I suppose it could but I expected to see no more than 13psi with the new heads cam and ported manifold. An open bypass would account for low boost and boost dips but not the 15psi spikes. I did test the bypass with my mightyvac upon reinstallation and it functioned properly.

Yes. 4" intake tube, 9" long by 6" round K&N style filter as seen in the below pic. It was recently cleaned and is still light pink in color. I have not inspected it since the track outing. With an inlet restriction, the boost should go down in the upper rpm, not up or are you thinking something else?

 

Yea I can think of plenty of reasons it would go down, but go up is a bit tougher...

Only thing I can think of is maybe valve springs are worn out, what set do you have on there?

 

Brand new TFS double springs installed by TEA with 160# seat and 460# open pressure. Valve train is the only thing I could think of as well but alot of thought went into building a very robust and stable valve train. Cam has QXX and HUC lobes so they are not all that aggressive. Pushrods were measured to have .056" preload and BTR SLR lifters were used. All brand new valve train components except for the rocker bodies(trunion upgrade).

Only thing valve train related I can thing of that could cause this problem is too much spring pressure causing the lifters to collapse at higher rpm and reducing the valve lift. I did do the first oil change from cheap dino 10-30 with Lucas break-in additive to 20-50 VR1 right before going to the track. Think the 20-50 may be too thick to pump up the lifters at higher rpm? That could explain why the first run was worst (oil was cold and thicker) and got progressively better on runs 2 and 3 as the oil warmed up and thinned out some.

 

Could be your exhaust back pressure going up at the higher rpms...

 

Hmm... wouldn't an exhaust restriction cause a gradual and consistent increase as the rpm's rose? BTW, exhaust setup is 1-7/8" to 2" stepped headers, 3" from collectors to Flowmaster merge collector to a 4" Magnaflow with single 4" over the axle, all mandrel bent piping. I could see the inconsistencies if there were a bad cat or something that could come apart and cause an intermittent blockage. I presume the Magnaflow could have blown apart. Thinking back I do recall the exhaust sounding a little off after the first pass. I will pull it out and have a look at it this weekend.



Sorry, I am not trying to be argumentative to all the responses. I surely appreciate all of the recommendations and brainstorming.

 

I haven't messed with the truck much to get this completely figured out yet but I thought I would at least update the thread with what I have diagnosed.

As to the intercooler circuit, I found the cap that is leaking is only a vent, not a pressure vent. The cap is directly above the return in the tank so being I was seeing 230+ IAT, it is possible the water was boiling in the intercooler and causing some pressure spikes and bubbling in the ic reservoir. As I was inspecting the exhaust last weekend, I had the truck jacked up in the rear and used that as an opportunity to try and purge any air that may be trapped in the IC by running the pump while in this position.





As to the exhaust, Kyle may have been on to something. Upon inspection, it was obvious that the muffler had been forced back ~1/8" by looking at the slip fit clamp. I went ahead and removed the Magnaflow to inspect the insides, expecting to see it had purged it's packing. However, everything seemed in intact other than a few small pieces of the stainless steel mesh protruding thru the perforations. Since the Magnaflow was sounding exceptionally raspy and loud with the new setup, I took the opportunity to install an Edelbrock diesel muffler I've had tucked away since I built the 4" exhaust a while back. I have not had a chance to get a full 3 gear wot blast in but rolling into a 2nd gear pull, the boost starts at 11.5psi, increases to and levels out at ~13.8psi. I am going to attempt some more testing with the exhaust and rig up a pressure gauge to go in an unused O2 bung. If I see more than 2psi in the exhaust before the muffler, I will know that's where my problem could be.

 

Try it with no muffler first

 

hello, would you mind to post your config file?

 

A little update... It is not an exhaust restriction. I pulled the muffler and tail pipe off at LS Fest on Saturday and ran the rest of the weekend with it off. Still get the inconsistent boost issue. I talked to a quite a few professionals at the vendor tents and the verdict is between the bypass valve fluttering or lifters leaking down causing decreased valve lift. I am going to try an even thinner oil (currently running 0-40 Mobile) to see if there is any change. I will also be removing the bypass valve and giving it a once over.

 

I bought my Whipple used and it had a bad valve. It was stuck shut, so making boost all the time. I took off the lever, and zip tied it open so it would not make boost.

Maybe you could do the opposite?