so I’ve been having an issue in the mid range and it has been suggested it might be valve springs. Although my engine will go to 6000 rpms if I wanted but I haven’t because of the funny business. The springs I have now are pac 1218s which are rated at .600 lift. Cam is .585. I should be good to go. I don’t really know if the springs can’t handle being almost maxed out or I got a bad set or one or two individuals. I’m not completely sure the 1219s are direct drop ins. I really don’t want to take heads of again. Should I just try another set of 1218s or upgrade? On my engine acting funny I’m also going to explore my fuel pump not getting correct voltage at higher rpms. I do have an extended cab and a walbro 450 pump on stock wiring relay and fuse. My truck ran fine when it was all installed but somewhere down the road it started the missing. Engines have been changed but springs were swapped over along with keeping the same fueling. Any pointers? Also with failing springs, if they are weak shouldn’t the engine refrain from going any higher of rpms? The engine doesn’t stall it just cuts out bad and sounds bad but continues to rev. I’ve already backed timing down to 3 degrees to eliminate preignition. It’s running on 93 octane. Stock low compression.

Do you have the ability to data log? Your just guessing with the spring deal. As said in the other post, it’s doubtful that your floating valves at 3500, even with old wore out junkyard springs. I bet the thing runs like crap with 3 degrees timing, turbo or not. Im betting it’s a fuel issue. If you can data log, you’ll figure it out quickly. Prolly something simple. It usually is.

Joe, what would you improve on that combo? You seem to know your **** but don’t like the common, cookie cutter, copied, overused proven 500+ hp combo. What do you not like about it?

So my cookie cutter build is fixed. It ended up being a weak valve spring or more. I replaced all of them this weekend. Before that I did look at the wiring to the fuel pump and ran new wires but it didn’t improve my issue. Of course this is something that was needed anyways. Also for Joe, yes my combo is copied, parts at minimum but built my own turbo manifold, which operates as one should and doesn’t look to bad either, ran the cold pipe, tuning it myself and so on. This is my first attempt for a turbo build so why would I go out of my way to use slightly different parts to be unique. The difference between 500ths lift on the cam and slightly less or more duration on a street driven turbo truck would not be noticeable to me. It’s smart to use something that works first and venture from there.

If the heads have had a valve job or two done with the factory valves; the installed height of the springs could be closer to 1.900” instead of 1.800”. This needs to be checked as opposed to “just pop a 600 spring on for a 585 cam”
springs work best and last longer when set up properly. Even your new springs may need minus fifty (-.050”) valve locks to prevent surge; particularly with boost pressure pushing at the back side all the time

Im coming to dinner with ya. Hard to believe a year old set of Pac’s are bad, but stuff happens. For them to give up at 3500, they must have had a hard life. When you said that you could get engine to go to 6k, and you didn’t mention backfiring, I ruled springs out. Glad it’s fixed.