LT1 Rebuild/Cam Question(s)
 

Eventually the snow will stop and it'll be warm enough to pull things apart ... I hope! In the mean time, I'm trying to make a list of parts to order for my upcoming rebuild. Primary goals are to 1) get the car running again (blown HG), so no long drawn out builds 2) make some good power, somewhere between 350 - 400rwhp N/A (if possible, no nitrous).. Car will mainly be a weekend fun car for cruises and occasional Friday night T&T, so it should be reliable. Although tempting, not looking to sink my life savings so sticking with the stockish cubes

So far I've been thinking the following:

Pull motor, send block for hot tank/inspection to clean HG crap out and verify no cracks or other issues. While there, new main/rod/cam bearings, polish crank, re-ring pistons.

CC503
Crane 10308-1 spring/retainer/lock kit
Ultra Pro Mag 1.6rr
GMPP guide plates
Hardened pushrods
LS7 Lifters
ARP Head bolts
ARP Main bolts
ARP Rod bolts
ARP 7/16" Rocker studs
All engine gaskets (0.039 HG)
Cloyes HD timing chain
30# injectors w/ stock fuel pump
Tune

-You don't need a HV pump.
-I would be very wary of LS7 lifters
-I would replace the stock fuel pump to be safe with a genuine walbro or aeromotive.
-Stock oil pan and pickup are prob better than moroso windage wise.
-Save up for LE2 package
-Look into resizing the rods for ARP hardware
-If you have the money, do ARP mains too

I'll sell you my 385 for 5 grand intake to oil pan, way more into it then that and way more power than that yet still very streetable.

I'd keep the stock fuel pump. Too many issues with aftermarket ones. If you find you need one, get it from a reputable dealer, get a hot wire kit, and hope you get a good one!

Don't forget a mail order tune. I'd skip the sa rockers and go nsa, that cam will be in the rpm range to warrant them.

You should be figuring out your quench and compression ratios too.

You're right, HV pump probably won't help if the bearings are fresh, should be tighter clearances. I'll probably leave the stock oil pump/pan for now and reconsider if I continue to have the drop in pressure under WOT.

I forgot to write it up top, I plan on ARP head studs/main bolts and I'll have the rods machined for ARP rod bolts as per your suggestion.

Why no LS7 lifters? I thought they were the replacement for the LT1 and seeing as the LS7 revs quite a bit higher than Ill be (6200 max) I should be ok? Unless you have a better suggestion

As for LE2, I think Ill put the extra $400 elsewhere if the LE1 will get me to my goal. Future plans for the car may involve FI so a different set of heads would probably replace the stock ones.

Tempting as your setup is, I'll let you keep it lol fuel pump was replaced a few years ago, not sure of the brand but we'll see if it can keep up.

Found CC Magnum 1.6rr NSA with guide plates and pushrods for a good price. I know they're not full roller rockers, but I'm leaning towards steel vs aluminum for fatigue strength.

Updated the top a bit.

You can get ultra pro mags, which are a full bodied roller rocker in steel.

Get a gm white spring for the pump, arp drive, and braze the pickup to the pump. LS7's have been a crap shoot especially in lt1 rebuilds. They use a much lighter valve train and I'm sure the qc in mexico isn't the greatest. If you are revving to a max of 6200, the stock cam is capable of that or something similarly sized. Your cam will probably make power till 6600-6700 with those heads, higher with le2s. Honestly, you should write out exactly how much you'll be spending between the machine shop, the hard parts, the little things, shipping, taxes, and the unexpected. I think you'll be right around 5 grand give or take. I was nearly 5 in machine shop labor. I'd throw in the tune/pcm but I'm a 95 unless you want to convert. Honestly, give it a little consideration. Its callies/compstar crank and rods, srp pistons, 4 bolt mains, le2s, 238/246 cam, and supporting parts.

I'm shooting for the +/- $3.5k range which I think is do-able if I can resist unnecessary/top of the line parts for a ~400hp build. Free shipping helps too.

