pdbq

iTrader: (7)

I've been reading that the smaller intake runners on a set of 5.3 heads seem to flow just a tiny bit less (within 5 cfm) than what stock LS1 heads flow. You would think that bolting on a pair of stock 5.3 heads on a bone stock LS1 would actually produce more power and torque over the stock LS1 heads because they would increase the compression ratio 0.8 points over stock. Even if the 5.3s flow about 5 cfm less than LS1 heads, it still looks like the increase in the compression ratio would offset the slightly less amount of intake air flow and give a more powerful "bang" when the piston is being fired at TDC.

Now if I were to have 5.3s ported and reuse the stock 1.89" intake valves, how much of a gain would this be? How big of an improvement in cfm and power/torque are we talking about?

I've also been reading that a smaller intake valve with a smaller runner size would actually produce more intake port velocity, which would in turn, produce much more bottom end/mid range torque. Is anyone here using a pair of ported 5.3L heads with stock sized intake valves on their bolt-on LS1? Please discuss and share your experiences.

hellbents10

iTrader: (10)

We have good luck with them when installed with a 2.00 intake valve and a competition valve job. Good way to go on a budget, but I would not install them with the 1.89 valve as it would be a waste of time.

synisterC5

i would agree> you can reuse the stock 2.00 valves from your current heads and just have a machine shop regrind your valve seats to the 2.00 valves. I only paid $80 for the machine work and as a nice side effect when they regrind your valve seats it automatically will leave you with a nice 3 angle valve job