and it would still allow you to select which settings, where as whats i think he's saying is he has no vacuum to select the settings until he's high up in the rev range when it's starting to create the vacuum.

What do the brakes feel like, have they decrease at all?

[MANARO]

is there a little "x" in the left hand corner of your trip display??

What does the little x mean as i have that on my climate control after the car was put back together a vacuum hose was left off the air con and the little x is still there?

[JBonDSS]

What does the little x mean as i have that on my climate control after the car was put back together a vacuum hose was left off the air con and the little x is still there?

I second this Question, :)

[nieo]

thanks for ideas guys! jezz the man saved the day once again! it was a vacume line issue.

[blackass]

the little x means there is a problem in your climate control.

[MickmeMate]

I never thought a cam would cause those kind of problems.Well i guess you do learn something new on this forum everyday.

[macca33]

I never thought a cam would cause those kind of problems.Well i guess you do learn something new on this forum everyday.
Yes, it is well documented that the increased valve overlap of the bigger cams results in decreased dynamic cylinder pressure, thus vacuum.

cheers

[KrisR]

The 236/242 @ 0.050 roller cam I have in my 400 idles at about 75-80kpa. Mind you it's a single plane manifold. It's not uncommon at all for big cams on tight LSA's to idle like pigs producing minimal vacuum at idle.

A crutch fix we use is to run more timing advance at idle (similar to the old ported vacuum advance in old distributor cars) which helps with idle quality and off idle response.

The 236/242 @ 0.050 hyd roller cam I have in my pontiac engine idles at about 75-80kpa. Mind you it's a single plane manifold. It's not uncommon at all for big cams on tight LSA's to idle like pigs producing minimal vacuum at idle.

A crutch fix we use is to run more timing advance at idle (similar to the old ported vacuum advance in old distributor cars) which helps with idle quality and off idle response.