Hi All,

Just ordered the APU-1 kit from moates and officially set in motion my build to get my suburban back to being reliable.

Previously I build an L05 with stock swirl port heads and did no tuning to it while putting in a summit k1102 (.421/.443 112 LSA IIRC) in it. It ran OK but never like I wanted it to.

I am planning this time on buying a Chevy performance L31 long block as a jumping off point and possibly upgrading the cam to build more low end torque. It just seems this is cheaper than having a block remachined/etc.

With that I plan on bumping the stock injectors (should be either 61# or 65# I believe) up in pressure to compensate for the better flow using an AFPR and upgrading to the stock AC Delco pump for the 96-up vortec trucks (higher pressure than the TBI pump). Also will be running a carb'd intake (no smog where I live)

Question mainly is a couple things. First of all, has anyone had a build like this? Secondly, what is the cam limit on stock L31 heads, I have read nothing over .450" which seems awfully small but it seems you can change springs/retainers and get around this without machining?

Any help is appreciated. Thanks!

 

Have to cut the guides down to go more.

 

Look up Alex Spring Kit for Vortec heads. Around $100 great deal

 

0.480-0.490 is the upper limit on all the L31 heads I have had in my possession. You can use a GM LS6 spring and a Comp 787 retainer on them and get clearance for 0.550" lift.

If you are looking for low-end torque, it is hard to beat the GM 395' Marine cam that comes in the Ramjet and HT383 engines as well as thousands of ~300 hp boat engines.

The GM Ramjet crate engine has 0.461/.0481" lift with the 395' cam and its factory 1.6:1 roller rockers on factory Vortec heads.

 

Fast355 you seem to be one of the more knowledgeable folks on this forum, among many others. Do you feel like this would be a relatively easy combo to tune? I am a complete novice in terms of tuning, but I am reading and learning as much as possible. It seems the idea from the start is to set the AFR so that it is permanently rich (12.5 or so; preventing internal damages) and then adjust the VE/Spark Advance Tables first then move to PE tables after that (using a WBO2)?

I'm also struggling to navigate the forum and find a base tune to start with, which I have concerns about. I don't want to fire on the stock L05 tune and have the engine running terribly lean.

Again I am a novice, and I am a bit nervous to do this, although I am confident I am capable of it.