beaugott

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!

mmadden55

Have to cut the guides down to go more.

dmccain

iTrader: (2)

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

Fast355

iTrader: (2)

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.

beaugott

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.