If I am retaining the stock crank, pistons (new rings), and rods (arp bolts), and basically freshening the bearings/surfaces, will that require a balancing of the rotating assembly? How much machine work should I even be doing? I know you said the deck height is off from the factory which might contribute to my original issue.

I could go with a smaller cam too, like a 224/230. Stock cam is tiny and would be a shame to leave in there if I'm pulling the motor out!

I would balance it, and you really can't judge machine work till the shop has it.

Your car is a manual?

When I have my H/C LE2s, that 224/230 was big :lol: Don't set your sights on a HP number that won't agree with how you drive the car.

You'll be close with your budget but like Matt said, we can't say without getting it stripped down and inspected. Talk to the guys doing the work, tell them your goals, your allotted budget, your desired goals, and their honest opinions. Hopefully they are good, genuine guys that want to help you instead of take your money and shut the door.

I think your suggested rpm range, your rocker selection, and your cam are not jiving. The cam will want a higher rpm range, the rockers won't like that, and the extra money towards the le2s will go a long way with making good power over 6k where these heads will normally choke power. This is all my opinion and others will differ so just use it as helpful guidance in planning your build. Whatever you do will obviously be leaps and bounds over stock, its just how far past that you want to be is what determines your build.

Agreed with what others have already said, but I'll add my .02

I'm also a fan of the LE2 heads, I've seen some nice results from them.

$3500 might go quick with all you want to do? and how many miles are on the other parts? Remember things like replacing the opti ($300), maybe the water pump ($200) if you have allot of miles, do all at once and be done with it. All the gaskets maybe motor mounts, fluids, new hoses, plugs, wires, new lower temp thermostat, new belt etc all start to add up quickly.

Coulpe items on your list to validate:

Make sure with the timing chain you get one designed for an LT1, and they aren't cheap either. GM HD set runs around $275. I've used it in a few builds and it's a nice unit. To run a standard SBC double requires the time cover modified and an electric water pump.

I've had issues with the alignment of aftermarket guideplates with LT1 heads, so I always just buy the GM make.

Pushrods, you need to get quality hardened pushrods. You don't want cheap when running guideplates

My Personal Opinion: Why head studs? They are a PITA on our cars and you will certainly be fine just using ARP head bolts. Make sure you get the 12 point heads so you have clearance on the aftermarket springs.

As Sweetbmxrider pointed out - change your rocker selection. You are going to need to spin the engine up, don't go cheap on you valve train - look into Comp Cam Promags.

I'd suggest doing a complete price list of everything you need as worst case. Just so you don't get half way through and run out of funds.

So what shape is your clutch in? A tired stocker would last long agianst 400HP.

Ok, how bout we just iron the bottom end/machine work out first then go from there. Ill come back to the other stuff after. Although this motor has 118k, it also made ~22psi hot, ~40psi @ 1800 rpm, and 60psi cold oil pressure, so it's not like this motor was trashed. I just figured it'd be a good time to throw new bearings in while its out and address any weakness that would interfere with my cam choice (such as reconditioned rods/arp bolts). So machine work should be minimal, I think.

I've been reading the stock rotating assembly is quite strong and can handle almost 7k rpm with ARP bolts, some argue for stock spec bearing cleanances while others vote up to 0.0025-0.0030 instead of 0.0015 (stock?) and 20w50 . If that's true Id have no issue spinning to 6500 with LE2s?

Aside from bearings I have hot tank/bake/blast, cylinder hone/rings, and crank balance/polish. I emailed the shop and asked for some prices, they listed cutting the crank ... Is that necessary?

Weather is getting warm, so hopefully I can get this party started and find out what's going on.

I don't think a cut would be needed, but you won't know until you get a crank out and bearings to examine.

Regardless of cut/hone, you will prob have a sizable machine shop bill. Downside to just doing stock rebuild, you essentially pay for the machine work a 383 would need anyways.

More than likely you will see excessive wear on the cam bearings.

http://www.ls1lt1.com/forum/parts-sa...t1-engine.html

http://www.ls1lt1.com/forum/parts-sa...hortblock.html

Something to compare price to.

