LT1 rebuild
 

For those of you that have rebuilt an LT1, I have a couple of questions.

I'm going with stock compression and stroke, either a stock crank and drop ins or a fully forged rotating assembly. Any suggestions on where to buy? How's the stuff from Texas speed?

Also what's the deal with the thrust bearing on these engines? Are they really welded to the block? (Think I read this somewhere) Is it pretty straightforward to replace? I've seen 180 degree thrust bearings and 360, does this depend on stock vs aftermarket crank?

I'm not looking to add power via a stroker kit, I don't want to sink the money into an upgraded fuel system. I will however be getting rid of the current jannetty cam which has never really ran correctly and looking for a different one. Probably katech from what I've been reading but if you have suggestions I'm open to them. It's a track only car, looking to keep near the 550-560 whp I have now with E85. Reliability is the main goal.


If you have some advice I'm open to it, I've rebuilt engines before, I'm confident in my ability to do that, but I've never opened up the bottom end of an LT1.

Hope you dont mind me tagging along in this thread but can anyone tell me who has experience in machining the LT1 block to accept a full face thrust bearing?

If youre not boosting and staying NA then theres no need for forged internals unless youre trying to spin them to more than 7400rpm.
Id avoid texas speed like the plague, GPI or BTR are the most trustworthy in the game currently. For cams on an engine with stock Piston To Valve clearance you can go with a GPI LT SS3 cam, the GPI LT NFC cam(not a fan of this one) or a BTR 225 cam. Anything bigger will require flycutting, and obviously you need .660 springs in the heads for these cams.

IMO GPI and tsp are closer to each other than to btr. Then you have BTR being closer to Katech.

If you go with the stock pistons it will limit you in the future if you ever want to go supercharged. But if your keeping it NA then your fine. Never had a problem with Texas Speed but Weapon X their thermostat failed pretty quick on me. Katech has been pretty good to me.

GPI drop in kit holding up fine at 1059 WHP, FWIW. Pretty good testament to their kit’s quality IMO.

If staying around 550wheel you shouldn't have to touch your rotating assembly.

I personally went with GPI, Customer service is great over there. IF you reach out to them and let them know your goals they will get you the right cam. Can even get a custom spec cam for 25-50$ more.

For what it's worth- I'm stock bottom end and closer to the 600whp range on my track car build. Revving over 7k.

Thanks for the responses. Without first hand knowledge it's tough to gauge who to buy from.

Definitely leaving it NA, at least until the mid life crisis fully kicks in. I'd like to build it to be ready for more power, but right now I don't want to add weight. I definitely want to put a forged rotating assembly in. After something failing (haven't disassembled yet, not sure exactly what) with the stock stuff I don't want to rinse and repeat.

Anyone have experience with the thrust bearing? I guess I may just have to figure it out for myself when I do the tear down in a couple weeks.

You may find a few answers to your questions in our LT1 build found here:

Supercharged LT1 Build

Thanks for the link! Good read.

I didn't see much on the thrust bearing though. I'm curious about aftermarket cranks and bearings vs OEM. Say, if I was to opt for a stroker, is that just a simple swap or is it more complicated than that, with regards to the thrust bearing? It's very interesting that they only use a 180 degree thrust bearing. Also that you can buy a 360, but is the #3 main cap even machined for that? Also if it's not used for a thrust bearing there's likely no alignment dowels and thus the possibility of the cap walking would increase. I'd say it'd likely be rare but technically possible.

I guess not being able to find the answer I'll try to get technical help from the vendor I decide to buy the rotating assembly from. I'd assume that they'd have the answers.

Baddawg53 - Reference the thrust bearing: I thought the images were pretty clear LT1 uses a 360 degree thrust from the factory and the Mahle/Clevite bearing still required removing the tang to properly seat. Believe they were set of LS bearings...*

Our engine is a 416 so there are challenges we ran into - piston hitting crank position wheel and the oil squirters crammed between piston skirt and rods...

Good luck on the build!

Man ... Not sure how I glossed over that part about grinding off the tang on the bearing. Need a bit better attention to detail there. Thanks for following up with that.

