Vacuum Questions

[Matts50]

Looking for some opinions before I start tearing into vacuum lines. Recently purchased the car and installed a boost gauge so I do not know much of the history.

1) At idle, I'm getting, at best, 2" of vacuum, but mostly 0".

2) I'm only seeing a MAX of barely 1psi at 5500rpm in 3rd gear. It's a 6psi set-up, but with my set-up, I was expecting to see around 3psi.

3) I'm not sure if this is related, but when the car is idling and I stab the throttle, it lags quite a bit and doesn't react to the full amount of throttle that was given to it.

4) Through research I'm pretty sure this is completely unrelated, but the car HATES to start when hot and sometimes won't even start with the gas pedal to the floor. I thought this may be related needing a chip/dyno tune.

Let me know what you guys think. Worse comes to worse, I'm gonna replace a bunch of lines and make sure they are fastened well.

Thanks,
Matt

 

[Matts50]

Hey thanks for the info guys! lol

I did find a vacuum leak that wasn't there yesterday when I installed the boost gauge, so maybe I knocked it loose. I tightened up and replaced a lot of vacuum lines, but I'm still only seeing 4-8 inches at idle. Although, I did see 18 inches while decelerating in 2nd gear.

 

[Steven]

Alot of the vacuum has to do with the camshaft though. Some cams make almost 0 vacuum, while others, like factory, make over 20 inches. You may very well have a intake leak. Is the car doing anything wrong in particular?

 

[Matts50]

When the car is hot, I have to pump the gas to start it. That's the only drive ability issue that I can tell. I haven't brought it up too high because the injectors are a bit small, but I saw 3psi at 4500 in 3rd. I can check the manifold bolts, but we recently did the manifold and checked and re-checked the bolts.

 

[2slo95fiveoh]

hmm.... why don't you put the 42lb inj. with Matching Mass air (in your sig for sale) on the car? you mentioned that the
30lb inj. were too small, that may help the overall performance of your car, but as far as the hard to start problems, I would
normally suspect an ignition component on the fritz, but you said it only starts after pumping the gas, maybe a fuel issue?
Do you have an aftermarket Fuel Pump?

 

[Matts50]

hmm.... why don't you put the 42lb inj. with Matching Mass air (in your sig for sale) on the car? you mentioned that the
30lb inj. were too small, that may help the overall performance of your car, but as far as the hard to start problems, I would
normally suspect an ignition component on the fritz, but you said it only starts after pumping the gas, maybe a fuel issue?
Do you have an aftermarket Fuel Pump?

I fixed my sig. to make sure it made more sense. The history of this car is unclear, but I can assume that with what is done there must be some kind of fuel pump upgrade. When I do 42lb injectors and a MAF, I will also make sure there is a 255lph in-tank. I did some research on the hot start issue and I'm pretty sure it's not vacuum related. It appears to be a fairly common issue when 30lb or larger injectors are used.

 

[Steven]

Is the car tuned?

 

[Matts50]

Is the car tuned?

Absolutely not. Not until the 42's are in. A dyno tune should fix the hot start issue.

 

[94 DropTop]

really stupid question but are you running a underdrive crank pulley? that might mess up your boost issue.

 

[Matts50]

really stupid question but are you running a underdrive crank pulley? that might mess up your boost issue.

Pretty sure it's the normal pulley.

 

[94 DropTop]

Ok, i ask cuz it happend to a buddy of mine, he bought the car and didnt realize it had udp's on it.

 

[Matts50]

I'll look more closely at some of the pulley's.

 

[Steven]

The tune will probably fix most of the issues. I'm sure the cars on the fritz even though it seems alright outwardly.

 

[94 DropTop]

take a can of carb cleaner and start spraying everything.