Wow the guy in the second link did the bottom end for more than the OP's total budget. The machine shop will make or break your budget for sure. You can't figure anything till then. 3500 is doable but its gonna be difficult

Mine was 4ish at the machine shop too. It takes a lot to do any motor right with quality components.

Thanks for the insight guys! I appreciate the links Adam, good reference for some real world costs. As you guys said, I'll have to assess the motor when it comes out. I'd rather have a fresh bottom end with ARP hardware and will forgo heads for the time being if I have to to save room for a good valve train. Future plans would be 383 with forged internals, for now the car just needs to move under its own power. Plenty of good off the shelf cans to hold me over for now.

Mainly cause I am lazy, what makes you think you have a warped block and not just crappy heads or poor install of heads?

Only speculating at this point and several people have said the factory deck is not flat. Could be a bad head too. Doubtful it was install error, guy that did it is a great mechanic and I don't think I'd've gone 50k miles if it was installation error. I'll find out soon enough.

As far as machining goes, should I have the rod bearings loosened up to 0.0025" or stock spec? And if so, do I have to run a thicker weight oil or just a white spring with 5w30? I wanna spin to 6500 With stock crank/rods/pistons.

I would do stock tolerance with ARP hardware and leave it as factory as you can. Ask the machine shop their preferences, but larger bearing clearances waste power and for your application are not needed IMO.

You are running a very fine line between a stock cleanup/rebuild, and F-it, 355ci H/C build. Don't try for both here.

I spun my SBE well past 6500 for a couple years and never had an oil pressure issue. One day I will pull it apart and check bearings for how bad they were.

It sure is a fine line!

I guess the last question is do I have the deck machined and if so, how much? I see it ranges between 0.022-0.027". Assuming the heads are flat, I figured I could have it decked to have a 0.015" piston-to-deck clearance and use Fel-Pro 4.125" Bore x 0.39" CT gaskets for a quench of 0.405". I've read between 0.30-0.50" would be ok. SCR would be 11.29:1 and a CC503-ish cam would yield a DCR of 8.82:1 and cylinder pressure of 180psi. Should be safe for 93 octane ? Am I doing any of this right?
:bertstare:

You only want a mild build so find a good block and stay with the stock deck hight. Unless you have some real need to reduce the deck I wouldn't bother doing any more then the bare minimun. You start talking about changing the deck height and you are getting into allot more time and money. If you end up having to do something like commetic gaskets you'll need to remachine the block and heads to get the right surface finish.

For the CR, you also want to check static but understand the cam choice will bleed off some compression. Now your looking at a 503 cam, that not going to give you much of an issue with your P~T~V clearance. If you do go big on the cam, just remember you run a manual trans so you run the risk of a mis shift and overrevving. So you do want to stay on the higher side of your P~T~V. I rev high and mis shifts LOL! I wanted allot of clearance!

If you do a stock or near stock deck, mild cut on the heads and a .39 gasket you will be fine. I've used the 306 and GM847 cams with stock heads, thinner .029 head gaskets. PTP was fine with 1.5 rockers, I felt the 1.6 make it a bot close for what I like to have. These ran fine on pump gas with no problems.

Ok, I'll leave the deck alone if it checks out ok. Instead can I run a 0.026" gasket without trouble?

Worth investing $200 in my connecting rods (machine work + ARP bolts) or buy a set of forged SCAT rods with ARP bolts for $250? I know, I'm at that line again :lol:

New rods will almost def require you to rebalance the assembly (which I would do regardless)

118k mile bearings ... Normal wear? Dropped off block/heads/rotating assembly at the machine shop today, gonna talk to them Monday and figure out what will be done. They are gonna check the notes and stuff first and make a build sheet, so nows the time to fix any underlying issues!

http://i892.photobucket.com/albums/a...pseute572m.jpg

http://i892.photobucket.com/albums/a...psne9lpll9.jpg