I've seen where guys have had piston cooler clearance issues as well as the relucter wheel, good info, it'll be coming apart Hopefully next week.

I believe my oil pump went bad and then I started getting some valvetrain noise, not running very good. It still starts and has oil pressure, but it dropped off and the oil temp climbed, as you can see in the picture ...

https://www.youtube.com/watch?v=paizumY5Ygs

IMO, a mild cam remove the AFM lifters, a good mild spring and you are golden to 7000 or so RPM,

Aftermarket cranks are going to run into fillet problems, but if you have a commitment engine builder you should be OK.

Thanks for sharing that video, really good stuff in there. Definitely subscribed to that channel.

I'm going to build the engine myself, I've built enough to have the confidence to do it, just not the LT1 engine.

Just to follow up, the oil pump looked perfect and it was a 7/8 rod bearing failure and a cracked crankshaft.

yikes!

How many miles did you have one it? If those are scratches, looks like debris in the oil made its way to the journal

I have 48k miles on the car. It's been modded, cam, ported heads FBO. Last few years it's only been a track car.

I had an issue with the original set of ported heads I purchased, the intake port was ported too much and allowing coolant to flow into the port, burning it and also getting in the oil. It was pretty difficult to diagnose, I was losing coolant and it wasn't smoking and the oil appeared fine. After getting an oil sample taken and seeing the coolant in the oil along with excessive wear I took it apart and after a long ordeal ended up with another set of heads. Even after that my oil samples all showed more than normal wear and the 0w-40 oil wasn't really holding up even after 3 track days. It was going to fail eventually. I believe it was probably a spun bearing first even though the oil pressure was ok, and then the heat cracked the crankshaft. However it coulda happened in the reverse order also. I don't think I'll ever know.

I've found the LT1 to be an easy engine to work on. The parts I would be carful of are:
1) the thrust bearing, Tim M did his I never did mine (stock crank)
2) do you need to line bore mains when changing to studs, normally yes but if the mains have guide pins, maybe not. It has been explained to me as put the crank in and if it spins easily, you are golden.
3) I did multiple torques before final torque using APR lube on the con bolts, IMO I should have found my old one or got a new bolt stretch gauge (after market rods). Use stretch gauge if applicable period.
4) I would have and should have gone with a 3 bolt cam and gear and toss all that phasing stuff away.
5) luv the Katech oil pump, it was not available when I built my engine
6) C5R timing chain (don't know if it works with 3 bolt cam and gear)
7) I torque my ARP head studs -10 ft-lbs less from memory, I did a few calculations and have no idea why the ARP studs are so tight that IMO the studs are actually deforming. Never had a problem, your milage may vary.
8) cracking in the port is a problem and I found that aftermarket studs or the bolts that come with rocker fulcrums are too long and increase the chances of cracking in the top of the port
9) aggressive lift race cams make power but they compromise valvetrain, guide, valve and seat integrity, live with 20 HP less and a cam that can go 100K miles
10) get an LT1 valve spring installer, on the car or off it was easy peas' to use.
11) Johnson lifters, LS7 lifters are not really made for most aftermarket cams.

Things common to all good builds
1) get a piston ring filler, don't do that by hand
2) check and check again lifter preload
3) get that funnel shaped piston installer, made it so easy
4) run the clearance called for by application, a heavy track car needs more clearance.

Excellent advice! I appreciate the time you took to share that knowledge.

Luckily the katech pump was available after some searching and I have that part already.

I installed Johnson lifters during my coolant loss debacle, and after I had an LS7 lifter on the verge of pushing the roller out. They look ok still but I'm going to change them again because I just don't want to risk anything.

I definitely worry about the valve seats with those big cams, but from what I've read the spintron cams don't have the valvetrain instability issues. If you have any feedback on that I'm all ears

. I've also decided a while ago that valve springs were now a maintenance item and I was going to swap them yearly. I just don't want to risk anything and with that valve spring tool they're an easy enough swap. Honestly I want the horsepower, and if that requires some extra maintenance I'll do that.

My plan is to bring the block to a reputable machine shop and have it cleaned up, the cylinders look pretty good, there was no issues with the rings, it looks a lot cleaner than I expected.

