FarmTruc

iTrader: (5)

Hey guys,

Ok, I got this Denali here, w/ 408, 10cr, heads, custom PatG cam, headers.
It has the 8 rib pulley setup, pinned crank.
It has the K081079 belt, which fits just right.

The issue is, the charger isn't making enough boost, we've seen a max of 4psi peak, but it usually stays around 3 to 3.8psi.

The tvs2300 is the truck style, no shaft, so we're limited on pulley downsizing, we have the 2.7" charger pulley on there and the largest crank pulley on there.

Two things could be the problem:

1- the charger isn't big enough to support the engine
2- the belt is slipping

If it's 1, then oh well, there's nothing we can do. Meaning, we want about 12-14psi, so any small changes isn't going to get us 10psi increase.

If it's 2, then what is the next step? The setup already has the larger 8rib, which was supposed to keep this from happening. It has a new belt installed. Tensioner is in the correct position. Pressure was confirmed with another gauge.

thanks for any input,

Coban

iTrader: (14)

Is the bypass valve operating correctly?

1slow01Z71

iTrader: (36)

Belt dust? What type of pulley? A lot of people have had good luck with the RIP pulley from leftcoast Joe.

FarmTruc

iTrader: (5)

I'll check that today. It's operational, but not sure if it's working like it's supposed to.

no dust, leftcoast setup.

AKlowriderZ71

iTrader: (22)

Specs on the cam? Maybe the cam isn't what you think it is, or is installed incorrectly?

Or maybe your/his boost gauge isn't reading correctly?

FarmTruc

iTrader: (5)

I'm open to any suggestions, but like I said, it's a PatG spec'd cam, about as good as you can get. Even if it wasn't an ideal cam, it would still make boost.

Like I mentioned above again, confirmed with another gauge.

thanks,

KySilverado

iTrader: (7)

My first thought was an underdrive crank pulley. Took a couple readings of the original post to see that's not the case.

I would think a 2300 would feed a 408 no problems. Maybe not 20 psi but more than 5psi easily.

Somewhat stumped but as mentioned the bypass valve or a big intake gasket leak?

FarmTruc

iTrader: (5)

This kind of falls under the same situation I ran into with a 383 and a TVS1900 truck style. I built the engine for 15psi and thought it could feed it, i could only get 9-10psi from the charger. It ran awesome and customer was more than happy, but 15psi would have been more fun.

Being that this is kind of the same thing, I would think 10psi would be possible from this setup easily. We didn't buy or spec anything out on this setup, but from all the docs I got from the customer, it's a good build.
We have another truck here, 408 , tvs2300 but it's a shaft style, we can 12psi from that, with belt slip. But those have more pulleys than just one snout pulley.

I'm checking the bypass valve today.

old motorhead

iTrader: (10)

What is the pulley setup for the rear drive? You can do a little math and be able to compare the two.

EVILGMC

iTrader: (47)

try the K081079HD belt...i am using that on my 370 and making 13psi with a 3.0 pulley and 10%OD IW 8 rib setup truck style 2300.

sounds like its either the bypass or another vac related issue.

are you running the HD tensioner?