Hi everyone, I apologize if this has been covered a million times already. I have an LM7 5.3 for an '04 Avalanche that needs an overhaul. It's going to live at 5000' - 8000' above sea level. It's not going to be towing very much very often and I'd like to leave the stock Torque Converter alone as well. I want 11.5:1 and I'd like to see what you all think about cam and piston recommendations.

 

Summit Pro LS 5.3 pistons come with a 2cc dome that will get you closer to your target. Then a head mill to 58cc or so would pop 11.5:1 with .040 piston to head clearance. What connecting rod would you like to use? We've got several cams as well that are happy with the stock converter. The Pro LS Stage 1 truck SUM-8719 is a 209/217 112 + 1 with .550/.550 lift.

 

Thanks for your response this is very helpful and to answer your question, I would like to use the stock con-rods. Those numbers are similar to my previous non-LS builds except for a notably bigger relative difference between intake and exhaust duration numbers. What factors in to the difference? It might help to mention that I am not opposed to using the existing factory exhaust including the manifolds; as at a first glance they seem big enough for what I'm doing. The next question I have is milling the heads down to 58cc - I'm assuming that this involves more than just having the machine shop clean and surface them. How big are the existing chambers? If there are a variety, where are the casting/part #'s?

 

It's actually a fairly straight forward build then. The engine switched to full floating rods in 2005, and there's a strong likelyhood your 2004 was equipped with press-fit pistons. In that case, the piston part number you would need is SUM-326945785-2P (.005 hone, but bigger bores available). Depending on your timeline, we are ramping up production in response to orders. We have the standard bores in stock, but not the overbores yet. They will be triggered by orders by customers and will take approximately 5 weeks to come in. From that point forward, they will be in stock. So get them on order sooner so you won't have a lot of downtime when you pull the engine down. If your cylinders are extremely worn, you may want to consider one of the SUM-326945820-2p pistons. These are .040 over and would bump displacement from 325 to 332 Cid. We have .030 overs as well.SUM-326945810-2P.

Casting numbers will be either a 862 or 706, but both have the same 61ccc chamber. They would need to be milled approximately .024 in. to hit 58cc

As for the cam, the factory exhaust manifolds won't be much of a detriment. The cam has -10 degrees of overlap and not overly sensitive to backpressure. The duration, lobe separation and advance are created by the individual valve events. The valve events or I/O -7 (which has a noticeable idle depending on where you set the rpm). I/C is 36 abdc, so it makes great power in the midrange without the expense off too much torque off idle. Exhaust opening is 41 bbdc which is a balance of torque, power and fuel efficiency. Finally exhaust closing at -4 degrees for a total of -10 overlap. This number is chosen for to maintain fuel mileage and efficiency. .550 lift so it will work with inexpensive LS6 springs.

 

That's excellent and very informative, thank you!

Just for a side note - The engine is high mileage, was mistreated and the pistons seized on #3 and #7. Among many other deficiencies, I'd be surprised if anything less than a 30 over would work. Thanks again for everything!

 

Glad to help. We're looking forward to you getting the engine back together and stronger than ever.

 

Our complete rebuild kit will give you EVERYTHING you need for rebuild minus cam and lifters and runs about the same price as a set of forged pistons. Plus we have flat top 5.3 pistons so bring your cr up for the same price!!

$699 shipped.
Let me know if you want more info!!!

As far as cams, we like the tsp stage 3 high lift. Great power and torque where you need it, doesnt need a stall, and i have one in a 2500hd truck and i haul anywhere from 5k to 16klbs.
Great option.

 

Whats the link for the rebuild kits for 5.3's?

Have ben looking on the site and cant find them

 

http://www.ws6project.com/user_stor/...oducts_id=8564