NEED HELP!!! Procharger Not making enough boost

[WELTERRACER]

THe motor in my camaro was a 355 with dart pro 1 heads and 750 holley and had 10.3-1 compression and no intercooler.. It was an animal.. Probobly around 700hp had 10lbs of boost and was crazy fast.. but within 2 months i shattered a piston and blew the engine.. im sure lack of an intercooler or bad fuel was the cause..

So anyways.. I had to build a new motor.. its now a 355 with 8.9-1 compression and i reused all the other parts, same cam, heads and everything.. just now it has a 5140 forged crank and forged rods.. and i added a huge intercooler and got rid of the low stock carb bonnet and got one of those fancy big racing bonnets that are supposed to flow 10 percent better..

Here is my problem.. i was only getting 6psi of boost instead of 10psi like i originally had.. so i called ATI and they told me that reducing the compression made me loose boost.. That i can understand because i increased the compression chamber size.. So i ordered a smaller pulley 4.75inch.. and that did nothing.. so i ordered an even smaller pully 4.5inch that also did nothing.. .. I took it to the track and it ran a best of 11.70 at 122mph... a few weeks later i drove the car and out of the blue it was only making 2psi of boost and i could tell it had a lot less power.. So i thought maybe i had a boost leak.. I bypassed the intercooler and ran the tubing directly from the blower into the bonet and im still only getting 2psi of boost.. I have switched back to the 5inch pulley thinking the belt was slipping and that didn't help.. i checked the impeller on both sides and it is not damaged..

ATI has been no help.. they give me the run around on what could be wrong..

What do you think is the problem?? I want to push 10-15psi out of this thing and run consistantly..

Thanks

Brian welter

[elcamino80]

Sorry I can't help you but I got a déjà vu, https://www.pro-touring.com/showthread.php?32796-Smaller-pulley-but-no-more-boost, have you got this same problem for 4 years now?

[WELTERRACER]

Yes i still have the problem.. in fact its worse.. Im only getting 2-4psi now.. ive ruled out the intercooler and bypass valve.. i ran the procharger directly to the carb and it made no difference.. the belt is very tight.. Im not hearing any belt squeel although there is some belt dust on the pulley and charger..

I really wish someone could tell me whats wrong with this damn thing.. It cant be the the unit is bad because i see no damage and my seals are not leaking..

[JBCO]

Have you pressure tested the motor and all the intake paths? I usually do it on turbo cars in my shop -- if there is a vacuum/boost leak ANYWHERE -- most often the car won't make or hold any pressure - or it will be very limited.

Sounds like with all the other testing you've done it could be a leak somewhere in the charger itself or on the carb.

Reducing your compression ratio should have nothing to do with the procharger and it's boost level. Just because there is more room for air to be squeezed into each cylinder, doesn't mean the compressor (procharger) is making less boost or PSI.

The valves are not open 100% of the time while the motor is running (or else you would have bent valves) so the intake path is able to build or hold pressure, unless you have some sort of leak.

Hope that helps/makes sense :)

Try a pressure tester like this -- on your intake path :
https://static1.pt-content.com/images/noimg.gif

[rsssconv]

I know you can lose at least .5 lb. through a regular PCV and perhaps the brake booster check valve. I am experiencing a boost loss issue as well as a pressurized crank case causing oil messes from lack of check valves.

Hope you find your problem and get your power back soon.

[Blown73]

Have you checked every single boot on the intercooler line? A hairline crack or not sealed boot will lose boost. Also, check to make sure that under boost they do not balloon out and lose the connection. Have you checked compression in the motor? A single bad ring would cause you to lose boost fast.

A vacuum leak could cause you to lose boost, an easy way to check is to use a spray bottle with water/soap and spray the intake runner/head connection. if it bubbles, you have a leak. Have you ported your intake runners to where it might not seal at the intake?

I had a fitting blow out on my carb for the boost referenced fuel pressure. Couldn't figure it out until I stared at it long enough...

[OLDFLM]

Did you flip that toggle switch on the dash? It worked in Mad Max!

[Concept One Pulleys]

You mentioned that you had good luck with your setup previously, before the shattered piston, and you mentioned that you're reusing the parts from the previous setup. Have you tested some of those parts to see if they could haven been damaged and/or faulty?

Kevin
Concept One Pulleys
Made in the USA
Aftermarket Car Parts (http://c1pulleys.com/aftermarket-car-parts.html)

[opnwide]

Boost is measured in the intake manifold, not the combustion chambers. Make sure your boost guage is plumbed accurately and there are no leaky fittings (ask me why!)

Going to lower compression reduces dynamic compression ratio-not the ability to make boost (at least not significantly).

A single bad ring will cause a small boost leak, but not 5-6lbs loss. A hole in a single piston might cause 5-6lbs boost loss. Maybe you have multiple bad rings. A leakdown test may prove interesting.

I believe you have a leak in the plumbing (maybe a bad seal on that carb hat!) or your procharger isn't putting out the way its supposed to. Check the impeller. Replace the belt if you have to. Make sure you have high pressure clamps everywhere. Maybe you can make a test pipe with an air fitting so you can hook up your shop's air compresssor to it and check for leaks. You'll have to back off your rocker nuts to make sure the intake valves are all closed or you'll never be able to pressurize it. Check your PCV, Check your brake booster check valve. Heck, double check your valves.

[SS PUNISHER]

If it's leaking that much boost you will definatly hear it, I'd be looking at the impeller. Maybe you lost some fins, that could be what did your last motor in also. Hope you get it figured out.