I'll look into that ring filer, I was just gonna do it by hand but I'm sure you're right.

My plan is to have a notebook handy with all the specs I want and record everything. I have read about the tight clearances and was planning on buying 0.001 extra clearance bearings.

It's a long list of parts I need to buy.

I think your HP goals can be reached by a sub .600 lift gentle lift cam by Cam Motion. I don't know if Cam Motion has a spintron, what I do know is I was in the LS1 valvetrain wars and silly me, I went ahead and did it again with a .660 lift cam (you will be alright with LS7 lifters) only to fail the lifter / cam. My advice is the LEAST lift availably for your HP goals.

I think I understand valve motion enough to understand that small changes in temp, RPM, valve guide wear, and valve spring wear... will change your are golden to stuff breaks. That said I do like the conical springs and their ability to absorbed spring harmonics. A gentler cam does several things:

1) there is or can be a cracking issue of the head ported with high valve spring pressure (not a big deal if it is just at the bottom of the rocker stud). The lower lift and gentle ramp cams require far less spring pressure for example the hot cam uses stock LT1 springs and it is a pretty big cam in terms of duration (not sure of overlap as I've seen two different specs). So there are a bunch of off the shelf single beehive springs that will work and I can't find one, but I would hope there is at least one conical that would work (all are too stiff IMO), say the most mild conical not shimmed 1.8" install height. I have been running the TSP dual valve springs titanium retainer (due to be changed out as I'm nearing 20K on them). Long story short a milder lift / ramp cam probably can get away with a single beehive and definitely can get away with a non-shimmed conical. I'd still change them every year / 20K.

2) I never believed there was a seat issue with the stock head, or at least the issue was related to using stock parts with racing application cams (lift and profile). Same goes with any sort of valve failure, the stock stuff was never meant for stress and heat and I've gone to Manley valves with undercut heads, which I've run forever and I've never had one fail. Once again, problem solved NA at least if you stay with a gentler cam.

3) it is really a pain to adjust preload and I may one day just install adjustable rockers. This way the is a stud into the head so I'm not always working the same stock head threads and I can easily dial-in and check preload and yes after 20K they do change a few thousands.... maybe my cam is set in and I'll be dead before preload changes again dunno. It would be interesting to track preload changes on a race engine. You may even go with the SR short travel Johnson lifter which is more finicky but supposedly more stable under race conditions.

IMO you WHP SAE goals are reachable by a build that should last a long time with cheaper parts both on top and bottom end, but once again IMO shy away from an aggressive ramp / lift cam don't care if god or a spintron designed it. This may have changed as I had my heads ported by Pray in 2017 and back then, the LT1 heads stock or ported seem to flat spot or even lose flow over .550 to .600 lift. Maybe that has been all sorted out, maybe not. Note that there are FBO engines into the 9s where full built engines cars still can't do and at that performance range stock cam / AFM is junk a huge liability. Long story short the low hanging fruit is a 220 to 230 cam with a 112 or so LSA and .598 lift with some mild valve springs IMO of course. Will a .660 lift spintron cam make 20 HP more with the same duration? maybe so. Since this is a race car I'd add a 23x / 241 cam on 108 lobes installed straight up and get the 20 HP back plus a huge chunk of midrange torque at no reduction in reliability (idle will be choppy).

GM itself went with a mild lift, ramp profile and spring on the LS7 and spent a whole lot of time on a light valvetrain titanium intake. They had to warranty the stuff so I think replicating that maybe the way to go (new bronze guide and titanium intake) on a race car. Back to the same theory that the least lift, gentle ramp and least spring for application = reliability. It is pretty easy to check for guide wear (a big problem on the LS7). GM says it was an improper machined guide and went ahead and used titanium on the LT4 intake which seem to holding up just fine (way way milder cam). dunno but I am a bit jealous of the titanium valve folks... but if I was looking at a NA track car this would be something to think about.

Who TF built that engine so I know who not to go to?

it does show the thrust bearing was an issue with the stroker crank.

What I have learned by reading this thread? There’s a helluva lot I don’t know!

