help with lm7 build list

[Wyatt_S]

Bought an LM7. I've been reading about how to reach close to 400whp. Seems like I need to change the stock heads to milled 243. I'd like to stick with stock heads if possible. I will be changing to ls6 intake, not sure which fuel rails or injectors yet. Still undecided on cam. Is changing to ls7 lifters, ls2 timing chain, new springs and pushrods work it?

[usmcpi]

What are your goals for the car?  Tell us that first and i can help you select a cam, not that im claiming im an expert or anything, but after looking at cams non stop for 2 weeks i have a pretty good idea.  The ls7 lifters supersede the ls1 lifters, however there is controversy if they are actually better.  You will absolutely need springs if you change your cam, you cannot skip this or you will have valve float and good by heads, valves, pistons, etc.  What heads are on the LM7?  317 heads?  If so, they flow the same as 243 heads, just a bigger CC, hence lower compression.   You will also need new pushrods, not only are aftermarket stronger to deal with higher lift cams and more aggressive lobes, but also if you mill the heads you will need shorter length.

[digitalsolo]

The LM7 has 853 heads (or another casting number with the same design).   These are small chamber heads with smaller intake valves.

A set of 243 heads with a little milling to bring the compression back will help a lot.   Getting the stockers ported and bigger valves installed isn't a bad path either.  With a decent intake, well done 853 castings, mid length headers and a small cam (224/230, .581/.591 114 LSA X-ER lobes) I made somewhere a little north of 400 RWHP.   It's not too difficult on those motors really. 

[Wyatt_S]

I'm on a budget, I'd like to keep the heads that are on already, so what do I need to do to them. This is a street racer only. Would z06 pushrods work? and gm yellow z06 springs or comp 918 spring? Probably with ls6 cam or similar. Does JTR 1 7/8 headers bolt on to the LM7? Do i need to change the lifters and timing chain or will the stock ones work?

[Wyatt_S]

I could go with 243 heads milled if that's what is necessary . Any ideas on how much they cost? Also need to know how much do they need milled? I've been told to get LS9 MLS head gaskets, any thoughts on those?

[usmcpi]

You can prolly pick up a set of 243/799/etc heads around $500.  If they are milled and ported, you are looking at $800-1000.  If possible, try to get them from a CTS-V as they have lighter valves.  What springs you choose depends on the cam.  If you are swapping to any aftermarket cam you cannot use GM springs, regardless what they came out of.  The stock springs can barely keep up with stock cams.  For a small/mild cams you can get away with beehive/918 springs.  If you use a bigger, more aggressive lobed cam you will need dual springs.  Why not just use LS1 gaskets that match your bore size, not something .2" bigger.

Didnt see it before, but stock ls1/6 fuel rails and injectors (26-28lb/hr depending on what year car they came from) will be plenty for 400rwhp.  You should prolly be able to pick up the ls6 intake, rails, and injectors around $500.  Your rails may even work with ls6 intake w/ would save you money and allow you to pick up the intake alone for $300ish, but im not sure.  After that you'd benefit from from bigger injectors such as 36lb/hr+.  Not sure about the 5.3, but the LS1/6 use EV1 harness style injectors.

[digitalsolo]

What exactly is different from the CTS-V LS6 (243) heads and the sodium filled lightweight valves in the Z06 LS6 (243) heads?

[Wyatt_S]

Awesome, thank you so much for your help. Sorry to anyone who thinks my questions are annoying.
So far my list is:
Milled 243 heads
1 7/8 headers
255 walbro
LS6 Intake, rails, and injectors
Comp 918 beehive spring (I have actually been told by 3 people to use these soooo i will)

Still undecided on cam. Probably use LS7 lifters (not much more $ then LS1) and unsure which lifter tray (LS7?.. LS2?). Should I switch to LS2 timing chain? From what I've read, LS9 MLS head gaskets are being used because they are 7 layer and better for people using boost? I may just use LS1 head gaskets. also read about ported LS6 oil pump, any thoughts on that?

[mattster03]

I'd go with the 1-3/4" headers to save a few bucks and I'd also go with an aeromotive 340LPH pump for a little more headroom down the line.  Then I would get a lightly used TR224 112 or 114LSA from someone and preferably try and procure it with some springs (CC918s, PRC, Patirot Golds or PAC are all popular) and hardened 7.400" pushrods.  I sold that exact combo fo $400 about a year ago on LS1tech. 

Milled 243's or 799's would be a good addition to get the compression up a bit, and you can't go wrong bang-for-your buck with an LS6 intake and ported throttle body and stock 28.8 lb/hr injectors.  Depending on the miles on your engine, I wouldn't touch the chain, lifters or oil pump...

[usmcpi]

What exactly is different from the CTS-V LS6 (243) heads and the sodium filled lightweight valves in the Z06 LS6 (243) heads?

my bad, i meant to say 02-04 243 LS6 heads (possibly also 05 for cts-v) have the lighter weight valves, the 01 and prior do not.

[Wyatt_S]

Ill look into the 1-3/4" headers and aeromotive 340LPH pump. The engine has 63,xxx miles on it so I'll leave the chain, lifters, and oil pump alone to help save money. Do i need to replace any bolts with ARP while Im taking things apart?

[usmcpi]

Have to? No.  However, you will need new head bolts and might as well get ARP.  If you can fit it into the budget, get studs over bolts.

[Wyatt_S]

Any other bolts need replaced? rod bolts? cam bolts? balancer bolt? crank pulley bolt?