I found a little surprise when I removed the crankshaft. The #4 main bearings had also spun. Interestingly that journal is actually the best looking journal on the entire crankshaft. The bearings were somehow not completely burned up, and the crank spun fairly decently. Remarkable that this engine still ran with what was just a light tapping noise like a lifter.

So I guess this block is junk and I'll be ordering a built short block for this car.

block good enough for core, it is really crush that retains the bearing not that little notch and all that should clean up with a line bore. TSP has nice sleeved blocks....

So I was watching a LS7 tear down (three race seasons) and was surprised to see the mains were walking, looking at your main failure I'd be thinking something like this:
https://katechengines.com/i-30497627...n-caps-lt.html

I've decided to go with a 416 katech short block and their track day camshaft. Cost wise I think it was the best move and I'm pretty confident in katech. I'm going to install the LT4 fuel system to make sure it doesn't run lean. I'm going to reuse my current LT1 heads that have been worked but installing new valve springs. New BMR engine mounts, ATI damper, all the goodies...

I'm curious if I should invest in a 103mm throttle body or stick with the 95mm I have. Any insight would be appreciated ... And if a 103 then which intake tubing do you use with that large of a throttle body? Thanks

If I am building a 416 then I want to utilize all the potential airflow capabilities.

my course of action would be -> Higher Flowing heads, Ported MSD, 103tb, and a Rotofab big gulp or 5" intake of some sort.

Shoot me a message when your ready. We have pistons on order for the next batch of higher compression N/A 416 shortblocks now.

Thanks for your response. I'll have to start looking for the 103 TB

Thanks, I already called and placed the order. Lead time supposedly 8 weeks. Hopefully its sooner.

Alright, so I've ordered a bunch of stuff, and I'm looking for feedback. Have I ordered anything that is wrong? Missing something that I should be replacing? Here's my list

Katech 416 NA short block, fully forged, 11.5:1 compression
LT4 injectors, in tank and high pressure pumps, and fuel lines
ATI balancer
BTR 660 dual springs/seals
Katech oil pump
NW 103 T/B
JLT 5 inch cold air intake
Katech LT1 track day camshaft
I have a year old set of Johnson 2110r lifters that seem ok, but with the metal that went through the system I am thinking those should be replaced like I'm doing with the oil cooler.

I already have an MSD unported manifold and 1 7/8 kooks headers and exclusively run E85. I plan on buying a new OEM clutch because I don't think I'll exceed it's capabilities

I expect to make over 600whp, considering I was at 550whp with the stock bottom end. Thoughts? Suggestions?

If I were you. I'd bump up compression abit.
A combination of a thin gasket and milling the heads a little will get you to 12.5:1 compression. Will be fine on pump gas, and respond well to E85.

I thought about this actually, decided on a slightly thinner gasket but I want to measure the piston to valve clearance before deciding on any other changes.

It's going to have a mile of clearance with the aftermarket forged pistons.

Milling .006 nets roughly 1cc of volume if you want to do some rough calculations.

Great to know I'll have plenty of clearance. Thanks for those rough calculations.

Well I was finally able to get the new engine installed, and it's running. Car will be at the tuner next week, so we'll see how she does

Here's the mod list, I'm very curious what the numbers will be, I had about 550whp 460tq previously. I'll be disappointed if it doesn't break into the 600's with a increase in torque.

Katech 416 NA short block
Ported stock heads, BTR springs, CHE rocker trunnions
Cometic 0.040 head gaskets
Katech track day camshaft
Johnson lifters, 7.825 and 7.850 3/8 pushrods
Katech oil pump
Katech lightweight flywheel
ATI damper
LT4 fuel system
Flex fuel conversion
160 degree katech thermostat
MSD manifold
NW 103 mm throttle body
JLT 5 inch intake
BMR engine mounts with solid bushings
LT4 clutch

AC compressor and lines have been deleted, using motul break in oil and will swap out to mobil 1 0-50 before the first track day.

Car sounds good even before the tune.

Bravo! A significant undertaking for sure. Good luck at the dyno!

Definitely need some videos of that thing!

Haha ... I do have one video, I was planning on taking a better one after I actually get it out of the garage and cleaned up ... 7 months of dust on her right now!! But she sounds good!!